·
assettype · drop-in viewer
computeShader.assetType
A `.computeShader` is a GPU compute (GPGPU) program with a **zero-scaffolding** authoring contract: you write only `@compute fn main(...)` plus a declarative `bindings.yaml`, and the engine GENERATES every `@group/@binding` declaration — storage buffers, textures, samplers, stora…
byzero-proxy @ DESKTOP-DB3UJOJ·posted 3mo ago
What it does
Compute shader (asset type)
A .computeShader is a GPU compute (GPGPU) program with a zero-scaffolding
authoring contract: you write only @compute fn main(...) plus a declarative
bindings.yaml, and the engine GENERATES every @group/@binding declaration —
storage buffers, textures, samplers, storage textures, and a params: uniform —
expands #includes, naga-validates the result, and registers it. The single
source of truth for the binding layout is bindings.yaml; there are no
hand-written @binding lines to keep in sync.
New to how content lives across the CPU and GPU? Read
core/resource-modelfirst: it covers the asset / CPU / GPU forms every resource takes, the upload path, and how compute fits the performance ladder (core/performance).
Folder shape
A .computeShader is a folder asset:
<name>.computeShader/
shader.wgsl # the WGSL body — only `@compute fn main` + helpers (required)
bindings.yaml # the binding + params schema (required)
README.md # a one-paragraph description of THIS shader (required)
.metadata # asset metadata
Each file carries a committed .meta sidecar pinning its stable guid. The
identity is <name> (the .computeShader suffix strips).
Resolve the shader once, then dispatch through the reference:
local carve = asset.resolve("carve", "computeShader")
carve:dispatch({ buffers = { heights }, workgroups = { 64 } })
asset.resolve is what records your script's dependency on the shader, so the
shader travels with the world your script lives in — packed, pulled, or
published. It compiles on first dispatch; there is no setup step.
bindings.yaml
One ordered bindings: list — the binding index is the list position
(0, 1, 2, …) — plus an optional params: scalar-uniform block. kind defaults
to buffer when omitted.
bindings:
- { name: clouds, kind: storage3d, format: rgba16f } # texture_storage_3d<rgba16float, write>
- { name: occupancy, kind: texture3d } # texture_3d<f32>
- { name: smp, kind: sampler } # sampler
- { name: out_tex, kind: storage2d, format: rgba16f } # texture_storage_2d<rgba16float, write>
- { name: U, kind: buffer, access: read, element: f32 } # var<storage, read> U: array<f32>
- { name: Uniforms, kind: buffer, access: read, element: VolumeUniforms, array: false } # var<storage, read> Uniforms: VolumeUniforms
params:
- { name: scale, type: float, default: 2.0 }
- { name: count, type: int, default: 0 }
kind | extra keys | generated WGSL declaration |
|---|---|---|
buffer (default) | access: read | read_write (default read_write), element: <wgsl type> (default f32), array: true | false (default true) | var<storage, ACCESS> NAME: array<ELEMENT>; (or … NAME: ELEMENT; when array: false) |
texture3d | — | var NAME: texture_3d<f32>; |
texture2d | sample: float | uint | sint (default float) | var NAME: texture_2d<f32>;, or <u32> / <i32> for the other classes |
texture_depth | — | var NAME: texture_depth_2d; — the one sampled shape with no sample: of its own; a depth-aspect channel (@scene.depth) binds here, not through texture2d |
storage3d | format, access: write | read | read_write (default write) | var NAME: texture_storage_3d<FMT, ACCESS>; |
storage2d | format, access: write | read | read_write (default write) | var NAME: texture_storage_2d<FMT, ACCESS>; |
sampler | — | var NAME: sampler; |
textureCubeArray | — | var NAME: texture_cube_array<f32>; — the environment cube array, bound to @scene.environment by a render feature's pass |
vertices | access: read | read_write (default read_write) | var<storage, ACCESS> NAME: array<u32>; plus the mesh's layout uniform and the zeroVertex* accessors |
acceleration_structure | — | var NAME: acceleration_structure; (hardware ray tracing) |
- Eight storage buffers per shader — the WebGPU guarantee, and what the
engine asks every device for.
bufferandverticesbindings spend that budget; textures, samplers, storage textures andparams:do not. Anacceleration_structurebrings engine-owned buffers with it — three where the device has hardware ray query (the tableszeroHitSurface/zeroMaterialread) and five on the software backend (those, plus the scene triangles and the hierarchy over them) — so a traced pass has three slots of its own on the backend web users get. Over budget, the engine refuses the shader and logs which buffers it declared. - A
bufferdefaults toarray<ELEMENT>. Setarray: falsefor a single NON-array storage buffer — a struct binding (e.g.element: VolumeUniforms,array: false→var<storage, read> NAME: VolumeUniforms;). The struct definition itself lives inshader.wgsl, notbindings.yaml. - A sampled texture binds under the class its FORMAT puts it in, so
samplestates that class and the generatedtexture_2d<..>matches it. An integer channel —@scene.material, which isRgba8Uint— isuint; everything else is thefloatdefault. Bind an integer channel to afloatslot and the engine refuses the pass and names both classes, because the device would otherwise reject the bind group and invalidate the pipeline. - A storage texture's
accessdecides both the generated declaration and the layout the engine registers, so the two always agree. It defaults towrite, the access every target grants every storage-compatible format.read_writeis granted onr32falone; declaring it on any other format is refused at the compile, with the reason oncompute.programState. A pass that needs to read a wider target reads it through a separatetexture3d/texture2dbinding, or through a second storage binding declaredread. formattags (storage textures):r8,r16f,r32f,rgba8,rgba16f,rgba32f. Storage textures only allow storage-compatible formats (r32f/rgba8/rgba16f/rgba32f).- An
acceleration_structurebinding resolves to the scene acceleration structure when the shader runs as a render-pass with ray tracing enabled (renderer.setRaytrace(true)). Declaring one makes the engine emit the helper functions the body can call:zeroTraceClosest(origin, dir, t_min, t_max) -> ZeroHit(struct:hit, t, instance, primitive, bary, attr, whereinstanceis the hit object's render slot),zeroTraceAny(origin, dir, t_min, t_max) -> bool(terminate-on-first-hit, for shadow/occlusion rays), andzeroHitSurface(hit) -> ZeroSurface(normal, uv, material) +zeroMaterial(index) -> ZeroMaterial(base_color, emissive, metallic, roughness) to shade what a hit landed on. The same surface works on both backends — hardware ray query and the software/compute path — so the shader doesn't branch onrenderer.raytraceCapability(). Bind it from a render-pass, which is where the scene acceleration structure exists.
params: declares scalar uniforms (type: float | int). When non-empty the
engine appends a ZeroComputeParams uniform as the trailing binding (read it in
WGSL as params.<name>) and tunes its values at runtime with
shaderRef:setParam(prop, value).
The kernel ABI: columns, counted and appended outputs, specialize, determinism
One shader asset can serve many shapes of data. bindings.yaml states the shape
with these extensions, and the engine's compile path lowers them to the plain
bindings and WGSL above (modules/compute_abi, whose README has the whole
surface):
workgroup: 64 # the size the body declares (default 64)
bindings:
- { name: cols, kind: columns, access: read } # a table of columns in one binding
- { name: src, kind: buffer, access: read, element: T }
- { name: dst, kind: buffer, access: read_write, element: T, count: "len(src)" }
- { name: hits, kind: buffer, access: read_write, element: vec4<f32>, capacity: "n * 4", append: true }
specialize:
- { name: T, options: [f32, i32, vec2<f32>, vec3<f32>, vec4<f32>] }
- { name: FOLD, options: [add, min, max] }
- { name: BODY, kind: source, default: "0.0" } # text that replaces the identifier
determinism: exact # or float_order
- A
bufferof a scalar or vector element getsNAME_get(i),NAME_len()and (unlessaccess: read)NAME_set(i, v). Avec3element is stored as a flat scalar array, so a column of vec3 keeps its 12-byte stride.zero_n()is the dispatch size. columnsbinds a table of columns (compute_abi.table) as one storage buffer;cols_f32(c, i, lane),cols_vec3(c, i)and the rest read it.count/capacitygive the size, in elements, of an output the run allocates.append: trueadds a live counter binding,NAME_count, withNAME_store(slot, v),NAME_set_count(n)and, underdeterminism: float_order,NAME_append(v).specializeparameters are compile-time: type options becomealias NAME, named options becomeconst NAMEandNAME_<option>,kind: sourcetext replaces the identifier. Each specialization compiles once.determinism: exactrefusesNAME_append: an exact output is written at ranks the kernel computed.
Dispatch such a shader through its program:
local variant = shaderRef:program():variant({ specialize = { T = "vec3<f32>" } })
local run = variant:run({ n = 64, inputs = { src = srcBuffer } })
local values = require("@builtin::modules.compute_abi").read(run.outputs.dst.buffer)
shaderRef:program() answers the same program, with the variants it has lowered and compiled, for as long as
shader.wgsl and bindings.yaml hold the bytes they held when it was made. A write to either file, from any origin
(vfs.contentVersion moves), makes the next program() a new one, and a dispatch through it runs the new text. The
schema getBindings() answers is the one the program was made over.
Writing a mesh's vertices — kind: vertices
A mesh's vertices are raw bytes on the GPU, and the engine stores a mesh in one
of two layouts: 92 bytes a vertex with every attribute a f32, or 32 bytes a
vertex with normals and tangents quantized to bytes and UVs to shorts. Which one
a mesh got depends on the mesh.
Declare kind: vertices and the shader is handed both the buffer and the layout
that mesh is in, plus accessors that address it:
bindings:
- { name: verts, kind: vertices } # the mesh, writable
- { name: heights, kind: buffer, access: read, element: f32 }
params:
- { name: lift, type: float, default: 1.0 }
@compute @workgroup_size(64)
fn main(@builtin(global_invocation_id) id: vec3<u32>) {
if (id.x >= zeroVertexCount()) { return; }
var p = zeroVertexPosition(id.x);
p.y = p.y + heights[id.x] * params.lift;
zeroSetVertexPosition(id.x, p);
zeroSetVertexNormal(id.x, vec3<f32>(0.0, 1.0, 0.0));
}
carve:dispatchOnVertices({ model = meshRef:handle().guid, buffers = { heights }, workgroups = { 64 } })
The accessors, over a binding declared read_write:
| read | write |
|---|---|
zeroVertexCount() -> u32 | — |
zeroVertexPosition(i) -> vec3<f32> | zeroSetVertexPosition(i, vec3<f32>) |
zeroVertexNormal(i) -> vec3<f32> | zeroSetVertexNormal(i, vec3<f32>) |
zeroVertexTangent(i) -> vec4<f32> | zeroSetVertexTangent(i, vec4<f32>) |
zeroVertexUv(i) -> vec2<f32> | zeroSetVertexUv(i, vec2<f32>) |
zeroVertexColor(i) -> vec4<f32> | zeroSetVertexColor(i, vec4<f32>) |
zeroVertexNodeIndex(i) -> u32 | — |
zeroVertexWord(i, offset) -> u32 | — |
access: read gives you the readers only — a var<storage, read> binding
cannot be assigned to, so the writers are left out rather than handed to you
broken.
Once a pass has written a mesh's vertices, the engine bounds that mesh by what
the pass wrote: it reduces the vertices to an AABB every frame and culls against
that, so geometry a pass moves across the scene needs no oversized placeholder
to survive culling. renderer.mesh.boundsSource(guid) reports "compute" for
such a mesh and "geometry" for one still bounded by what it was created with.
A shader declares at most one vertices binding; the accessors are generated
for that mesh. It can be declared anywhere in the list — the mesh is bound by
the dispatch, and buffers fills the other storage slots in declaration order.
The tangent's w carries handedness, and quantized normals/tangents come back
in -1..1 while quantized UVs and colours come back in 0..1, so the values are
the same ones a surface shader sees whichever layout the mesh is in.
shader.wgsl
Write only @compute fn main (and any helpers / #includes). The names declared
in bindings.yaml are in scope — data, out_tex, params.scale, … — with no
@group/@binding lines of your own.
// @domain: compute
// Bindings are declared in bindings.yaml — do NOT write @group/@binding here.
@compute @workgroup_size(64)
fn main(@builtin(global_invocation_id) id: vec3<u32>) {
if (id.x < arrayLength(&data)) {
data[id.x] = data[id.x] * 2.0;
}
}
Dispatch & runtime
Everything a compute shader does, it does through its reference:
| method | what it does |
|---|---|
ref:dispatch(opts) | { buffers, workgroups, params? } — bind one buffer per declared storage binding, in order |
ref:dispatchOnVertices(opts) | { model, buffers?, workgroups, params? } — bind the mesh model names to the vertices binding, buffers filling the rest |
ref:dispatchEx(opts) | { resources, workgroups } — for shaders mixing textures, samplers and storage textures: one { kind, name } per declared binding, in order |
ref:setParam(prop, value) | write one params: scalar uniform |
ref:createBuffer(name, opts) | { type, len, usage? } — a GPU buffer owned by this shader |
ref:buffer(name) | the buffer this shader last made under name |
ref:getBindings() | the parsed bindings.yaml schema, read and parsed again only after the file is written |
ref:getSource() / ref:setSource(wgsl) | read / overwrite shader.wgsl |
ref:compile() | compile now instead of on the first dispatch |
ref:status() | what the engine did with this shader's dispatches, one record per target |
The params: uniform is engine-owned and takes no entry in buffers or
resources, and neither does a vertices binding's layout.
setParam writes the uniform every later dispatch reads. A dispatch that
passes params = { name = value } reads those values instead, in a copy of the
uniform only it binds, with every name it leaves out at the value the shader
holds — so one shader dispatched twice in a frame over different data reads
different values each time:
lift:dispatch({ buffers = { a }, workgroups = { 4 }, params = { height = 1.0 } })
lift:dispatch({ buffers = { b }, workgroups = { 4 }, params = { height = 3.0 } })
A name the shader does not declare fails that dispatch, and the failure names what it does declare.
dispatchEx resources
Each resources entry fills the binding at its position. Its kind says what
the resource is, in the words bindings.yaml uses, and the binding decides how
it is read. A slot takes the kind it is declared with; a texture2d slot also
reads a storage texture, a side of a history pair or the scene depth, and a
storage2d slot also writes this frame's side of a history pair:
binding's bindings.yaml kind | resources entry | name |
|---|---|---|
buffer | { kind = "buffer", name = buf } | a buffer handle from ref:createBuffer |
texture3d | { kind = "texture3d", name = vol } | a 3D texture handle from ref:createTexture3D |
storage3d | { kind = "storage3d", name = vol } | a 3D texture handle from ref:createTexture3D made with storage = true |
storage2d | { kind = "storage2d", name = target } | a storage texture handle from ref:createStorageTexture2D |
storage2d | { kind = "history_curr", name = history } | a history pair from ref:createTextureHistory: this frame's side |
texture2d | { kind = "texture2d", name = tex } | a handle ref:copyBufferToTexture returns, or a texture asset's guid once texRef:handle() has made it GPU-resident |
texture2d | { kind = "storage2d", name = target } | a storage texture handle, read as a texture |
texture2d | { kind = "history_prev", name = history } / { kind = "history_curr", name = history } | a history pair: the previous frame's side or this frame's |
texture2d | { kind = "scene_depth" } | none: the frame's scene depth |
sampler | { kind = "sampler", name = smp } | a sampler handle from ref:createSampler |
texture3d and storage3d name the same resource, a 3D texture, so either one
fills either slot. The engine's own spellings name the same resources and keep
working: texture_3d for texture3d and storage3d, texture_2d for
texture2d, and storage_2d for storage2d. Any other kind is refused at the
call, naming every kind it accepts. A vertices binding is filled by
ref:dispatchOnVertices, and texture_depth, textureCubeArray and
acceleration_structure bindings by a render feature's pass.
local march = asset.resolve("volume_march", "computeShader")
-- bindings.yaml: density (storage3d), out_tex (storage2d), U (buffer)
march:dispatchEx({
resources = {
{ kind = "storage3d", name = density },
{ kind = "storage2d", name = target },
{ kind = "buffer", name = uniforms },
},
workgroups = { 8, 8, 8 },
})
workgroups is { x, y, z }, { x }, or a bare x, and every dimension it
leaves out is 1. A zero in any dimension is refused: the dispatch is dropped and
recorded as a failure, so it surfaces in ref:status() and compute.failing()
with the reason. A count derived from how much data there is passes through
math.max first, so an empty set dispatches one workgroup rather than none:
carve:dispatch({ buffers = { heights }, workgroups = { math.max(1, math.ceil(#points / 64)) } })
Buffers and readback (the CPU side)
A buffer is created through the shader that owns it and comes back as a handle. Pass the handle to a dispatch — including another shader's — to bind it there:
local double = asset.resolve("@builtin::shaders.compute_double", "computeShader")
-- `type` is the element the shader declares, `len` how many of them.
local data = double:createBuffer("data", { type = "f32", len = 4, usage = { "readback" } })
data:write({ 1.0, 2.0, 3.0, 4.0 }) -- :writeU32 for integer words, :writeBytes for packed bytes
double:dispatch({ buffers = { data }, workgroups = { 1, 1, 1 } })
local pending = data:read() -- starts an async GPU->CPU readback
-- a frame or two later, drain it (nil until it has arrived):
local out = pending:result() -- :resultU32 / :resultBytes read the same bytes another way
data:destroy() -- free it when done
type is one of "f32", "vec3", "vec4", "quat", "mat4", and usage
adds "readback", "vertex", "index" or "indirect" on top of the storage a
buffer always has. An "indirect" buffer holds a draw's arguments where the GPU
reads them, so a shader that compacts geometry writes the drawn count into the
same dispatch that produced it and a render feature's kind = "draw" pass
submits exactly that — the renderFeature asset type's README documents that
pass and the storage.indirect name it reads.
The handle's key is the shader's guid plus the name you gave it and
a serial, so two shaders that both want a buffer called data get one each —
and so do two callers asking this same shader for one. ref:buffer(name)
returns the last one made under that name, which is how two callers share one
on purpose.
A buffer that no shader computes — a vertex or index run that is only ever
drawn — is allocated straight from the primitive instead:
substrate.createBuffer({ name = ..., type = ..., len = ..., kind = "gpu", usage = { "vertex" } }).
The first dispatch of a shader compiles it, so the very first readback can still
reflect the un-run shader; dispatch again once it is compiled, or ref:compile()
to pre-warm. This create/write/dispatch/readback loop is the CPU side of the
resource model in core/resource-model.
Is it compiled?
ref:compile() queues the compile; the pipeline is built on the render side
frames later, so that call cannot say whether it produced a program.
compute.programState(ref) is where that lands:
if compute.programState(carve) == "ready" then carve:dispatch(opts) end
local state, reason = compute.programState(carve)
if state == "failed" then print(reason) end
"absent"— the engine holds nothing under this key and nothing is in flight: never asked for, or released."pending"— a compile was asked for and has not reached the device. A recompile of a resident program reads pending too, because what it produces is a different program from the one bound now — which is what makes this the precondition to wait on after an edit."ready"— compiled and resident, so a dispatch naming it binds it."failed"— the most recent compile produced no program, and the second return says why.
A dispatch issued while the program is "pending" is held behind the compile
and dropped if it never lands, so a readback taken before "ready" reports the
buffer as it was. Wait for "ready", not for a count of frames.
Did it run?
A dispatch is recorded into a command encoder frames after the call that asked
for it returned, so that call's true means "queued", not "ran". ref:status()
is where the outcome lands — one record per target, cumulative:
for _, d in ipairs(carve:status()) do
print(d.target, d.ok, d.dispatches, d.failures, d.lastError)
end
target is the mesh guid for a dispatchOnVertices and the buffers it bound
for a dispatch that writes only those, so two systems driving one shader over
their own buffers read as the two passes they are. ok is the most recent outcome; lastError says
why the last failure failed and is kept after a recovery. An empty result means
nothing has dispatched this shader at all. compute.failing() answers the same
question across every shader at once.
A failing dispatch also posts a notice, so a pass that stops running reports itself rather than waiting to be found.
Running one every frame
A kind = "compute" substrate job queues one dispatch per frame:
jobs.register({
phase = "main",
executor = {
kind = "compute",
shader = asset.resolve("carve", "computeShader"),
buffers = { "heights" },
workgroups = { 64 },
},
})
Registration & hot reload
Writing shader.wgsl or bindings.yaml fires the .computeShader assetType's
onChange, which compiles it: the binding declarations are generated,
#includes expanded, the WGSL validated, and the shader registered. This happens on
create and on every edit, so saving recompiles with no world reload. A shader
with invalid WGSL (a type mismatch, an undefined name) fails to compile with
the reason logged ([compute] Compile of '<name>' failed: …) and is not
registered. You don't need to register a shader before dispatching it — the first
dispatch auto-compiles it on use. ref:compile() remains as an optional explicit
pre-warm, only to avoid the one-frame first-dispatch warm-up in a
latency-critical spot.
What compute is holding, and why a key names nothing
Every buffer, volume, storage target, history pair and sampler a dispatch can
bind is filed under a key, and compute.observe() lists all of them with what
each costs:
local r = compute.observe()
print(r.totals.count, r.totals.bytes)
for _, res in ipairs(r.resources) do
print(res.key, res.kind, res.bytes, res.owner.name)
end
A row carries the key verbatim — the same string a dispatch names it by and a
dispatch-failure message prints — plus its kind, its bytes, its extent and
format where it has them, the usage bits it was created with, and the frame
it was created on. owner is read back out of the key
(<shader-guid>::<name>#<serial>), so a resource nothing has ever dispatched
over still names the shader that made it. compute.resources(ref) narrows to
one shader's — including the <shader-guid>::__params uniform the compile
created for a params: block, which the shader owns like any other resource.
r.totals.bytes is the compute figure of renderer.gpuMemory() — the two are
read off the same registries, so a listing accounts for the category exactly.
The same reading is served at /zero/runtime/compute.
When a key names nothing, compute.diagnose(key) says which of the states the
inventory distinguishes it is in, from the closed set compute.absentReasons()
enumerates:
| reason | what the inventory read |
|---|---|
resident | a resource is filed under exactly this key; the row is on resource |
replaced | the owner holds the same name at a different serial — current names the live key |
nameUnused | the owner holds resources, none under this name |
ownerAbsent | no live resource carries this key's owner |
unowned | the key carries no owner segment, and nothing is filed under it |
notPublished | no renderer has published an inventory, so no key can be answered for |
So a key out of [compute] dispatch '…' failed resolves against what exists,
and a typo reports which part of it the engine could not match rather than
coming back empty.
A reason is the inventory at the moment the call read it. The reading is republished on a frame where a registry gained or lost an entry, so a resource created and diagnosed inside one script sees the reading from before it was made; wait a frame and ask again.
Discovery
asset.list("computeShader")— every registered compute shader.asset.inspect("<name>")— status, source, parse errors, this README.computeRef:getBindings()— the parsedbindings.yamlschema ({ bindings, params }).compute.programState(ref)— whether the program is compiled, still compiling, or failed, and why.compute.observe()— every GPU resource compute holds, and what it costs.compute.diagnose(key)— whether a key names a live resource, and why not.profiler.gpuFrame()— what each dispatch of this shader spends on the GPU. A dispatch is timed undercompute.<identity>— the same identityasset.resolvetakes, so a timing row names the shader that produced it.
Common pitfalls
- Compute shaders don't render — verify output via a buffer readback or a debug pass, not a screenshot.
ref:compile()returns before the program exists — the pipeline is built on the render side;compute.programState(ref)says when it is"ready". A dispatch issued before that is held behind the compile and dropped only if the compile never lands.- A dispatch call returning true means queued — ask
ref:status()whether it ran. - A destroyed buffer is refused where it is bound — a handle outlives its
storage, and
buf:alive()reports which. - Binding order is the contract —
buffersandresourcesbind inbindings:list order; reordering the list reorders the bindings. - Don't write
@group/@bindinginshader.wgsl— the engine owns them; re-declaring is the fastest way to a layout mismatch. - Don't infer a mesh's vertex stride — declare
kind: verticesand use the accessors. A wrong stride writes positions correctly and normals into the wrong word, which renders as flat lighting rather than as broken geometry. - Storage-texture format must be storage-compatible —
r32f/rgba8/rgba16f/rgba32f; others are rejected at compile. - A key that comes back empty is not the same as one that failed —
compute.diagnose(key)separates a name never used from a generation that was replaced, and names the live key in the second case.
Related types
.shader: render-domain shaders (surface, sky, post-process, screen).
In the Inspector
Selecting a compute shader opens its Compute section: whether its program is ready (and why not), how many dispatches it has run and failed in this session (and the last error), tables of the bindings and params its bindings.yaml declares, and openers for shader.wgsl and bindings.yaml.
Interface
What this asset declares: the schema it conforms to, what it exposes, and the rendered structured payload.
conforms to
zero/asset-type/v1⌬ Spec
suffix
.computeShadercontainernoprimary aliasesshader.wgslplural dircomputeShadersrequired filesshader.wgsl, bindings.yaml, README.md, .metadataExposed API
⌬ Instance methods
program(self: ?) → any
This shader's kernel ABI as a program: `program:variant(spec)` lowers and compiles one specialization, and `variant:run(env)` allocates the outputs `bindings.yaml` declares (`count`, `capacity`, `append` with a live counter), binds and dispatches. See `modules.compute_abi`.
| arg | type | description |
|---|---|---|
| self | ? |
examples
local variant = shaderRef:program():variant({ specialize = { T = "vec3<f32>" } })local run = variant:run({ n = 64, inputs = { src = srcBuffer } })getSource(self: ?) → string
Read the compute WGSL body (`shader.wgsl`) as raw text.
| arg | type | description |
|---|---|---|
| self | ? |
examples
local src = computeRef:getSource()
setSource(self: ?, src: string) → boolean
Overwrite the compute WGSL body on disk. Hot-reload recompiles the shader on the next frame. Returns true on success.
| arg | type | description |
|---|---|---|
| self | ? | |
| src | string | New WGSL source (only `@compute fn main` + helpers). |
examples
computeRef:setSource(myWgsl)
getBindings(self: ?) →
List this compute shader's declared bindings + params (parsed from `bindings.yaml`). Returns `{ bindings = { {name, kind, access?, element?, format?}, ... }, params = { {name, type, default}, ... } }`. This is the editor-discovery surface, and the SAME parse the compile uses. Raises, naming the file, when `bindings.yaml` is text the YAML decoder refuses (with the line) or `bindings:` / `params:` holds anything but a list of mappings (with the key).
| arg | type | description |
|---|---|---|
| self | ? |
examples
for _, b in ipairs(computeRef:getBindings().bindings) do print(b.name, b.kind) end
createBuffer(self: ?, name: string, opts: { [string]: any }) → any
Create a GPU buffer this compute shader owns. It is a substrate buffer — the same one every other part of the engine deals in — filed under this shader's guid, `name`, and a serial, so two callers asking this shader for a `params` each get their own. Pass the handle to any shader's dispatch, including another shader's, to bind it there. The shader remembers what it made: `shaderRef:buffer(name)` returns the last buffer created under that name, which is how two callers share one instead. `"vec4"`, `"quat"`, `"mat4"`), `len` is how many of them, and `usage` adds what the buffer is used for beyond the storage it always has: `"readback"` to read it on the CPU, `"vertex"` to draw it as geometry, `"index"` to draw it as an index run, `"indirect"` for a draw to read its arguments out of. A buffer can carry several. There is no integer element: a buffer is a block of 32-bit words, so a binding the shader declares as `u32` or `atomic<u32>` in `bindings.yaml` is created as `"f32"` here and written with `buf:writeU32`. The element type sets the STRIDE; what the words mean is the shader's to say.
| arg | type | description |
|---|---|---|
| self | ? | |
| name | string | What this buffer is for, e.g. `"params"` or `"verts"`. |
| opts | { [string]: any } | `{ type, len, usage? }` — `type` is the element (`"f32"`, `"vec3"`, |
examples
local verts = shaderRef:createBuffer("verts", { type = "vec3", len = 1024, usage = { "readback" } })verts:write(packed) -- an array of numbers, or a `buffer` already holding the words
local values = verts:read():result()
local counts = shaderRef:createBuffer("counts", { type = "f32", len = 64 }) -- bindings.yaml: element: u32counts:writeU32({ 0, 0, 0, 0 })local geo = shaderRef:createBuffer("geo", { type = "vec3", len = 4096, usage = { "vertex", "readback" } })local args = shaderRef:createBuffer("args", { type = "f32", len = 5, usage = { "indirect" } }) -- DrawIndexedIndirectArgsbuffer(self: ?, name: string) → any
The buffer this shader last made under `name`. Two systems driving one shader over the same data reach for this rather than each creating their own; a system that wants its own calls `createBuffer` again.
| arg | type | description |
|---|---|---|
| self | ? | |
| name | string | The name the buffer was created under. |
examples
local params = shaderRef:buffer("params") or shaderRef:createBuffer("params", { type = "vec4", len = 3 })createTexture3D(self: ?, name: string, opts: { [string]: any }) → TextureHandle
Create a 3D texture owned by this compute shader — a density volume, an occupancy grid, a signed-distance field. Keyed by the shader's guid plus `name`, so it cannot collide with another asset's.
| arg | type | description |
|---|---|---|
| self | ? | |
| name | string | Texture name, unique within this shader. |
| opts | { [string]: any } | `{ width, height, depth, format?, storage? }`. |
examples
local density = shaderRef:createTexture3D("density", { width = 64, height = 64, depth = 64, format = "r16f", storage = true })createStorageTexture2D(self: ?, name: string, opts: { [string]: any }) → TextureHandle
Create a write-only 2D storage texture owned by this compute shader — the target a raymarch or image pass writes.
| arg | type | description |
|---|---|---|
| self | ? | |
| name | string | Texture name, unique within this shader. |
| opts | { [string]: any } | `{ width, height, format? }`. |
examples
local out = shaderRef:createStorageTexture2D("out", { width = 1920, height = 1080, format = "rgba16f" })createTextureHistory(self: ?, name: string, opts: { [string]: any }) → TextureHandle
Create a temporal history pair owned by this compute shader — the previous frame's result to read while writing this frame's.
| arg | type | description |
|---|---|---|
| self | ? | |
| name | string | History name, unique within this shader. |
| opts | { [string]: any } | `{ width, height, format? }`. |
examples
local history = shaderRef:createTextureHistory("taa", { width = 1920, height = 1080, format = "rgba16f" })createSampler(self: ?, name: string, opts: { [string]: any }?) → TextureHandle
Create a sampler owned by this compute shader, for its texture bindings.
| arg | type | description |
|---|---|---|
| self | ? | |
| name | string | Sampler name, unique within this shader. |
| opts | { [string]: any }? | Sampler options — filtering and addressing. |
examples
local smp = shaderRef:createSampler("linear", { filter = true, clamp = true })copyBufferToTexture(self: ?, source: any, name: string, width: number, height: number, format: string?) → TextureHandle
Copy one of this shader's buffers into a cached GPU texture, staying on the GPU — the path for an image a compute pass produced.
| arg | type | description |
|---|---|---|
| self | ? | |
| source | any | The buffer holding tightly-packed rows in the format's texel layout. |
| name | string | Texture name, unique within this shader. |
| width | number | Texture width in texels. |
| height | number | Texture height in texels. |
| format | string? | Texel format: `"rgba16f"` (default), `"rgba32f"`, `"rgba8"`. |
examples
local tex = shaderRef:copyBufferToTexture(packed, "foam", 256, 256, "rgba16f")
dispatch(self: ?, opts: { [string]: any }) → boolean
Dispatch this compute shader with named buffers bound to its declared storage bindings, in order. Compiles on first use. A zero in any workgroup dimension is refused and recorded as a dispatch failure, so a count derived from how much data there is passes through `math.max(1, ...)` first. declared storage binding; `workgroups` is `{ x, y, z }`, `{ x }`, or `x`. in `shaderRef:status()` and `compute.failing()`.
| arg | type | description |
|---|---|---|
| self | ? | |
| opts | { [string]: any } | `{ buffers, workgroups }` — `buffers` names one compute buffer per |
examples
shaderRef:dispatch({ buffers = { "positions" }, workgroups = { 64 } })dispatchOnVertices(self: ?, opts: { [string]: any }) → boolean
Dispatch this compute shader with a model's vertex buffer bound at the first storage binding, and `opts.buffers` filling the rest. Use to mutate vertex positions directly. A zero in any workgroup dimension is refused and recorded as a dispatch failure, so a count derived from how many vertices there are passes through `math.max(1, ...)` first. vertices the shader writes. in `shaderRef:status()` and `compute.failing()`.
| arg | type | description |
|---|---|---|
| self | ? | |
| opts | { [string]: any } | `{ model, buffers?, workgroups }` — `model` is the mesh guid whose |
examples
shaderRef:dispatchOnVertices({ model = meshHandle.guid, workgroups = { 64 } })dispatchEx(self: ?, opts: { [string]: any }) → boolean
Dispatch this compute shader with explicit texture / storage-texture / sampler resources, one per declared binding in order. A `params:` block's uniform is engine-owned and takes no entry here. A zero in any workgroup dimension is refused and recorded as a dispatch failure, so a count derived from how much data there is passes through `math.max(1, ...)` first. A resource's `kind` says what it is, in the words `bindings.yaml` uses: `buffer` (`name` is a buffer handle), `texture3d` / `storage3d` (a 3D texture handle), `storage2d` (a 2D storage texture handle), `texture2d` (a `copyBufferToTexture` handle or a texture asset's guid), `sampler` (a sampler handle), `history_prev` / `history_curr` (one side of a history pair) and `scene_depth` (the frame's scene depth, no `name`). A slot takes the kind it is declared with; a `texture2d` slot also reads a `storage2d`, a history side or `scene_depth`, and a `storage2d` slot also writes `history_curr`. The engine spellings `texture_3d`, `texture_2d` and `storage_2d` name the same resources. Any other kind is refused, naming the accepted ones. in `shaderRef:status()` and `compute.failing()`.
| arg | type | description |
|---|---|---|
| self | ? | |
| opts | { [string]: any } | `{ resources, workgroups }`: each resource is `{ kind, name }`. |
examples
shaderRef:dispatchEx({ resources = { { kind = "storage2d", name = target } }, workgroups = { 8, 8 } })shaderRef:dispatchEx({ resources = { { kind = "storage3d", name = density }, { kind = "buffer", name = params } }, workgroups = { 8, 8, 8 } })setParam(self: ?, prop: string, value: number) → boolean
Set one scalar parameter declared in this shader's `bindings.yaml` `params:` block. The next dispatch sees the new value; a value set before the shader's first compile is the value it starts with.
| arg | type | description |
|---|---|---|
| self | ? | |
| prop | string | Parameter name as declared in `bindings.yaml`. |
| value | number | New scalar value. |
examples
shaderRef:setParam("scale", 4.0)compile(self: ?) →
Compile this shader now, rather than on its first dispatch. Idempotent. NORMALLY UNNECESSARY — a dispatch compiles on first use. Reach for this only to avoid the one-frame first-dispatch warm-up in a latency-critical spot.
| arg | type | description |
|---|---|---|
| self | ? |
examples
shaderRef:compile()
status(self: ?) →
What the engine did with this shader's dispatches, one record per target. A dispatch is recorded into a command encoder frames after the call that asked for it returned, so this is where its outcome lands: `ok` is the most recent outcome, `dispatches` counts what reached the encoder, `failures` how many of those could not be recorded, and `lastError` says why the last failure failed (kept after a recovery). `target` is the mesh guid for a `dispatchOnVertices`, empty for a dispatch that writes only its bound buffers. This answers "is this pass running?" — an empty result means nothing has dispatched this shader. lastFailedFrame?, lastError? }`, most recently dispatched first.
| arg | type | description |
|---|---|---|
| self | ? |
examples
for _, d in ipairs(shaderRef:status()) do print(d.target, d.ok, d.lastError) end
forPlugin(self: ?) → void
| arg | type | description |
|---|---|---|
| self | ? |
⌬ Hooks
compileByName(ref: string) → boolean
Compile a compute shader by reference from its `.computeShader` VFS source — the lazy compile-on-first-use entry. A system that must guarantee the shader is registered before its first dispatch calls this (via `compute.compileByName`) to bring it online through the same generic `compileCompute` path an edit runs. Resolution goes through the universal asset system — a reference that doesn't resolve is a bad reference in the content that owns it, not something to special-case here. was attempted; false when nothing resolves under it.
| arg | type | description |
|---|---|---|
| ref | string | A compute-shader asset reference (identity / guid) resolvable by `asset.resolve`. |
examples
require("@builtin::assetTypes.assetType.shared.ref").loadTypeModule("computeShader").compileByName("@builtin::shaders.compute_double")dispatchKey(self: ?) → string
Compile this compute shader through the engine: read the WGSL body + the declared binding schema and hand both to `compute.program.compile` primitive, which generates the `@group/@binding` declarations, expands `#include`s, naga-validates, and registers the compiled program. Convergent — `compute.program.compile` registers into the shader registry (it does not write the VFS), so it cannot re-trigger `onChange`. The key the compiled program is registered under, and the key every dispatch resolves by: the shader's stable GUID — canonical, location-independent and collision-safe. Falls back to the identity only when the asset somehow has no guid (a transient / in-memory asset).
| arg | type | description |
|---|---|---|
| self | ? |
onChange(ref: ?, change: ?) → void
Asset-type change callback: (re)compile the compute shader whenever its WGSL body or `bindings.yaml` is written. This is the ONLY thing that compiles a `.computeShader` — so it fires on the initial create (the template write) AND on every later edit, with no world reload. Convergent: see `compileCompute`.
| arg | type | description |
|---|---|---|
| ref | ? | |
| change | ? |
onDelete(ref: ?) → void
Asset-type delete callback: release the program a removed `.computeShader` folder registered. The teardown counterpart of `onChange`'s compile, so the type owns both halves of its runtime lifecycle the way `.material` does: the program, the params uniform it carried and the dispatch history under its key go with the asset, and a shader authored afresh at the same path registers a new program rather than inheriting the one the removed asset left.
| arg | type | description |
|---|---|---|
| ref | ? |
Sub-parts
Everything contained inside this part. Assets are composite children (clickable cards). Files are leaf payloads. Expand any row to view its source.
Showing up to 3 levels deep. Open a part to see what it holds further down.
58+items
# assetType (asset type)
An asset type says what a kind of asset is: the files an asset of the kind is
made of, the code that gives it behaviour, the interface a person uses to work
with it, and how it is found, pictured and checked. A `<typename>.assetType/`
folder declares a type called `<typename>`, and every `<name>.<typename>/`
folder is an asset of it. `assetType` is itself a type, so a type is an asset
like any other: it is created, versioned, installed and contributed the same way.
## Making a type
`asset.create("assetType", "<typename>")` scaffolds a type. The type registers
the moment its folder is written, anywhere under `/zero/source/`, and from then
on `<name>.<typename>/` folders are its assets. An asset of a type that is not
registered yet is not an asset, so make the type first.
A type folder is a root: `~.x` in any file inside it names the type's own `x`,
wherever the type is installed. Keep the type's whole implementation inside its
folder and reach it that way.
What a type folder must hold is set by this type's own `type.yaml`, the same way
every type's `type.yaml` sets what its assets hold. `asset.validate` on a type
reports anything missing, and the scaffold produces a folder that passes.
## What sets your type's schema (`type.yaml`)
`type.yaml` is the structural contract every asset of the type is checked
against. The keys below are the ones the engine reads; a key not listed here is
ignored.
| Key | What it controls |
|---|---|
| `suffix` | The folder suffix of the type's assets. Defaults to `.<typename>`. |
| `primary` | The file or files that are the asset's content: what the asset resolves to when it is used. |
| `entry_files`, `primary_aliases` | Further files that load as the asset or share its identity. |
| `is_container` | Whether the suffix stays in the identities of what the asset holds. |
| `is_opaque_walker` | Whether a walk of the tree stops at the asset and registers only its primary. |
| `plural_dir`, `classify_exts` | Loose files in a folder of this name, or with these extensions, are assets of the type. |
| `is_text_default` | Whether the asset's files are text unless stated otherwise. |
| `broadcasts_subassets` | Whether assets nested inside an asset of the type are found by their own short name. |
| `root` | `true` makes every asset of the type a root, so `~.x` inside one names that asset's own `x`. |
| `contract_ref: { field, category }` | A key of the primary file that names another asset the asset is built on. |
| `files: { required, optional }` | The files an asset holds (below). |
| `allow_unlisted` | `false` reports every file the type does not declare. |
| `aliases_from: [{ file, key }]` | Further names an asset answers to, read from its own files. |
| `settings:` | Typed per-asset settings (below). |
| `inspector:` | The interface people use for the type and its assets (below). |
| `preview:` | How an asset is pictured (below). |
| `references:` | Names of other assets the type's files carry (below). |
| `indexing:` | What search reads for each asset (below). |
| `describe:` | How a missing description is generated (below). |
### The files an asset holds
Each entry under `files.required` or `files.optional` is
`{ path, kind: file | folder, one_of_group?, content? }`. `*` in a path matches
within one segment. Entries that share a `one_of_group` are satisfied by any one
of them. `content` lists checks on the file's bytes:
| Check | Passes when |
|---|---|
| `non_empty` | the file has content |
| `json_field { key, type?, non_empty?, accept? }` | the JSON holds the key (a dotted path) with that shape |
| `yaml_field { key, type?, non_empty?, accept? }` | the same for YAML |
| `described { keys?, headings?, message? }` | the file says what the asset is (see "Ask your assets to say what they are") |
Each check takes a `message`, which is what the author is told when it fails.
### Settings
`settings: { values, schema: { type | instance, export? } }` gives every asset
typed settings. `values` names the file an asset's values live in; `schema.type`
declares one schema for the whole type, and `schema.instance` names a file each
asset declares its own in. `asset.create` writes the resolved values, and a write
to the values file reaches `onChange` with what changed.
## The human side (`inspector.luau`)
A type is used by people through its Inspector, and without one the type is
usable only from code. The Inspector is the type's interface for a person: for a
procedural graph it is the graph editor, for a kit it is the tracking view of
what the kit holds and what is still missing. Writing it is part of writing the
type.
`inspector: { type, instance? }` in `type.yaml` names the files. `type` is the
interface for the type itself and for its assets; `instance` names a file an
asset may ship to add its own. Each returns:
```luau
return {
sections = { { id = "graph", title = "Graph", build = function(ctx) ... end } },
replace = { contents = { ... } }, -- replace a default section by id
order = { "graph", "contents" }, -- section order
}
```
`build(ctx)` receives the asset and builds the section. A section's `title`, and
the text its rows carry, is a string or an `i18n.text` value read from a catalog
(`i18n.text("inspectors.mesh.title")`), which follows the editor's language. `asset.create("assetType",
...)` scaffolds a working `inspector.luau` to start from. `asset.validate` on a
type that names no inspector, or names one that does not load, reports it.
## Say what your type is for (`about.yaml`)
Every type carries an `about.yaml` that says what the type is for, in three
plain-language texts:
```yaml
intent: "Sets the typeface of the text in your game: UI, labels, signs and 3D lettering."
function: "A font, from a TTF, OTF or WOFF file, made available to all of Zero's text, including 3D text."
usage: "You choose it by name for your UI or your text, and the text appears in that typeface."
```
- **`intent`** is what the type is for in someone's game, in the words a game maker uses. Up to 800 bytes.
- **`function`** is how it works today: what an asset of it is made of and what the engine does with it. Up to 1500 bytes.
- **`usage`** is what a person or an agent does with one. Up to 1200 bytes.
Write about the type as a whole, not one asset of it, and say what it does now.
Agents read these texts to learn when to reach for the type and how; people
searching find the type by them. The scaffold starts each text with
`[[describe]]` and a note on what to write; a text that still starts that way
counts as not written. `services describe` can write them.
They show up in `asset.inspect` as `detail.about`, in
`assetTypeRef:getAbout()`, at the end of the type's `types/<typename>` guide,
and at the top of the type's Inspector.
## Ask your assets to say what they are
A type can require each asset to carry a description: a file, written by the
author or generated, saying what the asset is and what it is for. Declare it with
a `described` check:
```yaml
files:
required:
- path: "README.md"
kind: "file"
content:
- { check: "described", message: "Say what this widget is for and where it goes." }
```
A file that is missing, empty or still has a line starting with `[[describe]]`
fails the check, and so does a YAML file whose named `keys` are missing or over
their `max_bytes`, or a Markdown file missing a named heading. `asset.validate`
names the asset, and a push that carries it is refused with `message`.
`services describe` finds such assets and writes their descriptions.
`describe:` steers what is generated:
```yaml
describe:
guidance: "Say what the widget shows, what input it reacts to, and where it fits in a UI."
examples:
- "<identity of an asset of this type whose description reads well>"
```
An example is an asset of your type whose description is a true, written one,
never a placeholder and never the asset being described; with none, leave
`examples` empty. A type whose assets the model cannot perceive (a sound, a
motion) says so in `guidance`, and the description is drawn only from what the
asset's own files state.
Start the file unwritten in your `template/`: a heading and one line starting
with `[[describe]]`, never example content, which every new asset would carry
verbatim. A type whose assets say what they are through their own content (a
mesh, a texture) declares no check.
## The type's code (`behavior.luau`)
`behavior.luau` returns one table. These are the keys the engine reads from it;
anything else on the table is the type's own.
### What the type's assets can do
| Key | Shape | What the engine does with it |
|---|---|---|
| `ref` | `{ [name] = function(self, ...) }` | Every function becomes a method on every asset of the type: `ref:name(...)`. |
| `modules` | `{ [name] = require(".x") }` | Code the type's assets reach with `asset.containing(__FILE__).modules.<name>`. |
| `events` | an events schema | Events an asset fires. Readers subscribe through `ref.events.<name>:connect(...)`; the type fires them. |
| `refShapes` | `{ [method] = function(self) -> (typeExpr, source?) }` | The result type of a `ref` method for one particular asset (below). |
| `namePattern` | a Lua pattern | The names `asset.create` accepts for the type's assets. Default `^[A-Za-z][A-Za-z0-9_]*$`. |
| `derive` | `{ output, module, compute, fingerprint, matches?, required?, timeout? }` | A file computed from the asset when it is committed; a `required` one holds the commit until it lands. |
Some `ref` names mean the same for every type, and the engine calls them:
- **`instantiate(self, target?, opts?) -> (root, idMap)`**: puts the asset in a scene. Defining it is what makes the type scene-instantiable. Its return is a contract (below).
- **`inspect(self) -> detail`**: what `asset.inspect` reports for the asset beyond the common record (below).
- **`preview(self, opts)`**: renders the asset's picture; it wins over the type's `preview:` recipe.
- **`previewMaterial(self) -> { material }`**: the material a `surface` preview paints.
- **`saveDefinition(self)`**: writes the asset's in-memory edits back to its files in edit mode.
Some names are answered for every asset before the type is asked, so a `ref`
entry of the same name is never reached: `getSource`, `getBytes`, `getText`,
`exists`, `deps`, `canInstantiate`, `canPreview`, `preview` (which calls yours
when you define one), `meta`, `runtime`, `events`, `typeRef`, `modules`, and the
residency flags `has_backing_asset`, `has_runtime_changes`, `cpu_resident`,
`gpu_resident`.
### When the engine calls the type
| Hook | Signature | When it runs |
|---|---|---|
| `onCreate` | `(name, opts) -> { [path] = contents }` | On `asset.create`. Returns the files of the new asset, laid over the type's `template/`. Annotate `opts`: its type is the schema `asset.create` checks the caller's arguments against. A `""` key writes a single loose file. |
| `onReplace` | `(dest, files) -> files` | On an `asset.create` over an asset already at `dest`, after `onCreate`, so what the author added can be carried into the replacement. |
| `onRegister` | `(self)` | Once per asset, when it first registers: when the world loads, on a live `asset.create`, and when an asset arrives later (installed, pulled, synced). This is what makes an asset take effect the moment it is written. |
| `onChange` | `(ref, change)` | On every write to a file inside an asset of the type. `change` is `{ path, asset, type, kind, origin }`, plus `settings` and `settingsChanged` for a write to the settings values file; `kind` is `edited` or `seeded`, `origin` is `local` or `remote`. Filter on `change.path`. Writes to one asset arrive in order, each after the hook for the one before has finished, and the hook may wait on what it reads. A write the hook makes inside its own asset arrives later like any other, so keep the hook convergent. |
| `onDependencyChange` | `(ref, change)` | When a module the asset's code requires is re-run, or a name the asset carries starts resolving. `change.kind` is `dependency`. |
| `onDelete` | `(ref)` | When an asset of the type leaves the world: deleted, or the world it is in is swapped away. |
| `validate` | `(ref) -> { { code, message, severity?, path? } }` | On `asset.validate`, after the `type.yaml` checks, for the type's own rules. `severity` defaults to `error`. Runs on every push, so a type's rules hold at publish. A hook that fails reports `validate.hook_failed`. |
### Settings hooks
| Hook | When it runs |
|---|---|
| `settingsDefaults(name, opts, asked) -> table` | Once per `asset.create`, for values the schema's defaults do not give. |
| `settingsCorrections(values, name, opts) -> (corrections?, reasons?)` | On every settings write. A correction to a field the writer named refuses the write, giving the reason. |
| `settingsDerivedDefaults(values, explicit, changed)` | On a settings write, for fields derived from others. |
| `normalizeSettings(values, stored?)` | On every read and write, to map an earlier spelling of a field to the current one. |
| `settingsHealed(values, stored)` | On a read, to repair stored values. |
| `settingsSchemaProblem(schema, ref) -> string?` | When an asset's own schema is read; a returned string refuses the schema. |
`creationInputs` (`{ [opt] = true | selectorOpt }`) names `asset.create` options
that are inputs to the type rather than settings.
### Reloading
An edit to `behavior.luau` reaches existing assets with no restart.
## How an asset is pictured (`preview:`)
| `kind` | The picture is | The type provides |
|---|---|---|
| `instantiate` | the asset placed in the preview studio through its `instantiate` | `ref.instantiate` |
| `image` | a file the asset holds, fitted to the frame | `source: { files }`, the candidate files in order |
| `surface` | the asset painted on a mesh | `mesh`, and `ref.previewMaterial` |
| `custom` | whatever `ref.preview` returns | `ref.preview` |
```yaml
preview:
kind: surface
mesh: sphere
```
`angle: [yaw, pitch]` turns the camera. The studio owns the light, the backdrop
and the framing, so an asset pictures the same in every world. A type with no
`preview:` that defines `instantiate` still answers `ref:preview()`.
A picture is rendered when something asks to view it (the editor showing the
asset, `ref:preview()`), when previews are generated on request
(`assets.generatePreviews`), and when the asset is staged. An edit alone
renders nothing. The picture records what it was made
from, so a stale one is told from a current one.
## The names your type's assets hold (`references:`)
Where your type's own format or API carries the name of another asset, declare
it here:
```yaml
references:
keys: # a top-level key of the type's files that holds a name, or a table of them
- { key: "shader", type: "shader" }
args: # an argument of a call, counting from 1
- { call: "g:node", position: 2, type: "procNode" }
fields: # a field of the options table a call takes
- { call: "fx.beam", field: "material", type: "material" }
```
`type` is the category the name resolves in. `asset.declareReferenceKey`,
`asset.declareReferenceArg` and `asset.declareReferenceField` declare the same
from a script.
## What search reads (`indexing:`)
`indexing:` is how assets are found. Search reaches an asset only through what
its type's `indexing:` names, and adds nothing of its own. That includes you: an
asset indexed badly is one you cannot find later, when you are making something
else and need it. A type whose assets are never looked for says `indexing: none`.
```yaml
indexing:
data: # text, read from the asset's files
- role: identity
extractor: verbatim
source: { file: "README.md" }
- role: interface
extractor: symbols
source: { files: ["init.luau"] }
- role: implementation
extractor: verbatim
source: { files: ["init.luau"] }
content: # the picture
- role: identity
modality: image
source: { file: "preview.png" }
facets: # what a query filters and re-ranks by
file: ".metadata"
rigged: { type: bool, from: { components: { contains: SkinnedModel } } }
roughness: { type: number, filter: range, from: { file: "mat.yaml", field: "floats.roughness" } }
```
**Roles.** Each `data` and `content` entry has a `role`, and a query matches in
two slots:
- **`identity`**: what an asset is. For anything you look at, the picture; for anything else, the text that says what it is.
- **`capability`**: what it does and how it is made. `interface` (the signatures or shape a caller uses) and `implementation` (the body) both count as capability, and a type with code usually declares both.
Ask what a person would recognise an asset of the type by, and what it does, and
point each role at the file that says it. For text, that is the asset's
description: the file your template starts with a `[[describe]]` block, which the
author writes or `services describe` fills in (see "Ask your assets to say what
they are").
**`data`.** `extractor: verbatim` embeds a file's text as it is; `symbols` embeds
the declared signatures of code. `source` is `{ file }` or `{ files: [...] }`.
Never index a file name (`source: { field: name }`): one
or two words carry nothing to match.
**`content`.** `modality: image` embeds the picture itself, so a text query
matches what the asset looks like. A type whose assets are looked at makes the
picture its identity.
**`facets`.** What a query narrows and re-ranks the matches by. `file` is embedded
whole, so keys nobody declared in it are still found. Each further key is
computed for every asset and states a value for every one, including `false`: a
file can imply "not rigged" but never say it, and a query separates rigged from
unrigged only because the unrigged ones say `rigged: false`. A key is
`{ type: bool | number | enum, filter?: range, from }`, where `from` is
`{ file, field }` (a field of one of the asset's files, dotted for nesting),
`{ metadata: key }`, or `{ components: { contains | any_outside } }` (what the
asset's entities carry).
## What blocks a push
A push checks every asset it carries against its type. These refuse it:
- a required file that is missing, a `content` check that fails, a `described` file not written yet;
- an error from the type's `validate`.
Unlisted files and warnings do not. A `described` file blocks only a push that
changes the asset. When a push is refused, the message names each asset and what
it lacks. `world.publishBlockers()` and `zm status` read the same list without
pushing.
## Typing a result from the asset (`refShapes`)
A `ref` method whose result depends on the asset (one entry per child folder, per
row of a config, per control a map declares) can only be annotated as
`{ [string]: Thing }`, which accepts any key. `refShapes` states the result for
each asset instead: a function returning a Luau type expression for that asset,
and the module whose types the expression uses. Read the asset; never run it.
```lua
-- inputMap.assetType/behavior.luau
M.refShapes = {
activate = function(self): (string, string)
local names = {}
for _, control in ipairs(M.ref.controls(self)) do
table.insert(names, control.name .. ": Handle")
end
if #names == 0 then return "", "" end
return "{ " .. table.concat(names, ", ") .. " }", "@builtin::modules.zinput.scheme"
end,
}
```
With it, `map.jump:onPressed(fn)` is checked and `map.noexisting` is reported.
A per-asset type applies where the call site names which asset: a component
field whose default names it, or an annotation `AssetRef<"inputMap", "<identity>">`.
`asset.resolve(name, category)` carries only the category, and a name computed
at runtime carries nothing, so calls on those keep the declared return. The type
belongs to the call's result: index it there, or bind what you need from it
there, and the names stay checked.
`require("@builtin::assetTypes.assetType.shared.refShapes").published()` shows
what was published: `categories` (each type's method surface) and `returns`
(per-asset results by identity, then method). An identity missing from
`returns` was never published. Results are recomputed when an asset is written;
at most 64 assets of one type are read.
## Putting an asset in a scene (`ref.instantiate`)
A caller writes one piece of code against every instantiable type, so what
`instantiate` returns is fixed:
```lua
local Instantiable = require("@builtin::assetTypes.assetType.shared.instantiable")
M.ref = {
instantiate = function(self, target, opts)
local root = Instantiable.root(self, target, opts)
-- compose the asset under `root`, now
return Instantiable.result(self, root, idMap)
end,
}
```
**In.** `target` is the entity the asset lands under, or onto for a hierarchy
type; with none, the type spawns a new root. `position`, `rotation` (three
numbers in degrees, or a quaternion), `scale`, `name` and `temporary` mean the
same for every type: `Instantiable.root` applies them to a root you make,
`Instantiable.place` to one you adopt. Document any options of your own in the
hook's `--!arg` docs.
**Out.** `(root, idMap)`. `root` is the composed root, live when you return:
build synchronously, never defer to a component's `awake`. `idMap` maps each
original id to the spawned one, so a component that composes the asset again on
every load can pass it back in and keep references into the composition. Every
call goes through `Instantiable.result`, which refuses a root that is not live
and turns a missing `idMap` into `{}`.
## Inspecting an asset (`ref.inspect`)
`asset.inspect(ref)` builds a record every asset shares (`identity`, `name`,
`guid`, `source`, `typeName`, `typeDefinitionPath`, `scope`, `origin`,
`description`, `tags`), then calls `ref.inspect(self)` for the type's own
`detail`:
```lua
M.ref = {
inspect = function(self)
-- read the asset's own files, never runtime state: inspect works on an asset
-- that has not been compiled, uploaded or registered
return { --[[ what makes this asset what it is ]] }
end,
}
```
Without it, the record is the shared part alone, and an agent inspecting the
asset learns nothing of what it is. A hook that raises leaves `detail` empty and
sets `record.warning`.
## Discovery
- `asset.list("assetType")`: every registered type.
- `asset.inspect("<typename>")`: the type, its README and its `about.yaml` texts.
- `asset.resolve("<typename>", "assetType")`: the type itself.
▲ 0↑ born
# substrate Module
Public Luau surface over the `__substrate` Internal FFI namespace — the
engine's typed data buffer, on the CPU or the GPU.
## Purpose
A substrate buffer is a typed run of values you hold a handle to. The
element type (`f32`, `vec3`, `vec4`, `quat`, `mat4`) sets the stride, so
a buffer knows its own shape and a read comes back in the units it was
written in. `kind` places it: a `"cpu"` buffer is storage the engine holds
outside the Luau heap, a `"gpu"` buffer is storage a compute shader binds.
Everything a buffer does hangs off its handle, so a buffer travels as a
value rather than as a name someone else has to resolve. This is what
animation poses, IK chains, particle pools, and compute-shader storage
are all made of.
This is a distinct primitive from the standard Luau `buffer` library. A
Luau `buffer` is untyped bytes held in the Luau heap, where what it holds
counts in full, so it suits small amounts. A large block of data belongs
in a substrate buffer and passes through Luau a chunk at a time:
`writeBytes` places a packed chunk at a byte offset, and reading the
buffer's bytes back into Luau (`:bytes()`, `:read():resultBytes()`) makes
a copy in the Luau heap. The type here is
`TypedBuffer` for that reason.
## Usage
```luau
-- A CPU buffer: 64 bone poses, 10 floats each
local pose = substrate.createBuffer({ type = "f32", len = 64 * 10 })
pose:write({ 0, 1, 0, 0, 0, 0, 1, 1, 1, 1 }, 0)
local values = pose:read(0, 10):result()
pose:fill() -- every value back to 0
pose:destroy()
-- A GPU buffer a compute shader reads back
local field = substrate.createBuffer({
type = "vec3", len = 4096, kind = "gpu", usage = { "readback" },
})
```
A buffer a compute shader works over comes from the shader, which names
it for the dispatch and allocates it here:
```luau
local sim = asset.resolve("@builtin::mySim.computeShader")
local verts = sim:createBuffer("verts", { type = "vec3", len = 1024 })
sim:dispatch({ x = 16 })
local out = verts:read():result()
```
## Reads
`:read()` answers with a `Readback` for both kinds — a CPU read is one
that is simply already done. Code that reads a buffer therefore never
branches on where the buffer lives:
```luau
local rb = field:read()
if rb:ready() then
local floats = rb:result() -- also :resultU32() / :resultBytes()
end
```
`:state()` reports `"pending"` / `"ready"` / `"unknown"` without draining
and without raising.
## Size
A `"cpu"` buffer holds at most 1 GiB. A `"gpu"` buffer holds at most what the
device creates in one buffer, its `max_buffer_size`, which each GPU, driver and
browser states for itself. A `len` past either bound raises at `createBuffer`,
naming the bytes it needs, the bound, and the most records of that type one
buffer holds; nothing is allocated and no handle exists for it. Data larger
than one buffer is split across several.
## Lifetime
A handle outlives the storage it points at: `destroy` frees the allocation, and
every other holder of that buffer keeps its handle. `:alive()` is what they ask,
and it answers false the moment the storage is gone, through this handle or any
other. When the render device is lost, a `"gpu"` buffer is allocated again on
the device built to replace it, empty, and its handles keep answering; one past
the new device's `max_buffer_size` is gone instead, and its handles answer
false. Binding a dead handle to a compute dispatch is refused at the call that
binds it.
## Exports
- `substrate.createBuffer({ type, len, kind?, usage?, name? })` → `TypedBuffer?`
On the handle: `write` `read` `length` `type` `kind` `alive` `destroy`, the CPU
arithmetic `fill` `add` `scale` `addStrided` `axpby` `lerp`, the indexed
accessors `getVec3` `setVec3` `getQuat` `setQuat`, and `bytes` for
per-element access through the Luau `buffer` library.
For element-wise NumPy-style kernels over these buffers, use the `nx`
module; for slice-and-target position / orientation forms, `mathx`.
▲ 0↑ born
# compute_abi Module
The kernel ABI of a `.computeShader`. A `bindings.yaml` that uses the ABI
extensions is lowered to the plain bindings and WGSL the engine compiles; this
module parses, lowers, compiles variants, allocates outputs, packs column tables
and dispatches.
## Purpose
A kernel is one asset that serves many shapes of data. `bindings.yaml` states:
```yaml
bindings:
- { name: cols, kind: columns, access: read }
- { name: src, kind: buffer, access: read, element: T }
- { name: dst, kind: buffer, access: read_write, element: T, count: "len(src)" }
- { name: hits, kind: buffer, access: read_write, element: vec4<f32>, capacity: "n * 4", append: true }
specialize:
- { name: T, options: [f32, i32, vec2<f32>, vec3<f32>, vec4<f32>] }
- { name: FOLD, options: [add, min, max, mean, set] }
- { name: BODY, kind: source }
determinism: exact
```
- `columns`: a table of columns in one storage binding (header: the column count, then four words a column: first word, lanes, count, kind). WGSL reads it through `NAME_count(c)`, `NAME_lanes(c)`, `NAME_f32/i32/u32(c, i, lane)`, `NAME_vec2/3/4(c, i)`; `access: read_write` adds `NAME_set_*`. Columns named at specialization are constants `NAME_col_<column>`.
- `count` / `capacity`: the size, in elements, of an output the host allocates. The expression uses `n` (the dispatch size), the shader's params, `len(binding)`, `max`, `min`, `ceil`, `floor` and `+ - * / ( )`.
- `append: true`: the output carries a live counter, `NAME_count`, bound right after it. `NAME_store(slot, v)`, `NAME_set_count(n)`, `NAME_count_value()`, `NAME_capacity()` are generated. `NAME_append(v)` (unordered, atomic) is generated for `determinism: float_order` only.
- `specialize`: compile-time parameters. Type options become `alias NAME = type;`, named options become `const NAME: u32` plus `NAME_<option>`, and `kind: source` parameters replace the identifier with text.
- `when` on a binding: a condition over the specialization options, `NAME=option` or `NAME=option|option`. The binding exists in the variants whose option holds and is left out of the others. Terms separated by spaces all hold (`COUNT=device STAGE=table`); alternatives separated by `;` hold when any one does (`COUNT=plain; COUNT=device STAGE=table`). Two bindings may share a name when their conditions never hold together.
- `// @when NAME option option` ... `// @end` in the WGSL: the lines between them stay in the variants where the specialization `NAME` takes one of the options and are blanked in the others (the lines keep their numbers). Blocks may nest. Code that reads a binding a variant leaves out sits in such a block.
- `bits: true` on a binding states that its words are raw bits (an f32 held in a u32 word, an atomic word): a column of another element type bound to a read binding that states it is bound as it is, where an i32, u32 or f32 read binding takes a column of another element type cast by value.
- `determinism`: `exact` or `float_order`. An `exact` shader that calls `NAME_append` is refused.
- `workgroup`: the workgroup size the body declares (default 64).
Every scalar or vector `buffer` binding gets `NAME_get(i)`, `NAME_len()` and, unless `access: read`, `NAME_set(i, v)`. A `vec3` element is stored as a flat scalar array, matching a column of vec3 that is 12 bytes an element. `zero_n()` is the dispatch size.
## Usage
```luau
local abi = require("@builtin::modules.compute_abi")
local schema = abi.parse(bindingsYaml)
local program = abi.program({ key = "my_kernel", schema = schema, wgsl = body })
local variant = program:variant({ specialize = { T = "vec3<f32>" } })
local run = variant:run({ n = 4, inputs = { src = srcBuffer } })
local values = abi.read(run.outputs.dst.buffer)
```
A computeShader asset reference exposes the same through `ref:program()`.
## API
| Function | Does |
|---|---|
| `abi.parse(text)` | `bindings.yaml` to `{ bindings, params, specialize, determinism, workgroup }`; a text parses to one schema, the same table each time it is read |
| `abi.isExtended(schema)` | whether the schema uses an extension |
| `abi.lower(schema, wgsl, spec)` | the lowered source, bindings, params and host slots |
| `abi.compile(key, lowered, label)` | compile a lowered variant once, answering its dispatch key |
| `abi.program(def)` | a program; `program:variant(spec)` lowers and compiles a variant. A program over the schema and source of the one standing under its key is that program, with the variants it has lowered |
| `variant:run(env)` | allocate outputs, bind, dispatch; answers the outputs and live counters. `env.outputs[binding]` is a buffer (or `{ buffer, count?, capacity?, counter? }`) the dispatch writes in place of an allocation; an appended output given one keeps the count its `counter` holds. The first run of a variant waits for its program to be built, so a read of an output asked for after the run sees what the dispatch wrote |
| `abi.table(columns, opts)` | pack columns into one buffer for a `columns` binding |
| `abi.evaluate(text, vars, lengths)` | evaluate a count expression |
| `abi.read(buffer, asU32?)` | read a buffer back, waiting for the frames it takes |
▲ 0↑ born
# shader_includes Module
Resolves the `#include` lines of a WGSL source against the asset system, so a
shader includes a `.shaderModule` by every name form `require` and
`asset.resolve` accept.
## Purpose
A shader names a module the way any content names any asset — a guid, an
identity, a package-relative `~.tail`, a `.relative.tail`, an `@root::` or
`@builtin::` path. The engine's include expansion is a flat key lookup, so a
relative form means nothing on its own: `~.tail` is a different module depending
on which package asked for it.
This module closes that gap in the one place that knows both — the including
asset, which holds its own VFS path. Every literal is resolved against that path
and rewritten to the module's guid before the source reaches the compiler, so a
relative include resolves exactly where a relative `require` would.
The rewrite applies to the source handed to the compiler. What the author wrote
stays on disk, which is what the reference extractor records, with its line,
when the file is written.
## Usage
An assetType canonicalizes its own WGSL, passing the asset's path as the base
the relative literals expand against:
```luau
local ShaderIncludes = require("modules.shader_includes")
local wgsl = ShaderIncludes.canonicalize(vfs.read(path .. "/shader.wgsl"), path)
```
Given `path` inside a package, both of these reach the compiler as the same
guid-keyed include:
```wgsl
#include "~.ssr_common"
#include "@builtin::systems.reflections.ssr_common"
```
A literal that resolves to no asset is left as it was written, so a
framework name — `zero::surface` and its siblings, which are
registry keys rather than assets — reaches the expander untouched. Source
carrying no `#include`, or given no base path, is returned unchanged.
▲ 0↑ born
# rt_ao_pass
Traces short hemisphere rays against the scene per pixel, so a surface darkens
by how much geometry actually stands around it rather than by what a depth
buffer happens to show.
## Bindings
| name | kind |
|------|------|
| `scene_color` | `texture2d` |
| `scene_depth` | `texture_depth` |
| `scene_normal` | `texture2d` |
| `scene_tlas` | `acceleration_structure` |
| `frame_cam` | `buffer` |
| `ao_params` | `buffer` |
| `ao_out` | `storage2d (rgba8)` |
## Params
| name | type | what it is |
|------|------|------------|
| `samples` | `float` | hemisphere rays per pixel |
| `radius` | `float` | world-space occlusion reach |
▲ 0↑ born
# assetType runtime
The machinery that reads a `<typename>.assetType/behavior.luau` and turns its
declarations into live behaviour.
A `behavior.luau` is a table of declarations — `ref` methods, `modules` shared
code, an `events` schema, a `namePattern`, `refShapes`, and the `onCreate` /
`onRegister` / `onChange` / `onDelete` / `validate` / `settingsDefaults` /
`settingsCorrections` hooks. None of it runs itself. This is the code that
runs it, and it lives here because reading a type's declarations is the
**assetType type's own behaviour** — the same way `material.assetType` owns
what a `.material` does.
## Sub-modules
| Module | Reads | Responsibility |
|---|---|---|
| `ref.module` | `ref`, `modules` | Builds every `AssetRef` envelope, attaches the shared metatable, and dispatches per-type methods and shared modules onto it. Also owns edit-mode write-behind persistence. |
| `create.module` | `onCreate`, `namePattern`, `validate` | Backs `asset.create`: resolves the type, checks the name against its pattern, runs `onCreate` (or clones `template/`), and writes the instance. `validate.module` beside it checks a creation `opts` table against the type's `createSchema`. Before running `onCreate`, resolves the type's settings chain (below) and hands the result to the hook as `opts.settings`. |
| `settings.module` | `settings`, `settingsDefaults`, `settingsCorrections` | A type's declared settings schema and where its values live (`type.yaml`'s `settings:` block). `Settings.resolveForCreate` layers the schema's own defaults, the type's own `settingsDefaults(name, opts, asked)` hook (a DEFAULT the schema can't express — a name-derived convention, a fact read off a payload the caller handed it, a value following a field `asked` shows a higher layer naming; any later layer overrides it), the Preset Manager, an importer's settings, the caller's `settings` table, then the type's own `settingsCorrections(values, name, opts)` hook (a CROSS-FIELD CONSTRAINT the schema can't express, applied last over the fully merged values). A correction over a default/preset/importer value lands silently; a correction that would override what the caller's own `settings` table explicitly asked for refuses the creation instead, naming the field and why. Neither hook is ever handed a table to mutate; each returns what it wants changed (`settingsCorrections` may also return a `{ [field]: reason }` table for that refusal message). `Settings.cloneValues` deep-copies a values table — `create.module` hands `onCreate` a copy, never the table it stamps. `Settings.valuesOf` / `writeValues` read and write an asset's own values file. |
| `typeYaml.module` | `type.yaml` | The folder a type lives in and its parsed `type.yaml`, decoded once per content version of the file. `settings.module` and `inspector.module` read their blocks through it. `about` / `aboutAt` read a type's `about.yaml` (`intent`, `function`, `usage`), leaving out any key that is empty or still starts with `[[describe]]`; `aboutRows` and `aboutMarkdown` lay the texts out for the Inspector and the `types/<name>` guide. |
| `inspector.module` | `type.yaml`'s `inspector:` block | Which inspector a type declares for its assets (`inspector: { type: ... }` or `{ instance: ... }`), and the declaration that file returns — the sections it adds, the generic ones it replaces, and their order — or the problem that kept it from loading. |
| `onRegister.module` | `onRegister` | Fires an instance's once-only registration hook — on arrival, on world load, and for `@builtin` library instances. |
| `changeDispatch.module` | `onChange`, `onDelete`, `refShapes` | Routes a VFS source write or a folder delete to the enclosing typed asset's type hooks. |
| `refShapes.module` | `refShapes`, `ref` | Publishes what every `AssetRef<category>` answers to, so a member read on an asset-typed value is checked against that category's real surface. |
| `events.module` | `events` | The per-asset event runtime behind `ref.events`. |
| `instantiable.module` | `ref.instantiate` | The instantiation contract an asset type opts into: `root` stands the root entity, `place` applies the base placement opts to one the type adopted, and `result` shapes the `(root, idMap)` every `instantiate` returns. Also registers the `sceneInstantiable` field-constraint validator. |
| `declaration.module` | `type.yaml` | The type's decoded declaration, read once and held until a write inside an `.assetType` folder; what every question about a type as a whole reads. |
| `previewRecipe.module` | `type.yaml` `preview:` | How an instance's `preview.png` is produced: which of the four recipes (`instantiate`, `image`, `surface`, `custom`) the type declares, and what that recipe needs. |
## Reaching it
```luau
local rt = require("@builtin::assetTypes.assetType.shared")
rt.ref.loadTypeBehavior("material")
```
Fields resolve lazily. The prelude requires the sub-modules directly, in
dependency order (`ref`, then `changeDispatch`, `onRegister.install()`,
`refShapes.install()`) — a table that required all six on load would take that
ordering away from it.
▲ 0↑ born
# Module (asset type)
A module is a reusable, stateless (or globally-stateful) Luau library
that other code pulls in with `require()`. Modules are the unit of
factored-out logic in a world: helpers, math libraries, format
parsers, registries, shared algorithms.
## When to use one
- You have logic you want to share across multiple components,
services, scenes, or tools.
- You have a registry, lookup table, or shared cache that callers all
read from / write to.
- You want a stable API surface (`M.fn`) other code can depend on.
If the logic is bound to one entity, use a `.component`. If you want a
named UI of fields rather than functions, use a `.preset`.
## Where it lives
- Source: `/zero/source/.../<name>.module/`
- Identity: the source path with `/` written as `.` and each segment's
type suffix dropped — `/zero/source/demo/beats.module` is
`demo.beats`, and `/zero/source/kit.package/beats.module` is
`kit.beats`, the container's name kept and its `.package` suffix
gone. `asset.create` returns this string, `asset.resolve(...).identity`
reads it back, and the `require` forms below write it as
`<identity>`.
- Folder shape:
- `init.luau` (or `init.lua`) — module body. **Required.** Returns
a table (conventionally named `M`).
- `README.md` — instance-level documentation. **Required.**
- `.metadata` — agent-editable tags + free-form fields. **Required.**
## How to create one
```luau
asset.create("module", "<name>")
-- Creates: /zero/source/<name>.module/
-- init.luau (canonical `local M = {} … return M`)
-- README.md (instance README template)
-- `folder` places it in a subfolder of /source, and that subfolder
-- leads the identity: `{ folder = "lib" }` produces `lib.<name>`.
-- `into` authors it inside a resolved container (a package, a toolbox),
-- whose own identity leads the same way:
asset.create("module", "<name>", { folder = "lib" })
asset.create("module", "<name>", { into = asset.resolve("myPkg.package") })
```
## How it operates
1. **Registration.** Writing `init.luau` into a `.module/` folder
indexes the asset and registers the module path with the resolver.
2. **Loading.** The first `require("<identity>")` runs
the file's body and caches the returned table. Subsequent requires
from anywhere return the **same table** — this is the
shared-state lever for "module-local" registries. The body runs in
an environment of the module's own: a name it declares without
`local` is readable by the module's own functions and by no other
script, so an export reaches its callers through the returned table
and nothing else. Requiring a component's folder runs its chunk the
same way, once, and its `update`, `start` and `public` stay in that
environment; a component runs on an entity through
`entity(id).component.add(name)`.
3. **Hot reload.** Editing the file re-runs the module body and folds
what it returns into the table already loaded, so that table keeps
its identity: a caller that captured it with `require` reads the new
source's functions and values through the reference it already
holds, and a later `require` returns that same table. A key the new
source drops goes away; a key something set at runtime stays. The
body's own `local`s start again from their initial values, so state
that must outlive an edit lives in `modules.state()`
(`guides { path: "core/scripting-and-tasks" }`).
4. **Identity resolution.** A module is reached by its `<identity>`,
and where the caller lives decides which spelling of it resolves.
For a module in a **world**, from a caller in that same world —
another module, a component, a scene entrypoint, or an `execute`
chunk:
- `require("<identity>")` — the identity on its own, resolved
against the caller's own root. It carries every folder segment,
so a module created with `{ folder = "demo" }` is
`require("demo.beats")`.
- `require("@root::<identity>")` — the same root-relative
resolution, written out.
- `require(".sibling")` — a module in the same folder, by its bare
name; `..name` steps up one folder, `...name` two.
Logs, stack traces and hot-reload notices name that same module
`@local.source.<identity>` — its key under the world source root.
The `<identity>` tail of that key is the form above, so a trace
reading `@local.source.demo.beats` is `require("demo.beats")`.
For a module in a **library** — content under
`/zero/source/libs/@<lib>/` — `@<lib>::` addresses that library's
root from anywhere: `require("@builtin::modules.transform")`.
Mounting a world as a library moves its files under such a root and
flips the caller root to `@<lib>::`, which is what keeps the
root-relative forms above resolving across the move.
## Discovery
- `asset.list("module")` — every registered module.
- `asset.inspect("<name>")` — public functions, source path, this
type README.
- `ls /zero/source/<name>.module` lists the files the folder holds.
## Authoring conventions
- Return a single `M` table from `init.luau`. Top-level statements
with side effects run on first require — useful for one-time
initialization, dangerous if they touch the engine before it's
ready.
- Write exported functions as `typed function`, not `function`: the
argument types are enforced at the call and the checker knows the
signature, so a caller's mistake is reported where they made it.
- Annotate exported functions with `--!desc` / `--!arg` / `--!return`
/ `--!example` so the LSP, `tools.list`, and `asset.inspect`
surface them. A function with no `--!desc` is reachable only by
someone already reading this file.
- Declare a VALUE with `Field.<kind>(default, mode, description)`, and
a table whose members are reached through a metatable with
`--!members <TypeName>` — the latter gives the surface its accepted
member set, its type, and its documentation from one table. See
`guides { path: "core/authoring" }` for all four rules and
`modules/api/engine/entity.module/members.module` for a worked
member table.
- Keep module state in module-local upvalues or in `modules.state()`.
A name the body declares without `local` lives in the module's
environment, which every run of the module shares: a function the
previous run left in place reads what the reload assigned. Module-locals start again from their
initial values with each hot reload; the table `modules.state()`
returns is the same table on both sides of every reload.
- Prefer focused modules over kitchen-sink modules. If two halves of a
module have no shared state, split them.
## Common pitfalls
- **Cyclic requires.** A `require` chain that loops will return the
partial table (the half built before the cycle was detected).
Design for one-way dependencies.
- **Engine-time side effects.** Don't `entity.spawn` at module
top-level — the engine may not be ready. Expose an `M.init` and
call it from a scene entrypoint.
- **Hot-reload + module-local cache.** A module that caches
expensive computation in upvalues loses that cache on reload —
fine for dev, but be aware in performance work.
- **`init.lua` vs `init.luau`.** Either works, `.luau` is canonical.
- **Writing one while play runs.** A `/source` write made while play is
running lands on the play shadow, and a guarded play-exit discards it
unless it is kept. One `.module` write shadows `init.luau`, the
`README.md` and the `.metadata` together.
`vfs.write(path, bytes, { durable = true })` skips the shadow, and
`vfs.promotePlayShadow` keeps what is already on it — the `core/vfs`
guide has the model and what each route costs.
## Related types
- `.component` — for entity-bound state + lifecycle hooks.
- `.service` — generates content you don't have yet (a mesh, sound, texture, …) via a metered provider.
- `.tool` — for a single agent-callable function with a YAML schema.
- `.package` — to group several modules + components + scenes into
one shippable folder.
## In the Inspector
Exports: what the module exports (name, kind, signature), parsed from its source without running it, with **Check** (the LSP's diagnostics for its entry file) and **Open**.
▲ 0↑ born
# yaml.module
YAML decode + encode for authored engine content. Pure Luau, no engine
dependencies — a general parsing library, not data-system plumbing.
```luau
local Yaml = require("@builtin::modules.yaml")
local doc = Yaml.decode(vfs.read(path))
vfs.write(path, Yaml.encode(doc))
```
## Supported subset
- Block mappings (`key: value`) and block sequences (`- item`), nested
to any depth.
- Compact sequence-of-mapping entries (`- path: x` / ` kind: y`).
- Flow collections — `{ a: 1, b: 2 }` and `[1, 2, 3]` — single line.
- Plain scalars with type inference: `~` / `null` → nil, `true` /
`false` → boolean, numeric literals → number, everything else →
string.
- Single- and double-quoted strings (`''` escapes a literal quote
inside a single-quoted string; `\n` `\t` `\r` `\\` `\"` inside a
double-quoted one). A quote opens a quoted scalar where a scalar
begins — after `key:`, after a `- ` entry marker, or inside a flow
collection — so a plain scalar carries an apostrophe as data
(`note: the world's rules`). Quoted keys are read in flow mappings.
- `#` comments — honored outside quotes, so a `#` inside a quoted
string is kept as data.
- Literal (`|`) and folded (`>`) block scalars, with a chomping
indicator (`-` strips the final newline, `+` keeps every trailing
blank line, none keeps one newline) and an indentation indicator
(`1`-`9`: the content's indent past the parent's), in either order
(`|-`, `>+`, `|2`, `>1-`). A block scalar's content is literal text:
quotes (balanced or not), `#`, `key: value` and `---` inside it are
data.
- An optional leading `---` document marker.
## Loud-error contract
Constructs outside the subset above raise instead of misparsing:
anchors/aliases (`&`, `*`), tags (`!`), directives (`%`),
multi-document streams (a second `---`), a block-scalar header
it cannot read (`|x`, `|-+`, `|0`), tab indentation, and inconsistent indentation (both block structure and
block-scalar bodies). Every error carries the offending line number
(`yaml: line N: ...`), so a bad config points straight at the line to
fix.
Tab indentation is rejected everywhere — including block-scalar body
lines whose leading whitespace contains a tab. A tab after the first
non-space character of a line is content and passes through.
## API
- `Yaml.decode(text: string): any` — decode a YAML document into a
Luau value (table, scalar, or nil for an empty document). Raises on
malformed input or an unsupported construct.
- `Yaml.decodeWithComments(text: string): (any, boolean)` — decode as
`decode` does, and report whether the text carries a comment by the
decoder's own rule: a `#` at a line's start or after whitespace, outside
a quoted scalar and outside a block scalar. Re-encoding the value drops
such comments, so an editor that writes a document back reads this first.
- `Yaml.encode(value: table): string` — encode a Luau table as YAML
(block style, two-space indent, alphabetically sorted keys). Raises
on values YAML can't represent (functions, userdata, non-string
mapping keys).
A top-level empty table encodes to an empty document, which decodes
back to `nil` (the YAML empty-document ambiguity).
▲ 0↑ born
# assetType.shared.settings
Resolves four questions about an asset's typed settings, all answered from its
type's `type.yaml` — nothing here is found by convention.
```lua
local Settings = require("@builtin::assetTypes.assetType.shared.settings")
-- or, from inside the assetType runtime:
local Settings = require("@builtin::assetTypes.assetType.shared").settings
```
## Where does a type's schema live?
`type.yaml` names it in a `settings:` block:
```yaml
settings:
values: "settings.yaml" # where an instance's own values live
schema: { type: "settings.luau" } # one schema for every asset of this type
```
or, for a type whose settings differ per instance (an importer):
```yaml
settings:
values: "settings.yaml"
schema: { instance: "settings.luau" }
```
or, for a type whose schema is a table its instance's own source declares and
whose values live elsewhere (a component: its `public` fields, valued on each
entity it is on):
```yaml
settings:
schema: { instance: "init.luau", export: "public" }
```
Whether an instance may lack its schema file is what the type's `files:`
block says of that file. Listed under `files.optional`, it may be absent, and
an instance without it declares no settings — the importer type lists it
there, since most importers take none. Listed under `files.required`, or not
listed at all, it must load, and an instance missing it is a broken
declaration and is logged.
`schema.type` is required at the folder relative to the TYPE's own
`.assetType/` directory (one schema shared by every instance).
`schema.instance` is required relative to each INSTANCE's own folder (`init`
resolves the instance's own identity; anything else is a sibling module under
it). Without `schema.export`, the file is required as a module and its return
value IS the schema. With `schema.export`, the file is run in an environment
of its own and `export` is read from a returned table carrying it, or else
from the globals the file assigned — a component's `public` is such a global.
That environment reads through to `_G` and takes every write itself; its own
`_G` is itself, its `declare` and `computed` record into it, and its `task`
records spawned, deferred and delayed work instead of starting it. Every other
global is the real one, so a call the file makes through one runs as it does
anywhere. The schema is the declared table's Field descriptors. A schema that
resolves to nothing says why through `Settings.schemaProblemOf(ref)`: the file
could not be read, compiled or run, or declared no such table. An instance
schema is read again when its file, its type's `type.yaml`, or the entry file
of any module the asset `require`s changes. `Settings.blockFor(typeName)`
returns the raw block; `Settings.schemaForType(typeName)` and
`Settings.schemaOfInstance(ref)` resolve the two schema shapes respectively;
`Settings.schemaFor(ref)` tries the type-level schema first, falling back to
the instance-level one. `ref` naming an assetType asset itself — e.g.
`asset.resolve("texture", "assetType")`, rather than an instance of it —
reports that type's own declared schema, the same one every instance of it
reports.
## Where do an asset's values live?
`settings.values` names a file living beside the asset's own content —
`Settings.valuesPathOf(ref)` joins it onto the asset's path.
`Settings.valuesOf(ref)` / `Settings.writeValues(ref, values)` read and write
it; this module only names where it is. A type that declares its schema with
no `settings.values` keeps no values in the asset — a component's live on each
entity it is on — so `valuesOf` answers nil for it, `asset.create` refuses a
`settings` table for it, and `asset.setSettings` refuses a write.
`Settings.recordedWrite(path, text)` writes a file the way every values file
is written, and an editor uses it for any other file it writes. It writes the
whole contents, records the write into the open undo operation when one is
open (so undoing it restores what the file held), and raises when the write
does not land.
## In what order are a schema's fields declared?
Every `Field.*` constructor stamps its descriptor with `declaredOrder`, one
more than the last. Luau evaluates a table constructor's entries in the order
they are written, so `Settings.orderedNames(schema)` lists a schema's fields —
and a struct's subfields — in the order the source writes them.
A values file, or a legacy `.metadata` settings block, may hold an older
spelling — a renamed field, an older enum member. Every read passes what is
stored through the type's `normalizeSettings` (`Settings.normalizeFor`), so
it answers in the fields the schema declares today, and writes nothing. The
next local edit of that asset rewrites the file in the declared spelling
(`Settings.healLegacyIfNeeded`).
`asset.setSettings(ref, patch)` writes a partial patch:
`Settings.resolvePatch(ref, patch)` normalises it, merges it over the current
values and applies the type's derived defaults for the fields it changed, and
`Settings.writeValues(ref, values, patch)` applies the corrections, checks the
schema and writes the file.
## How is a new asset's settings resolved at creation?
`asset.create` calls `Settings.resolveForCreate(typeName, name, destPath,
creationOpts, callerSettings, importerSettings)` before running the type's
`onCreate`, checks the result against the schema, writes it to the values
file, and hands `onCreate` a COPY of it as `opts.settings` (`Settings.
cloneValues`) — never the same table the values file gets, so nothing
`onCreate` does to its own copy can reach what was stamped. `onCreate` reads
settings from `opts.settings` and never writes to it. `asset.create` also
seeds the change baseline with the stamped values
(`Settings.seedChangeBaseline`), so the values file's own first dispatch
reports nothing changed and the payload `onCreate` encoded is the only
encode a create runs.
The layers, lowest priority first, each overriding the ones before it field
by field:
1. The schema's own declared defaults (`Settings.defaultsOf`).
2. The type's own `settingsDefaults(name, opts, asked)` hook, when its
`behavior.luau` exports one. `asked` holds what layers 3 to 5 name, so a
default can follow a field one of them sets.
3. The Preset Manager's matching row (`Settings.presetLayerFor`).
4. The creating importer's settings for this type.
5. The `settings` table the caller passed to `asset.create`.
6. The type's own `settingsDerivedDefaults(values, explicit, changed)` hook,
when its `behavior.luau` exports one — a field whose default follows
another field, set only when no layer from 2 to 5 named it.
7. The type's own `settingsCorrections(values, name, opts)` hook, when its
`behavior.luau` exports one — applied last, once every other layer has
merged.
Layers 2 to 5 are each read through the type's `normalizeSettings`, so a
layer naming a field in an older spelling sets the field it names today.
`asset.create`'s top-level settings alias accepts those older names too
(`Settings.acceptedFieldNames`).
Layer 7 is `Settings.applyCorrections(typeName, values, explicit, context)`,
the one corrections path every settings write takes — this create chain, and
`Settings.writeValues` for every later write (`asset.setSettings`, a type's
first-encode seed, the legacy heal). `explicit` names the fields the writer
asked for: the caller's `settings` table here, the patch for
`asset.setSettings`. A correction lands SILENTLY on a field the writer did not
name — nobody asked for that value, so overriding it just states a fact. A
correction that contradicts a field the writer named REFUSES the write,
naming the field, the value asked for, and why it cannot hold — the same as
every other place this codebase refuses an explicit request it cannot satisfy
(a `Field.checkSchema` violation, a BC7 alignment error) rather than silently
rewriting it into something else. So `asset.setSettings(tex, { compression =
"rgba16" })` on a mipped texture stores `generateMipmaps = false` beside it,
while `asset.setSettings(tex, { compression = "rgba16", generateMipmaps = true })`
is refused.
`Field.checkSchema` runs once, over the result AFTER the corrections hook has
applied — a bad value nothing corrects refuses the creation.
### Four hooks, four different jobs
Every hook is an optional export on a type's `behavior.luau`, alongside
`onCreate` / `onChange`. **None is ever handed a table to mutate** — each
reads what it's given and RETURNS a table of what it wants changed (or nil);
`resolveForCreate`, `resolvePatch`, `applyDerivedDefaults` and
`applyCorrections` are the only places that write to the values, by merging
what a hook returns the same way every other layer merges.
- **`normalizeSettings(values) -> values`** maps every older spelling a
stored file or a write may carry to the field and member the schema
declares now, returning a new table; a table naming both an older field
and its replacement keeps the replacement. The companion export
**`normalizedSettingNames = { ... }`** lists the older field names it
accepts beyond the schema, so a write naming one is not refused as an
undeclared field. `texture.assetType`'s maps the fields its earlier schema
stored to `colorSpace` + `compression`, and the older `filter` keywords to
`linear` / `nearest`.
- **`settingsDerivedDefaults(values, explicit, changed) -> partial?`**
answers the values of fields whose default follows another field. At
creation `changed` holds every field; on a write it holds the fields the
write moved. A returned field applies only where `explicit` — the fields
the writer named — does not name it.
- **`settingsDefaults(name, opts, asked) -> partial?`** supplies a DEFAULT
the schema itself has no syntax for — something only knowable at creation
time, like a naming convention, a fact read off a payload the caller handed
in, or a value that follows a field a higher layer sets (`asked` holds what
the Preset Manager, the importer and the caller name, the higher one's
value where two name a field). It runs early (layer 2 above), so any later
layer — Preset Manager, importer, caller — freely overrides it.
`texture.assetType`'s returns the `textureType` the name suggests (a
`_normal`-suffixed name is a `normalMap`), `compression = "uastc"` and
`maxDimension = 4096`, with `rgba8` for a `textureType` of `sprite` that a
higher layer names; for a pre-encoded ZTEX payload it returns the colour
space, compression and sampler the payload's own header carries. Either
way, an explicit `settings = { ... }` from the caller still wins.
- **`settingsCorrections(values, name, opts) -> (partial?, reasons?)`**
enforces a CROSS-FIELD CONSTRAINT the schema itself has no syntax for — a
fact about one field that depends on another field's resolved value, true
regardless of which layer produced that value. It runs last (layer 7
above), over the fully merged `values`, and again on every later write of
the values file. Nothing is left unmet in what gets
validated and stamped — but a value the caller explicitly asked for is
never silently rewritten to satisfy it; `applyCorrections` refuses instead
(see above). The optional second return, `{ [field]: reason }`, supplies
the "why" for that refusal message; a field with no reason falls back to a
generic one. `texture.assetType`'s returns `{ generateMipmaps = false,
maxDimension = 8192, colorSpace = "linear" }` whenever the RESOLVED
`compression` is high-precision (the encoder stores one verbatim, linear,
and refuses a mip chain or a downsample for it outright), paired with a
reason naming the compression, and `nil` otherwise.
## What does a declarer declare?
`Field.settingsOf(identity, mode)` embeds another declarer's schema as a
struct field without restating it. The identity names one of two kinds of
declarer, and `Settings.schemaOfDeclarer(identity)` tells them apart by what
`identity` resolves to:
- **An assetType** (e.g. `"@builtin::assetTypes.texture"`) — embeds the
schema every instance of that type carries, resolved via
`schemaForType`. This is the type-level shared schema from the section
above, not a per-instance one — an assetType has no settings of its own
to declare per instance.
- **Anything else** (an importer, or any other asset that declares settings
of its own) — embeds that asset's own schema, resolved via
`schemaOfInstance`.
Every schema this module serves has already run its `Field.settingsOf`
fields through this resolution — a caller reading `schema.someField.fields`
never sees an unresolved `declarer` with no `fields`. Resolution descends
into an already-literal struct's `fields` and a list's `element` the same
way, so a declarer embedded several fields deep is still reached. A declarer
that embeds itself, directly or through another declarer, stops one level
short of the loop instead of recursing forever.
## What are the defaults?
`Settings.defaultsOf(schema)` reads every field's declared `default` into a
plain table — a field declared without one is absent from the result rather
than holding a `nil` value.
▲ 0↑ born
# assetType.shared.typeYaml
A type's `type.yaml`, parsed. Every block a type declares in its `type.yaml`
(`settings:`, `inspector:`) is read through this module, so one file read and
one YAML decode serve all of them.
```lua
local TypeYaml = require("@builtin::assetTypes.assetType.shared.typeYaml")
local folder, identity = TypeYaml.folder("material")
-- "/zero/source/libs/@builtin/assetTypes/material.assetType", "@builtin::assetTypes.material"
local doc = TypeYaml.of("material")
print(doc.suffix) -- ".material"
print(doc.inspector.type) -- "inspector.luau"
```
- `TypeYaml.folder(typeName)` resolves the assetType and answers its folder
path and identity, or `(nil, nil)` when no such type resolves.
- `TypeYaml.of(typeName)` answers the decoded document, or nil when the type
does not resolve or its `type.yaml` does not decode to a table. The decode is
cached per type and read again whenever the file's content version moves, or
the type resolves to a different folder.
- `TypeYaml.described(typeName)` lists the files a type's assets must describe:
each file its `type.yaml` declares with a `described` content check, with the
keys and headings the check names and each key's byte limit. `TypeYaml.PLACEHOLDER`
is the marker a template puts where a description is yet to be written.
- `TypeYaml.describeBlock(typeName)` answers the `describe:` block of the
`type.yaml`: the type's own `guidance` on what a description covers and the
identities of `examples` whose descriptions show the shape.
▲ 0↑ born
# asset_change_dispatch (module)
Installs `_G.__zero_dispatch_asset_change`, the Luau half of the
asset-type **change-callback** system. The engine calls it once per VFS
source write (via `zero_scripting::ffi_callbacks::fire_asset_change_dispatch`,
queued as `VfsMutation::AssetSourceWritten`).
## What it does
1. Receives the written VFS path.
2. Walks up the path to the enclosing `<name>.<type>/` typed-asset folder
(deepest registered-type suffix wins, so the direct owner of the write
is chosen for nested typed assets).
3. Loads that type's `<type>.assetType/behavior.luau` via
`@builtin::assetTypes.assetType.shared.ref.loadTypeModule`.
4. If the module exports an `onChange` function, calls
`onChange(ref, change)` where `ref` is the typed `AssetRef` for the
changed asset and `change = { path, asset, type }`.
The engine runs each dispatch as its own yieldable task, so a hook can wait
on what it reads: a `vfs.read` of bytes only the blob store holds (a binary
file on the web build) fetches them. A hook that reads only what is resident
finishes inside the dispatch that started it. The writes routed to one asset
react in the order they were routed: a write routed while that asset's hook
is waiting queues behind it and reacts once the hook has finished.
This is the type-level analogue of the component-centric
`onAssetReload(field)` fan-out: components react to assets they
*reference*; an asset *type* reacts to writes inside its own *instances*.
## The source-write seam
A write inside a typed asset is also offered to the importer type's shared
layer (`onAssetWrite(assetPath, path, origin)`), the way a write with no
enclosing asset is offered to `onLooseWrite`. The asset's `import` record names
the file it was imported from (by guid and path); a write to that file re-runs
the importers on it, in place; the write that arrived is the only input. A type whose own `onChange` already keeps its retained source current
(a texture re-encoding its image, a sound clip its audio) sets
`reencodesRetainedSource = true` on its module, and the seam leaves that edit
to it.
## Re-entrancy
While an asset's `onChange` runs, a dispatch for that same asset made from
the hook's own coroutine is suppressed, so a handler that routes a write
back into its own folder inline doesn't recurse. A write the hook makes is
routed on a later frame like any other and reaches `onChange` again once
the hook has finished. `onChange` handlers must therefore be **convergent**: diff the meaningful
state before acting and short-circuit when there's nothing to do (the
`dynamicAsset` example only regenerates when the prompt actually changed
and bails while a generation is in flight). Idempotency is the contract,
exactly as it is for services' `start`/`stop`.
## Related
- `@builtin::assetTypes.assetType.shared.ref` — owns `loadTypeModule` + the per-type `ref` method
dispatch.
- `assetTypes/assetType.assetType/template/behavior.luau` — the documented
template that shows how to author `ref`, `global`, and `onChange`.
- `assetTypes/dynamicAsset.assetType` — the reference type that uses
`onChange` for prompt-driven regeneration with version control.
▲ 0↑ born
# asset_create
`asset.create` — the single, generic "instance a new asset of an existing type"
API. The same entry point scripts and agents use; there is deliberately no tool
wrapper, because agents author in Luau and call `asset.create(...)` directly.
```lua
local inst = asset.create("material", "my_metal", { base_color = { 0.8, 0.7, 0.2 } })
-- → AssetRef: inst.path == "/zero/source/my_metal.material", inst.guid, plus the
-- material type's ref methods.
```
`asset.create` makes a new *instance of an already-registered type* by running
that type's `onCreate(name, opts)` behaviour hook (declared in its
`behavior.luau`) and writing the produced files to
`/zero/source/<name>.<typeName>/` — the one authored location, in every mode.
While play runs, the play-mode write lock takes that write onto the **play
shadow**: live in the session, listed by
`vfs.playShadowPaths()`, and promoted or discarded on a guarded play-exit. The
asset created in play therefore carries the same identity, path and `require`
spelling it has in edit, and the session decides whether it stays.
A create whose output the world **reproduces** on every load — one made from a
component or a scene entrypoint — writes to the copy-on-write runtime store at
`/zero/runtime/assets/<identity>.<typeName>/` instead, so the code that rebuilds
it each load is its only source and the saved manifest never carries a second
copy.
## Placement
Four `opts` keys are consumed by the framework before the type's `onCreate`
hook runs, and steer where the instance lands:
| Key | Effect |
|-----|--------|
| `folder` | A relative subfolder under the source root: `/zero/source/<folder>/<name>.<typeName>/`. Groups a generator's output instead of accumulating it at the source root. |
| `into` | A resolved container ref (`.toolbox` / `.package`) to author INSIDE — lands at `<container>/<name>.<typeName>/` and registers as a member. Edit-mode only. |
| `dest` | An absolute destination path, owned by the caller (an importer building a `<name>.bundle/`). |
| `overwrite` | Re-author an existing destination in place, keeping its `.meta` guid so every reference stays valid. |
The `name` is always the asset's bare identity — the path goes in `folder`:
```lua
local rock = asset.create("mesh", "rock", { positions = p, indices = i, folder = "terrain/props" })
-- → rock.path == "/zero/source/terrain/props/rock.mesh"
```
`dest` and `into` both take precedence over `folder`. `folder` decides the
asset's identity, so it applies in every context: the runtime store is flat and
spells that identity in one folder name.
```lua
-- the same call from a component's awake()
-- → rock.path == "/zero/runtime/assets/terrain.props.rock.mesh"
-- → rock.identity == "terrain.props.rock", as it is from an execute
```
Types without an `onCreate` hook fall back to cloning their verbatim
`template/` skeleton to the same destination, so `create` works for every type.
Returns the created asset's `AssetRef` (`.path` / `.guid` plus the type's ref
methods — the same interned instance `asset.resolve` returns) on success and
raises (via `error`) on bad arguments or a failing `onCreate`.
Installed onto the FFI `asset` namespace by the prelude (`M.installInto(asset)`).
See `docs/specs/runtime-asset-copying.md`.
▲ 0↑ born
# declaration (module)
A type's `type.yaml`, decoded and held: the one reader behind every question
about a type as a whole — its files, whether it broadcasts its subassets, how
its instances are pictured.
## Exports
- `M.of(typeName) -> table?` — the decoded declaration, or nil when no type
answers to the name, it has no `type.yaml`, or the file does not decode (the
last with a warning naming the type). Shared: read it, do not write to it.
- `M.forget()` — drop every held declaration. The change dispatcher calls it
for every write inside an `.assetType` folder and for every removed type.
▲ 0↑ born
# asset_events
Per-asset runtime for declared asset events. An assetType's `behavior.luau`
declares an `events` schema the same way a component declares one; this
module turns that schema into the live objects an asset's ref fires and
listens on.
## Three faces, one Signal — keyed by the asset
The construction is `component_events`': one `Signal` per declared event,
reachable through a private fire-capable table, an owner-side emitter the
type's own behavior fires with, and a subscribe-only facade every other
holder of the ref sees. The facade exposes `connect` / `once` / `wait` and
has no `fire` at any key, so firing authority stays with the type.
What differs is the owner. A component event belongs to one instance on one
entity; an asset event belongs to the **asset**, so the runtime is keyed by
the asset's stable guid. Every resolver of that guid subscribes to the same
Signals, and a ref that is reclaimed and re-resolved re-attaches to the
subscriptions already there — the same reason `asset_ref`'s `runtime` table
is guid-keyed rather than stored on the envelope.
Both tables reject an undeclared event name: the private table's metatable
raises on a bad key and the facade raises on a bad key, so a typo surfaces
at the subscribe call instead of returning nil.
## Declaring events on a type
```lua
-- <name>.assetType/behavior.luau
local M = {}
M.events = {
changed = { payload = { value = Field.number(0, NoSync) } },
}
M.ref = {
poke = function(self)
local emitter = require("@builtin::assetTypes.assetType.shared.events").emitter(self.guid)
if emitter ~= nil then emitter.changed:fire({ value = 1 }) end
end,
}
return M
```
```lua
-- any holder of the ref
local ref = asset.resolve("@builtin::…")
ref.events.changed:connect(function(p) print(p.value) end)
```
## Exports
- `M.forAsset(guid, eventSchema)` — the runtime for one guid, built on first
use and reused after. A later call with a different schema reconciles:
surviving events keep their Signal and their subscribers, new events get a
fresh one, removed events are disconnected and dropped.
- `M.facade(guid)` — the subscribe-only view, or nil before a runtime exists.
- `M.emitter(guid)` — the owner-side `:fire` view, or nil before a runtime
exists.
- `M.has(guid)` — whether a guid holds a live runtime.
- `M.teardown(guid)` — drop one asset's runtime, disconnecting subscribers.
- `M.teardownAll()` — drop every runtime. Called on an engine mode flip so a
play-mode subscription does not survive into edit.
- `M.liveGuids()` — every guid holding a runtime, sorted.
## Notes
- Subscriptions made through the facade are ordinary `signal.module`
connections and disconnect the same way any other does.
- The runtimes table is held strongly, and its lifetime is bounded by the
mode flip that clears it.
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# assetType.shared.inspector
Which inspector a type declares for its assets, and the declaration that file
returns. The editor's Inspector (`edui.inspector`) reads it to add, replace and
order the sections an asset shows.
## The block
A type names its inspectors in `type.yaml`, with either key or both:
```yaml
# the Inspector for every asset of the type, a file in the type's own folder
inspector: { type: "inspector.luau" }
# a file each asset may ship in its own folder, for what that asset declares
inspector: { instance: "inspector.luau" }
# both
inspector: { type: "inspector.luau", instance: "inspector.luau" }
```
`type:` is what selecting an asset of the type shows. `instance:` applies to
the things an asset declares, never to the asset's own view: a component
names `instance: "inspector.luau"`, and a component that ships that file
shapes its card on every entity it is on. Each value is a `.luau` file name.
A block that is not a map, names another key, names neither key or names a
file that is not `.luau` is malformed; the assetType validator reports it as
`assetType.inspector_block`, and a `type:` file missing from the type folder
as `assetType.inspector_file_missing`.
## The declaration
The file returns a table:
```luau
return {
-- sections this inspector adds (before Operations)
sections = {
{ id = "summary", title = "Summary", build = function(ctx)
return { ctx.widgets.text{ text = "mode is " .. tostring(ctx.settings.mode) } }
end },
},
-- a generic section id -> the section shown in its place
replace = { tags = { id = "tags", title = "Labels", build = function(ctx) return {} end } },
-- section ids, first to last; ids it does not name follow in default order
order = { "summary", "identity" },
}
```
A section is `{ id, title, icon?, open?, build(ctx) }`; `build` returns the
section's body as a list of edui nodes. Any member of the declaration other
than `sections`, `replace` and `order` must be a function (a helper the file
exports). `material.assetType/inspector.luau` is a full example.
The Inspector rebuilds an asset's sections when the asset's files change. A
section that shows state held outside those files names it with a
`signature(ref)` member: text that moves when that state moves, read every
time the Inspector checks for a rebuild, so it has to be cheap.
`renderFeature.assetType/inspector.luau` folds in whether the feature runs
and its live settings, so a feature enabled or reconfigured from a script
shows in the Inspector as it happens.
## API
```luau
local InspectorDecl = require("@builtin::assetTypes.assetType.shared.inspector")
InspectorDecl.blockFor("material") -- { type = "inspector.luau" }
InspectorDecl.blockProblem({ other = "x.luau" }) -- why a block is malformed, or nil
InspectorDecl.declaresTypeInspector("material") -- true: the asset view reads one
local decl, problem, file = InspectorDecl.declarationFor(matRef)
local cdecl = InspectorDecl.instanceDeclarationFor(compRef)
InspectorDecl.shapeProblem(decl) -- nil when well-formed
```
`declarationFor(ref)` (and `typeDeclaration(typeName)`) read the `type:` file:
- `(nil, nil, nil)` when the type names no `type:` inspector;
- `(nil, problem, file?)` when the block is malformed, or the file is missing,
raises while loading, or returns the wrong shape — the problem names the
file and what is wrong with it;
- `(declaration, nil, file)` otherwise.
`instanceDeclarationFor(declarerRef)` reads the `instance:` file in the
declaring asset's own folder, and answers `(nil, nil, file)` when that asset
ships none.
▲ 0↑ born
# scene_instantiable (module)
The instantiation contract's shared implementation. An asset type opts into
scene instantiation by defining `instantiate(self, target?, opts?)` on its
behaviour `ref` table; this module carries the parts that mean the same thing
for every type, so a caller writes ONE piece of code against all of them.
```lua
local root, idMap = ref:instantiate(target?, opts?)
```
## The contract
**IN — the base opts.** `target` is an owning entity ref: the instance lands
under (or, for a hierarchy type like a bundle, onto) that owner. With no
target the type spawns a fresh root. `position`, `rotation`, `scale`, `name`
and `temporary` place that root and mean the same for every type. `rotation`
takes three numbers as pitch/yaw/roll in DEGREES, or four as a quaternion. A
type may honour more opts of its own — `params` for a type built from declared
inputs, `idMap` / `diff` / `sourceTag` for the bundle override contract — and
says so in its own `instantiate` docs.
**OUT — the two returned values.** Every type returns the same pair:
- **`root`** — the composed root, as an `EntityRef`. Composition is
**synchronous**: the root and everything the type built under it are live
the moment the call returns, so a caller can parent to it, read its
components and hand it on in the same statement. There is no frame to wait
for and no callback.
- **`idMap`** — the `originalId -> runtimeId` map naming what the composition
spawned, `{}` for a type with no addressable children. **Never nil.** A
component that re-composes the asset on every load (`Asset`) keeps this map
and passes it back in, which is how a cross-entity reference into the
composition — `SkinnedModel.skeletonRoot` pointing at a bone — survives a
reload.
The return is enforced, not merely described: `AssetRef` dispatches every
`ref:instantiate(...)` through `result` on the way out, whether or not the
type called it. A type that returns something else fails at its own call
rather than handing its caller a nil root or a map that is sometimes absent.
## Exports
- `M.root(self, target?, opts?) -> root` — stand the root entity for a type
that spawns one: parented to `target`, born temporary when
`opts.temporary`, named `opts.name` else the asset's own name, placed.
- `M.place(root, opts?) -> root` — apply the placement opts to a root the type
already has (the adopt path: a bundle exploding onto its target, a
sceneModule reconciling under one).
- `M.result(self, root, idMap?) -> (root, idMap)` — return through the
contract. Checks `root` is a live entity ref, normalises a missing map to
`{}`, and errors naming the asset type when either is something else.
- `M.isOwned(opts?) -> boolean` — whether a component drives this call. The
`Asset` / `SceneModule` components tag their own calls with `sourceTag`;
they hold the reference and re-compose on every load. An untagged call came
straight from `ref:instantiate(...)` and has no such owner.
- `M.own(root, self, idMap?) -> root` — hand an already-composed root to an
`Asset` component pointing at `self`, so the reference and its map persist
and the composition is rebuilt on the next load. The component adopts the
live composition rather than building a second one.
- `M.check(value, constraint) -> ok, reason?` — the `sceneInstantiable`
field-constraint validator, also registered under that kind on load.
## The field constraint
`Field.instantiableRef` emits `constraint = { kind = "sceneInstantiable" }`,
and this module registers the validator for it on load. Given a written value:
1. `nil` passes — the field is optional (no asset assigned).
2. Reads the value's identity — a bare string, or a table's `__ref` / `guid` /
`identity` / `name`.
3. Resolves it (`asset.resolve(identity)` — any category) and asks the
resolved ref `ref:canInstantiate()`: true iff the asset's type defines an
`instantiate` method.
This is what lets `Field.instantiableRef` accept by CAPABILITY rather than a
hardcoded type list — a new scene-instantiable asset type is accepted the
moment it defines the hook, with no edit to the field or its consumers.
▲ 0↑ born
# asset_on_register
Drives the optional `onRegister(self)` assetType lifecycle hook — the surface that lets an asset instance run code exactly once when it first registers, operating on the per-instance ref (`self`). This is what makes "write an asset into the world → it takes effect live, no restart" work for content that registers into a runtime registry (editor panels, and anything else that opts in).
A type opts in by exporting `onRegister` from its `behavior.luau`. The hook fires exactly once per instance:
- On `engine.onWorldLoaded` — a batched sweep over every world instance of every type that implements `onRegister`, yielding every 32 instances so a large instance count never stalls a frame. The @builtin library (`/zero/source/libs/`) is excluded.
- On live `asset.create` — the create path calls `M.fireFor(ref)` on the freshly-created instance.
A per-VM once-guard keyed by the instance's VFS path ensures the two triggers can't double-register the same instance.
## Exports
- `M.fireFor(ref, onRegisterFn?) -> boolean` — fire one instance's `onRegister(self)` hook exactly once. Resolves the type's hook from `ref.type` when `onRegisterFn` isn't supplied. Idempotent: a second call on the same instance is a no-op. Returns true if the hook fired this call.
- `M.sweep()` — batched sweep: fire `onRegister` once for every world instance of every registered type that implements it. Yields, so it must run inside a task. Safe to call repeatedly.
- `M.install()` — install the world-loaded sweep. Idempotent. Runs the sweep on a system task so it ticks through pause and never blocks the caller.
▲ 0↑ born
# previewRecipe (module)
How a type makes its instances' pictures. A type declares it in its
`type.yaml`, under `preview:`, and every instance's `preview.png` is produced
by the recipe named there.
```yaml
preview:
kind: surface # instantiate | image | surface | custom
mesh: sphere # surface: the builtin mesh the asset is painted on
```
| `kind` | The picture is | Needs |
|---|---|---|
| `instantiate` | the asset stood in the studio through its own `instantiate` | — |
| `image` | a file the instance already holds, fitted to the frame | `source.file` or `source.files` |
| `surface` | the asset painted on a builtin mesh | `mesh` |
| `custom` | whatever the type's `behavior.luau` `ref.preview` returns | — |
`angle: [yaw, pitch]` (degrees) states the bearing the camera looks from, for
any kind that renders.
The `preview:` block says how the picture is PRODUCED. Whether search embeds
that picture is a separate declaration — an `image` chunk under
`indexing.content` naming `preview.png` — so a type states both, and a type
that states one without the other gets exactly what it stated.
## Exports
- `M.of(typeName) -> PreviewRecipe?` — the recipe `typeName` declares, or nil
when it declares none or no type answers to that name. Read once and held;
a block naming an unknown `kind`, or missing what its kind needs, is refused
with a warning naming the type.
- `M.forget()` — drop every held recipe. The change dispatcher calls it, with
`declaration.forget()`, for every write inside an `.assetType` folder and for
every removed type, so an edited `type.yaml` is read again.
▲ 0↑ born
# assetType.shared.ref
Builds the metatable every `AssetRef` (the `{ __ref, type, name, guid, identity, path }` envelope returned by `asset.resolve` / `asset.ref`) carries. Replaces the per-call C metatable that used to live in `crates/zero_scripting/src/ffi/bindings/asset.rs::attach_asset_ref_metatable`.
## Public API
```lua
local assetRef = require("@builtin::assetTypes.assetType.shared.ref")
-- Called by the Rust factory (push_asset_ref_handle) via
-- _G.__build_asset_ref_proxy after the envelope fields are set.
assetRef.build(envelope) -- attaches AssetRefMT, returns the table
```
The module exposes no invalidation surface — discovery is registry-driven and hot-reload is transparent (see "Discovery and hot-reload" below).
## Method dispatch order
`ref.foo` is resolved in this order:
1. **Default methods** — `getSource` / `getBytes` / `getText` / `exists` / `inspect` and the lazy `meta` property. Per-type definitions cannot override these (engine contract from gh#1889).
2. **Per-type `ref` table** — discovered through `asset.resolve(<typename>, "assetType")` + `require(<identity>.behavior)`. The lookup resolves to whichever `<typename>.assetType/` folder is currently registered for the typename (built-in, user, or library-vendored) and pulls its `ref` methods.
3. **Nil** — unknown key, same shape as the original C metatable.
## Adding methods for a new asset type
Drop a `behavior.luau` into the type folder:
```
src/lua/lib/assetTypes/<typename>.assetType/
├── type.yaml -- structural spec (existing)
├── behavior.luau -- ref + global behaviour (new)
└── template/ -- placeholder body (existing)
```
`behavior.luau` returns:
```lua
return {
ref = {
--!desc Per-instance method on every `<typename>` AssetRef.
myMethod = function(self, ...) ... end,
},
global = {
-- Reserved for the asset.<typename>.* surface — not consumed
-- yet; included so the contract from gh#1889 lands cleanly.
},
}
```
Within `ref` methods, `self` is the AssetRef envelope: `self.path`, `self.identity`, `self.guid`, `self.type`, `self.name` are available. Engine-required fields (`guid`, `path`, `identity`, `type`) must not be redefined.
## Discovery and hot-reload
Type discovery uses the asset registry, so it doesn't matter where a `<typename>.assetType/` folder lives — engine built-ins under `@builtin::assetTypes.<X>`, user types dropped under `/zero/source/<X>.assetType/`, or types vendored inside an imported library all resolve identically. The dispatcher walks `asset.resolve(<typename>, "assetType")` → canonical identity → `require <identity>.behavior` on every miss; the asset registry is the cache for the resolve half and Luau's `_LOADED` is the cache for the require half.
Hot-reload is transparent. When a `<typename>.assetType/behavior.luau` is rewritten through VFS, the engine's `invalidate_require_cache_for_state` re-runs the module and mutates the cached `_LOADED[<identity>.behavior]` table in place. Dispatch reads `mod.ref` on every access (rather than caching a sub-pointer), so existing AssetRefs see the new methods on the very next access — no Rust-side hook into this module is needed, and no invalidation API is exposed for callers to call.
The same registry-driven path also handles type **registration** correctness: dropping a new `<typename>.assetType/behavior.luau` updates the asset registry, the next `asset.resolve(<typename>, "assetType")` returns the new ref, and AssetRefs of that type immediately gain the new methods.
## Why Luau, not Rust
The asset surface needed per-category behaviour (`material:getProperties()`, `bundle:instantiate(entityId)`, `tool:run(args)`) and the old shape couldn't grow without an FFI change per method. Owning the proxy in Luau means:
- Type-specific methods ship as content (the `<typename>.assetType/` folder), not engine code.
- Adding a new asset type drops in a new folder; no Rust rebuild.
- Methods can call any other Luau global (`vfs`, `asset`, `Material`, `entity`, etc.) directly, instead of going through narrow FFI primitives.
## Consumers
- `crates/zero_scripting/src/ffi/bindings/asset.rs::attach_asset_ref_metatable` — the Rust factory that pushes envelopes invokes `_G.__build_asset_ref_proxy` once per push.
- Every Luau call site of `asset.resolve` / `asset.ref` / `entity(id).component.X.material` / any binding declared `AssetRef<...>` — they all receive envelopes built through this module.
▲ 0↑ born
# asset_ref_shapes
Publishes what every `AssetRef<category>` answers to, so a member read on an
asset-typed value is checked against the category's own surface.
An asset category's per-instance surface is authored: a
`<name>.assetType/behavior.luau` declares `M.ref = { ... }`, and each category
declares its own. The members an `AssetRef<inputMap>` carries are therefore
knowable only to `inputMap` itself — no fixed set of types covers the ones a
world defines, and the checker has no way to guess them.
This module reads each registered category's `M.ref` table from its source
(never executing it), renders it as a Luau table type, and hands the set to
the engine. From there a `ref:method(...)` on an asset-typed value resolves
against the category's real surface: a name it does not carry is reported
along with the ones it does.
## Results shaped by the asset
Some results are shaped by the asset rather than by its category —
`inputMapRef:activate()` answers one handle per binding THAT map declares, a
set that is authored and differs per map. A category states those by
declaring `refShapes`, and this module asks it once per instance and
publishes the answers keyed by asset identity. `types/assetType` documents
the authoring side.
## When it publishes
Publishing is driven by use: every entry point that produces diagnostics
calls `ensure`, which is a no-op once the set is current. A world load, a
write inside a type definition, and a write inside any asset whose container
computes shapes each mark it stale, so the cost lands on the next check and
only if one comes.
The sweep is complete and replaces what was published before, so a category
whose type is removed stops being published.
## Reading what the checker believes
From a call site, a type that is correct and one that was never published are
the same absence of a diagnostic. `published()` tells them apart:
```lua
local shapes = require("@builtin::assetTypes.assetType.shared.refShapes").published()
shapes.categories.inputMap
--> "{ activate: () -> any, controls: () -> { any }, ... }"
shapes.returns["@builtin::inputMaps.default"].activate
--> "{ crouch: Handle, interact: Handle, jump: Handle, ... }"
```
▲ 0↑ born
# texture
An **image asset** — the raw bytes of a `png` / `jpg` / `jpeg` / `hdr` /
`ktx2` / `webp` / `bmp` / `tga` file. A loose image written into the world is
imported into a `<stem>.texture/` container (see "Internal layout").
> New to how a texture exists as an asset, as CPU-side pixels, and as a live GPU
> texture (and how `renderer.texture.*` and render targets move between them)?
> Read `core/resource-model` first.
`texture` is a first-class assetType (not a bare plural-dir category) so
that:
- a texture has a stable asset **identity** and an explicit `asset_type`
link, and
- a material that references a texture records a real `.refs` edge to it
— which is what lets the CPU-residency system cascade from a material to
the textures it actually uses.
## CPU residency vs GPU residency
A texture can be resident two fundamentally different ways, and they must
not be conflated:
- **CPU residency** (this assetType): the raw image **bytes in memory** —
readable, hashable, decodable. You can operate on the bytes.
- **GPU residency**: those bytes uploaded to the device as a
GPU texture the renderer binds/samples. Byte-level reads are **not
possible** on the GPU variant — that is simply how the device works. GPU
residency is managed separately and is **not** part of this assetType.
Same texture identity, two separate residency states, two separate
operation sets, two separate reference counts.
## Internal layout
A `.texture/` holds these files, and its child set is open. `asset.create("texture",
name, ...)` and the **texture importer** (which creates through it when a loose
raster image lands in `/source/`) produce this shape:
```
<name>.texture/
source.<ext> the retained source raster — see below
source.ztex the full-resolution texels a cook dropped some of — see below
settings.yaml the texture's settings — see below
data.ztex canonical pre-encoded + pre-mipped payload (ZTEX magic)
.metadata what data.ztex holds and was encoded from
```
`asset.create` keeps a copy of the image bytes it was given as `source.<ext>`;
the importer moves the uploaded image in under its own name instead
(`foo.png` stays `foo.png`). Either way it is the texture's retained source:
rewriting it re-encodes `data.ztex` from the new pixels, and a rewrite carrying
the bytes `data.ztex` was already encoded from changes nothing.
`data.ztex` is the **preferred primary**: when present the renderer resolves
and uploads it verbatim — no re-mip. When absent the primary falls through to
a raster image in the folder, so a container holding only an image file reads
that image.
That fallthrough takes the lowest-named raster image in the folder and never
the rendered preview, which is made from the payload. A
container that lost its encoded payload and holds no other image has no
primary: `asset.diagnose(ref)` reports `noPrimaryFile`, `asset.validate(ref)`
reports `texture.no_payload`, and `renderer.texture.loadCpu` refuses it.
`asset.primaryFile(ref).path` names the file the resolution landed on; the
asset-system guide covers `diagnose`.
#### `settings.yaml` settings
A texture's settings are declared in `settings.luau` and live in its
`settings.yaml`. `asset.create` stamps them when the texture is made, and
`texRef:setSettings({ ... })` (or `asset.setSettings(ref, patch)`) changes
them. Editing an encode-relevant one re-runs the encode against the retained
source and rewrites `data.ztex`.
```lua
local tex = asset.create("texture", "hero_albedo", {
bytes = png, ext = "png",
settings = { maxDimension = 1024 },
})
tex:setSettings({ uastcRdo = "medium" })
```
| key | values | default | meaning |
|-----|--------|---------|---------|
| `textureType` | `color` / `normalMap` / `mask` / `sprite` | `color`, or guessed from the name | what the texture holds, recorded in the payload. `normalMap`: tangent-space normals — when `generateMipmaps` builds the chain, every level of it, the base included, is renormalised to unit length; with `generateMipmaps = false` the one stored level is the source as given, and the chain the GPU builds from it at upload is a plain box filter. `mask`: linear data (roughness, metallic, occlusion, height, masks). `sprite`: a 2D image with transparency. A new texture's type is guessed from its name — `_normal` / `_nrm` / `_n` / … → `normalMap`, `_rough` / `_metal` / `_ao` / `_height` / `_mask` / … → `mask` — unless it is given. |
| `colorSpace` | `srgb` / `linear` | follows `textureType`: `srgb` for `color` and `sprite`, `linear` for `normalMap` and `mask` | how the stored values are read when sampled. `srgb` for albedo/emissive/base-color, UI and sprites; `linear` for normal/RM/AO/height/mask data. |
| `compression` | `uastc` / `rgba8` / `rgba16` / `rgba32f` | a new texture: `uastc`, a `sprite` `rgba8` | what the texels are stored as — see "What each compression stores" below. |
| `effort` | `fastest` / `fast` / `thorough` | `fastest` | how long a `uastc` encode searches for each block — see "Block compression" below. |
| `uastcRdo` | `none` / `low` / `medium` / `high` | `none` | how far a `uastc` encode moves from the source to make a payload that compresses smaller on disk and over the network — see "Block compression" below. |
| `generateMipmaps` | `true` / `false` | `true` | bake the full mip chain into `data.ztex` at encode time. |
| `maxDimension` | integer, `1` to `8192` | a new texture: `4096` | the longest side the encoded texture may have; a larger source is downsampled to fit, and a `uastc` texture's longest side is the largest power of two within it. A value past 8192 is refused. |
| `filter` | `linear` / `nearest` | `linear` | sampler filtering recorded in the payload. A material slot and a UI image widget sample the texture with it. A post-process effect's texture property, a render pass's `@texture` input and a compute shader's `texture_2d` binding sample through a sampler of their own (the effect's `postprocess.setSampler`, the pass's, the compute shader's named `sampler` binding), which this setting does not change. |
| `wrapU` | `repeat` / `clamp` / `mirror` | follows `textureType`: `clamp` for `sprite`, else `repeat` | how a material samples the texture past its left and right edges: tiled, the edge texel held, or mirrored. Recorded in the payload. |
| `wrapV` | `repeat` / `clamp` / `mirror` | follows `textureType`: `clamp` for `sprite`, else `repeat` | the same, past its top and bottom edges. |
| `anisotropy` | `world` / `1` / `2` / `4` / `8` / `16` | `world` | samples taken along a surface seen at a grazing angle. `world` follows the `render.anisotropy` world setting (`renderer.setAnisotropy`); a number fixes it for this texture, clamped to what the device supports. A `nearest` texture samples with 1. A write may give the number itself (`anisotropy = 8`); it is stored as the string. Recorded in the payload. |
| `alpha` | `input` / `premultiplied` / `none` | `input` | what the encode does to alpha. `input`: kept as the source has it (straight alpha). `premultiplied`: colour multiplied by alpha — decoded to linear light, multiplied and re-encoded for an `srgb` texture, multiplied as stored for a `linear` one — the source a material with the `premultiplied` blend mode (`src + dst * (1 - src.a)`) composites. `none`: every texel opaque, colour kept. |
| `alphaIsTransparency` | `true` / `false` | follows `textureType`: `true` for `sprite`, else `false` | fill every fully transparent texel with the average colour of its non-transparent neighbours, spreading outward, so bilinear filtering and mip averaging never pull black into the edge of a transparent area. Alpha stays 0. Runs before `alpha` and before the mips. |
| `keepCpu` | `true` / `false` | `false` | keep the decoded pixels in the CPU store after the GPU upload — see below. |
The type's colour space, `alphaIsTransparency`, `wrapU` and `wrapV` are
stamped when the texture is created, and a later write that changes
`textureType` moves them with it, unless the same write names them.
A cook that drops texels — a `maxDimension` smaller than the source, or a
`uastc` cook resampling a side to a power of two — keeps the full-resolution
input as `source.ztex` (one RGBA8 level) when the container holds no source
image, so raising `maxDimension` later re-encodes from every texel. A cook
that drops nothing keeps nothing extra. A texture made from raw pixels whose
cook dropped nothing keeps its payload as its only source, so a settings
change re-encodes from that payload read back with straight alpha: what an
earlier encode discarded stays discarded, after `alpha = none` its alpha is
opaque, and a `uastc` payload re-encoded is the blocks' texels, not the
pixels first given.
A new texture's settings start from the texture type's own defaults —
`uastc` with a `maxDimension` of 4096; `rgba8` for a `sprite`; a 16-bit PNG
or `.hdr` source left to the schema's `rgba8` unless a layer names a
compression — and a world's Preset Manager rows
for `texture` override them (a world that ships at 2048, say), then an
importer's settings, then the `settings` the create names.
`filter`, `wrapU`, `wrapV` and `anisotropy` say how the texture is sampled,
not what its texels are. A write that changes only those rewrites the
payload's header (`renderer.texture.withSampler`): every level keeps its
bytes, and no preview is rendered, because no pixel changed. Every material
slot samples through its own texture's state, so two textures on one material
can wrap and filter differently. UI image widgets honour `filter` and draw each
image over its own bounds, so the wraps apply to materials. A post-process
effect, a render pass `@texture` input and a compute shader sample through
samplers of their own, so none of the four settings reaches them.
`keepCpu` is a lifecycle setting, not an encode input — it never re-runs the
encode. It acts on an already-materialised texture right away instead: `true`
loads the decoded pixels into the CPU store when the texture is GPU-resident,
`false` drops a resident CPU copy.
The `data.ztex` payload is a `ZTEX` magic, a 32-byte header and the mip
levels; the CPU encoder is exposed to Luau as
`renderer.texture.*` and consumed by the texture importer and this assetType.
#### What each compression stores
| `compression` | In `data.ztex` | On the GPU | Limits |
|---|---|---|---|
| `uastc` | UASTC 4x4 blocks, whole mip chain, one byte per texel, each level compressed for storage. | Transcoded at upload to a block format the adapter samples: `Bc7RgbaUnorm[Srgb]` where it samples BC textures (desktop native, desktop WebGPU), ASTC 4x4 where it samples ASTC and not BC (phones, a browser on one), ETC2 RGBA8 where it samples only ETC2, each one byte per texel; RGBA8 at four bytes per texel on an adapter that samples none of them, and for a texture with a side under four texels. | each side is resampled to the nearest power of two (halfway rounding up), nearest-neighbour for a `nearest` texture. |
| `rgba8` | From an image with `generateMipmaps = false`, a `maxDimension` the image fits within, `alpha = input` and `alphaIsTransparency = false`: the source PNG / JPEG / WebP itself, decoded at load. Otherwise raw 8-bit RGBA with the encoder's box-filtered mip chain. | `Rgba8Unorm` / `Rgba8UnormSrgb`, four bytes per texel. | none |
| `rgba16` | Raw 16-bit unsigned normalized, one level. An image is decoded at its own depth: a 16-bit PNG keeps every bit, an 8-bit channel `v` is stored as `v * 257`. The frames of an animated image are decoded at 8 bits. | `Rgba16Unorm` where the adapter grants 16-bit normalized textures (native); half float (`Rgba16Float`, about 11 significant bits) where it does not (every browser). | one level, no `maxDimension`, `linear` only. |
| `rgba32f` | Raw 32-bit float, one level. An image channel is stored as its value over the channel's maximum. | `Rgba32Float`. Where the GPU filters 32-bit float, every consumer samples it. Where it does not (every browser): a material slot draws the shader's declared default; a UI image draws nothing; a render pass naming it as an `@texture` input is skipped; a compute shader that declares no sampler binds it and reads it with `textureLoad`, and one that declares a sampler refuses the dispatch — each logging once, naming the texture and its format. CPU reads (`:load()`, `renderer.texture.decode`) return every bit on every device. | one level, no `maxDimension`, `linear` only. |
A high-precision compression turns `generateMipmaps` off, `maxDimension` to
8192 and the colour space to `linear` when the same write does not name them,
and refuses a write that names a contradicting value.
#### Block compression
`compression = "uastc"` stores every mip level as UASTC blocks — sixteen bytes
per 4x4 texels — a format no GPU samples directly but every one can be handed:
at upload each level is transcoded to a block format the adapter samples, BC7
on a desktop GPU and ASTC 4x4 on a phone's (ETC2 on one that samples ETC2
alone), so one payload is resident at one byte per texel on each, and RGBA8 on
an adapter that samples none; `renderer.textureMemory().blockFormat` names the
format this adapter holds it in. Only the levels a device keeps are
transcoded: under a texture-size cap (`renderer.setMaxTextureSize`) a texture
is uploaded from the first level of its chain within the cap. Compression is
lossy, which makes it the choice for colour, normal and detail maps; `rgba8`
holds a texture exactly, which is what pixel art and a mask whose exact codes
matter need.
`effort` is how long the encode searches for each block. `fastest` tries one
candidate for an opaque block, `fast` takes about 6 times as long and
`thorough` about 17 times, each landing closer to the source texels. What the
GPU holds is the same size at every effort, and so is the time a load takes.
`uastcRdo` trades accuracy for a payload that compresses smaller: `none`
encodes each block as close to the source as the encoder finds, and `low`,
`medium` and `high` let a block move further from the source when a nearby
block's bytes would let the payload compress better. What the GPU holds is the
same size either way; what moves is the size of `data.ztex` on disk and over
the network, and the encode time, which a pass more than doubles.
The encode runs on the CPU when the texture is created or a setting that
decides its texels changes. A call from a task that can yield cooks off the
frame and the task waits for it, so the world keeps running: a 1024x1024
texture with its mip chain takes about a second on a desktop CPU.
A texture whose settings say `rgba8` is never compressed.
## Reading an asset from its ref
`texRef:settings()` reads the container's settings with every schema default
filled in and `texRef:setSettings({ maxDimension = 1024 })` patches them;
`texRef:load()` decodes the payload's pixels into the CPU store for per-pixel
access, `texRef:handle()` puts the texture on the GPU under the asset's own
guid, and `texRef:preview()` renders it as a swatch.
`texRef:info()` reads the compiled `data.ztex` payload's header: the format it
was compiled to — also as its `compression` and `colorSpace` — the
`textureType`, `alpha` and `alphaIsTransparency` it was encoded under, its width and height, its mip and array-layer counts, the
sampler recorded in it (`filter`, `wrapU`, `wrapV`, `anisotropy`), and, for an animated sequence, each layer's
display time and the length of one pass:
```lua
local info = texRef:info()
print(info.width, info.height, info.format, info.mipCount)
```
It answers off that payload's own header, so a compiled texture reports how big
it is for a header read where `load()` decodes its pixels and `handle()` uploads
them. A container whose primary is a source image answers `(nil, err)`, and
`load()` reads its size. The `compression` and `colorSpace` it reports are what
the payload holds; the settings table holds what the encode was asked for.
## In the Inspector
Selecting a texture opens its **Texture** section right below the asset's
identity, then its Settings. The section draws the encoded texture through the
texture's own sampler, so a `filter = "nearest"` texture reads crisp at every
zoom. The zoom row offers **Fit** and each integer zoom (1×, 2×, 4×, 8×) whose
drawn size fits 512 px; a 128 px texture offers up to 4×, and one wider than
512 px offers Fit alone. Below the view, the section lists every field of the
`data.ztex` header (`texRef:info()`) — size, format, mip levels, filter, layers,
and a sequence's frames and duration — and the GPU memory the encoded mip chain
takes across its layers. The filter and the other encode settings change in
the Settings section; the Texture section reports the re-encoded result.
▲ 0↑ born
# `.font` asset type
A `.font` is a first-class font asset: font-file bytes (TTF / OTF / WOFF /
WOFF2) converted into a guid-anchored asset via
`asset.create("font", name, { bytes = … })`.
A font is a **general CPU resource** usable by any text surface. The
`onRegister` hook calls the engine `font.register(name, bytes)` primitive,
which installs the parsed face into **both** the 2D/3D text system (`text.*`)
and the egui UI text system, under the family name the font file itself
reports. A registration is what puts the face in the database; whether
`fontFamily = "<name>"` selects it is the separate question of whether the
shaper matches that name, and `font.reconcile()` answers it per family:
```lua
for _, f in ipairs(font.reconcile()) do
if not f.selectable then
print(f.family .. " is registered but shapes as " .. f.shapedWith)
end
end
```
`text.face(handle)` gives the same answer for one label. A family the shaper's
database holds is selectable under its own weights and for the glyphs its faces
cover: a row that reads `familyCoveredNoGlyph` names a family the shaper picks
whose faces have no glyph for the text asked of it. `topics/text` covers reading
a label that came out in the wrong face.
Fonts are CPU resources (not GPU), so the primitive lives in the `font.*`
namespace, the CPU analogue of `renderer.texture.create`.
## Layout
```
<name>.font/
data.zfnt the baked payload `asset.create("font", ...)` writes
face.json optional: family group, role, aliases, on-demand entries
```
## Editing a font's files
A write to a file the registration reads (`face.json`, `data.zfnt`, or a raw
font file in the folder) installs the font again from what the folder now
holds. The names the new `face.json` gives it (its group and each alias) select
it on every text surface from then on, and a name the earlier descriptor gave it
and the new one does not stops selecting it; a changed `group` moves the face to
that group. Text laid out under a name the edit decides is laid out again, and a
`Text3D` label draws it again on the next frame. For an on-demand face the
same holds for the font and coverage files its entries name: the entries are
declared again from their coverage files, and an entry already installed is
registered again from its font file with the names the descriptor now gives.
## On-demand faces
A face whose file is large and whose script most sessions never draw is
declared by the codepoints it covers instead of being read at boot. Its
`face.json` lists the font files of the folder under `onDemand`, each beside a
coverage file:
```
NotoSansCJK.font/
face.json { group, role, aliases, license, onDemand = [ { name, file, coverage }, ... ] }
kana.otf a font file (TTF / OTF)
kana.coverage the codepoints it maps: "3000-30ff,ff01-ff5e,..."
...
OFL.txt the license the files are distributed under
```
`onRegister` reads the coverage files and calls `font.declare(name, coverage,
{ file, family, role, aliases })` for each entry; no font file is read. The first
time a label or a `text.*` object meets a character an entry covers and no
installed face draws, the engine requests that entry: its file is read without
blocking the frame and registered with `font.register`, and from then on every
text surface draws the character from it. `font.onDemand()` reports each entry
as `declared`, `requested`, `installed` or `failed`, and `font.prefetch(text)`
requests the entries a text needs before it is drawn.
`font.coverage(bytes)` writes a coverage file from a font file's character map.
Splitting one large face into several entries (by script, and by how common a
character is) means a session reads only the part its text reaches: the
built-in `NotoSansCJK.font` is cut that way, and a page of Japanese reads its
kana and common-ideograph entries alone.
Every registered face, on-demand or not, is a per-glyph fallback for every
family the UI holds: a character the selected family has no glyph for is drawn
from the first face that has one.
## In the Inspector
Selecting a font opens its **Font** section: the family the face registers under, its role and aliases from `face.json`, whether the text system has the family registered and, when it holds it, how many faces and which weights. Below the facts, a sample line is drawn in the family at 14, 20 and 32 px.
▲ 0↑ born
# Component (asset type)
A component is a reusable behavior + data unit attached to an entity.
The component file declares public fields, methods, and lifecycle
callbacks; the engine instantiates one per attachment and drives its
hooks every frame. Components are the primary unit of gameplay code —
movement, AI, animations, UI panels, network sync, and per-entity state
all live here.
## When to use one
- You need per-entity state that survives across frames.
- You need per-entity behavior driven by engine lifecycle hooks
(`start`, `update`, `onDestroy`).
- You want to expose configurable fields to designers / `entity.spawn`
callers / scenes without code changes.
If you need a stateless pure-function library, use a `.module`. If you
need to generate content declaratively, use a `.service`; compute work
belongs in a `.computeShader`.
## Where it lives
- Source: `/zero/source/.../<Name>.component/`
- Identity: `<Name>` (the `.component` suffix strips from the
identity, but the folder retains the suffix on disk).
- Folder shape:
- `init.luau` (or `init.lua`) — declares the component. **Required.**
- `README.md` — instance-level documentation. **Required.**
- `.metadata` — agent-editable tags + free-form fields. **Required.**
The structural contract is enforced by `asset.validate` against this
type's `type.yaml`.
## How to create one
Always start with the scaffold — it guarantees the folder shape
matches `type.yaml` from the moment it's on disk:
```luau
asset.create("component", "<Name>")
-- Creates: /zero/source/<Name>.component/
-- init.luau (canonical declare + public block + hooks stubbed)
-- README.md (instance README template)
```
After scaffolding, edit `init.luau` to fill in the actual fields and
behaviour. The component registers as soon as the file is written —
hot-reload is automatic; no engine restart required.
## How it operates
1. **Registration.** Writing `init.luau` into a `.component/` folder
indexes the asset, mints a guid (in the `.meta` sidecar), and
surfaces the type to the engine's component registry. Same-frame
visible to `entity.component.add`.
2. **Attachment.** `entity(id).component.add(name, data)` (or the
batch form `tools.use("entityOps", "addComponents", targets,
{ [name] = data })`) attaches an instance.
The `data` table's fields override the component's declared
defaults; omitted fields take the declared default. The `data`
values are copied into `public.*` BEFORE `awake()` runs.
3. **Lifecycle.** The hooks run in this order:
- `awake()` — same frame as attach, immediately after the data
copy. Initialise state, set up native bridges, register with
other systems. Other components on the same entity may not have
awoken yet.
- `start()` — the next frame. Every component on the entity has
completed `awake()` by then, so cross-component setup is safe
here.
- `update(dt)` — same frame as `start()`, then every frame after,
for as long as the gameplay clock is running. `fixedUpdate(dt)`
runs once per physics step, straight after it, with the step's
`dt`, so a frame can run it several times or not at all;
`editorUpdate(dt)` runs
while the clock is held. Which of them ticks is decided by
`engine.mode` AND `engine.paused` together — see **Per-frame
hooks and the two axes** below, and `man modes`.
- `onDestroy()` — when the component is removed via
`component.remove` or when the owning entity is despawned.
Release resources, drop native ECS components.
For the full list (`onEnable`, `onDisable`, `fixedUpdate`,
`editorUpdate`, `onPropertyChanged`, `onAssetReload`,
`onModuleReload`,
`onBeforeSave`, …) and the timing details, **read `man components`
— that is the canonical lifecycle reference. Generic component
patterns (declare blocks, public fields, sync, ECS bindings,
typed methods) all live there.**
4. **Public surface.** Fields declared in `public` are inspectable,
editable in the inspector, and persist with the entity. Methods are
declared on that same table with a colon —
`typed function public:method(args)` — and every one of them takes
the component ref as `self`, so a caller invokes it with a colon
too: `entity(id).component.get(name):method(args)`. That is the one
calling convention a component ref answers to: the reflection
methods `ref:fields()` / `ref:getField(name)` /
`ref:setField(name, value)` take the same spelling. A function the
chunk declares at file scope (`function helper()`) is the
component's own, reachable from its hooks under its bare name;
`public` is what the ref carries.
5. **Settings and the Inspector card.** `type.yaml` names the component's
settings schema as `settings: { schema: { instance: "init.luau",
export: "public" } }`: the `public` table IS the schema, and its values
live on each entity the component is on, so `asset.schema(componentRef)`
answers the Field descriptors and no values file exists. On an entity
the Inspector shows the component as a card whose generic `settings`
section edits those fields as typed controls, each edit checked against
the schema and written to the live component as one undoable operation.
`type.yaml` also names `inspector: { instance: "inspector.luau" }`: a
component that ships an `inspector.luau` beside its `init.luau` shapes
its card — the file returns `{ sections, replace, order }` (see
`assetTypes/README.md`, "`inspector:`"), each section's `build(ctx)`
reading `ctx.component` (the live component) and `ctx.selection.id` (the
entity). `SceneModule.component/inspector.luau` replaces `settings` with
the bound module's declared inputs.
6. **Events.** An `events` block declares typed moments the component
fires from inside — `events = { onHit = Event({ dmg =
Field.number(0, NoSync) }) }`. The owner fires with
`events.onHit:fire({ dmg = 10 })`; outside code subscribes through
the proxy's subscribe-only facade,
`entity(id).component.get(name).events.onHit:connect(fn)`
(`:once` / `:wait` too). Pass `Sync` as the event's second argument
to replicate a fire to other peers. Events let one component react
to another's moments without polling. Full reference: **`man
components`**, Events section.
7. **Hot reload.** Editing `init.luau` reloads the component
definition; live instances are reconciled with the new declaration
in-place, and each crosses one lifecycle boundary: `onDestroy()`
ends the running life, then `awake()` and `start()` construct the
one that replaces it, and `update()` resumes on the next frame.
`public` and `private` values carry across; module-level `local`s
belong to the chunk, so the new life starts with them at their
initial values and its `awake`/`start` are what fill them in.
Whatever the old life handed elsewhere — a subscription, a shared
registration, a spawned entity — is released in `onDestroy`, the
call that pairs with the construction about to run. An edit that
leaves the source byte-identical crosses no boundary at all.
A field carries its value across when something stated it: a key of
the `data` table the instance was attached with (a scene record's
data is that table), or a write made since. Every other field takes
the edited source's declared default, so changing a default reaches
every instance that left the field to it. An instance that states
its own value for a field whose default the edit changed keeps that
value, and the reload logs a `[HotReload]` warning naming the field,
the entity, the value kept and both defaults.
## Discovery
- `asset.list("component")` — every registered component (engine +
world + libraries).
- `asset.inspect("<name>")` — identity, scope, public fields,
lifecycle methods, source path, and this type README. `detail`
carries the component's declared `fields`, `methods`, and `events`,
parsed from its source — `tools.use("assets","describe", "<name>")`
renders it as markdown, so a component's events are visible without
opening its source.
- `ls /zero/source/<Name>.component` lists the files the folder holds.
- `entity(id).component.list()` — components attached to an entity.
## Per-frame hooks and the two axes
`engine.mode` (`"edit"` / `"play"`) and `engine.paused` (the gameplay
clock) are independent, and the per-frame hooks read them separately:
- `update(dt)` / `fixedUpdate(dt)` tick while **the gameplay clock is
running** — whichever mode the engine is in.
- `editorUpdate(dt)` ticks while **the clock is held** — because the
mode is `edit`, or because play is paused — and also alongside
`update` whenever edit is running.
Which gives four states, and this table is the contract:
| `engine.mode` | `engine.paused` | hooks that tick |
|---|---|---|
| `edit` | `true` | `editorUpdate` |
| `edit` | `false` | `update`, `fixedUpdate`, `editorUpdate` |
| `play` | `false` | `update`, `fixedUpdate` |
| `play` | `true` | `editorUpdate` |
Entering edit sets `paused = true` and entering play sets it back to
`false`, so a session that never writes `engine.paused` only ever sees
rows 1 and 3 — which is where the shorthand "`update` is the play tick,
`editorUpdate` is the edit tick" comes from. It is the two default rows
of a four-row table, not the rule.
**Row 2 is the one that surprises.** With `engine.paused = false` in
edit — set by hand, or by a tool that advances the gameplay clock to
sample it, such as a `capture.collage` given a `duration` — `update` and `editorUpdate`
both fire, once each, every frame. A component that declares both and
routes them to one body therefore runs that body **twice per frame**:
```luau
local function drive(dt) ... end
function update(dt) drive(dt) end
function editorUpdate(dt) drive(dt) end -- twice per frame in row 2
```
Nothing reports the doubling; it reads as an animation running at twice
its intended speed. To get exactly one tick per frame in every row, ask
which axis you meant and answer it in the body:
```luau
function update(dt) drive(dt) end
function editorUpdate(dt) if engine.paused then drive(dt) end end
```
A scene `entrypoint.luau` declaring the same two hook names is dispatched
by the scene loader, not by this table: there `update` needs play AND
running, `editorUpdate` needs edit, and play-paused ticks neither. Read
`man scenes` before carrying a component's rule to an entrypoint.
## Authoring conventions
- Annotate public fields with `--!desc` so the inspector + LSP show
documentation alongside the field name.
- Declare lifecycle hooks (`start`, `update`, `onDestroy`) explicitly
rather than relying on engine defaults — readers can see at a glance
what runs when.
- Keep `update(dt)` cheap — it runs every frame per instance. Move
heavy work to `start`, to a `.computeShader`, or behind a job (`man jobs`).
- For multi-entity batching, prefer
`tools.use("entityOps", "addComponents", targets, components)` over
a loop of `entity(id).component.add` — it takes many targets and
many components in one call.
## Common pitfalls
- **Naming.** The component identity is the folder stem with
`.component` stripped (e.g. `<Spinner>.component/` → identity
`Spinner`). Don't repeat the suffix in the identity passed to
`component.add`.
- **`init.lua` vs `init.luau`.** Either is accepted (it's a
`one_of_group: "entrypoint"`), but `.luau` is canonical. Mixing both
in one folder is invalid.
- **`update` in edit mode.** It runs whenever the gameplay clock is
running, and entering edit stops that clock — so `update` is idle in
a freshly-entered edit session and ticks again the moment anything
sets `engine.paused = false`. Use `tools.use("wld", "play")` to test
update logic under the mode it ships in; `tools.use("wld", "edit")`
to return. See **Per-frame hooks and the two axes** above.
- **Renaming.** Renaming the folder changes the identity. References
to the component are recorded against the component itself, so
renaming or moving it does not break them.
## Related types
- `.module` — pure-function library, no per-entity state.
- `.service`: a declarative content generator, no per-entity state.
- `.preset` — a captured component configuration, replayable into
`component.add` without re-typing fields.
- `.bundle` — entity hierarchies that may carry component attachments
as part of the bundle.
## In the Inspector
Fields: its execution order, hooks, and how many methods and events it declares, then the fields its `public` table declares as read-only typed controls holding their defaults, with **Check** and **Open** for its entry file. Instances: a link to every entity carrying it. What its card shows on an entity comes from the component's own `inspector.luau`.
▲ 0↑ born
# Shader (asset type)
A shader is a WGSL program that runs on the GPU. Materials reference shaders and
supply property values; renderable entities reference materials, not shaders
directly. This README is the canonical reference for writing **every** kind of
shader — it covers all domains, the surface authoring contract, the material
property schema, the engine library functions you can call, and how a shader
registers and compiles.
> New to how shaders, materials, meshes, and textures relate as assets and live
> GPU resources? Read `core/resource-model` first.
## Folder shape
A `.shader` is a folder asset:
```
<name>.shader/
shader.wgsl # the WGSL body (required)
properties.yaml # the material property schema (optional; surface shaders)
README.md # a one-paragraph description of THIS shader (required)
.metadata # asset metadata
```
Each file carries a committed `.meta` sidecar pinning its stable guid. The
identity is `<name>` (the `.shader` suffix strips).
A shader's material properties are exactly the ones its `properties.yaml`
declares: a shader with no `properties.yaml` declares none, and the engine
reads no property from the WGSL body. A `.wgsl` file standing on its own,
outside a `.shader` folder, is WGSL source rather than a shader: a material
draws with the `.shader` folder that holds it as `shader.wgsl`. Materials and other assets
reference a shader by **AssetRef** (a typed, guid-backed handle), never by a raw
string.
## Domains
The first line of `shader.wgsl` declares the domain:
```wgsl
// @domain: surface
```
| Domain | What it is | You write |
|---|---|---|
| `surface` | A material on a mesh (the common case). | `fragment()` (+ optional `vertex()`/`vertex_clip()`). The engine generates everything else. |
| `post-process` | A full-screen pass over the rendered frame, in the space it declares (bloom, vignette, grade). | `fragment(in: PostInput) -> vec4` only. The engine generates the fullscreen `vs_main`/`fs_main` and the group(1) interface from `properties.yaml`. |
| `screen` | A standalone full-screen visual (UI background, procedural). | `fragment(in: ScreenInput) -> vec4` only. The engine generates the fullscreen `vs_main`/`fs_main` and the group(1) interface from `properties.yaml`. |
| `sky` | The sky background (a fullscreen material). | `fragment(in: SkyInput) -> vec4` only. The engine generates the fullscreen `vs_main`/`fs_main` and the group(1) interface from `properties.yaml`. |
| `compute` | GPU data processing, no rasterization. | An `@compute @workgroup_size(...)` entry over storage buffers; you write the `@group/@binding` lines yourself. For compute work, the `.computeShader` assetType (see below) generates them for you. |
`// @domain:` resolves the names above and `postprocess` / `screenspace` / `ui`
as further spellings of `post-process` and `screen`. A body carrying no
`@domain:` line is `surface`. `shaderRef:domain()` answers the domain a body
declares, a further spelling as the domain it names. Any other name is refused where the shader
registers, with an error naming the spellings that resolve, so a shader reaches
the renderer only under a domain the compiler scaffolds.
Particles are drawn and simulated through these domains like anything else: the
particle package's `particle_sprite` and `particle_mesh` are `surface` shaders,
and its simulation, culling and sorting steps are `.computeShader` assets.
## Texture coordinate space
A shader that samples a texture through a coordinate it builds itself declares
which space that coordinate lives in, on a line beside `@domain:`:
```wgsl
// @domain: surface
// @uv_space: world
```
| Value | The coordinate | A material's `uv_scale` means |
|---|---|---|
| `mesh` (the default) | The mesh's own UV attribute, `input.uv`. | How many times the texture repeats across a surface. |
| `world` | The fragment's world position, as a triplanar projection samples. | How many times the texture repeats per world unit, so a larger surface carries more. |
Texture residency reads the declaration to work out how finely a frame samples
each texture: a material laying eight copies of its texture across a surface
samples each copy at an eighth of the surface's size, and the mip level that
serves it is three levels coarser than the surface's own footprint implies.
Leaving the line out puts the shader in mesh space, which is what sampling
`input.uv` is. `renderer.textureStreaming().textures` reads back the span each
texture was measured at and the level that span asked for.
**Compute shaders have their own assetType.** A `.computeShader/` folder gives compute the same zero-scaffolding contract surface/sky/post/screen get: you write only `@compute fn main` (+ helper fns/structs, **no `@group/@binding` lines**) and declare bindings in a sibling `bindings.yaml` (storage buffers, textures, samplers, storage textures, plus a `params:` uniform); the engine generates the `@group(0)/@binding(N)` declarations. Dispatch it through a resolved reference (`asset.resolve("name", "computeShader"):dispatch(...)`). See the `.computeShader` assetType README and `man compute`.
**Surface**, **sky**, **post-process**, and **screen** shaders all get
engine-generated scaffolding — you write only `fragment()` and declare properties in
`properties.yaml`; the engine generates the entry points and the group(1) material
interface. (Each domain's `fragment` takes a domain-specific input instead of
`FragmentData`: `SkyInput`, `PostInput`, or `ScreenInput` — see "Sky shaders" and
"Post-process & screen shaders" below.) Compute shaders get the same treatment via
the separate `.computeShader` assetType (write only `@compute fn main`, declare
bindings in `bindings.yaml`). The `compute` domain here writes its own
entry points directly — see `man compute`.
## Surface shaders
A surface shader writes **only** the parts that are unique to it. The engine owns
all the scaffolding — the vertex stage, every render-mode entry point
(`vs_main` / `fs_forward` / `fs_gbuffer`), group(0) (camera, transforms, lights,
shadows, and the material rows), and the material interface generated from
`properties.yaml` (`material` and your texture slots). Adding a render path never
touches your shader.
Inside `fragment()` you have access to exactly four things — nothing is hidden:
1. **`input: FragmentData`** — the interpolated per-fragment surface data the
engine hands you: world position, world normal, uv, view direction, vertex
colour, and more. Every field is in the `FragmentData` table below.
2. **`material.*` and your textures** — the material inputs **you** declare in
`properties.yaml`. The mapping is mechanical: a scalar property named `foo`
becomes `material.foo`; a texture property named `bar` becomes `bar` (the
texture) and `bar_sampler` (its sampler). `material` has **exactly** the fields
your `properties.yaml` declares and no others — to add an input, add a property.
List what a shader exposes with `shaderRef:getProperties()` or
`asset.inspect("<name>")`.
3. **Engine state** — the scene's camera, lights, time, and shadows that the
renderer binds for every surface shader. `uniforms.*` (sun direction/colour,
ambient, `camera_pos`, `time`) and the punctual lights (`zero_point_light(i)`)
are always in scope; the shadow functions come from `#include "@builtin::shaderModules.shadows"`. This is how
you light a surface **without** the prebuilt PBR — see "Engine state" and
"Writing your own shading" below.
4. **Library functions** you `#include` (see "Library includes").
A shader and its property schema go together. The two files below are a complete
surface shader:
`properties.yaml` — declares the material inputs:
```yaml
properties:
- { name: base_color, type: color, default: [1, 1, 1, 1] }
- { name: roughness, type: float, default: 0.5, min: 0, max: 1 }
- { name: metallic, type: float, default: 0.0, min: 0, max: 1 }
- { name: base_color_texture, type: texture, default: white }
```
`shader.wgsl`; those declarations are read as `material.base_color`,
`material.roughness`, `material.metallic`, and the `base_color_texture` /
`base_color_texture_sampler` pair:
```wgsl
// @domain: surface
#include "@builtin::shaderModules.pbr_shading" // the PBR helpers — see "Library includes"
fn fragment(input: FragmentData) -> vec4<f32> {
var s = zero_pbr_default_surface(input);
s.albedo = material.base_color.rgb
* textureSample(base_color_texture, base_color_texture_sampler, input.uv).rgb;
s.perceptual_roughness = material.roughness;
s.metallic = material.metallic;
return vec4<f32>(zero_pbr_shade(input, s), material.base_color.a);
}
```
`fragment()` returns the final colour. The engine forces no lighting model on
you — flat, toon, PS1, dithered, or PBR are all just different `fragment()`
bodies. Calling `zero_pbr_shade` is opt-in.
### The two surface bodies, and what each gives up
A surface shader exposes one of two entry points, and which one decides how
much of the shader the engine can see:
| Body | The engine gets | PBR debug passes read |
|---|---|---|
| `fn fragment(input: FragmentData) -> vec4<f32>` | the finished pixel, and the `PbrSurface` too when the body hands one to `zero_pbr_shade` | the real channel where a surface was handed over; magenta, the "no data here" marker, where the body shades by its own math |
| `fn surface(input: FragmentData) -> PbrSurface` | the surface (albedo, roughness, metallic, emissive, normal, occlusion), which the engine then lights | the real channel |
Both are first-class: `fragment()` is what you want when the shader owns its
own look, `surface()` when you want engine lighting. `capture { pass = "albedo" }`
(and `roughness` / `metallic` / `ao` / `emissive`) answers about your material
for either body wherever the engine has the surface — writing the same
`PbrSurface` behind `surface()` or behind `fragment()` + `zero_pbr_shade` gives
one answer per channel. A body that lights itself by its own math draws those
channels magenta. `pbr.shader` exposes `surface()`.
`capture { pass = "normal" }` is a geometry read rather than a material one, so
it answers for every shader: the normal of the surface where one was handed
over, and the interpolated normal of the triangle where none was. It is the same
normal the frame's normal buffer carries, which is what a screen-space pass
reading `@scene.normal` sees.
`shaderRef:shadingModel()` reports which one a shader ended up with —
`"engine-lit"` for `surface()`, `"self-shading"` for `fragment()`.
### Optional vertex hooks
```wgsl
// Displace geometry in OBJECT space. Runs on skinned meshes too (it sees the
// already-skinned, morph-applied local position). Return the modified vertex.
// The `v` parameter is immutable (WGSL function params are), so copy it into a
// `var` first and modify that.
fn vertex(v: VertexData) -> VertexData {
var out = v;
out.position += out.normal * sin(out.time) * 0.1;
return out;
}
// Post-transform vertex hook (runs AFTER the engine's world/skin/projection). Two
// things you can do here, separately or together:
// * move `clip_position` — vertex jitter, PS1 snapping, render-resolution lowering;
// * write `color` — PER-VERTEX (Gouraud) shading: light the vertex from its
// world_normal + the light context and the engine forwards the result into the
// interpolated `vertex_color` the fragment reads.
fn vertex_clip(v: ClipVertex) -> ClipVertex {
var out = v;
// Gouraud: Lambert sun + ambient, evaluated once per vertex (flat-banded shading).
let n_dot_l = max(dot(v.world_normal, -normalize(v.light_direction)), 0.0);
let lit = v.ambient_color * v.ambient_intensity + v.light_color * v.light_intensity * n_dot_l;
out.color = vec4<f32>(v.color.rgb * lit, v.color.a);
out.clip_position = round(out.clip_position * 80.0) / 80.0; // PS1 snap
return out;
}
```
#### Declaring how far a hook moves geometry: `vertexBoundsDilation`
Static geometry is culled per cluster against its bounds as authored. A hook that moves vertices — wind sway, an outline hull, a vertex wave — can move them outside those bounds, and the cull then drops clusters whose displaced triangles are still on screen. Declare the farthest the hook moves any vertex, in world units, as a `vertexBoundsDilation` float property, with a default that covers the shader's own properties across their ranges:
```yaml
properties:
- { name: sway, type: float, default: 0.5, min: 0, max: 4 }
# 0.4 x sway, at sway's largest value.
- { name: vertexBoundsDilation, type: float, default: 1.6, min: 0, max: 100 }
```
Each material sets its own value — a material that sways less can set less, one moved farther sets more — and a material that sets none takes the default. The cull adds the material's value to every bound in its frustum and occlusion tests (not to the level-of-detail cut). A shader with a hook and no `vertexBoundsDilation` property is named once in the engine log when it compiles; its geometry is culled against its undisplaced bounds.
### Structs the engine passes you
`FragmentData` (input to `fragment()`):
| Field | Type | Meaning |
|---|---|---|
| `world_position` | `vec3<f32>` | fragment world-space position |
| `world_normal` | `vec3<f32>` | interpolated geometric normal (normalized) |
| `world_tangent` | `vec4<f32>` | xyz = world tangent, w = handedness (mikktspace) |
| `uv` | `vec2<f32>` | primary texture coordinates (perspective-correct) |
| `affine_uv` | `vec2<f32>` | the same UVs interpolated **without** perspective correction — the PS1 texture "swim". Always available; sample with it instead of `uv` for affine texture mapping |
| `vertex_color` | `vec4<f32>` | interpolated per-vertex colour (white if unset; carries per-vertex lighting if `vertex_clip()` wrote it — see Gouraud below) |
| `view_position` | `vec3<f32>` | camera world position |
| `view_direction` | `vec3<f32>` | normalized world-space direction to the camera |
| `light_direction` | `vec3<f32>` | directional (sun) travel direction, unit length; surface→sun is `-light_direction`. Where no sun reaches the camera it points straight down |
| `light_color` | `vec3<f32>` | sun colour |
| `light_intensity` | `f32` | sun intensity; 0 where no sun reaches the camera |
| `ambient_color` | `vec3<f32>` | ambient colour |
| `ambient_intensity` | `f32` | ambient intensity |
| `frag_coord` | `vec4<f32>` | framebuffer pixel coords (xy) + depth (z) — for screen-space dither |
| `receives_shadows` | `f32` | per-instance: > 0.5 if this surface receives shadows |
| `material_index` | `u32` | per-instance: the index standing for the material this surface draws with — the number `renderer.materialIdentity()` maps to a name |
| `shader_data` | `array<vec4<f32>, 4>` | per-instance: this entity's own four `vec4` lanes — its `ecs.ShaderData` component's `lane0`..`lane3`, or what `renderer.instanceData.set` put in them (zero until something does). A procedural graph's elements set them through the `data0`..`data3` attributes |
| `front_facing` | `bool` | true for front faces (double-sided shading) |
| `time` | `f32` | gameplay seconds: advances with the world at `engine.timeScale` and stands still while gameplay is paused (edit mode starts paused), so an effect slows and stops with the world |
`shader_data` is the per-instance channel, and it is what lets ONE material serve
many entities that differ in a value — a dissolve at its own progress per subject,
a hit flash at its own age, a fill level per instance. The alternative is a
material per entity, which is a separate pipeline binding and a separate row in
the material table for every one of them.
```wgsl
const DISSOLVE_LANE: u32 = 0u;
fn fragment(input: FragmentData) -> vec4<f32> {
let progress = input.shader_data[DISSOLVE_LANE].x;
...
}
```
```lua
-- one material on twenty entities, each at its own progress
renderer.instanceData.set(subject, 0, progress)
renderer.instanceData.clear(subject) -- back to zero lanes
```
The engine attaches no meaning to a lane: a shader and whatever writes it agree
what each one carries. Name the indices in the module that writes them.
`renderer.instanceData.laneCount()` is how many there are. The same lanes reach a
hardware-instanced population through `renderer.mesh.drawInstanced`'s
`instanceDataBuffer`, on slots no entity owns.
`VertexData` (in/out of `vertex()`): `position` (object-local, model-scale + morph
applied), `normal`, `uv`, `color`, `time`.
`ClipVertex` (in/out of `vertex_clip()`) — the post-transform vertex. Read context:
`clip_position`, `world_position`, `world_normal`, `uv`, `view_position`,
`view_direction`, `light_direction`, `light_color`, `light_intensity`,
`ambient_color`, `ambient_intensity`, `time`, `view_proj` (the view-projection of
the frame being evaluated), and where the vertex stands on its instance:
`local_position` (its position in the mesh, after `vertex()` and before the
instance's world transform), `object_origin` (the world position of the instance's
origin), `object_scale` (the world length of the instance's x, y and z axes) and
`object_axes` (`mat3x3<f32>`, the world direction of those axes, unit length) —
what a camera-facing card, a shard grown about its own base, or anything placed
per instance is built from. **Writable:** `clip_position` (snap /
jitter) and `color` (write a lit colour here for per-vertex Gouraud shading; the
engine forwards it to the interpolated `vertex_color` — left untouched, the mesh's
own vertex colour passes through).
`vertex()` and `vertex_clip()` run in the vertex stage, which reads the frame
uniforms (`uniforms.*`, and the `ClipVertex` members built from them), the scene
buffer (`zero_object_data`, `zero_object_visuals`, the node transforms), the
material interface and a `read` buffer property. The point, spot and area lights
(`zero_point_light`, `zero_punctual_projection`), the shadow maps, the
environment and light probes, the feature textures, the scene depth, colour and
reflection copies and a `@group(2)` buffer the shader declares `read_write` are
visible to the fragment stage alone: read them in `fragment()` or `surface()`. A
shader whose vertex hook reaches one fails to compile, and the error names the
stage, the binding and the calls that reach it.
### Each hook runs twice: this frame and the one before it
A vertex hook decides where the surface IS, so it also decides where the surface
WAS. The engine runs every hook a shader declares a second time, over the same
vertex standing one frame back — the previous-frame position stream, with
`time` = the clock that frame was drawn at and (for `vertex_clip()`)
`view_proj` = the view-projection it was drawn with. The motion vector the
renderer publishes is taken between the two results, so a displacement that
moves with time reports the velocity of the displaced surface, and a
displacement that does not move reports the motion of the transform alone
because the identical offset appears on both evaluations and cancels.
What that asks of a hook:
- **Take the frame from the argument.** `v.time` is the clock of the evaluation
being run; `uniforms.time` is always this frame's. A displacement built on
`uniforms.time` is identical on both evaluations, so its motion vector cancels
to exactly zero. The same holds for `v.view_proj` against
`uniforms.view_proj`: a clip hook that rebuilds its position from world space
through `uniforms.view_proj` reprojects the previous frame with this frame's
camera, and reports no camera motion at all. The wind helpers come in both
shapes for this reason — `zero_wind_sway_at_time(world_pos, stiffness, v.time)`
inside a hook, `zero_wind_sway(world_pos, stiffness)` outside one.
- **Anchor a wrap to `uniforms.time`.** A displacement that jumps discontinuously
— a falling drop that restarts at the top, a looping offset — differences its
jump as velocity on whichever frame it wraps. Compute the wrap COUNT from
`uniforms.time` and the position within the cycle from `v.time`, and both
evaluations share the same cycle, so the surface reports the speed it fell at.
`@builtin::shaders.rain_material` and `snow_material` do exactly that.
The per-vertex attributes (`world_normal`, `uv`, `color`) and the lighting and
camera-position context are this frame's on both evaluations, so a hook that
displaces along its normal reports the motion of the transform plus this frame's
displacement.
## Engine state — point lights & shadows
The common lighting state — the sun (`input.light_direction` / `light_color` /
`light_intensity`), the ambient (`input.ambient_color` / `ambient_intensity`), the
camera (`input.view_position` / `view_direction`), and `input.time` — is already on
`FragmentData`, so most shaders never touch the raw engine state. The one thing not
on `FragmentData` is the punctual-light array (its length varies), which is always
in scope:
| Expression | Type | Meaning |
|---|---|---|
| `uniforms.point_light_count` | `u32` | number of active point/spot lights |
| `zero_point_light(i)` | `PointLightData` | one point or spot light (fields below) |
| `zero_punctual_projection(i)` | `PunctualProjection` | a spot or area light's projection: `view_proj`, the frustum its cookie and shadow are placed by, and `cookie_layer` |
`PointLightData`: `position`, `radius`, `color`, `intensity`, `direction`,
`cone_outer_cos`, `cone_inner_cos`, `kind` (0 = point, 1 = spot).
Shadows come from `#include "@builtin::shaderModules.shadows"`:
- `compute_directional_shadow_factor(world_pos, normal, light_dir) -> f32` — 1.0 lit, 0.0 fully shadowed.
- `compute_spot_shadow_factor(...)` / `compute_point_shadow_factor(...)` / `compute_area_shadow_factor(...)` — one shadow shape each.
- `compute_punctual_shadow_factor(light_index, world_pos, normal) -> f32` — the row's own shape, read off its `kind`, for a loop that walks the punctual lights and does not want the switch.
- `zshadow_light_reach(light_index, world_pos, normal, object_channels) -> f32` — how much direct light that row puts on a surface on those light channels: the channel mask, falloff, cone or rect orientation, and the cosine, times intensity. Zero exactly where the light contributes nothing.
## Writing your own shading
The engine forces no lighting model — `zero_pbr_shade` is just one option. You can
light a surface yourself from the state above. Here is a complete custom-lit
(Lambert diffuse) surface with no PBR:
```wgsl
// @domain: surface
#include "@builtin::shaderModules.shadows" // exposes compute_directional_shadow_factor
fn fragment(input: FragmentData) -> vec4<f32> {
let n = normalize(input.world_normal);
let albedo = material.base_color.rgb;
// Directional (sun) light: Lambert N·L, attenuated by its shadow.
let sun = normalize(-input.light_direction); // surface -> sun
let sun_shadow = compute_directional_shadow_factor(input.world_position, n, input.light_direction);
var lit = input.light_color * input.light_intensity * max(dot(n, sun), 0.0) * sun_shadow;
// Point + spot lights (the punctual-light array, varying length).
for (var i = 0u; i < uniforms.point_light_count; i = i + 1u) {
let pl = zero_point_light(i);
let to_light = pl.position - input.world_position;
let dist = length(to_light);
let l = to_light / max(dist, 1e-4);
let atten = max(1.0 - dist / max(pl.radius, 1e-4), 0.0);
lit += pl.color * pl.intensity * max(dot(n, l), 0.0) * atten;
}
// Ambient fill.
lit += input.ambient_color * input.ambient_intensity;
return vec4<f32>(albedo * lit, material.base_color.a);
}
```
- **Unlit:** skip the lights and return your colour directly.
- **Toon / PS1 / custom:** start from the loop above and band, quantize, or warp
it however you like.
- **PBR:** build a `PbrSurface` and call `zero_pbr_shade` (see "Library includes")
instead of writing the BRDF by hand.
## Material properties — `properties.yaml`
A surface shader declares its material properties in a sibling `properties.yaml`.
The engine GENERATES the entire group(1) interface from it — the uniform struct
(`material.<name>`) plus a texture/sampler pair per declared texture. You write
no `@group`/`@binding` lines.
```yaml
properties:
- { name: base_color, type: color, default: [1, 1, 1, 1] }
- { name: roughness, type: float, default: 0.5, min: 0, max: 1 }
- { name: metallic, type: float, default: 0.0, min: 0, max: 1 }
- { name: emissive, type: color, default: [0, 0, 0, 1] }
- { name: base_color_texture, type: texture, default: white }
- { name: normal_texture, type: texture, default: flat_normal }
```
| `type` | WGSL field type | Notes |
|---|---|---|
| `float` | `f32` | optional `min`/`max` for editor sliders |
| `float2`/`float3`/`float4` | `vec2/3/4<f32>` | |
| `color` | `vec4<f32>` | sRGB colour, default is `[r,g,b,a]` |
| `int` | `i32` | |
| `bool` | `u32` | |
| `texture` | `texture_2d<f32>` + `sampler` | `default:` is a built-in texture name (`white`, `black`, `flat_normal`) |
In the shader you read scalars as `material.<name>` and sample textures as
`textureSample(<name>, <name>_sampler, uv)`. A texture slot with no bound texture
samples its default, so a shader can always sample — no presence flag needed.
`vertex()` reads the same material interface, so a height or deformation map
drives displacement from the slot it was bound to. A vertex stage has no implicit
derivatives, so sample it at an explicit mip there:
`textureSampleLevel(<name>, <name>_sampler, uv, 0.0)`.
## Sky shaders
A `// @domain: sky` shader draws the sky as a fullscreen pass. You write **only**
`fn fragment(in: SkyInput) -> vec4<f32>` — the colour along the view ray for each
pixel — and declare tunables in `properties.yaml` exactly like a surface shader
(read as `material.<name>`, textures via `textureSample(<name>, <name>_sampler, uv)`).
The engine generates the fullscreen `vs_main`/`fs_main`, the group(1) interface,
and reconstructs the world-space ray; there is no separate sky renderer — a sky
material runs through the same material pipeline, just on a fullscreen triangle.
A sky pipeline binds group(0) and the group(1) interface alone, so a sky that
reads a `buffer` property or any other `@group(2)` binding fails to compile, and
the error names the binding and the calls that reach it.
`SkyInput` (the only argument) carries:
| Field | Type | Meaning |
|---|---|---|
| `ray_dir` | `vec3<f32>` | normalized world-space ray through this pixel |
| `ndc` | `vec2<f32>` | screen position in NDC `[-1, 1]` |
| `sun_direction` | `vec3<f32>` | unit vector TOWARD the sun (from the directional light) |
| `camera_pos` | `vec3<f32>` | world-space camera position |
| `time` | `f32` | gameplay seconds: advances with the world at `engine.timeScale` and stands still while gameplay is paused (edit mode starts paused), so an effect slows and stops with the world |
```wgsl
// @domain: sky
fn fragment(in: SkyInput) -> vec4<f32> {
let up = max(in.ray_dir.y, 0.0);
let col = mix(material.horizon_color.rgb, material.zenith_color.rgb, up);
return vec4<f32>(col * material.exposure, 1.0);
}
```
Day/night comes from `sun_direction.y` (the directional light's elevation), so a
sky shader never needs a time-of-day uniform — orient the light and the sky
follows. The builtin sky shaders (`procedural_sky`, `solid_sky`, `cubemap_sky`,
`equirect_sky`) are all authored this way; author a custom sky material and point
a `Skybox` component at it.
## Post-process & screen shaders
`// @domain: post-process` and `// @domain: screen` shaders are authored exactly
like surface and sky — you write **only** `fn fragment(in: PostInput) -> vec4<f32>`
(post) or `fn fragment(in: ScreenInput) -> vec4<f32>` (screen) and declare tunables
in `properties.yaml` (read as `material.<name>`, textures via
`textureSample(<name>, <name>_sampler, uv)`). The engine generates the fullscreen
`vs_main`/`fs_main` and the group(1) material interface. **There are no
`uniforms.params[i]` slots** — that convention is retired; every input is a named
property.
A **post-process** shader's `properties.yaml` carries one further, top-level key
beside `properties:` — `space`, either `light` (the default) or `display`:
```yaml
space: display
properties:
- { name: amount, type: float, default: 1.0, min: 0, max: 1 }
```
`light` is the scene's linear radiance — what every surface, the sky and every
`afterLighting` feature write, unbounded above 1.0. `display` is the code values
the `__display__` pass leaves behind after applying exposure and its tone curve
— the 0-1 range a colourist's tool and a dithered or quantized effect expect.
`postprocess.add`'s `opts.space` overrides what the asset declares for one
registration. The chain converts at both ends of an effect that runs on a
segment in the other space, so a light-space vignette still darkens a frame
graded after `__display__`, and a lookup table built from a `.cube` export
always sees the code values it was authored against, wherever the chain
runs it.
`space` also decides which layer a registration that names none lands on: a
`light` shader grades `scene`, the segment holding the scene's own light, and a
`display` shader grades `all`, the picture after `__display__` with the UI on
it. So `postprocess.add("glow", asset.resolve("~.shaders.bloom", "shader"))`
thresholds highlights that still stand above 1.0, and a lookup table registered
the same way reads the code values it was built for. `opts.layer` names one
explicitly — `"all"` is what an effect that must grade the interface says.
A **post-process** shader's `properties.yaml` carries a further, optional
top-level key — `passes:`, the pass list the frame draws through, in order:
```yaml
space: light
passes:
- { name: bright, entry: bright, scale: 0.5, inputs: [scene] }
- { name: down1, entry: downsample, scale: 0.25, inputs: [bright] }
- { name: up0, entry: upsample, scale: 0.5, inputs: [down1, bright] }
- { name: composite, entry: composite, inputs: [scene, up0] }
```
Every pass's entry — `fn <entry>(in: PostInput) -> vec4<f32>` — lives in the
one `shader.wgsl` the assetType recompiles on. `scale` is the fraction of the
view a pass draws at; the LAST pass takes none, since it draws at the view's
size and writes the chain's output. `inputs` names what a pass reads —
`"scene"`, the chain's input for this effect, or the name of an EARLIER pass —
and `inputs[0]` is what `zero_sample_scene(uv)` reads inside that pass's body;
every input, `inputs[0]` included, is also reachable by index through
`zero_pass_input(i, uv)` and `zero_pass_input_size(i)`, below. The one place
the two reads of `inputs[0]` disagree: in an effect whose declared space
differs from the segment it draws on, `zero_sample_scene` converts a `scene`
input into that space while `zero_pass_input(0, uv)` hands back the segment's
own, unconverted value. A shader declaring no `passes:` is one pass whose
entry is `fragment`, and its generated WGSL is byte-identical to what it is
without the key.
A pass that is not the last writes a scratch target the effect owns — in the
space the shader declared, view-sized times its own `scale` — allocated on the
first draw and replaced whenever the size changes. `engine.params`, below,
carries the drawing pass's own index, its scale, and its first input's texel
size, so one shader body serves every level of a chain built this way.
The worked example is the bloom: `@builtin::shaders.post.bloom` declares
twelve passes — a threshold pass, five downsamples, five tent upsamples and a
composite — out of four entries, since the five downsamples share one and the
five upsamples share another, each level reading the one below it through
`zero_pass_input` and telling itself apart by `engine.params`. Its own README
walks the declaration.
A declaration is refused at compile time — reported through `compileStatus()`,
`postprocess.add`'s second return value, or a live effect's
`status()[i].error` — for: an entry `passes:` names that `shader.wgsl` does
not define; an input naming a later pass, or naming neither `scene` nor an
earlier pass; a `scale` outside `(0, 1]`; a `scale` declared on the last pass;
a `buffer` property (group(2) carries the pass inputs); or a shader whose
group(0) plus declared texture slots plus widest pass's inputs ask for more
than the 16 FRAGMENT sampled textures one shader stage has.
A **post-process** shader runs as a full-screen pass over the already-rendered
frame. Its `fragment` argument and framework helpers:
`PostInput`:
| Field | Type | Meaning |
|---|---|---|
| `frag_coord` | `vec4<f32>` | framebuffer pixel coords (`@builtin(position)`) |
| `uv` | `vec2<f32>` | screen UV, `(0,0)` top-left … `(1,1)` bottom-right |
Framework helpers (always in scope — no include needed):
| Call | Returns | Meaning |
|---|---|---|
| `zero_sample_scene(uv)` | `vec4<f32>` | the rendered scene colour at `uv`, converted into the space this effect declared (`zero_scene_light` is the same call, for content that reads it by that name) |
| `zero_scene_depth(uv: vec2<f32>)` | `f32` | scene depth at `uv` — a screen UV here, where the surface domain's `zero::scene_depth` module takes a pixel coordinate under the same name (exact texel — an R32Float copy). Reversed: 1.0 is the near plane, 0.0 the far plane and empty sky, so a nearer surface reads GREATER and `d > 0.0` means "a surface was drawn here" |
| `zero_linear_depth(d, near, far)` | `f32` | that sample as a distance in metres — the one inversion of the reversed range |
| `zero_scene_motion(uv)` | `vec2<f32>` | per-pixel screen-space motion vector at `uv` |
| `zero_pass_input(i, uv)` | `vec4<f32>` | the pass's declared input `i`, at `uv`. Input 0 is what `zero_sample_scene` reads |
| `zero_pass_input_size(i)` | `vec2<f32>` | that input's size in texels, so one entry serves every level of a chain |
Engine data uniform `engine` (a `PostEngineData`):
| Field | Type | Meaning |
|---|---|---|
| `resolution` | `vec4<f32>` | `x`=width, `y`=height, `z`=1/width, `w`=1/height |
| `time` | `vec4<f32>` | `x`=elapsed seconds, `y`=dt, `z`=frame index |
| `view_proj` | `mat4x4<f32>` | this frame's view-projection |
| `prev_view_proj` | `mat4x4<f32>` | last frame's view-projection (motion) |
| `inv_view_proj` | `mat4x4<f32>` | inverse view-projection (world-space reconstruction) |
| `params` | `vec4<f32>` | `x`=this pass's own index, `y`=the scale it draws at, `zw`=1/size of its first input — for a pass the post-process chain draws. A pass a `renderFeature` fragment pass draws carries that feature's `spec.params` here instead; a shader declaring `passes:` is always drawn by the chain, so the two never meet in one shader. |
The engine fills all of it **per render target**. A registered effect runs over
the live viewport's frame AND over every offscreen one — a `capture` from a
world-space station or orbiting an entity, a capture of a named camera, a
render-to-texture camera — and in each of those, `view_proj`, `prev_view_proj`
and `inv_view_proj` are the camera THAT render was drawn from, while
`resolution` is that target's own pixel size. So a pass reconstructing world
space from `zero_scene_depth(uv)` reconstructs against the station and lens the
capture asked for, and an offscreen frame is a picture of the effect as it
stands at that station. (A render feature's passes reach an offscreen render the
same way, against the same camera — the `renderFeature` assetType README carries
that half, including `@frame.camera`, its own per-target camera input.)
An offscreen render keeps no view history of its own, so `prev_view_proj` there
holds that same matrix rather than the frame before it, and a pass taking camera
motion from the two reads none. On the viewport the pair is a frame apart, so
camera motion is the one reading a capture answers differently from the screen.
`postProcessing = false` on a capture is the one control that takes the chain
off the frame it returns; it names the camera property the ephemeral capture
camera is built with, so it scopes to that one capture. What a capture opts out
of is the registered effects; `__display__` still runs on it, so the exposure
and tone curve that turn the scene's light into a picture are on what a capture
returns.
A diagnostic capture (`albedo`, `normal`, `motion_vectors`, …) bypasses
`__display__` itself, since a channel like that is a reading of the scene
rather than a graded picture of it. The environment-cube capture bypasses it
too, and for the same reason: a probe face carries radiance into the cube
array, and `__display__` would fit that radiance to a display's code values —
a picture of it rather than the value the PBR indirect term multiplies into
its lighting.
A complete post-process effect — a vignette via `fragment()` + `properties.yaml`:
`properties.yaml`:
```yaml
properties:
- { name: intensity, type: float, default: 0.5, min: 0, max: 1 }
- { name: radius, type: float, default: 0.75, min: 0, max: 1 }
- { name: softness, type: float, default: 0.45, min: 0, max: 1 }
```
`shader.wgsl`:
```wgsl
// @domain: post-process
fn fragment(in: PostInput) -> vec4<f32> {
let color = zero_sample_scene(in.uv);
let intensity = max(material.intensity, 0.01);
let radius = max(material.radius, 0.01);
let softness = max(material.softness, 0.01);
let center = in.uv - vec2<f32>(0.5);
let dist = length(center);
let vignette = smoothstep(radius, radius - softness, dist);
let darkened = color.rgb * mix(vec3<f32>(1.0), vec3<f32>(vignette), intensity);
return vec4<f32>(darkened, color.a);
}
```
The asset above **defines** the effect. It enters the frame when something
registers it:
```luau
postprocess.add("vignette", asset.resolve("~.shaders.vignette", "shader"), { priority = 200 })
```
The registration names no layer, so the effect grades the layer its `space`
belongs to: this vignette reads light, so it runs on `scene`, over the picture
before the UI reaches it. Registering it is the one step that makes it render,
so a world's chain holds exactly the passes its content asked for. Editing the shader body afterwards
recompiles every effect registered from it, in place — the pass keeps its enabled
state, priority, layer, tuned property values and bound textures, and draws the
new pixels on the next frame. `postprocess.remove(name)` takes it back out of the
chain and leaves the asset alone.
Drive the named properties at runtime with `postprocess.setProperty(name, prop,
value)` and bind texture properties with `postprocess.setTexture(name, prop, path)`
(both keyed by the **property name**, never a slot index — see the post-process
section of `man shaders` / the `postprocess.*` API).
Read them back with `postprocess.describe(name)`: it carries the chain state
`postprocess.status()` lists for that effect, the `properties` schema it was
registered with, and the `values` each of those properties currently holds. Before
the effect exists, `shaderRef:getProperties()` on the asset names the same schema,
so what a pass takes is answerable either side of the registration.
A **screen** shader is a standalone full-screen visual (UI background, procedural
pattern). `ScreenInput` mirrors `PostInput` (`frag_coord` + `uv`); there is no scene
to sample, so it has no `zero_sample_scene` helpers. Its `engine` uniform is a
`ScreenEngineData`:
| Field | Type | Meaning |
|---|---|---|
| `time` | `f32` | gameplay seconds: advances with the world at `engine.timeScale` and stands still while gameplay is paused (edit mode starts paused), so an effect slows and stops with the world |
| `scroll` | `f32` | UI scroll offset |
| `resolution` | `vec2<f32>` | render-target size in pixels |
| `mouse` | `vec2<f32>` | mouse position |
| `velocity` | `f32` | scroll velocity |
```wgsl
// @domain: screen
fn fragment(in: ScreenInput) -> vec4<f32> {
let t = engine.time * 0.5;
let col = vec3<f32>(
sin(in.uv.x * 3.14159 + t) * 0.5 + 0.5,
sin(in.uv.y * 3.14159 + t * 0.7) * 0.5 + 0.5,
material.brightness
);
return vec4<f32>(col, 1.0);
}
```
## Library includes
A library module is a **`.shaderModule` asset**: it only EXPOSES functions and
structs and does nothing on its own (exactly like a Unity `.cginc`). You must
call what you include. Include one by its identity, the same string you would
hand `asset.resolve`:
| Include | Exposes |
|---|---|
| `@builtin::shaderModules.pbr_shading` | `struct PbrSurface { albedo, normal (world), metallic, perceptual_roughness, emissive, occlusion }`; `zero_pbr_default_surface(FragmentData) -> PbrSurface`; `zero_pbr_shade(FragmentData, PbrSurface) -> vec3<f32>` (the full forward PBR lighting) |
| `@builtin::shaderModules.shadows` | `compute_directional_shadow_factor(...)`, `compute_spot_shadow_factor(...)`, `compute_point_shadow_factor(...)`, `compute_area_shadow_factor(...)`, `compute_punctual_shadow_factor(...)`, `zshadow_light_reach(...)` |
| `@builtin::shaderModules.engine_bindings` | the group(0) declarations (camera, transforms, lights, shadow maps) — surface shaders get this implicitly; include it directly only for advanced raw access |
| `@builtin::shaderModules.shadow_bias` | `zshadow_offset_receiver(...)`, `zshadow_directional_depth_bias(...)` and the rest of the bias math, as pure functions |
| `@builtin::shaderModules.texturing` | `ztex_stochastic(...)` (tile without a visible repeat grid), `ztex_blend_normals(...)` (reoriented normal blending) |
| `@builtin::shaderModules.depth` | `zero_linear_depth(depth, near, far)` — the one reading of a stored depth |
| `@builtin::shaderModules.gbuffer_material` (`zero::gbuffer_material`) | `struct ZeroGbufferMaterial { base_color, metallic, perceptual_roughness }`; `zero_gbuffer_unpack_material(texel: vec4<u32>) -> ZeroGbufferMaterial`; `zero_gbuffer_material(t: texture_2d<u32>, coord: vec2<i32>) -> ZeroGbufferMaterial`, `zero_gbuffer_base_color`/`zero_gbuffer_metallic`/`zero_gbuffer_roughness(t, coord)` — the one unpacking of `@scene.material`'s `Rgba8Uint` texel into what a surface reflects |
| `zero::scene_depth` | `zero_scene_depth(px: vec2<f32>)`, `zero_scene_depth_uv(uv: vec2<f32>)`, `zero_scene_depth_texel(px: vec2<i32>)`, `zero_scene_depth_size()`, `zero_scene_depth_is_sky(d: f32)`, `zero_scene_world_position(px: vec2<f32>)`, `zero_scene_world_normal(px: vec2<f32>)`, `zero_scene_depth_fade(px: vec2<f32>, world_position: vec3<f32>, fade_distance: f32)` — every `px` is a pixel coordinate in two components, so a surface fragment passes `input.frag_coord.xy`, not the `vec4<f32>` `FragmentData.frag_coord` holds. The depth already drawn UNDER a surface fragment, and the world position and geometric normal of the surface standing there. What a decal projector box, a soft particle, a forcefield or water intersection foam shades against. Surface domain; the depth belongs to the view being drawn |
| `zero::scene_color` | `zero_scene_color(px: vec2<f32>)`, `zero_scene_color_uv(uv: vec2<f32>)`, `zero_scene_color_texel(px: vec2<i32>)`, `zero_scene_color_size()`, `zero_scene_color_refract(px: vec2<f32>, offset_px: vec2<f32>)`, `zero_scene_color_refract_uv(px: vec2<f32>, offset_fraction: vec2<f32>)` — every `px` is a pixel coordinate in two components, so a surface fragment passes `input.frag_coord.xy`, not the `vec4<f32>` `FragmentData.frag_coord` holds. The scene colour already composed BEHIND a surface fragment, and the displaced read that bends it. What heat haze, a refraction shockwave, a cloaking or shield warp, glass and ice shade with. Surface domain; the colour belongs to the view being drawn, and is the lit opaque scene as it stood immediately before the transparent pass — so a `blend`-queue surface reads this frame's, an opaque one reads the previous frame's, and two overlapping blended surfaces both read the same picture and do not bend each other |
`asset.list("shaderModule")` enumerates the `.shaderModule` assets in this
engine, builtin and world-authored alike, and each one's README says what it
exposes. Those are the `@builtin::shaderModules.*` rows above; a module you
write is included exactly the same way, by its own identity or by the
`~.name` form.
The `zero::`-named rows come from the renderer itself. Their WGSL is baked into
the engine binary and registered under those names before any asset exists, so
they answer an `#include` in every engine and appear in no asset index. A shader
that includes one records no dependency on it: the engine reading the shader is
the engine that already holds the module.
Two spellings reach the same `.shaderModule`: a module's declared alias
answers as well as its identity, so a shader written against `zero::pbr`
compiles and pins the asset that name resolves to. Prefer the identity: it
says which asset travels with the content.
Whichever punctuation an include is written with — `#include "name"`,
`#include 'name'` or `#include <name>` — names the same module and records the
same dependency.
The engine's own scaffolding — `zero::surface`, `zero::sky`, `zero::post`,
`zero::screen` — is injected by the compiler around the matching domain and is
never written by hand. The surface framework puts `safe_normalize`,
`mat3_from_mat4` and `apply_normal_map(FragmentData, tangent_normal)` in scope
for every surface shader.
## Shader features — compile-time variants
A **property** is runtime uniform data (a colour, a float, a texture): set per
material, read as `material.<name>`, no recompile. A **feature** decides which
code is in the program at all. Use a property when the value changes at runtime,
a feature when it changes what the shader is.
Declare features in `properties.yaml`, alongside the properties:
```yaml
properties:
- { name: base_color, type: color, default: [1, 1, 1, 1] }
features:
- { name: PARALLAX, default: false, description: silhouette parallax march }
- { name: DETAIL, default: true, description: detail-normal overlay }
```
Guard the code each feature owns with `#ifdef`:
```wgsl
fn surface(input: FragmentData) -> PbrSurface {
var s = zero_pbr_default_surface(input);
#ifdef PARALLAX
s.normal = parallax_normal(input); // absent when PARALLAX is off
#else
s.normal = input.world_normal;
#endif
return s;
}
```
`#ifdef` / `#ifndef` / `#else` / `#endif`, one per line, and they nest. The
directives resolve before the WGSL reaches the compiler, so the program holds
exactly the lines its feature set selected and every other line is an empty one,
which keeps a compiler message on the line number the file shows. An unbalanced
block is a compile error naming its line.
A material is what chooses a feature set, so `features:` shapes the shaders a
material draws with — the surface, sky and screen-space domains.
A material names the features it wants in its `mat.yaml`:
```yaml
name: worn_rock
shader: "@builtin::shaders.pbr_layered"
features:
PARALLAX: true # on, over the shader's default
DETAIL: false # off, against the shader's default
```
or through `asset.create`:
```lua
asset.create("material", "worn_rock", {
shader = "@builtin::shaders.pbr_layered",
features = { PARALLAX = true, DETAIL = false },
})
```
### A property that switches a feature on
A feature can also be switched on by a material's property values. List the
properties under the feature's `properties:`, and the feature is on for every
material whose value for one of them stands away from that property's declared
default:
```yaml
properties:
- { name: clearcoat, type: range, default: 0.0, min: 0, max: 1 }
features:
- { name: CLEARCOAT, properties: [clearcoat], description: the coat lobe }
```
```wgsl
#ifdef CLEARCOAT
s.clearcoat = material.clearcoat;
#endif
```
A material at `clearcoat: 0` draws a program holding none of the coat's code; one
that sets `clearcoat: 0.6`, in its `mat.yaml`, through `asset.create` or with
`renderer.material.setProperty`, draws the `CLEARCOAT` variant, and setting it
back to 0 returns it to the base program. The property stays a runtime value the
program reads; the feature decides only whether the code reading it is there.
This is how a shader with costly optional parts keeps every material that leaves
them at rest on the cheap program without each material having to name a
feature. A material naming the feature off under `features:` keeps it off
whatever the property holds. Write the guarded code so that, with the feature
off, the shader computes what it would with the property at its default: the
material sees one look either way, and pays for the part only where it shows.
Each distinct set of switched-on features is a program to compile the first time
a material reaches it. A material keeps the programs its values switched it onto
compiled while it lives, so a property crossing back and forth reuses them; when
the shader's variant budget is spent, the ones no material draws with are given
back first. A `properties:` entry is a value property (`float`, `range`, `int`,
`bool`, `color`, `float2` to `float4`) the shader declares; one naming no declared
property, or a texture or buffer, is refused by name.
The engine compiles one program per feature set its materials ask for, named
`<shader>#<features>`. Materials sharing a set share that program. A feature the
shader does not declare selects nothing, so a stray name cannot make the engine
compile anything, and the compile names both halves of a mismatch: a guard on a
name `features:` does not declare, and a declared name no guard tests.
**Permutations are the cost.** A shader with n features can express 2^n
programs, each its own compile and pipeline. One shader holds at most 32
variants; a material asking for a set past that draws with the shader's default
features and the engine logs which shader ran out. Read what a scene is
spending:
```lua
for _, s in renderer.shaderVariants() do
print(s.shader, #s.variants, "of", s.budget)
print(renderer.variantSource(s.base.program)) -- what it ships as
for _, v in s.variants do
print(v.program, renderer.variantSource(v.program)) -- what one asked for
end
end
```
A shader registers under every key it answers to — its identity, its guid, each
alias — and each key is a row. A variant lands on the row for the key the
material named, which for authored content is the guid, so take a program name
from the report rather than composing one.
## Materials reference shaders
A `.material` applies a shader to entities. Its `mat.yaml` references the shader by
its identity string and supplies property values:
```yaml
name: my_material
shader: "@builtin::shaders.pbr"
render:
blend: alphaBlend
cull: back
depth_write: false
properties:
roughness: 0.5
base_color: [1.0, 1.0, 1.0, 1.0]
textures:
base_color_texture: { ref: "default:white" }
```
`shader:` is a plain identity string, and a colour is an array. A key's
value is the rest of its line, so every value above stands alone on one.
### The render block
Render behaviour (the blend equation, alpha
cutout, which faces are drawn) lives in the `render:` block and drives the
pipeline, not the fragment. These are the keys that reach the pipeline from both
authoring routes, and the values each one takes:
| Key | Values | Sets |
|-----|--------|------|
| `blend` | `opaque` `transparent` `alpha` `alphaBlend` `additive` `add` `cutout` `alphaCutout` `premultiplied` `premultipliedAlpha` `multiply` | the equation the fragment composites with |
| `cull` | `back` `front` `none` `off` `disabled` | which faces the rasterizer keeps |
| `depth_write` | `true` `false` | whether the draw writes depth |
| `depth_compare` | `less` `lessEqual` `lequal` `equal` `greater` `greaterEqual` `gequal` `always` `never` | the test a fragment's depth passes |
| `topology` | `triangleList` `lineList` `lines` `line` | what consecutive vertices assemble into |
| `queue` | a whole number: `2000` opaque, `3000` transparent, `4000` overlay | the draw order of the material; a number inside a queue orders within it |
`blend` is also spelled `type`, and the two name one key. Its equations, over
the fragment the shader returned (`src`) and the value already in the target
(`dst`): `opaque` is `src`; `transparent`, `alpha` and `alphaBlend` are
`src * src.a + dst * (1 - src.a)`; `additive` and `add` are `src + dst`, the
mode a glow, a light shaft or a spark card is written for; `premultiplied` and
`premultipliedAlpha` are `src + dst * (1 - src.a)`, taking a source that already
carries its own coverage; `multiply` is `src * dst`, which is how a soot, grime
or shadow card darkens what stands behind it. `cutout` and `alphaCutout` keep
the fragment or discard it on its alpha and go on writing depth.
The same block is what `asset.create`'s `render` argument takes, key for key and
value for value, so one material named in Luau and the same material standing on
disk ask for their pipeline with the same words. `depth_write` is the one key
whose value takes the shape of its route: the word `false` on a `mat.yaml` line,
the boolean `false` in the Luau table.
```lua
asset.create("material", "heat_plume", {
shader = "@builtin::shaders.pbr",
render = { blend = "alphaBlend", cull = "none", depth_write = false },
})
```
Where a value outside a key's set is reported is what the two routes differ on.
`asset.create` refuses the call on any of these keys and names the set it
measured the value against, or for `queue`, that it takes a number. A
`mat.yaml` standing on disk registers either way, each key falling back to a
value of its own: `blend` to `opaque`, `cull` to `back`, `depth_write` to
`true`, `depth_compare` to `less`, `topology` to `triangleList` and `queue` to
`2000`. The engine log carries the blend fallback, naming the value and
the set it was measured against, so a `mat.yaml` value is worth putting through
`asset.create` once — that is where every key answers with its set.
## Registration & hot reload
A `.shader` is compiled by the asset system, not by the renderer: writing
`shader.wgsl` or `properties.yaml` fires the `.shader` assetType's `onChange`,
which compiles it: the body + the property schema are read, the group(1)
interface and (for surface) every render-mode entry point are generated,
`#include`s are expanded, the result is **validated**, and the shader is
registered. Validation
happens at this compile step — the whole point of "compile". A shader with invalid
WGSL (an unknown field, a type mismatch, an undefined function) **fails to compile**
with the real reason — readable directly from Luau via
`shaderRef:compileStatus()` (`{ status = "compiled" | "failed" | "pending",
error?, pending? }`), and also in the author log and `asset.inspect`; it is **not**
registered. This fires on create and on every edit, so saving a `.wgsl` recompiles
with no world reload; the change is visible on the next frame. Compilation is
async, so a `compileStatus()` of `"pending"` immediately after a write means check
again next frame.
A surface shader is also checked for the material resolve, the pass that
shades each pixel of the visibility buffer through the shader's own code. That
check reaches its verdict a few frames after the raster compile. Until it
does, `compileStatus()` reads `"pending"` with `pending` saying so, and the
shader already draws. A shader the check refuses reads `"failed"`, and `error`
names the construct the resolve cannot evaluate and where it sits; its pixels
resolve through the error shader until it changes.
The stage the compile checks comes from one of two places: the hook the engine
scaffolds entry points around (`fragment()`, or `surface()` for an engine-lit
surface), or the `vs_main` / `fs_main` pair the body writes itself. The pair is
a pair: a body that writes its own entry points owes both stages. A body
carrying neither route — a hook whose name is a letter off, say, or half a pair
— holds no stage the rasterizer can enter, so the compile **refuses it** and
names both the entry point it looked for and what the body carries, in the same
`compileStatus()` error every other compile failure reads back through.
### Reading a compile error against the text it is about
What the compiler reads is not the file you wrote. The engine generates the
group(1) material interface from `properties.yaml`, wraps the body in its
domain's framework and every entry point that domain needs, expands every
`#include`, and resolves every `#ifdef` — so a 100-line body reaches naga as
tens of thousands of lines. **Every line number in a compile error, and every
`[N]` handle index naga prints where it has no name to print, is a position in
that composed module.** A fault at module scope (`no definition in scope for
identifier: 'zero_scene_depth'`) reads fine without it; a fault inside a
function body does not.
`renderer.compiledSource(name)` returns that composed module, and
`shaderRef:compiledWgsl()` returns it for a ref you already hold. Both answer
for a shader that declares no features, needs no material, entity or draw, and —
the case they exist for — **answer for a shader whose compile failed**, holding
the text the compiler was refused over for as long as `compileStatus()` reports
that failure. `renderer.compiledShaders()` lists every name they answer for.
```lua
local ref = asset.resolve("myShader", "shader")
local status = ref:compileStatus()
if status.status == "failed" then
print(status.error) -- the line, the caret, and the cause
local wgsl = ref:compiledWgsl() -- the text those positions are in
local line = tonumber(string.match(status.error, "wgsl:(%d+):"))
print(string.split(wgsl, "\n")[line])
end
```
The composed text carries every `zero::*` module the shader included, so the
signature a call was rejected against is in the same text as the rejection —
which is the whole of what a "wrong argument type" error needs to be actionable.
A material bound to a broken (or missing) shader renders with the **magenta error
shader** — never invisibly — so a shader problem is impossible to miss on screen as
well as in the log. **Fixing the shader and re-saving recovers it live**, with no
engine restart: the recompile clears the failed-shader state and the object returns
to normal on the next frame.
## Discovery
- `asset.list("shader")` — every registered shader.
- `asset.inspect("<name>")` — domain, status, source, parse errors, this README.
- `shaderRef:compileStatus()` — did it compile? `{ status, error?, pending? }`, no
log needed. `"pending"` with `pending` set means the material resolve check
is still reaching its verdict; a resolve refusal reads as `"failed"`.
- `shaderRef:compiledWgsl()` / `renderer.compiledSource("<name>")` — the WGSL the
compiler received, which is what a compile error's positions index into.
Answers for a failed compile too.
- `renderer.compiledShaders()` — every name that call answers for.
- `shaderRef:getProperties()` — the parsed `properties.yaml` schema.
- `shaderRef:listMaterialsUsing()` — materials bound to this shader.
## Common pitfalls
- **A compile error shows up in one of three ways at the draw.** A shader that
never compiled has no pipeline, so the renderer binds the magenta placeholder.
A shader that compiled once and was then edited into brokenness KEEPS the
pipeline that build produced — the surface goes on drawing the last good
program, pixel for pixel, and looks entirely intact while the source is broken.
A geometry-pass-only shader has no magenta tell either, since it is not on a
forward mesh. `shaderRef:compileStatus()` gives the status + error text (as
does `asset.inspect("<name>")`), and `renderer.drawDiagnostics()` names which
renderables are in which of the three states — a row carries `substituted` for
the placeholder, `stale` for a program that no longer compiles, and the cause
either way.
- **A compile error's line numbers are lines of the composed module, not of your
file.** `renderer.compiledSource("<name>")` / `shaderRef:compiledWgsl()` is
that module; resolve the position against it rather than counting lines in
`shader.wgsl`. The `[N]` a message prints in place of a name is a naga handle
index — it moves with the size of the body and is the same value for two
unrelated faults in one file, so it is neither a line number nor a way to tell
two failures apart.
- **Don't declare group(0) or group(1) in a surface shader.** The engine owns
group(0) and generates group(1) from `properties.yaml`. Re-declaring them is the
fastest way to a layout mismatch.
- **`#include` does nothing by itself** — it only exposes functions; you must call
them.
- **Renaming a property** changes the generated uniform field; materials setting the
old name silently fall back to its default.
- **Compute shaders don't render** — verify output via a buffer readback or a
debug pass. Author them as a `.computeShader` (its own assetType), not a
`.shader` — see `man compute`.
## Related types
- `.material` — the required wrapper that applies a shader to entities.
- `.style` — UI cascade, not GPU shaders.
## In the Inspector
Selecting a shader opens its **Shader** section: its domain and shading model (and, for a post-process shader, the space its `fragment()` reads and returns), whether it compiled (and the compiler's error when it did not), a table of its declared properties (type, default, range), its post-process passes when it has any, the bindings it declares, and openers for its source. The **Materials** section (collapsed at first) has a Find materials action that lists, as links, every material drawing with the shader; it scans every material, so it runs only when asked.
▲ -1↑ born
backing path · assetTypes/computeShader.assetType
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