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asset⌬ modulemoduleprimary: init.luau·part ofpackage deprecatedParticles.package·originates fromworld 07158574-5…●3problems

engine

Deprecated.** This belongs to the earlier particle substrate. It stays loadable by identity and guid for content that already uses it; nothing new should use it, and search does not offer it. Particles are procgen sim nodes (`sim.spawn`, `sim.particles`, `sim.shader`) played thro…

byzero-proxy @ DESKTOP-DB3UJOJ·posted 2mo ago

What it does

`modules.particles` — Generic GPU-driven Particle System (deprecated)

Deprecated. This belongs to the earlier particle substrate. It stays loadable by identity and guid for content that already uses it; nothing new should use it, and search does not offer it. Particles are procgen sim nodes (sim.spawn, sim.particles, sim.shader) played through an effect: use @builtin::assetTypes.effect.

A generic, GPU-driven particle substrate for VFX. Every active particle lives in a GPU storage buffer; physics runs entirely as a compute dispatch each frame; per-frame vertex output feeds the renderer directly via renderer.mesh.create — no CPU readback, no re-upload. Spawning happens on the CPU (cost bounded by the emission rate, not the active particle count) and writes new particle slots directly into the GPU state buffer.

It is the substrate behind the ParticleEmitter component but works equally well as a script-side API for hand-rolled effects, custom WGSL update shaders, and per-particle scripted state.

Quick start

local particles = require("@builtin::deprecated.deprecatedParticles.engine")
local NumberSequence = particles.NumberSequence
local ColorSequence = particles.ColorSequence

local fire = particles.create({
    maxCount = 2000,
    rate     = 120,                            -- particles/sec
    lifetime = { 0.8, 1.6 },
    speed    = { 1.5, 3.0 },
    shape    = { kind = "cone", size = {0.6, 1.2, 0.6}, partial = 0.4 },
    gravity  = { 0, 1.5, 0 },                  -- buoyant
    drag     = 0.4,
    size     = NumberSequence.new({
                  { time = 0,   value = 0.25 },
                  { time = 0.3, value = 0.7, envelope = 0.15 },
                  { time = 1,   value = 0.0 },
              }),
    color    = ColorSequence.new({1, 0.9, 0.3}, {1, 0.2, 0.05}),
    transparency = NumberSequence.new(0, 1),
    blendMode = "additive",
    brightness = 2.0,
})

-- Each frame, in your update tick:
fire:setOrigin(torch.position.x, torch.position.y, torch.position.z)
fire:update(dt)

For a declarative wrapper that lives on an entity, use the DeprecatedSimpleParticleEmitter component (deprecated/deprecatedParticles.package/DeprecatedSimpleParticleEmitter.component).

Why GPU-driven

	CPU per-particle	GPU per-particle
1 000 particles	OK	OK
10 000 particles	starts skipping frames	trivial
100 000 particles	impractical	trivial
1 000 000 particles	impossible	feasible on mid-tier GPU
Custom physics	per-particle Lua call	one WGSL update shader
Trail / mesh particles	extra CPU work	extra WGSL pass

The substrate also leapfrogs Roblox-class engines on the long list of features they can't offer in their CPU-only model: mesh particles, particle ↔ world collision, neighbour queries, custom force fields, curl noise.

Architecture

Storage buffers, per system

Every system holds its particle state and its params. What it holds beyond that depends on how it draws.

Buffer	Size	Written by	Read by
`<id>_state`	`maxCount * 64 B`	CPU spawn, GPU update	GPU update
`<id>_params`	1556 floats (~6 KB)	CPU each frame + on change	GPU update

A sprite emitter builds a quad per particle:

Buffer	Size	Written by	Read by
`<id>_verts`	`maxCount * 4 * 92 B` (GPU vertex buffer, carrying the per-particle channel in its tangent words)	GPU update	renderer, and the material's fragment stage
`<id>_indices`	`maxCount * 6 * 4 B` (GPU index buffer)	CPU once at create	renderer

The vertex + index buffers are created with vertex=true/index=true flags so renderer.mesh.create can wrap them as a renderable mesh with zero CPU copy. The renderer binds the same GPU allocation the compute shader just wrote to.

A mesh emitter uploads its source mesh once and draws it once per particle, so it holds a placement and a colour instead of geometry:

Buffer	Size	Written by	Read by
`<id>_xforms`	`maxCount * 64 B` (one column-major 4x4 per particle)	GPU update	renderer
`<id>_instdata`	`maxCount * 64 B` (four `vec4` shader-data lanes per particle)	GPU update	the material's fragment stage

Those two buffers are what renderer.mesh.drawInstanced reads: the matrices place each copy, and the lanes arrive in the fragment stage as input.shader_data[lane], which is how copies sharing one mesh and one material each keep their own colour. 100 000 cube particles (24 verts) hold 12.8 MB this way, against the 220 MB the same emitter would hold as replicated geometry.

What one particle carries into its material

A material a particle system draws with reads four numbers belonging to the particle covering the fragment — its life (normalised age, 0 → 1), its own seed in [0, 1] fixed for its whole life, the world-space size it is drawn at, and alive. Include the reader and take them off either emitter kind:

#include "@builtin::deprecated.deprecatedParticles.particle_data"

fn fragment(input: FragmentData) -> vec4<f32> {
    let p = particle_sprite_data(input);        // particle_mesh_data for a mesh emitter
    let flicker = 0.6 + 0.4 * sin(input.time * 8.0 + p.seed * 6.2831);
    return vec4<f32>(input.vertex_color.rgb * flicker, input.vertex_color.a * (1.0 - p.life));
}

A sprite emitter carries the four in the four words of each vertex the render pipeline reads as the tangent, a mesh emitter in the instance lane beside its colour, and particle_layout declares the order both compute passes pack. The seed is what lets a population vary out of unison: it differs between the particles of one emitter and reproduces for the same particle at any age, so a noise phase or an atlas frame chosen from it holds still while that particle lives. @builtin::deprecated.deprecatedParticles.fx.fx_noise takes it as a phase or an offset.

renderer.instanceData is the per-ENTITY channel: an emitter is one entity, so the lanes it sets there are shared by every particle the emitter draws.

Per-particle state (16 f32 = 64 bytes)

[0..2]  position (xyz)
[3]     age (seconds since spawn; >= lifetime means dead)
[4..6]  velocity (xyz)
[7]     lifetime (seconds)
[8..10] tint rgb (per-particle multiplicative tint; default 1)
[11]    base size (sampled at spawn)
[12]    rotation (degrees, current)
[13]    rot speed (degrees/sec)
[14]    per-particle seed in [0, 1] (used for envelope sampling)
[15]    reserved / user data

Params buffer layout

The first 32 floats are per-frame data; the next 32 are a user-controlled param block for custom WGSL update shaders; the next 4 × 49 floats are NumberSequence packs (size, transparency, squash, rotSpeed); the final 129 floats are the ColorSequence pack. See init.luau's PARAM_LAYOUT for the canonical offsets and particle_layout.shaderModule for the matching WGSL constants. Past the ColorSequence pack come the collision header, the collider records, and the grid a bound world distance field covers.

Frame loop

1. CPU: spawn pending particles  → writeBuffer on state buffer
2. CPU: pack per-frame uniforms  → writeBuffer (first 32 floats only) on params
3. GPU: dispatch update shader   → reads state, integrates, samples curves,
                                   and writes this particle's output: a sprite
                                   emitter's 4 vertices, or a mesh emitter's
                                   matrix + shader-data lanes; collapsed to
                                   nothing with area if dead
4. GPU: renderer draws the mesh — as an entity's model for a sprite emitter,
                                   as a population for a mesh emitter

Vertex buffer is rebuilt every frame from the latest particle state. Dead particles emit a zero-area quad that the rasterizer drops for sub-pixel cost. That quad sits on the particle's own position, and a slot that has never carried a particle holds the emitter's origin — the vertex buffer is part of the scene's geometry, so a pass that gathers it (a distance field, a bake, a BVH) covers an extent the emitter actually occupies.

Curves: NumberSequence + ColorSequence

-- constant
NumberSequence.new(1.0)

-- two-point lerp
NumberSequence.new(0, 1)

-- full keypoint table (up to 16 keypoints; envelope is ± range per keypoint)
NumberSequence.new({
    { time = 0,   value = 0.0 },
    { time = 0.3, value = 1.0, envelope = 0.2 },
    { time = 1,   value = 0.0 },
})

-- a number keypoint list also takes its entries written positionally
NumberSequence.new({ { 0, 0.0 }, { 0.3, 1.0, 0.2 }, { 1, 0.0 } })

ColorSequence.new({ 1, 0.5, 0 })             -- constant
ColorSequence.new({ 1, 0, 0 }, { 0, 0, 1 })  -- lerp
ColorSequence.new({
    { time = 0,   value = { 1, 1, 1 }, envelope = { 0.1, 0.0, 0.1 } },
    { time = 1,   value = { 0, 0, 0 } },
})

-- a keypoint list also takes its entries written positionally, and a list of
-- bare colours spreads its stops evenly across [0, 1]
ColorSequence.new({ { 0, { 1, 1, 1 } }, { 1, { 0, 0, 0 } } })
ColorSequence.new({ { 1, 0.85, 0.35 }, { 1, 0.35, 0.05 } })

Every field of a keypoint reaches the GPU pack as one float, so a time, value, channel or envelope that is not a number is refused by the constructor, naming the keypoint's index and the types it read. Both classes pack a fixed 16 stops: a longer list is resampled down to 16 keeping both endpoints, and the resample logs a warning naming the cap and how many stops it dropped.

Sampling:

seq:evaluate(t)                  -- deterministic
seq:sample(t)                    -- envelope-randomized (math.random under the hood)
seq:sample(t, seed)              -- envelope-randomized with a specific seed

The GPU shader samples each curve per particle per frame using the per-particle seed stored at state slot 14, so envelope randomness is deterministic across frames for a given particle and runs with no per-frame CPU cost.

Emission shapes

shape = {
    kind = "cone",          -- "point" / "box" / "sphere" / "cylinder" / "disc" / "cone"
    size = { x=1, y=1, z=1 },
    style = "volume",       -- "volume" | "surface"
    inOut = "outward",      -- "outward" | "inward" | "inandout"
    partial = 0,            -- shape-specific (hemisphere cap, annulus inner, taper)
    spreadAngle = 0,        -- cone broadening around the sampled direction, degrees
}

Sampling runs on the CPU at spawn time only — the cost is per emitted particle, not per active particle. Shapes are pure functions in shapes.module/init.luau.

Collision

An emitter meets things when collision names what a hit does — "bounce", "stop" or "kill" — and its collider list says what it can hit:

local sys = particles.create({
    rate = 400, lifetime = 6, speed = 0, gravity = { 0, -9.81, 0 },
    collision = "bounce", restitution = 0.3, friction = 0.4,
    colliders = {
        { kind = "world" },                                   -- the scene itself
        { kind = "sphere", position = { 0, 2, 0 }, radius = 1.5 },
    },
})

plane, sphere and box are shapes the emitter carries — eight at most, because they ride the params buffer the update shader already binds.

world is the scene's own geometry: terrain, stairs, a rock, anything nobody described as a shape. It reads the distance field sceneProxy builds — the same coarse volumetric stand-in long-range lighting queries use — so contact costs one texture read wherever a particle happens to be, on- or off-screen. The first emitter to ask for one builds it (worldResolution voxels per axis, 64 by default); after the scene changes, sceneProxy.refresh() rebuilds it and the emitter picks the new grid up on its next update.

Two things follow from the field being coarse: contact lands within about one voxel of the true surface — raise worldResolution or the collider's radius to place particles where you want them — and a particle that starts deep inside geometry has no direction to be pushed out along, so it is pushed up.

The field is unsigned — it says how far the nearest surface is, not which side of it a point is on — so the world collider resolves against the segment the particle travelled this frame rather than against where it ended up. The march starts from the position the particle held last frame, which the previous resolve left outside, and stops where that path first comes within radius of a surface. Contact therefore lands on the side the particle approached from, and a step of any length is caught rather than carrying the particle through.

The world collider is resolved by the built-in sprite update. A mesh emitter runs the mesh-instance update, which integrates without resolving colliders, so every collider it carries reports no contact. An emitter running its own WGSL binds no distance field, so the world collider reports no contact there while its other colliders resolve as that shader resolves them. Both are said out loud, once per emitter, the first time one runs.

Shadow casting and render layers

An emitter declares whether its particles block light and which render layers they draw on. Both reach the sprite path and the mesh path through the same value, so an emitter's kind decides neither one:

local debris = particles.create({
    mesh = "cube", maxCount = 300,
    castsShadows = true,
    renderLayer  = "vfx",
})

debris:setCastsShadows(false)
debris:setRenderLayer("vfx fpsWeapon")
print(debris:getRenderLayer())        -- "vfx fpsWeapon"
print(debris:observe().castsShadows)  -- false

castsShadows defaults to false. A caster is drawn into the shadow map as the geometry it is — a sprite emitter's quads as quads, a mesh emitter's copies as copies — so a soft alpha card casts the hard outline of its whole quad. That is right for debris, rubble and solid mesh copies, which declare it, and wrong for the smoke, dust and spark sheets that make up most of what an emitter draws, which leave it alone.

renderLayer takes a layer name, an array of names, or a space-separated string, and defaults to "default" — the layer a renderable with no layer of its own sits on. A camera or a capture whose include spec names the layer draws the emitter and one excluding it does not, so a reflection probe, a portal camera, a minimap, a clean screenshot or an agent's capture takes the scene with the effect in it or without:

capture({ renderLayers = "all !vfx" })   -- the scene, no emitters

Naming a layer interns it, which is what puts it in renderLayer.list and makes it addressable from a capture's include spec.

Both are readable back — :getCastsShadows(), :getRenderLayer() — and both are reported by observe(), so what an emitter declares is checkable without capturing a frame and without reaching for the render host.

Depth fade

A particle card that runs into a floor, a wall or a prop draws a straight line along the intersection, which is what makes a large soft sprite read as a flat billboard. depthFade is the distance, in world units, over which the card dissolves into that surface instead:

local smoke = particles.create({
    maxCount = 400, rate = 60, lifetime = { 2, 4 },
    size = NumberSequence.new(0.5, 3),
    depthFade = 1.5,          -- world units
})

smoke:setDepthFade(2.5)
print(smoke:getDepthFade())   -- 2.5
print(smoke:observe().depthFade)

The quantity the distance is compared against is the straight-line distance between a fragment and the surface already drawn behind it, both taken in world space — so the ramp covers the same number of metres however far the camera stands from it. A fragment at least depthFade in front of that surface keeps its alpha whole; one standing on the surface is fully transparent; and one with nothing behind it keeps its alpha, there being nothing to dissolve into.

The default is 0, which is off: an emitter that declares no fade draws through a program that reads no depth at all, and the frame it draws in copies none for it. Both emitter kinds take it — a sprite emitter's card and a mesh emitter's copy alike. The value has to be a finite number at or above 0; anything else is refused where it is declared rather than accepted and thrown once a frame.

An emitter drawing an authored material (material = ... / :setMaterial) shades through that material's own shader, and fades over the distance that shader reads from the material's own depth_fade. The emitter says so once, because the material is shared by every entity drawing it and holds one distance for all of them. A particle material carries a fade by declaring a depth_fade float property, turning its shader's DEPTH_FADE feature on, and shading through a shader whose block for that feature includes zero::scene_depth and scales its alpha by zero_scene_depth_fade(frag_coord.xy, world_position, depth_fade). particle_sprite.shader is the worked form.

Custom WGSL update shaders

Pass updateShader = "/source/path/to/file.wgsl" to particles.create. The shader must match the binding layout:

// sprite emitter
@group(0) @binding(0) var<storage, read_write> particles: array<f32>;
@group(0) @binding(1) var<storage, read_write> vertices: array<u32>;
@group(0) @binding(2) var<storage, read_write> params: array<f32>;

// mesh emitter
@group(0) @binding(0) var<storage, read_write> particles: array<f32>;
@group(0) @binding(1) var<storage, read_write> transforms: array<f32>;
@group(0) @binding(2) var<storage, read_write> instance_data: array<f32>;
@group(0) @binding(3) var<storage, read_write> params: array<f32>;

Inside the shader, read per-frame data from the params array at the offsets documented in particle_update.computeShader/shader.wgsl (and exported as Lua constants from particles.PARAM_LAYOUT). A sprite shader writes the engine's standard 23-u32 Vertex layout into vertices; a mesh shader writes a column-major 4x4 per particle into transforms and four vec4 lanes per particle into instance_data, the shape particle_mesh_instance.computeShader/shader.wgsl documents.

User uniforms live at params[32..63]. Set them from Luau:

system:setUserParam(1, 0.5)            -- writes params[32] = 0.5
system:setParam("user1", 0.5)          -- same

See demos/particles_showcase/ParticlesShowcase.component/init.luau for a worked example with a curl-noise field driving 4000 particles.

Performance notes

Compute pass cost is proportional to maxCount, not to active count — dead slots still execute one workgroup invocation each, but only do the dead-check + degenerate-quad write (~10 instructions).
CPU spawn cost scales with the per-frame emit count (rate × dt + bursts), not with maxCount. A typical effect doing 100 particles/sec at 60 fps spends ~1.7 spawns/frame on the CPU.
GPU memory is dominated by the vertex buffer at 368 B/particle. For 100 k particles that's ~37 MB. For 1 M particles ~370 MB — still fits on a mid-tier GPU but profile first.
Sorting: a sprite emitter that alpha-blends rewrites its own index buffer every frame, on the GPU, into the order that walks its particles back to front against the camera the frame is drawn from. While the emitter can be holding at most 2 048 live particles it does that in ONE compute dispatch (particle_sort_local: one workgroup sorts the live particles' depth keys in workgroup memory and writes the index buffer), so a step costs two dispatches, the simulation and the sort, whatever maxCount is, and the sort holds 32 B of buffers. Past 2 048 live it orders them by radix: a key pass, three dispatches per eight bits of key and the index write, eight dispatches at the default bucket count, over maxCount, in buffers of 12 B/particle plus a 1 KB digit histogram for every block of 256 slots. What a sorted emitter spends is dispatch overhead far more than per-particle work, so the dispatch count is the cost to read: eleven emitters of 2 100 slots holding ~800 particles each spend 22 dispatches a frame rather than 99. sys:observe() reports sortPath ("local" or "radix"), dispatchesPerStep for the population the emitter holds now, lastStepDispatches, and the running totals computeDispatches, sortDispatches and localSorts. An emitter that adds skips all of it: addition commutes, so its draw order cannot change its image. sort = false on the spec (or sys:setSorted(false)) turns it off; sort = true turns it on for an additive emitter. sys:observe().sorted reports which way an emitter resolved, and getGpuBytes().sort what the buffers cost it.

The order is a total order on (depth bucket, slot): two particles the bucketing cannot tell apart keep slot order between them, and both paths produce the same order, byte for byte in the index buffer. sortBuckets is that resolution: 65535 by default, each bucket spanning 0.018% of its own depth, which at five metres is under a millimetre. The one-dispatch sort needs the bucket and the slot index to fit 32 bits together, which the default does for every emitter of up to 65 536 slots. On the radix path every eight bits of bucket index is one more radix pass and three more dispatches, so sortBuckets = 255 sorts in five dispatches instead of eight at 2.7% of depth per bucket.

simulate reorders once at the end of the prewarm rather than once a step: each step rewrites the index buffer the step before it wrote, so only the last step's order can reach a draw.

What this orders is one emitter's particles against each other. Two emitters are two draws, and the renderer orders draws rather than the particles inside them, so two overlapping alpha plumes still composite by draw order. Particles composite against opaque geometry through the depth test, as they always did, and against other transparent surfaces by draw order. A mesh emitter draws instanced copies rather than an index buffer, and is not sorted.
Frustum culling: a sprite emitter's mesh AABB is set to ±10 000 m so per-emitter culling never trims active particles — emitter-level culling happens at the entity level via the host entity's transform. A mesh emitter's copies are culled one by one, each against the source mesh's own extent under that particle's matrix. A dead particle's matrix is zero, which parks its copy at the world origin with no area — it survives the cull whenever the origin is on screen and then emits no fragments. The submitted count is the slots the emitter has ever filled, not its cap: emission walks a write pointer from slot 0, so an emitter with a cap of 100 000 that has spawned five particles submits five instances.

Roadmap (follow-up issues)

The substrate is intentionally minimal. The follow-up issues track features that build on top:

Issue	Layer
#2674 ParticleEmitter component (38-property Roblox-shape surface)	shipped here as `deprecated/deprecatedParticles.package/DeprecatedSimpleParticleEmitter.component`
#2682 GPU compute backend (VFX-Graph-shaped)	shipped here
#2673 NumberSequence + ColorSequence Luau bindings	shipped here in Luau (Rust FFI is the future home)
#2679 Emission shapes	shipped here
#2680 Orientation modes	FacingCamera + FacingCameraWorldUp + VelocityParallel + VelocityPerpendicular shipped here
#2678 Flipbook texture animation	future — needs texture-atlas UV math
#2684 Particle ↔ world collision	analytic shapes and the scene's own geometry shipped here; see "Collision" below
#2685 Force fields / curl noise	curl-noise demoed via custom WGSL; first-class ForceField component is future work
#2681 LightEmission / LightInfluence HDR	brightness shipped; LightInfluence (read GI) future
#2683 Mesh particles	shipped here — one instanced draw of the source mesh, placed and coloured per particle by the compute pass
#2690 VFX editor (curve inspector, profiler)	future
Back-to-front sorting for alpha-blended emitters	shipped here — see "Sorting" above

API reference

See the --!desc doc-comments at every public method in init.luau, curves.module/init.luau, and shapes.module/init.luau for the authoritative API surface. lsp.describe("particles/create") and lsp.search("particles") from the engine also work after the engine has indexed the module.

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assettype · born here

❒asset

# 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. 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()`. Globals leak across reloads. 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**.

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radix_scatter.computeShader

computeshader · born here

❒asset

# radix_scatter Stage 3 of one pass of the shared GPU radix sort. One workgroup of 256 per 256 items, once per radix pass. Each thread extracts its item's digit for this pass and counts how many earlier threads in its own block carry the same digit. That rank, added to the scanned histogram entry for (digit, block), is the item's slot in the output permutation. The rank is a count over a fixed range of workgroup memory, so it depends on nothing but the block's own keys: two runs over the same keys place every item in the same slot. Items sharing a digit keep their relative order from the input permutation, which makes the pass stable and the whole multi-pass sort a total order on (key, item index) — one permutation, reachable from the keys alone. On the last pass an item whose key reaches `sort[4]` resolves to `0xffffffff` instead of its index. Such an item carries a key past the last real one, so it occupies the tail of the permutation, and the consumer reads `0xffffffff` as "this slot draws nothing". ## Bindings | Slot | Access | Contents | |------|--------|----------| | `keys` | read | Per-item sort key. | | `indices_in` | read | This pass's input permutation. | | `indices_out` | read_write | This pass's output permutation. | | `hist` | read | Scanned digit histogram from `radix_scan`. | | `sort` | read | `[0]` count, `[1]` blocks, `[2]` shift, `[3]` last-pass flag, `[4]` dropped key. | Dispatch one workgroup of 256 per 256 items.

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shapes

module · born here

❒asset

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Model

component · born here

❒asset

# Model Loads and displays a 3D mesh on an entity. Disabling the component hides the mesh. Supports procedural meshes (`cube`, `sphere`, ...), model files, and remote URLs. Tint and outline are shader effects applied to the mesh. **Material lives on this component.** There is no standalone `Material` component — a material only renders where there is a mesh to render it on, so the `material` field is part of Model (and SkinnedModel). Set it at add time or assign the field later; properties are registry-wide. Public fields: `model`, `material` (`AssetRef<material>`), `tintR/G/B`, `tintBlend`, `outlineR/G/B`, `outlineIntensity`. Methods: `:setTint(color, blend?)` (color: `{r, g, b}` array or `{r=, g=, b=}` map), `:clearTint()`, `:setOutline(color, intensity?)`, `:clearOutline()`, `:setMaterialProperty(prop, value)`, `:getMaterialProperty(prop)`, `:getMaterialPropertyNames()`. ```luau entity(id).component.add("Model", { model = "cube", material = "gold" }) entity(id).component.get("Model").material = "checkerboard" -- swap material entity(id).component.get("Model"):setTint({1, 0, 0}, 0.5) entity(id).component.get("Model"):setMaterialProperty("roughness", 0.2) ```

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particle_update.computeShader

computeshader · born here

❒asset

# particle_update Default update shader for the generic GPU-driven particle system. Runs once per frame over the full particle buffer: integrates physics (gravity, drag, wind, accel), samples the size/transparency/squash/rotation NumberSequences and the ColorSequence on the GPU, and writes a billboard quad (4 vertices) per particle in the engine's standard 92-byte vertex layout. Bindings (see bindings.yaml): `particles` (read_write `array<f32>`, 16 f32/particle), `vertices` (read_write `array<u32>`), `params` (read_write `array<f32>`). Usage: dispatch by identity with `compute.dispatch("@builtin::deprecated.deprecatedParticles.particle_update", ...)` (buffers in bindings order) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

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radix_hist.computeShader

computeshader · born here

❒asset

# radix_hist Stage 1 of one pass of the shared GPU radix sort. One workgroup of 256 per 256 items, once per radix pass. Each thread reads its item's sort key through the pass's input permutation, extracts the 8-bit digit this pass sorts on, and counts it in workgroup memory. The workgroup then writes its 256 digit populations to `hist`, laid out digit-major: entry `digit * block_count + block`. Digit-major is what makes the sort stable. A plain exclusive scan over the whole array — `radix_scan` — then yields, for every (digit, block) pair, the first slot that pair's items occupy. The block size, the workgroup size and the radix are all 256, so each thread writes exactly one histogram entry and every entry is written on every pass. The histogram therefore needs no clearing between passes. ## Bindings | Slot | Access | Contents | |------|--------|----------| | `keys` | read | Per-item sort key, written by whatever produced the keys. | | `indices` | read | This pass's input permutation. | | `hist` | read_write | Digit populations, digit-major. | | `sort` | read | `[0]` = item count, `[1]` = block count, `[2]` = digit shift. | Dispatch one workgroup of 256 per 256 items.

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curves

module · born here

❒asset

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particle_mesh_default

material · born here

❒asset

# Particle Mesh Default The default surface for mesh particles — the one material every copy in a mesh-particle population draws with, while each copy still carries its own colour and opacity in its per-instance shader-data lanes. A neutral white base colour (`1.0, 1.0, 1.0`) with no emissive, so the per-particle colour and any bound texture fully drive the look. Transparent, double-sided (`cull: none`), in the transparent queue (`3000`). Built on `@builtin::deprecated.deprecatedParticles.particle_mesh`. ## Inputs - `colors.base_color` (`1.0, 1.0, 1.0`) — neutral tint that lets per-particle colour show through. - `colors.emissive` (`0.0, 0.0, 0.0`) — no self-illumination by default. - `textures.base_color_texture` — the image mapped over the source mesh (`default:white` placeholder). - `float2.uv_scale` (`1, 1`) / `float2.uv_offset` (`0, 0`) — how the texture is mapped over the source mesh's own UVs.

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particle_sort_indices.computeShader

computeshader · born here

❒asset

# particle_sort_indices The last stage of a sprite emitter's per-frame back-to-front sort. One thread per draw slot, once per frame the emitter sorts. Thread n reads which particle the sort put n-th and writes that particle's two triangles into the n-th six-index run of the emitter's index buffer. The vertices stay where the update pass wrote them, so the whole sort costs one u32 per slot of traffic and nothing per vertex. A slot the sort resolved to the sentinel holds no live particle. It takes six copies of index 0 — three zero-area triangles the rasterizer drops. ## Bindings | Slot | Access | Contents | |------|--------|----------| | `indices` | read | The final permutation: entry n names the slot that draws n-th. | | `out_indices` | read_write | The emitter's index buffer, six indices per slot. | | `sortview` | read | `[0]` slot count. | Dispatch one workgroup of 64 per 64 slots.

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particle_update_world.computeShader

computeshader · born here

❒asset

# particle_update_world The sprite update shader with the scene's geometry as a collider. Same simulation as `particle_update` — it shares `particle_sim` — plus a fourth binding: a distance field covering the scene, which is what a `world` collider in the emitter's collider list consults. Bindings (see bindings.yaml): `particles` (read_write `array<f32>`, 16 f32 per particle), `vertices` (read_write `array<u32>`), `params` (read_write `array<f32>`), `pw_field` (`texture_3d<f32>`, r32f — world-space distance to the nearest surface per voxel). The grid the field covers is described by the params buffer's world block, which the particles module writes from the field's own settings. With the block's flag clear the world collider reports no contact, so an emitter whose field has gone away keeps simulating against its analytic colliders. Contact is resolved where the field reads the collider record's radius, so accuracy follows the field's voxel size — a coarser grid rests particles further from the surface.

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particle_mesh_instance.computeShader

computeshader · born here

❒asset

# particle_mesh_instance Mesh-particle path of the generic GPU particle system. One invocation per particle: it integrates the particle, samples the size/transparency/colour sequences, and writes the particle's world matrix and its shader-data block. The emitter's source mesh is uploaded once and drawn `maxCount` times from those matrices, so both the memory this path holds and the work it does each frame are proportional to the particle count and independent of how many vertices the source mesh has. Bindings (see bindings.yaml): `particles` (read_write `array<f32>`, 16 f32 per particle), `transforms` (read_write `array<f32>`, 16 f32 per particle — one column-major 4x4), `instance_data` (read_write `array<f32>`, 16 f32 per particle — four `vec4` lanes), `params` (read_write `array<f32>`). Shader-data lanes, as `particle_mesh.shader` reads them: | Lane | Contents | |------|----------| | 0 | `rgb` the particle's colour, tinted and brightened; `a` its opacity | | 1 | `(life_t, seed, world size, 1 while alive)` | Usage: dispatch by identity with `compute.dispatch("@builtin::deprecated.deprecatedParticles.particle_mesh_instance", ...)` (buffers in bindings order) — it resolves to the shader's stable guid and auto-compiles on first use.

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particle_mesh_additive

material · born here

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sceneProxy

module · born here

❒asset

# sceneProxy The public surface: `build`, `refresh`, `destroy`, `built`, `building`, `settings`, `sampleAt`, `distanceAt`, `gridParams`, and — for a field that keeps itself current — `track`, `untrack`, `tracking`, `maintain`, `trackingStats`, `claim`, `release`, `claimed`. It owns the grid and drives the passes. Geometry reaches the GPU through `compute.buildBvh`, whose triangle buffer the voxelize pass reads directly, so scene geometry never passes through the scripting heap. The BVH's root node also bounds every triangle it was built from, which is where the grid's default extent comes from — exact, and cheaper than re-deriving it from instance transforms, which carry a centre rather than a size. `refresh` reallocates the occupancy volume rather than clearing it. The scatter only ever sets voxels, so a stale mark left by a surface that has since moved would never be cleared by the pass itself. `sampleAt` and `distanceAt` answer through the `proxy_probe` pass, which reads the field with the entry points `scene_proxy.shaderModule` publishes — so a script and a consuming pass get their answers from one piece of code. They yield while the GPU answers. A consuming shader includes the module and samples the volume directly instead. ## Following the scene `track` records what to follow and returns at once; `maintain` is the tick that does the work, and it never yields, so a component `update` can drive it. A walk over the scene reads each entity's placement through `Baking.entityWorldMatrix`, which is where `gatherMeshInstances` gets the transform it puts in the instance record too, so the tick and the build derive what they compare the same way. A refresh is started when one placement moved further than `motion` voxels from where the landed field put it. Because the comparison is against the landed field rather than the previous frame, a surface drifting below the threshold never accumulates into a refresh. Every entity has to be looked at to find the few that carry geometry, so the walk is spent a slice at a time: the interval decides when a walk starts, a tick steps it for a bounded couple of milliseconds, and the walk decides nothing until it has seen the scene through. A tick's cost is therefore bounded by the slice rather than by how many entities the scene holds. A tick with nothing built yet builds the grid, which is what lets a scene say only what it wants followed, and one whose grid stands at a resolution nobody is asking for any more rebuilds it. Geometry that has left the extent the grid covers rebuilds it around the scene's new size while `refit` is on. `claim` and `release` are `track` for something whose own presence is the request — a component, a system. Tracking is on while at least one claim stands, the settings in force are the newest claim's, and the grid goes when the last claim does, so two of them share one grid instead of one turning the other's off. `claimed` is what a claimant asks to find out whether a release elsewhere took its claim with it. A build runs inside a task and holds a lock while it does. The lock carries both a deadline and the identity of its holder: past the deadline the next caller takes it, and a holder can only release the lock it took, so a build that overran cannot release its successor's. `destroy` releases the work in flight along with the grid — what it was making is a grid nothing asked for any more — rather than letting it land afterwards over torn-down volumes.

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particle_sort_local.computeShader

computeshader · born here

❒asset

# particle_sort_local A sprite emitter's whole back-to-front sort in one dispatch, for a population of up to 2048 live particles. One workgroup of 256 threads, once per frame the emitter sorts and its live particles fit. The threads walk every slot, give each live particle its depth key (`particle_sort_depth`) and gather it into workgroup memory as one word: the key in the high bits and the slot in the low `sortlocal[0]` bits. A bitonic network sorts those words, sized to the next power of two at or above the live count, so the population comes out ordered by key and, inside one key, by slot: the same total order the radix path (`particle_sort_key`, three `gpuSort` passes per eight bits of key, `particle_sort_indices`) produces. The sorted words are written out as the emitter's index buffer. Run n takes the two triangles of the n-th particle, and every run past the live count is six copies of index 0, so the buffer holds exactly what the radix path leaves. Only the runs between this write's live count and `sortlocal[1]` (the runs the previous write may have left holding triangles) are cleared, so the write costs the live population rather than the emitter's capacity. An emitter takes this path when the slot and the key fit one 32-bit word together and its live count is at most 2048; past that, the radix path orders it. ## Bindings | Slot | Access | Contents | |------|--------|----------| | `particles` | read | The emitter's particle state, 16 f32 per slot. | | `params` | read | The emitter's parameter block: the camera position. | | `out_indices` | read_write | The emitter's index buffer, six indices per slot. | | `sortview` | read | `[0]` slot count, `[1]` bucket count, `[2]` near, `[3]` far. | | `sortlocal` | read_write | `[0]` slot bits, `[1]` runs that may hold triangles, `[2]` live particles found. | Dispatch exactly one workgroup.

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particle_sprite_default

material · born here

❒asset

# Particle Sprite Default The default sprite surface for the particle system — a neutral white base colour (`1.0, 1.0, 1.0`) with no emissive, so per-particle tint and the bound sprite texture fully drive the look. Transparent, double-sided (`cull: none`), non-instanced, in the transparent queue (`3000`). Built on `@builtin::deprecated.deprecatedParticles.particle_sprite`. ## Inputs - `colors.base_color` (`1.0, 1.0, 1.0`) — neutral tint that lets per-particle colour show through. - `colors.emissive` (`0.0, 0.0, 0.0`) — no self-illumination by default. - `textures.base_color_texture` — the sprite image (`default:white` placeholder). - `floats.roughness` (`1.0`) / `floats.metallic` (`0.0`) — flat, dielectric sprite.

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particle_census.computeShader

computeshader · born here

❒asset

# particle_census Counts a particle emitter's live slots on the device. One invocation per slot over the state buffer the update pass writes, applying the same test that pass applies — a slot is alive while `age < lifetime` — and accumulating into a two-slot `u32` counter. | Slot | Counts | |---|---| | 0 | live particles | | 1 | live particles a dispatch has advanced (`age > 0`) | The gap between the two is what a state buffer the simulation has not run over looks like: the emitter's spawns wrote slots at age 0, and nothing moved them. Bindings (see `bindings.yaml`): `particles` (read `array<f32>`), `census` (read_write `array<atomic<u32>>`), `params` (read `array<f32>`, whose `P_MAX_COUNT` bounds the pass). The particle module dispatches it for an emitter that has been asked to confirm its population — `sys:requestCensus()`, or any `sys:observe()` — and reads the counter back over the following frames. The answer reaches content through `observe().confirmation`, carrying the simulated time it was taken at.

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frameDriver

module · born here

❒asset

# frameDriver The per-frame loop a library module runs on its own behalf: the driver behind a system that advances itself without an owner calling `update(dt)`. The particles package steps every `autoUpdate` emitter through one, and the light cookies advance through another. ```luau local FrameDriver = require("@builtin::modules.frameDriver") local live = {} local driver = FrameDriver.new({ name = "ripples", gameplayClock = true, hasWork = function() return #live > 0 end, step = function(dt) for _, ripple in ipairs(live) do ripple:advance(dt) end end, }) local function addRipple(ripple) table.insert(live, ripple) driver:ensure() end ``` ## API | Call | Effect | |---|---| | `FrameDriver.new(opts) -> Driver` | Make a driver. `opts.name` names it in warnings and `stats()`; `opts.hasWork()` says whether there is work this frame; `opts.step(dt)` advances it; `opts.gameplayClock` holds the step while a play session is paused; `opts.maxStep` caps one frame's `dt` (default 0.1 s). | | `driver:ensure() -> boolean` | Start the loop when it is not running and there is work. Returns true when this call started it. Call it every time work is added. | | `driver:isRunning() -> boolean` | Whether the loop is running now. | | `driver:stats() -> Stats` | `{ name, running, starts, steps, held, failures, lastError }`. | | `FrameDriver.gameplayClockRunning() -> boolean` | False only in a play session that is paused. | ## Semantics - **The loop belongs to the module.** It runs as a system task (`task.spawnSystem`), so the code that added the first piece of work (a one-shot `execute`, a task scope, a component hook, a scene entrypoint) can end without ending the loop. Work added from anywhere is stepped every frame for as long as it exists. - **It runs while there is work.** The first frame `hasWork()` answers false ends the loop; the next `ensure()` starts a fresh one. - **A loop ended from outside is replaced.** `ensure()` reads the loop's task status, so a loop cancelled by its handle or halted by the watchdog reads as stopped, whether it ended at its frame wait or in the middle of a step, and the next `ensure()` starts another. A task a step spawns reads the loop as running while that step is on the stack. - **The gameplay clock.** With `gameplayClock = true`, a frame that arrives in play while `engine.paused` is set calls nothing, and the next frame after the pause lifts carries on from there. In edit the step keeps arriving, as the editor's preview. `engine.timeScale` reaches `dt` through the scheduler. - **A step that raises** is caught; the loop carries on with the next frame. The first raise of each distinct message is logged as a warning, and `stats()` counts every one.

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meshes

module · born here

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particle_sort_key.computeShader

computeshader · born here

❒asset

# particle_sort_key Stage 1 of a sprite emitter's per-frame back-to-front sort. One thread per particle slot, once per frame the emitter sorts. Each thread measures how far its particle stands from the camera and files it into one of `bucket_count` depth buckets ordered far to near, so sorting the keys ascending walks the population back to front. It also seeds the sort's input permutation to the identity, which keeps a four-byte-per-slot fill off the upload path. The distance is radial rather than along the view axis: a particle draws as a quad turned to face the camera, so which of two quads is in front is decided by which centre the camera is nearer to. Buckets are spaced logarithmically between `near` and `far`, so each bucket spans a constant ratio of depth. Resolution is finest close to the camera, where overlapping particles are largest on screen, and one key space covers a scene of any size. A dead slot takes `bucket_count`, one past the last real bucket. That parks it in the tail of the permutation, where `radix_scatter` resolves it to the sentinel and `particle_sort_indices` writes it a degenerate quad. ## Bindings | Slot | Access | Contents | |------|--------|----------| | `particles` | read | The emitter's particle state, 16 f32 per slot. | | `params` | read | The emitter's parameter block — camera position, slot count. | | `keys` | read_write | Per-slot depth bucket. | | `indices` | read_write | The identity permutation the radix passes start from. | | `sortview` | read | `[0]` slot count, `[1]` bucket count, `[2]` near depth, `[3]` far depth. | Dispatch one workgroup of 64 per 64 slots.

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radix_scan.computeShader

computeshader · born here

❒asset

# radix_scan Stage 2 of one pass of the shared GPU radix sort. Exactly one workgroup, once per radix pass. Turns the per-block digit populations `radix_hist` wrote into their exclusive prefix sum, in place. The histogram is laid out digit-major, so the scan gives every (digit, block) pair the first order slot its items occupy: every item of a lower digit comes first, and within one digit every item from an earlier block comes first. The scan is blocked: each thread sums a contiguous stripe of entries, the stripe sums are scanned in workgroup memory, then each thread rewalks its stripe applying the running base. One workgroup keeps the whole scan inside a single barrier domain, which is what makes it correct without a second dispatch, and the two barriers keep each thread's read pass clear of every other thread's write pass. ## Bindings | Slot | Access | Contents | |------|--------|----------| | `hist` | read_write | Digit populations, scanned in place. | | `sort` | read | `[1]` = block count; the scan covers `block_count * 256` entries. | Dispatch `{ 1, 1, 1 }`.

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particle_mesh

shader · born here

❒asset

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particle_sprite

shader · born here

❒asset

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assetType.assetType

assettype · born here

❒asset

# assetType (asset type) The `assetType` is the **type of types** — the meta-type that every `<typename>.assetType/` folder is an instance of, including itself. A `<typename>.assetType/` folder declares a new asset type called `<typename>`: its on-disk shape, its identity rule, and the structural contract instances of the type must satisfy. This type is self-hosting. `assetType.assetType/` conforms to its own schema — a `type.yaml` plus a `README.md` — so the type system is defined in terms of itself rather than a hidden engine special-case (the same way a C compiler is written in C). Every asset in the engine, including each `.assetType` definition, now resolves to a registered assetType: a `.material` resolves to `material.assetType`, and `material.assetType` resolves to `assetType.assetType`, which resolves to itself. ## Why it exists Assets used to be mapped to their type *implicitly*, by matching the folder suffix against a name-keyed registry. That match carried no stored link: nothing on a `Foo.material` recorded *which* `material.assetType` it was written against, so two worlds shipping a same-named type could silently disagree. Making `assetType` a real, resolvable asset closes that gap — the link from an asset to its type is now an explicit reference pinned in the asset's `.refs` sidecar (`via: "asset_type"`), exactly like every other dependency. ## Where it lives - Source: `/zero/source/.../<typename>.assetType/` - Identity: `<typename>` (the `.assetType` suffix strips from the identity; the folder retains the suffix on disk). - Folder shape: - `type.yaml` — the structural spec the validator reads. **Required.** - `README.md` — type-level documentation. **Required.** - `about.yaml` — three short plain-language texts saying what the type is for (see "Say what your type is for" below). Every built-in type ships one. - `behavior.luau` — optional behavior/scaffolding module. - `template/` — optional canonical placeholder body the templater copies into a new asset of the type. - `<name>.module/` — optional shared code the type ships to **every instance** of it, conventionally `shared.module/` (see below). ## Shared code its instances reach (`asset.containing` + `.modules`) A type ships code every instance of it uses by declaring the modules in its own `behavior.luau`, as a map of tracked `require`s: ```luau -- inside <typename>.assetType/behavior.luau M.modules = { shared = require(".shared") } -- the sibling shared.module/ ``` An instance reaches it with one location-independent line: ```luau -- inside any foo.<typename>/init.luau local api = asset.containing(__FILE__).modules.shared ``` `__FILE__` is the chunk's own VFS path; `asset.containing` resolves the calling asset, and `.modules.<name>` follows the instance's pinned `typeRef` (the type's **guid**, recorded in the instance's `.refs` as `via = "asset_type"`) to the module its type declares. Because resolution follows that link rather than a category name, the same line in an instance of a different type resolves to that type's module, and identically-named modules in two types never collide. `asset.typeRef(target)` reads that guid for any target; `asset.resolve(asset.typeRef(target))` gives the full `AssetRef<assetType>`. See `assetTypes/README.md` § "Shared code: type-owned modules" for the full mechanism. ## How to create one Authoring a new asset type is just creating a `<typename>.assetType/` folder under `/zero/source/`. The engine registers `<typename>` as a category **the moment the folder is written** — no engine restart, no Rust change, and it works for built-in (`@builtin/assetTypes/`) and user-defined types identically. Once `<typename>` is registered, `<name>.<typename>/` folders are recognised as assets of that type and resolve their `asset_type` link back to this definition. Creating a `<name>.<typename>/` folder *before* its `<typename>.assetType/` exists fails fast: the suffix has no registered type, so the folder can't be a valid asset. Author the type first. ## Say what your type is for (`about.yaml`) Every type carries a small `about.yaml` beside its `type.yaml`, and the README you write for the type documents how to author an asset of it. Both are required, and both are meant to be written as you make the type, while you know what it is for. `about.yaml` answers three questions in plain words, one key each: ```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. Name the whole range of things it covers, in the words a game maker would use for them. - **`function`** is how it works today: what an asset of the type is made of and what the engine does with it. - **`usage`** is what a person or an agent does with one: how they pick it, place it, call it, or hand it to something else. A few habits keep it useful. Write about the type as a whole, so the text holds for every asset of it, and leave out any one asset's name. Say what the type does right now. Stay with words a game maker would say, and mention a file name or a call only where a game maker would know it. The limits are in bytes: `intent` 800, `function` 1500, `usage` 1200. Each is generous, and a few sentences usually say it. Why bother: agents working in a world read these three texts to learn what your type is for, so they reach for it when it fits and use it the way you meant. People searching find the type by what they want to make, and the three texts let them tell at a glance whether it is the one they need. `asset.create("assetType", name)` scaffolds the file with all three keys, and a README whose first paragraph is a `[[describe]]` note. Each value starts with `[[describe]]` followed by a note on what to write; replace the whole value with your own words. A value or a README line that still starts with `[[describe]]` counts as not written yet, which the push's check of each asset it carries against its type reports, naming the file. A type you leave as it was is not asked, so older types stand. Many types at once, or one you would rather not write by hand: `services describe` lists the types that lack these texts and what filling them costs, and `{ mode = "all" }` writes them into the same files, where you edit them like anything else you wrote. Where the texts show up: `asset.inspect("<typename>", "assetType")` returns them as `detail.about`, `assetTypeRef:getAbout()` returns them as a table with the keys `intent`, `function` and `usage`, the type's `types/<typename>` guide page ends with an "About this type" section holding them, and the Inspector's Type section lists them at the top. The guide page is this README plus that section, so a README that explains the type well and an `about.yaml` that says what it is for read well together. ## Ask your assets to say what they are A type can ask each of its assets to carry a description: a file, written by the author or generated, that says what that asset is and what it is for. The people and agents who find an asset read it to decide whether it fits, and the author knows what it is for at the moment of making it. **1. Declare the file with a `described` check.** This is the whole requirement: ```yaml files: required: - path: "README.md" # any file name works kind: "file" content: - { check: "described", message: "Say what this widget is for and where it goes." } ``` With that in place: - An asset whose file is missing, empty, or still has a line starting with `[[describe]]` does not meet the type's requirements. `asset.validate` names it, `zm status` and `world.publishBlockers()` list it, and a push that carries it is refused with `message`. - `services describe` finds it (`mode = "find"` lists it and the price) and can write the description for it (`mode = "all"`). It writes only this file. For a YAML file that holds several texts, name the keys and their limits in bytes, the way this type does for `about.yaml`: ```yaml content: - check: "described" keys: - { key: "intent", max_bytes: 800 } - { key: "usage", max_bytes: 1200 } message: "Write intent and usage." ``` `headings` names sections a Markdown file must have. `assetTypes/README.md` has the full check. **2. Optionally, steer what gets generated with a `describe:` block:** ```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>" ``` `guidance` says what a description of your type covers, and `examples` names assets whose descriptions show the shape you want. Without the block, generation still works from the general describing guide and the check's `message`. An example is an asset of your type in the library whose description is a true, written one, never a scaffold's placeholder, and never the asset being described. When the library has none, leave `examples` empty rather than name one that is not. A type whose assets the model cannot perceive (a sound it cannot hear, a motion it cannot see) says so in `guidance`: the description comes only from what the asset's own files state, such as its name and the `.metadata` where a generation service records the prompt that made it, and when they state nothing the model answers `cannot` with that reason. `services describe` then fails that one asset with the reason and leaves its file as it was. **3. Start the file unwritten in your template.** Put a heading and one line that starts with `[[describe]]` and a short note on what to write, in `template/<file>`, so a new asset starts unwritten rather than with text that only looks written. Do not put example content in it: every new asset carries the template verbatim, and the same text on many assets makes them impossible to tell apart in search. Types whose assets say what they are through their own content (a mesh, a texture, a sound) leave this out: declare nothing and nothing is asked. ## The `behavior.luau` contract `behavior.luau` is the type's code. It returns ONE table, and the keys below are the ones the framework reads off it for EVERY type — the surface you get by declaring them. Anything else on the table is your own: reachable by name through `require("@builtin::assetTypes.assetType.shared.ref").loadTypeModule("<typename>")` for a system that knows your type (`computeShader` publishes `dispatchKey` that way), and never called by the framework. ```luau local M = {} M.ref = { ... } -- methods on every AssetRef of this type M.modules = { ... } -- shared code the instances reach M.global = {} -- reserved key; ship the empty table function M.onCreate(name, opts) ... end return M ``` ### The tables | Key | Shape | What the engine does with it | |-----|-------|------------------------------| | `M.ref` | `{ [name] = function(self, ...) }` | Every function becomes a method on every `AssetRef` of this type: `ref:name(...)`, with `self` the ref. This is how a type gives its instances an API. Two names in here are contracted — see below. | | `M.modules` | `{ [name] = require(".sibling") }` | Shared code the type's instances reach through `asset.containing(__FILE__).modules.<name>`, resolved by the instance's pinned `typeRef` guid. See the section above. | | `M.refShapes` | `{ [method] = "TypeName" }` | Declares the result type of a `M.ref` method so the LSP can check what a call site does with it. See the `M.refShapes` section below. | | `M.events` | an events schema | The events an ASSET of this type fires, declared the way a component declares its own. Readers subscribe through `ref.events.<name>:connect(...)`; firing authority stays with the type. Keyed by the asset's guid, so every resolver of the same asset shares the signals and a re-resolved ref re-attaches to subscriptions already there. | | `M.namePattern` | a Lua pattern string | The name shape `asset.create` enforces for instances of this type, replacing the default `^[A-Za-z][A-Za-z0-9_]*$`. | | `M.global` | `{}` | Reserved. Ship the empty table. | ### The lifecycle hooks Each is optional; a type that omits one costs nothing. The engine calls them: | Hook | Signature | When it fires | |------|-----------|---------------| | `M.onCreate` | `(name, opts) -> { [filename] = contents }` | On `asset.create("<type>", name, opts)`. Returns the files that scaffold the new instance, as a map of relative path to contents; the framework writes them. The `opts` type annotation is the schema `asset.create` validates the caller's arguments against, so annotate it. | | `M.onReplace` | `(dest, files) -> { [filename] = contents }` | On an `asset.create` that writes over an asset already at `dest`, after `onCreate`. Receives the files `onCreate` produced and returns the files to write, so a type that re-derives its content (a rig re-imported from its source file) can carry what an author added to the asset it replaces. Optional. | | `M.onRegister` | `(self)` | Once per instance, the first time it registers: on `engine.onWorldLoaded` for instances already in the world, immediately on a live `asset.create`, and when an instance arrives after that sweep (installed, pulled, or synced from a peer). Guarded by the instance's path, so a double trigger never double-registers. An instance that leaves the runtime releases the guard, so one arriving at the same path again registers. This is what makes "write an asset into the world and it takes effect live" work for content that registers into a runtime registry. The `@builtin` library is excluded from the sweep. | | `M.onChange` | `(ref, change)` | On every VFS write to a file INSIDE one of this type's instances. `change` is `{ path, asset, type, kind, origin }`: `kind` is `"edited"` or `"seeded"`, `origin` is `"local"` or `"remote"` (an importer runs on the originator only). **Filter on `change.path`**: the hook fires for any file under the folder, so act on the one you care about. It runs as its own task and may wait on what it reads: a `vfs.read` of bytes only the blob store holds (a binary file on the web build) fetches them. The writes to one asset reach the hook in the order they were made, each once the hook before it has finished. A re-entrancy guard suppresses writes back into the same asset routed inline from the hook, and a write the hook makes is routed on a later frame like any other, so the hook must be convergent on its own: diff the meaningful state and short-circuit while your own regeneration is in flight. | | `M.onDelete` | `(ref)` | When an instance of this type leaves the runtime: it is deleted, or the engine swaps away from the world binding that held it. Its files are gone from `/zero/source` by then. A removal routed while the instance's `onChange` is waiting reaches `onDelete` once that hook, and every write queued behind it, has finished. On a swap the instance still exists in the world it belongs to, and a VFS write the hook makes reaches the world now bound. | | `M.validate` | `(assetRef) -> { { code, message, severity? } }` | On `asset.validate`, after the structural `type.yaml` check, for the type's own SEMANTIC validation. `severity` defaults to `"error"`; error-severity problems flip `ok` to false, warnings do not. A hook that raises or returns a non-table is itself reported as a `validate.hook_failed` error. `world.push` runs this per user asset, so declaring it enforces your type's rules at publish time with no further wiring. | ### The two contracted `M.ref` names Most `M.ref` methods are your type's own surface: name them what you like, return what you like. Two are read by the engine and mean the same thing for every type, so their shape is fixed: - **`instantiate(self, target?, opts?) -> (root, idMap)`** — makes an instance part of the scene. Defining it is the whole opt-in: `ref:canInstantiate()` is true exactly when it exists. Its **return is a contract** — see the next section. - **`inspect(self) -> detail`** — the type-specific half of `asset.inspect`. See its section below. ### Names a type cannot shadow Some keys resolve on every `AssetRef` before per-type dispatch, so an `M.ref` entry of the same name is never reached: `canInstantiate`, `getSource` / `getBytes` / `getText`, `exists`, `deps`, `meta`, `runtime`, `events`, `modules`, `typeRef`, and the residency flags `has_backing_asset`, `has_runtime_changes`, `cpu_resident`, `gpu_resident`. These are the behaviours every asset must expose identically, which is why they win. ### Reloading A `behavior.luau` edit ripples to existing refs with no restart: dispatch reads `mod.ref` fresh each time and `require`'s cache is re-run in place. A type whose folder appears at runtime is picked up on the next dispatch — negative results are not cached either. ## The names your type's assets hold (`references:`) An asset that names another asset by a string depends on it: the named asset travels with it into a pack or a pull, and a name nothing answers to is an unresolved dependency `worldValidation` reports and the push gate refuses. The engine reads `require(...)` and the asset lookups on its own; a name your type's format or API carries anywhere else is one you declare, in `type.yaml`: ```yaml references: # A top-level key of this type's own files that holds a name (or a table of them). keys: - { key: "shader", type: "shader" } # A call's argument, counting from 1, wherever the call is written. args: - { call: "g:node", position: 2, type: "procNode" } # A field of the options table a call takes. fields: - { call: "fx.beam", field: "material", type: "material" } ``` `type` is the category the name resolves in, one of `asset.categories()`. An argument declared once per category, at the same `call` and `position`, takes the name from whichever category answers. A key or a field holds one category: declared again with another `type`, it takes the later one. The block is declared as the type registers, when the library or the world holding it is laid into the VFS, so every reference table reads it whatever script has or has not run. `asset.declareReferenceKey`, `asset.declareReferenceArg` and `asset.declareReferenceField` declare the same things from a script, for a surface that is no type's. ## What search does with your type (`indexing:`) A type declares what search embeds for its instances. **This is not optional and there is no useful default**: ZeroMind runs your declaration and adds nothing of its own, so anything you do not point at is absent from the index — silently, and for every instance of the type forever. Twenty types once shipped with no `indexing:` block and every instance of them was unfindable. A type whose instances are never searchable (a run record, a log) says so with `indexing: none`; every other type declares a recipe. A type without an `about.yaml` beside its `type.yaml` refuses every push that carries it, whether or not the push edited the type. Texts in it that are not written yet follow the rule every `described` file follows: they refuse the push that edits, stages or commits the type. Two words carry the whole thing, and they are the same two the search tool exposes: - **`identity`** — what an instance IS. For anything you can look at, that is the picture (`content:` + `modality: image`, matched directly by a text query). For everything else it is the authored text that says what it is. - **`capability`** — what it DOES and how it is made. Code, settings, the model-written summary of them. A type with no behaviour has no `capability` entry. A type with nothing to look at has no image. Leaving a slot empty is a statement; filling it with whatever happens to be lying around is not. The one you have to decide when authoring a type is: *for an instance of this, what is the thing a person would recognise it by, and what is the thing it does?* A texture answers "the image" and "its compression settings". A module answers "its README" and "its code". Write those two answers into `indexing:` and the rest follows. Three specifics worth knowing before you write one: - **`derive` is instructed by this type's own `README.md`.** A model reads an instance's source and writes a description; what it embeds is the description, not the source. It follows your README to know what it is looking at, so a type whose README says what its instances are gets good derivations for free. There is no prompt to name. - **`derive` loses detail.** It keeps the main technique and drops secondary ones. If the source is code you want searchable by its own vocabulary, declare the same files a second time as `capability` with `extractor: verbatim`. Two entries, same role, different failure modes. - **Never `source: { field: name }`.** A filename is one or two words with no usable embedding, and a corpus indexed that way answers "language runtime" with `say_runtime_2.soundClip`. `facets:` is the second stage: a `file:` embedded whole (`.metadata`, so keys nobody declared still get indexed) plus computed keys that state a value for every instance including `false` — the raw file can imply "not rigged" and can never say it. The full schema, every extractor and the facet sources are in [`assetTypes/README.md`](../README.md); the scaffolded block with inline guidance is in [`template/type.yaml`](template/type.yaml). ## A container whose contents work together (`system: true`) A type that is a container can say its contents are one working whole by declaring `system: true` at the top level of its `type.yaml`. `package` declares it: the components, modules, scenes and tools a package ships are parts of one system. The declaration is plain data, read from the decoded `type.yaml` (`require("@builtin::assetTypes.assetType.shared.declaration").of("package").system`), and a type that leaves it out is an ordinary type. ## What your type looks like (`preview:`) A type declares how its instances are pictured, and the engine makes the picture when something needs it: staging an instance whose `preview.png` is missing or pictures content it no longer holds queues a render, a view that shows the instance asks for one, and `ref:preview()` renders one on demand. An edit renders nothing on its own. Each `preview.png` records the content it pictured, which is how a stale one is told from a current one. The preview studio owns the light, the backdrop, the framing and the camera, and nothing in the world reaches it, so an instance pictures the same in every world. Declare one of four recipes: | `kind` | The picture is | Your type provides | |---|---|---| | `instantiate` | the asset stood in the studio through its own `instantiate` | `ref.instantiate` | | `image` | a file the instance holds, fitted to the frame, nothing rendered | `source.files`, the candidate files in order | | `surface` | the asset painted on a builtin mesh | `mesh`, and `ref.previewMaterial(self) -> { material }` | | `custom` | whatever `ref.preview(self, opts)` returns | `ref.preview` | ```yaml preview: kind: surface mesh: sphere ``` A scene-instantiable type that declares nothing still answers `ref:preview()` through its `instantiate`, but persists no picture: the declaration is what makes the engine keep one. List `preview.png` among the type's files so an instance may hold it. The picture is findable only when `indexing.content` names it. The two are separate statements, and neither is derived from the other: ```yaml indexing: content: - role: identity modality: image source: { file: "preview.png" } ``` `@builtin::assetTypes.assetType.shared.previewRecipe` reads the declaration; the scaffolded block with inline guidance is in [`template/type.yaml`](template/type.yaml). ## Typing a result from the instance (`M.refShapes`) Every method on `M.ref` is checked against the type its `--!return` names, and every asset of the type gets the same one. That is right for most methods and wrong for the ones whose result is shaped by the ASSET: a method answering one entry per child folder, per row of a config, per binding an input map declares. The widest true annotation for those is `{ [string]: Thing }`, and an indexer accepts every key — so a caller's typo reads as valid and nothing reports. `M.refShapes` lets the type state the result per instance. Each entry is `function(self) -> (typeExpression, source?)`: a Luau type expression for THIS asset, and the module whose type vocabulary the expression uses. Read the asset; never run it — stating a type must not take effect. ```lua -- inputMap.assetType/behavior.luau — the shipped example. -- `activate()` hands back one handle per control the map declares. 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)` resolves and `map.noexisting` is reported with the map's real controls. Without it, both pass silently. ### What the call site has to say A per-instance type is matched by the asset's IDENTITY, so it applies only where the reference the method is called on says WHICH asset. Two spellings do: ```lua -- a component field, whose declared default names the asset public = { map = Field.assetRef("inputMap", "@builtin::inputMaps.default", Sync) } local controls = public.map:activate() -- typed for THAT map -- an annotation, naming category and identity local m: AssetRef<"inputMap", "@builtin::inputMaps.default"> ``` `asset.resolve("<identity>", "<category>")` carries the CATEGORY, so the methods the category defines are checked on the result — but not which asset it found, so a per-instance result keeps the category's declared return. A reference that names no asset (`asset.resolve(someVariable)`, a value passed in as a parameter) carries neither, and calls on it are unchecked. That is the same rule everywhere: the checker states what the code states, and a name computed at runtime states nothing. ### The result is a value, not a binding The type belongs to the expression, so it travels the way any inferred type travels. Indexing the call's result is checked; stashing it in a module local and indexing it from another function is not, because the local's declared type is what carries across — and `any` (or no annotation) carries nothing: ```lua -- checked: `d.greting` is reported function awake() local d = public.dialogue:lines() d.greeting:say() end -- NOT checked: `lines` is a module local typed `any` local lines: any = nil function awake() lines = public.dialogue:lines() end function start() lines.greting:say() end ``` Bind what you need at the call site and the names stay checked in both places — the asset-derived type at the boundary, ordinary scoping after it: ```lua local lineGreeting = nil function awake() local d = public.dialogue:lines() lineGreeting = d.greeting -- `d.greting` is reported here end function start() lineGreeting:say() end ``` ### When nothing is reported and you expected something From a call site, a type that is correct and a type that was never published look the same: no diagnostic either way. `require("@builtin::assetTypes.assetType.shared.refShapes").published()` answers which it is. It returns two maps — the category surfaces, and the per-asset results keyed by identity and then by method: ```lua local shapes = require("@builtin::assetTypes.assetType.shared.refShapes").published() shapes.categories.dialogue --> "{ lines: () -> any, lineNames: () -> { string } }" shapes.returns.Shopkeeper.lines --> "{ browsing: Line, farewell: Line, greeting: Line, wares: Line }" ``` An identity absent from `returns` was never published for, which is a different thing from published-and-correct — and the reason to look here rather than at the call site. The answers are recomputed when an instance is written, so a control added to a map reaches the checker with no restart. Only types that declare `refShapes` are read per instance, and at most 64 assets of one type are — past that the type keeps its declared return and the engine log names what was dropped. ## The instantiate hook (`M.ref.instantiate`) — a contracted return A type opts into becoming part of the scene by defining `instantiate` on its `ref` table. That is the whole opt-in: `ref:canInstantiate()` is true exactly when the hook exists, so consumers offer a scene path — an `Asset.source` field, a viewport drop, a tool argument — by CAPABILITY rather than by a list of type names. Unlike `inspect`, this hook's **return is a contract**. A caller writes one piece of code against every instantiable type, so what comes back cannot vary by type: ```lua -- behavior.luau local Instantiable = require("@builtin::assetTypes.assetType.shared.instantiable") local M = {} M.ref = { instantiate = function(self, target, opts) local root = Instantiable.root(self, target, opts) -- IN: the base opts -- ... compose whatever this type is, under `root`, NOW ... return Instantiable.result(self, root, idMap) -- OUT: the contract end, } return M ``` **IN.** `target` is an owning entity ref: the instance lands under (or, for a hierarchy type, onto) that owner. With no target the type spawns a fresh root. `position`, `rotation`, `scale`, `name` and `temporary` mean the same for every type — `Instantiable.root` applies them to a root you mint, `Instantiable.place` to one you adopt, so you never re-read the spec. Honour more opts of your own if your type needs them, and document them in the hook's `--!arg` docs. **OUT.** Return `(root, idMap)` through `Instantiable.result`: - **`root`** — the composed root, as an `EntityRef`. Composition is **synchronous**: everything your type builds is live when you return, so the caller can parent to it and read its components in the same statement. Do not defer the work to a component's `awake` and return an empty shell — a root that is not live is refused. - **`idMap`** — the `originalId -> runtimeId` map naming what you spawned, or nil for a type with no addressable children (`result` normalises it to `{}`). **A caller never receives nil.** A component that re-composes your asset on every load keeps this map and passes it back in, which is how a cross-entity reference into the composition survives a reload. `AssetRef` runs every `instantiate` through `result` on the way out whether or not your type called it, so returning something else fails at your own call rather than handing a caller a nil root. Calling it yourself is still how you say what you return, and running it twice changes nothing. `@builtin::assetTypes.assetType.shared.instantiable`'s README is the full reference for both halves. ## The inspect hook (`M.ref.inspect`) `asset.inspect(ref)` resolves `ref`, builds a common envelope shared by every asset (`identity`, `name`, `guid`, `source`, `typeName`, `typeDefinitionPath`, `scope`, `origin`, `description`, `tags`), then calls the resolved type's own inspect hook — `M.ref.inspect(self)` on `behavior.luau` — for the type-specific `detail`. The hook returns *only* `detail`; the framework fills in everything else: ```lua -- behavior.luau local M = {} M.ref = { inspect = function(self) -- self.path is the asset's own folder. Parse the asset's OWN -- files — source text, a native payload header, its `.metadata` -- — never runtime state (a live component instance, a GPU -- upload, a compiled schema): inspect must work on an asset that -- hasn't been compiled, uploaded, or registered yet. return { -- type-specific fields, whatever this type wants to surface } end, } return M ``` A type that omits `M.ref.inspect` yields the generic record: the envelope alone, `detail = nil`. That's a valid, working state — not an error — but it means agents calling `asset.inspect` / `tools.use("assets","describe", ...)` on an instance of the type see only identity and scope, none of what makes an instance of it meaningful. Declaring the hook is what makes a type's instances inspectable for what they actually are. A hook that raises leaves `detail = nil` and sets `record.warning` to the error text — `asset.inspect` itself never raises for a resolved ref. ## Discovery - `asset.list("assetType")` — every registered asset type. - `asset.inspect("<typename>")` — the type's identity, source path, and this README, plus its `about.yaml` texts as `detail.about`. - `asset.resolve("<typename>", "assetType")` — the `<typename>.assetType` asset itself (used by the validator to find the type's `type.yaml`). ## Related - `assetTypes/README.md` — the full `type.yaml` schema and validator rules. - `@builtin::assetTypes.assetType.shared.instantiable` — the instantiation contract's shared implementation, both halves. - Every other `*.assetType/` here — the concrete types built on this meta-type. ## The Inspector a type ships Every type names the file its Inspector sections come from with `inspector: { type: "inspector.luau" }` in its type.yaml. `asset.create("assetType", name)` scaffolds the block and an `inspector.luau` whose Contents section lists an asset's files, built from `ctx.parts`. `asset.validate` on a type that names none reports `assetType.inspector_required` (an error for a `@builtin` type the engine's library authors; a warning for a world's own, and for one the library carries by reference, which the world that published it answers for), and one whose file does not load `assetType.inspector_invalid`. ## In the Inspector Type: what the type.yaml declares (suffix, container, primary files, the settings and inspector blocks), whether the type ships a behavior, how many instances it has, and **Open** for its files. Schema: the settings every instance carries, as read-only typed controls at their defaults (a type whose schema is per instance says where it is declared). Instances: a link to each of the first 20 assets of the type, and how many there are when there are more.

▲ 0↑ born

computeShader.assetType

assettype · born here

❒asset

# 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 `#include`s, 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-model` > first: 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: ```lua 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. ```yaml 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. `buffer` and `vertices` bindings spend that budget; textures, samplers, storage textures and `params:` do not. An `acceleration_structure` brings engine-owned buffers with it — **three** where the device has hardware ray query (the tables `zeroHitSurface` / `zeroMaterial` read) 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 `buffer` defaults to `array<ELEMENT>`. Set `array: false` for 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 in `shader.wgsl`, not `bindings.yaml`. - **A sampled texture binds under the class its FORMAT puts it in**, so `sample` states that class and the generated `texture_2d<..>` matches it. An integer channel — `@scene.material`, which is `Rgba8Uint` — is `uint`; everything else is the `float` default. Bind an integer channel to a `float` slot 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 `access` decides both the generated declaration and the layout the engine registers, so the two always agree. It defaults to `write`, the access every target grants every storage-compatible format. `read_write` is granted on `r32f` alone; declaring it on any other format is refused at the compile, with the reason on `compute.programState`. A pass that needs to read a wider target reads it through a separate `texture3d` / `texture2d` binding, or through a second storage binding declared `read`. - `format` tags (storage textures): `r8`, `r16f`, `r32f`, `rgba8`, `rgba16f`, `rgba32f`. Storage textures only allow storage-compatible formats (`r32f` / `rgba8` / `rgba16f` / `rgba32f`). - An `acceleration_structure` binding 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`, where `instance` is the hit object's render slot), `zeroTraceAny(origin, dir, t_min, t_max) -> bool` (terminate-on-first-hit, for shadow/occlusion rays), and `zeroHitSurface(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 on `renderer.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): ```yaml 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 `buffer` of a scalar or vector element gets `NAME_get(i)`, `NAME_len()` and (unless `access: read`) `NAME_set(i, v)`. A `vec3` element is stored as a flat scalar array, so a column of vec3 keeps its 12-byte stride. `zero_n()` is the dispatch size. - `columns` binds 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` / `capacity` give the size, in elements, of an output the run allocates. `append: true` adds a live counter binding, `NAME_count`, with `NAME_store(slot, v)`, `NAME_set_count(n)` and, under `determinism: float_order`, `NAME_append(v)`. - `specialize` parameters are compile-time: type options become `alias NAME`, named options become `const NAME` and `NAME_<option>`, `kind: source` text replaces the identifier. Each specialization compiles once. - `determinism: exact` refuses `NAME_append`: an exact output is written at ranks the kernel computed. Dispatch such a shader through its program: ```lua 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: ```yaml bindings: - { name: verts, kind: vertices } # the mesh, writable - { name: heights, kind: buffer, access: read, element: f32 } params: - { name: lift, type: float, default: 1.0 } ``` ```wgsl @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)); } ``` ```lua 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 / `#include`s). The names declared in `bindings.yaml` are in scope — `data`, `out_tex`, `params.scale`, … — with no `@group`/`@binding` lines of your own. ```wgsl // @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: ```lua 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. ```lua 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: ```lua 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: ```lua 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: ```lua 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: ```lua 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: ```lua 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 calls `__compute.compile` — that generates the binding declarations, expands `#include`s, naga-validates, and registers. 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: ```lua 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 parsed `bindings.yaml` schema (`{ 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 under `compute.<identity>` — the same identity `asset.resolve` takes, 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"`, and a dispatch issued before that is dropped. - **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** — `buffers` and `resources` bind in `bindings:` list order; reordering the list reorders the bindings. - **Don't write `@group`/`@binding` in `shader.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: vertices` and 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) and the legacy `@domain: compute` fallback. ## 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`.

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package · born here

❒asset

# gpuSort A stable least-significant-digit radix sort, run entirely on the GPU, over a caller-owned array of u32 keys. The three passes here are the body of one radix digit. They read a key array and a permutation and write a new permutation; they never touch whatever the keys describe, so any subsystem with a key per item can drive them. The caller supplies the keys, the identity seed, the per-pass constants and the dispatch sequence. ## One pass | Order | Shader | Dispatch | |-------|--------|----------| | 1 | `radix_hist` | one workgroup of 256 per 256 items | | 2 | `radix_scan` | `{ 1, 1, 1 }` | | 3 | `radix_scatter` | one workgroup of 256 per 256 items | Each pass sorts on one 8-bit digit and keeps the relative order of items sharing that digit, so `ceil(bits / 8)` passes over the low digits upward compose into a total order on `(key, item index)`. ## Driving it The caller owns six buffers: the keys, two permutation buffers the passes ping-pong between, the digit histogram (`ceil(count / 256) * 256` entries) and one constants buffer per pass. A pass reads its constants as | Word | Meaning | |------|---------| | `[0]` | item count | | `[1]` | block count, `ceil(count / 256)` | | `[2]` | this pass's digit shift — `0`, `8`, `16`, `24` | | `[3]` | `1` on the last pass, `0` otherwise | | `[4]` | the key a dropped item carries | Every value is fixed for the life of the sorted array, so the constants are written once rather than re-uploaded per frame. Each pass flips which buffer holds the permutation, so the parity of the pass count decides where the caller seeds the identity for the last scatter to land in the buffer the consumer reads. An item the caller wants dropped takes a key at or past `[4]` — one past the last real key — which parks it in the tail of the permutation; the last pass resolves it to `0xffffffff`, and the consumer reads that as "this slot draws nothing". A fixed dispatch size with a degenerate tail is what lets a consumer issue a constant draw with no read-back and no indirect arguments.

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gaussianSplats

package · born here

❒asset

▲ 0↑ born

❒

deprecatedParticles

package · born here

❒asset

# deprecatedParticles (deprecated) > **Deprecated.** This belongs to the earlier particle substrate. It stays loadable by identity and guid for content that already uses it; nothing new should use it, and search does not offer it. Particles are procgen sim nodes (`sim.spawn`, `sim.particles`, `sim.shader`) played through an effect: use `@builtin::assetTypes.effect`. The package holds the GPU particle engine module (`engine`), the `deprecatedParticles` module over it, the `DeprecatedParticleEmitter` and `DeprecatedSimpleParticleEmitter` components, the shaders, compute shaders and materials they draw with, and a demo scene. The package's `.metadata` carries the deprecation marker, so every asset inside is deprecated.

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component.assetType

assettype · born here

❒asset

# 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`, `destroy`). - You want to expose configurable fields to designers / `entity.spawn` callers / scenes without code changes. If you need a global service that outlives any entity, use a `.service` instead. If you need a stateless pure-function library, use a `.module`. ## 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 beside it on the fixed timestep; `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`, `destroy`) 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 service, 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. Update every `component.add(<oldname>, ...)` call and the scene JSON entries that reference it. ## Related types - `.module` — pure-function library, no per-entity state. - `.service` — globally-scoped behavior, 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`.

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material.assetType

assettype · born here

❒asset

# Material (asset type) A material is a named, configured instance of a `.shader`. The shader defines the surface look (lighting model, available property fields, texture slots); the material picks values for those fields and a shader to bind to. Renderable entities reference materials, not shaders, so the same geometry can wear different materials and the same material can be reused across many entities. Entities sharing one material can still differ in a value: every drawn object carries four `vec4` lanes of its own that a surface shader reads as `input.shader_data[lane]` and `renderer.instanceData.set` writes. Use that for a dissolve at its own progress per subject, a hit flash at its own age, a fill level per instance — a material per entity is for when the LOOK differs, not when a number does. > New to how a material relates to its shader, its textures, and the live GPU > material behind it? Read `core/resource-model` first. It also covers the > difference between an authored `.material` asset (this type) and a runtime GPU > material made with `renderer.material.create`. ## When to use one - You want a named surface configuration an entity wears by referencing it from its `Model` component (`material = "@.../<Name>"`). - You want runtime property tweaks (`asset.resolve(ref):setProperty(...)`) to affect every entity using the material at once. - You want to publish a curated look (`Gold`, `RedGlow`, `BrickWall`) other authors can reuse without re-typing shader bindings. If you need a brand-new lighting model or a custom visual effect, you need a `.shader` first; the material wraps it. ## Where it lives - Source: `/zero/source/.../<Name>.material/` - Identity: `<Name>` (the `.material` suffix strips). - Folder shape: - `mat.yaml` — canonical material spec (shader + property values). **Required.** - `preview.png` — the material's rendered shader-ball still, its persisted visual description. **Required.** Rendered when the material is staged (`zm add`) with its preview missing or stale, and by `generatePreviews`; it syncs, publishes, feeds image-based search, and gives browsers a thumbnail. - `README.md` / `.metadata` — optional prose + tags, indexed when an author writes real ones. - `textures/` — optional folder for embedded textures. Validator allows the folder; its interior is unrestricted. - `shaders/` — optional folder for a co-located custom shader. Same rule. ## How to create one ```luau asset.create("material", "<Name>") -- Creates: /zero/source/<Name>.material/ -- mat.yaml (shader binding + property scaffold) -- preview.png (rendered when the material is staged with `zm add`; the -- picture lands as a change the next `zm add` stages) -- `folder` places it in a subfolder of /source instead of the root: asset.create("material", "<Name>", { folder = "materials" }) ``` Pass the shader and initial values through `asset.create`, then tune with `setProperty` and keep what you tuned with `saveDefinition`: ```luau local mat = asset.create("material", "<Name>", { shader = "@builtin::shaders.pbr" }) mat:setProperty("base_color", { 0.8, 0.6, 0.1, 1 }) mat:setProperty("roughness", 0.3) mat:saveDefinition() -- writes the tuned values into mat.yaml ``` This mints the `.material` asset and returns a handle you tune with `setProperty`. A set is a runtime change: it reaches the GPU material and every entity wearing it, and `saveDefinition` is the call that writes it into `mat.yaml`, so a property driven every frame costs no file write and leaves the authored file as its author wrote it. A purely runtime `asset.create` lives only for the session. For an ephemeral, runtime-only GPU material that is not an asset at all, use `renderer.material.create` instead (see `core/resource-model`). ## How it operates 1. **Property reflection.** The bound shader's uniform struct fields become the material's configurable properties — no manual property declarations needed. `naga` introspects the shader at load. 2. **Property values.** `mat.yaml` groups values by type, each block keyed by the shader's field names: `properties:` holds scalars and colors/vectors, `ints:` holds integer-typed fields, `bools:` holds boolean-typed fields, and `textures:` holds texture slots. Omitted fields take the shader's default. A scalar is a bare number (`roughness: 0.5`); a color or vector is an array (`base_color: [1, 1, 1, 1]`). `shader:` is the shader's identity string. This is the shape every material the engine writes uses. A `saveDefinition` writes the changed values into the file where they already stand and leaves the rest of it — its comments, the order of its keys and blocks, the spelling of its literals — untouched. The older `floats:` / `colors:` blocks (with `{ r, g, b, a }` map colors) still load for materials hand-authored that way. 3. **Render state.** `render:` holds how the mesh is drawn rather than what the shader reads: `blend` (the equation the fragment composites with, also spelled `type`), `cull`, `depth_write`, `depth_compare` and `topology`. The `.shader` type README's "The render block" section lists every value each key takes, and `asset.create`'s `render` argument takes the same keys and values. 4. **Application.** An entity wears a material by referencing it from its `Model` component (`material = "@.../<Name>"`). Materials affect every entity that references them; runtime `asset.resolve(ref):setProperty(...)` changes propagate to all of them immediately, and last until the next mode change unless `saveDefinition` writes them into `mat.yaml`. 5. **Texture binding.** Texture slots accept `color:r,g,b,a` for solid colors, `default:white` / `default:black` / `default:normal` for the engine's own fallback texels, `@builtin::textures.<name>` for builtins, `path/to/image.png` for file textures, or a render-target handle for camera renders. The GPU texture cache reads the `color:` and `default:` forms from the string itself, so a slot written in one names no asset and carries nothing with the material when it travels; every other form names a texture asset the slot depends on. A texture in `base_color_texture` is multiplied by `base_color`: every built-in surface shader declaring both draws the texture's colour times `base_color`, channel by channel. Under the default white `base_color` the texture shows as itself, and a coloured `base_color` tints it. The two read a colour differently: `base_color` is linear, and the slot reads its texels as sRGB-encoded, a `color:` value's included, the way it reads an image. A colour stated in both places is therefore multiplied by a darker copy of itself: `color:0.62,0.14,0.05,1` in the slot decodes to `0.34, 0.017, 0.0039`, so beside `base_color` `0.62, 0.14, 0.05` the surface draws `0.21, 0.0024, 0.0002`, far darker than either. State a solid colour once, as `base_color`, and leave the slot at its default white. 6. **Hot reload.** Editing `mat.yaml` repacks the GPU uniform buffer on the next frame; visible immediately. 7. **Inspector.** `type.yaml` names `inspector: { type: "inspector.luau" }`, and `inspector.luau` declares the material's sections beside the generic ones: `shader` (the bound shader, swappable), `properties` (each shader field as its typed control) and `textures` (each texture slot as an asset chip). They read the material through `mat:getShaderRef()` (the bound shader's ref, `~` expanded) and `mat:getTextures()` (slot name → `{ ref, name }`: the bound texture's guid and the id the material names it by). An edit there is an authoring write: `mat:writeProperty(name, value)` and `mat:writeTexture(slot, texture)` write the value into `mat.yaml` (and drop the session's own value for it, so the material reads what the file holds), and `setShader` rewrites the file; inside an undo operation each file write is recorded, so undo puts `mat.yaml` back. `setProperty` / `setTexture` stay runtime writes that last until the next mode change. ## Discovery - `asset.list("material")` — every registered material. - `asset.inspect("<name>")` — shader binding, property values, source path, this type README. - `ls /zero/source/<Name>.material` lists the files the folder holds. - `asset.resolve("<name>"):getProperties()` — the property fields exposed by the bound shader, each at the value it currently holds: what `mat.yaml` authored until something writes to the material, and the written value from then on, whichever call wrote it. That is the value the surface is drawn with. Read them back rather than guessing names; which fields exist comes from the shader. - `asset.resolve("<name>"):getDefinition()` — the authored `mat.yaml` bytes, the value the material rests at. - `asset.resolve("<name>"):getShader()` — the shader the material binds. ## Authoring conventions - Use lowercase, descriptive names (`brushed_steel`, `red_glow`, `tarmac_wet`). Avoid shader-name suffixes in the material name — the binding lives in `mat.yaml::shader`. - Drive every property the shader exposes; defaults are a fallback, not a contract for which fields exist. - Embed textures alongside the material (`textures/` subfolder) when they're used only by this material; reference shared textures from `@builtin::textures.*` or a library. ## Common pitfalls - **Property names must match the shader's uniform struct exactly** (case-sensitive). Misnamed properties silently get the shader's default. - **`base_color_texture` multiplies `base_color`.** A `color:` texture holding the same value as `base_color` multiplies the colour by its own sRGB-decoded value, so the surface renders far darker than the value written. Write a solid colour as `base_color` alone. - **Broken shaders break the material.** A material whose shader has a parse error renders as the magenta checkerboard. Inspect the shader first if the material looks wrong. - **`setProperty` targets the material, not the entity.** Changes affect every entity that references the material. - **`setProperty` is a runtime change.** It reaches the GPU, not the file: call `saveDefinition` to write the current values into `mat.yaml`. For a per-entity override that no other entity sees, give the entity its own copy with `Model:applySessionMaterial(renderer.material.create(...))`. - **Renaming the folder changes the identity.** Update every `Model` component and `asset.create` callsite that references it. ## Related types - `.shader` — defines what properties exist; required before a material can bind to it. - `.preset` — captures a component configuration; conceptually similar to a material, but for components instead of shaders.

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sceneProxy

package · born here

❒asset

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shader.assetType

assettype · born here

❒asset

# 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). 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. | *(legacy)* An `@compute @workgroup_size(...)` entry over storage buffers — you write the `@group/@binding` lines yourself. **The canonical path is now the separate `.computeShader` assetType** (see below); `.shader` + `// @domain: compute` still compiles for back-compat. | `// @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 are now 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`. The `.shader` compute domain above remains only for back-compat. **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 legacy `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 now `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). ### 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_shadow(i)` | `PunctualShadowEntry` | that light's shadow record (its projected map or cube) | `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. `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 now); 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 package-relative `~.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`: an earlier name is kept working through the module's declared alias, so a shader written against `zero::pbr` still compiles and still pins the asset that name resolves to. Newly written shaders should use 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 }, }) ``` 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 floats: roughness: 0.5 colors: base_color: { r: 1.0, g: 1.0, b: 1.0, a: 1.0 } textures: base_color_texture: { ref: "default:white" } ``` `shader:` is a plain identity string, and each `colors:` entry is an `{ r, g, b, a }` map — the two forms `mat.yaml` accepts for those keys. A key's value is the rest of its line, so every value above stands alone on one. ### The render block Render behaviour that used to be material "flags" — 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 | `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. 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` and `topology` to `triangleList`. 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 calls `shader.compile` — that reads the body + the property schema, generates the group(1) interface and (for surface) every render-mode entry point, expands `#include`s, **validates the result with naga**, and registers it. 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.

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luau_introspect

module · born here

❒asset

# luau_introspect (module) Parses Luau/asset source TEXT into structured declarations. Pure string/pattern parsing (`string.find` / `string.match` / `string.gmatch`) over the literal source — no compiling, no VM spawn, no runtime state, no engine FFI. Given source text, it extracts what is written in the file. This is the shared parser every per-assetType `M.ref.inspect` hook uses to turn a component/module/tool's own source into the structured record `asset.inspect` returns. ## Exports - `docstrings(src) -> DocMap` — scans `--!desc` / `--!arg` / `--!return` / `--!example` comment runs and binds each run to the name of the declaration on the next non-comment line (the identifier after `function`, `public:`, `local function`, or `M.`). - `publicFields(src) -> { FieldEntry }` — parses `public = { name = Field.<kind>(default, mode), ... }` table-literal entries and module-scope `public.<name> = Field.<kind>(...)` assignments. - `events(src) -> { EventEntry }` — parses `events = { name = Event(payloadSchema?, syncMode?), ... }` table-literal entries. - `methods(src) -> { MethodEntry }` — parses `function public:<name>(...)` / `typed function public:<name>(...)` declarations (params + optional return type). - `lifecycleHooks(src, catalog) -> { string }` — top-level `function <name>(` declarations whose name is in the caller-supplied `catalog` array. - `moduleExports(src) -> { ExportEntry }` — parses `M.<name> = function` assignments, `function M.<name>(...)` declarations, and a trailing `return { foo = foo, ... }` export table. - `forSource(src, computeFn) -> any` — memoises `computeFn(src)` keyed on `src` itself in a module-local table. The same source text returns the cached result without re-running `computeFn`; different source text recomputes. Keyed on the source content (not an asset checksum) because composite/container assets (component folders, scene folders, etc.) all hash to the empty-string checksum — a checksum-keyed cache collapses every such asset's detail onto whichever one was inspected first. ## Usage ```luau local Introspect = require("modules.luau_introspect") local src = self:getInitScript() local detail = Introspect.forSource(src, function(s) return { fields = Introspect.publicFields(s), events = Introspect.events(s), methods = Introspect.methods(s), hooks = Introspect.lifecycleHooks(s, lifecycleCatalog), } end) ``` ## Notes - Every function is a pure string→table transform: same source text in, same structured table out, every time. No reads of live component state, no entity/world queries. - Structural scanning runs over a comment- and string-aware **mask** of the source (a same-length copy where comment bodies and string-literal contents are blanked to spaces, delimiters and newlines preserved). Pattern matches and brace/paren balancing run on the mask — so a brace, `Field.`, `Event(`, or a whole entry that appears inside a comment or a string literal never registers — while captured values are sliced from the original source at the same (aligned) indices. This makes the parser robust to apostrophes in comments, commented-out entries, string defaults containing `}` / `Field.` / `Event(`, and `[[ ]]` long strings. - `default` / `category` are raw trimmed source-text slices (with any trailing comment stripped), not evaluated values. - For a **ref constructor** (`Field.assetRef` / `dataRef` / `resource` / `componentRef`) the FIRST positional argument is the category / contract / componentType selector, captured under `category`; the SECOND argument is captured under `default`. - For every **other** Field kind the first argument is the `default` and `category` is nil. - A trailing `Sync` / `NoSync` identifier is captured as `sync`, tolerating a trailing comma or a trailing comment after the last argument. - Field/Event entries whose key is a computed or indirect expression (`[expr] = Field.number(...)`) are omitted — only literal identifier keys are recognised. - `methods` captures a `...` variadic parameter (as `name = "..."`), with its `: <type>` annotation when present. - A `--!desc` written above a field/event declaration (`<name> = Field.<kind>(...)` / `<name> = Event(...)`) or a `public.<name> =` assignment binds to that name in `docstrings`, and is folded into the corresponding `publicFields` / `events` entry's `desc`. - `lifecycleHooks` never hardcodes the lifecycle-callback catalog; the caller passes the list of names to match against. - `forSource`'s memo is bounded (oldest-key eviction) so a long session touching many distinct asset versions can't grow it without limit.

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ref

module · born here

❒asset

# 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.

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yaml

module · born here

❒asset

# 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 — the bare indicators only. 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 `---`), block-scalar chomping/indentation indicators (`|-`, `|+`, `>-`, `|2`, ...), 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).

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json

module · born here

❒asset

# json JSON encode/decode library for Luau. Encodes Lua values to JSON strings and decodes JSON strings back to Lua values. Used for communication with the Rust side of the engine, the VFS read/write bridge, and any wire-format that needs JSON. Pure Luau, no engine dependencies. Compact and pretty-printed encoders, plus a hand-rolled decoder that streams the input by position so it works under WASM as well as native. ## Exports - `Json.encode(value: any, indent?: string, currentIndent?: string) -> string` — compact encode. Functions / unknown types and NaN/Inf encode as `null`. - `Json.encodePretty(value: any, indentStr?: string) -> string` — pretty-printed encode with sorted object keys (diff-friendly). - `Json.encodeArgs(...: any) -> string` — encode varargs as a JSON array. - `Json.decode(str: string) -> any` — decode a JSON string. Returns the decoded value, or `nil` + error message on failure. ## Usage ```luau local Json = require("@builtin::modules.json") local widget = { type = "button", text = "Click Me" } local compact = Json.encode(widget) -- '{"text":"Click Me","type":"button"}' local pretty = Json.encodePretty(widget, " ") local decoded = Json.decode(compact) local v, err = Json.decode("oops") -- v = nil, err = error message ``` ## Notes - Object keys are sorted alphabetically in both encoders for consistent output across runs. - Numeric keys on objects are stringified at encode time (JSON has no numeric keys). Pure-integer key sets get detected as arrays via `isArray` and encoded with brackets. - NaN, +Inf, -Inf encode as `null` — JSON has no representation. Round trips through `decode` recover `null` (Lua `nil`), so they don't preserve. - Unicode `\uXXXX` escapes decode to UTF-8 by hand to stay WASM-safe. Only the BMP is covered; supplementary planes via surrogate pairs are not. - Functions encode as `null`. - Decode is character-streamed — no regex, no `string.match` patterns on the whole input — so the line-and-column information needs to be reconstructed from the position offset.

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shared

module · born here

❒asset

# 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.

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arg	type	description
x	?	World-space X coordinate.
y	?	World-space Y coordinate.
z	?	World-space Z coordinate.

arg	type	description
x	?	Direction X, or nil to reset to the shape's native +Y frame.
y	?	Direction Y.
z	?	Direction Z.

arg	type	description
t	?	Seconds to advance.
stepDt	?	Fixed step size in seconds (default 1/60).

arg	type	description
x	?	World-space gravity X component.
y	?	World-space gravity Y component (negative pulls down).
z	?	World-space gravity Z component.

arg	type	description
x	?	Acceleration X component.
y	?	Acceleration Y component.
z	?	Acceleration Z component.

arg	type	description
mode	string?	`"off"`, `"bounce"`, `"stop"` or `"kill"`.
opts	{ [string]: any }?	Optional `{ restitution, friction }`. `restitution` is how much

arg	type	description
min	?	Minimum lifetime (or single constant value when `max` is omitted).
max	?	Maximum lifetime; defaults to `min` if nil.

arg	type	description
min	?	Minimum initial speed.
max	?	Maximum initial speed; defaults to `min` if nil.

arg	type	description
min	?	Minimum initial rotation in degrees.
max	?	Maximum initial rotation in degrees; defaults to `min` if nil.

arg	type	description
min	?	Minimum rotation speed in degrees/sec (negative for CCW).
max	?	Maximum rotation speed in degrees/sec; defaults to `min` if nil.

arg	type	description
index	?	1-based slot index in [1, 32].
value	?	Float value to write.

arg	type	description
name	?	Named param (matches PARAM_LAYOUT, case-insensitive) or "user<N>".
value	?	Float value to write.

engine

modules.particles — Generic GPU-driven Particle System (deprecated)

Quick start

Why GPU-driven

Architecture

Storage buffers, per system

What one particle carries into its material

Per-particle state (16 f32 = 64 bytes)

Params buffer layout

Frame loop

Curves: NumberSequence + ColorSequence

Emission shapes

Collision

Shadow casting and render layers

Depth fade

Custom WGSL update shaders

Performance notes

Roadmap (follow-up issues)

API reference

Interface

conforms to

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`modules.particles` — Generic GPU-driven Particle System (deprecated)