fluidSurface.renderFeature

# renderFeature A **render feature** inserts custom GPU passes into the frame pipeline. The engine provides one generic capability — a per-frame render-pass queue and a set of pipeline-phase insertion points — and a feature is the authored Luau that decides what passes to enqueue, and where, every frame. ## Authoring contract A `.renderFeature` folder holds an `init.luau` that returns a feature module: ```luau return { setup = function(ctx) -- optional; runs once when the feature goes live -- A "fragment" pass's `shader` names a POST EFFECT, not a `.shader` -- guid directly — postprocess.add compiles the shader asset under -- that name once, here. Enqueueing a name never passed to -- postprocess.add runs the pass as a no-op every frame (the log -- reads "effect '<name>' not compiled — pass skipped"). postprocess.add("my_effect", asset.resolve("my.shader.guid", "shader"), { enabled = false }) end, render = function(ctx) -- required; runs every frame -- enqueue one or more passes. The spec shape depends on `kind` (see -- "Pass kinds" below): this is a "fragment" pass (full-screen shader over -- input textures); a mesh effect (outline, x-ray) is a "geometry" pass -- with `material` + `select` (see "Geometry passes"). ctx.enqueue { phase = "afterTransparent", shader = "my_effect", inputs = { src = "@scene.color" }, output = myRenderTargetGuid, } end, teardown = function(ctx) end, -- optional; runs once when the feature is destroyed } ``` Optional `materials/` and `shaders/` subfolders hold shader source the feature constructs GPU programs from. A feature constructs its GPU programs (it does not reference `.material` surface assets). ## `ctx` Built fresh each frame and passed to `setup` / `render` / `teardown`: | Field | Meaning | |-------|---------| | `ctx.enqueue(spec)` | Queue one render pass for the current frame. | | `ctx.viewport` | `{ w, h }` — the **main viewport's** size in pixels. | | `ctx.time` | Seconds since boot. | | `ctx.frame` | Monotonic frame index. | | `ctx.renderPath` | `"forward"` / `"deferred"` / … — branch passes on the active path. | | `ctx.settings` | The feature's knobs as they stand this frame — see "Settings". | ## Settings A feature declares the knobs it takes as `settings`, each a Field descriptor with a default, the way a component declares its public fields: ```luau local Fields = require("@builtin::modules.field") local Field, NoSync = Fields.Field, Fields.NoSync return { settings = { intensity = Field.number(1.0, NoSync, "How much of the effect reaches the image."), quality = Field.enum({ "low", "high" }, "high", NoSync, "How many samples the pass spends."), }, render = function(ctx) local s = ctx.settings -- { intensity = 1.0, quality = "high" }, or what a caller set ... end, } ``` The engine holds one settings table per live feature — every declared default, overridden by what it was handed — and passes it as `ctx.settings` on every `setup` / `render` / `teardown`. A feature reads its knobs there and nowhere else, so any caller tunes any feature by name: ```luau local h = renderer.feature.create(ref, { settings = { intensity = 0.5 } }) renderer.feature.configure(h, { quality = "low" }) -- lays over the rest renderer.feature.settings(h) -- { intensity = 0.5, quality = "low" } renderer.feature.find(ref) -- the live handle, or nil renderer.feature.schema(ref) -- the declared knobs, unrun ``` A knob the feature does not declare, or a value of the wrong shape, is refused by name. A scene authors its features on one `RenderFeatures` entity — a list of features, each with its settings — which adopts a feature already live rather than stacking a second, and takes every one down on disable and destroy. `render` runs **once per frame**; the passes it enqueues run **once per render target** drawn that frame — the live viewport, every offscreen capture, every RTT camera — each at its own resolution. So `ctx.viewport` is the main viewport's size, not the size of the target a pass ends up drawing into. Size a full-screen scratch RT with `screen = true` and let the engine track the drawn target (see "Screen-sized targets") rather than deriving it from `ctx.viewport`. ## Screen-sized targets `renderer.texture.create { screen = true }` marks a feature RT as full-screen: before each render target's feature passes, the engine resizes it to that target's resolution. Create it once — the engine owns its size from then on: ```luau myRt = renderer.texture.create { width = ctx.viewport.w, height = ctx.viewport.h, -- initial size only screen = true, format = "rgba16f", name = "my_effect", } ``` A target that holds a picture of the scene is `rgba16f`, which is what the scene target itself carries: linear light with headroom above the display's white and no 256-step floor under a dark gradient. Omitting `format` on a screen-sized target asks for the same thing. `format = "rgba8"` is for a mask, a weight or an occlusion term, where 0..1 is the whole range — hand one of those back over `@scene.color` and the frame loses every highlight and bands every gradient, and the engine says so in the log. `screenScale` (default `1.0`) takes a fraction of the drawn target's resolution, for a scratch that runs below composite resolution (a half-res blur passes `0.5`). A screen-sized RT is what makes a full-screen effect composite correctly at any resolution. Deriving the size from `ctx.viewport` instead pins the RT to the main viewport, and every differently-sized render target then composites a mismatched scratch — the scene scaled into a corner with the rest black. `screenSpace` names WHICH image a screen-sized RT follows: | value | what it tracks | |---|---| | `"scene"` (default) | the scene render target, at whatever resolution the render scale asked for. Resized before EVERY render target's feature phases — the main frame and each offscreen one — and cleared to transparent before an offscreen render, so one sink never reads what another left behind | | `"composite"` | the image the post-scene phases draw into. Resized on the presented frame only, and never cleared for an offscreen render, since none of those phases run there | The two carry the same size until the render scale drops below 1. From there, while the renderer presents the viewport itself, the scene reaches the display's resolution through an upscale that runs before `afterScenePost` — so a composite-space RT is the display's size while a scene-space one is the smaller rasterized frame. Under a UI viewport panel the panel draws the scene target at its own rect, nothing upscales beforehand, and both spaces carry the scene's size. A scene-space target is scratch: whatever a pass does not rewrite this render is transparent black. A composite-space target survives an offscreen render untouched, but it follows the presented frame alone. ## History targets An accumulation across frames (temporal antialiasing, a temporal denoiser, any pass that reads what it wrote last time) lives in a history target: ```luau history = renderer.texture.create { width = ctx.viewport.w, height = ctx.viewport.h, -- initial size only history = true, format = "rgba16f", name = "my_accum", } -- in render(ctx): ctx.enqueue { kind = "compute", program = myResolve, inputs = { scene_color = "@scene.color", accum_previous = history.previous.guid }, buffers = { accum_state = history.state }, storage = { accum_out = history.guid }, phase = "afterLighting", } ``` The passes a feature enqueues run once for every view the frame draws (the viewport, each render-to-texture camera, each capture), so an accumulation has to be one per view. A history target keeps one pair of images per view, sized to that view: for the length of a view's render `history.guid` names the image the render writes and `history.previous.guid` the image the same view's previous render wrote. Another view never resizes, clears or overwrites them, and a view's images are freed when it stops drawing. It follows `screenSpace` and `screenScale` like any screen-sized target; a composite-space one is kept for the viewport, the one view that draws the post-scene phases. Before each render of a view the engine writes `history.state`, one `vec4<f32>` a pass binds through `buffers`: | field | holds | |---|---| | `x` | 1 when `previous` holds this view's previous image; 0 on the view's first render, its first after a camera cut or a change of size, or after a render of the view that ran without the target, and `previous` then reads transparent black | | `y` | how many renders in a row have carried the history | | `zw` | this render's sub-pixel projection offset, in pixels (`renderer.setProjectionJitter`) | `renderer.setProjectionJitter` is the matching per-view sample sequence: every view walks it by its own count of renders, so the sequence a temporal pass expects is the one each view's renders sampled. ## Pass phases `enqueue` runs a pass at a named pipeline boundary — a real seam between the scene's discrete passes — ordered within a phase by `order`. Each phase is the point where the scene colour holds a specific, nameable state: | Phase | Scene colour there | |-------|--------------------| | `afterDepthPrepass` | the visibility raster written: `@scene.depth` holds this frame's complete opaque depth, and `@scene.motion` its opaque motion, before anything shades. Scene colour is not yet drawn; `@scene.colorHistory` holds the previous frame's lit colour, and the deferred g-buffer the previous frame's surfaces (`readsPrevious`) | | `afterShadows` | shadow maps populated; scene colour/depth not yet drawn | | `afterSky` | sky only; depth empty | | `afterOpaque` | opaque drawn, before transparents. `@scene.depth` (and the deferred G-buffer) are populated. Forward: lit opaque. Deferred: opaque is in the G-buffer, so the colour is still sky only until the composite (use `afterOpaqueLit`) | | `afterOpaqueLit` | the lit opaque scene, still before transparents, on **both** paths — the forward opaque draw, or the deferred lighting composite. The background a refractive or transmissive surface samples: the one phase whose colour holds what is behind such a surface without holding the surface itself | | `afterTransparent` | transparents drawn, before the OIT composite | | `afterLighting` | deferred-lighting + OIT composite done — fully lit, final geometry on **both** paths | | `afterScenePost` | scene-layer post (DoF/MB/…) done, before UI | | `afterUI` | scene + UI composited | | `afterPost` | all-layer post done — the final image, before present | The last three are the post-scene phases, and they work on the COMPOSITED image: `@scene.color` there is the target the UI lands on, not the scene render target. `@scene.depth` and `@scene.motion` still bind — they are the scene's own buffers for the frame just drawn, which is what lets a pass at these phases reproject the composite it is handed — but they keep the SCENE's resolution. Whenever the render scale is below 1 on the presented frame, that is smaller than `@scene.color`, so a pass here maps between the two by uv rather than by texel index, and takes its own output size from the target it writes. The `@scene.*` inputs (`@scene.color`, `@scene.depth`, …) bind the live frame buffers; the deferred g-buffer channels (`@scene.normal`, `@scene.shaded`, …) resolve only on the deferred path. Before the pass that shades has drawn — at `afterDepthPrepass` — a g-buffer channel holds the previous frame's surfaces, and a pass reading it there names the slot in `readsPrevious` (`readsPrevious = { "scene_normal" }`); one that does not is held back rather than handed a stale normal. `@scene.colorHistory` is the lit colour the target's previous render ended with, kept by the engine per render target and never cleared by a frame: what a pass tracing at `afterDepthPrepass`, against this frame's depth, takes its light from — reprojected through the previous view-projection `@frame.camera` carries. A capture drawn once, or a camera drawn again after a pause, is drawn lit first when a pass reads the history, so its first frame holds one. Every `@scene.*` channel, what it holds, its format, the phase it is first valid from, and the earlier spellings still bound to it: | Name | Holds | Format | Valid from | Aliases | |---|---|---|---|---| | `@scene.color` | the scene's lit colour; the display composite at a post-scene phase | the scene target's format at a scene phase, the display composite's at a post one | every phase | — | | `@scene.depth` | opaque depth, reversed (1.0 near, 0.0 far/empty sky) | `Depth32Float` — binds through a `texture_depth` compute slot, not `texture2d` | `afterDepthPrepass` on | — | | `@scene.motion` | screen-space NDC velocity since the previous frame | `Rg16Float` | `afterOpaque` on | — | | `@scene.normal` | world-space normal + the per-pixel surface-flag field | `Rgb10a2Unorm` | deferred path, `afterOpaque` on (previous frame's before — declare `readsPrevious`) | — | | `@scene.shaded` | what a surface SENT — its shaded colour, linear and scene-referred | `Rgba16Float` | deferred path, `afterOpaque` on (previous frame's before) | `@scene.albedo` | | `@scene.material` | what a surface IS — base colour (RGB565) + metallic + perceptual roughness | `Rgba8Uint` | deferred path, `afterOpaque` on (previous frame's before) | `@scene.mr` | | `@scene.emissive` | radiance a pass stamped on the surface, added at the composite | `Rgba16Float` | deferred path, `afterOpaque` on (previous frame's before) | — | | `@scene.ao` | scene occlusion a feature wrote, read back by shading | `Rgba8Unorm` | every scene phase (cleared at the top of the scene render) | — | | `@scene.reflection` | traced reflection radiance (`.rgb`) + confidence (`.a`) | `Rgba16Float` | every scene phase (cleared at the top of the scene render) | — | | `@scene.colorHistory` | the lit colour the target's previous render ended with | `Rgba16Float` | every phase | — | | `@scene.lights` | the per-frame punctual-light storage buffer: twelve vec4s per light, the light then its punctual shadow record | storage buffer | every phase | — | | `@scene.environment` | the reflection-probe cube array | texture cube array | scene phases only | — | | `@scene.environmentSampler` | the filtering sampler for `@scene.environment` | sampler | scene phases only | — | | `@scene.reflectionProbes` | the environment buffer: the probe blend data naming which probe reaches a point, then the irradiance light-probe volumes | storage buffer | scene phases only | — | `docs/topics/rendering.guide/guide.md` and `docs/topics/raytracing.guide/guide.md` both point here rather than repeating this table. **Two g-buffer channels describe the surface, and they answer different questions.** `@scene.shaded` is what a surface SENT — the colour the geometry pass shaded it to, linear and scene-referred, so a surface lit above the display's peak reads above 1 there. `@scene.material` is what the surface IS: the base colour it reflects, its metallic and its perceptual roughness, each in [0, 1] and each independent of how brightly the surface happens to be lit. A pass that multiplies incoming light by a reflectance — a bounce multiplier, a Fresnel tint, an ambient floor — reads `@scene.material`; a pass that filters the picture reads `@scene.shaded`. `@scene.material` is an `Rgba8Uint` channel packing all three into 32 bits, so its slot declares `sample: uint` and the module unpacks it: ```yaml # bindings.yaml - { name: scene_material, kind: texture2d, sample: uint } ``` ```wgsl #include "@builtin::shaderModules.gbuffer_material" let m = zero_gbuffer_material(scene_material, coord); let bounce = incoming * m.base_color; ``` The earlier spellings still bind: `@scene.albedo` resolves to `@scene.shaded` (the SHADED lit colour) and `@scene.mr` resolves to `@scene.material` (the material channel), so a feature written against either keeps resolving. The engine logs the substitution once per spelling, naming the canonical one to write going forward. `@scene.motion` carries screen-space velocity: the NDC displacement each pixel's surface underwent since the previous frame, so a still surface under a still camera reads `(0, 0)`. Opaque geometry contributes it on both render paths: the visibility raster writes it for every surface it records, and an opaque surface whose depth state the raster cannot express writes its own where it draws. A moving entity, a moving camera and an animated pose all reach it in the viewport; transparents, particles and sky carry none. A surface a material's `vertex()` hook displaces carries the displacement's own velocity. A render target's own camera and a capture keep no view history, so velocity there is the entity's motion with no camera term. `@frame.camera` is a reserved **buffer** input carrying the camera CURRENTLY being drawn: 10×`vec4<f32>` = the inverse view-projection (columns `[0..4)`, column-major) + camera world position (`[4].xyz`) + the previous render's view-projection (columns `[5..9)`), which projects a point into the picture that render left. A compute pass declares a `buffer` binding and binds it via `inputs = { name = "@frame.camera" }`, then reconstructs a pixel's world position from `@scene.depth`: ```wgsl let inv_vp = mat4x4<f32>(cam[0], cam[1], cam[2], cam[3]); // ndc.z is the `@scene.depth` sample itself. Scene depth is reversed — 1.0 is // the near plane, 0.0 the far plane and empty sky — and this matrix inverts // that same range, so a sample goes in unmodified. let wh = inv_vp * vec4<f32>(ndc, 1.0); let world_pos = wh.xyz / wh.w; ``` Like `@scene.*`, the engine resolves it **per render target** — so the same pass reconstructs against the live viewport's camera on screen and against an offscreen capture's / RTT camera off screen. (Pack a camera matrix into your own buffer instead and the offscreen render reconstructs against the wrong camera.) > Render-feature passes run in the main viewport render **and** in offscreen > captures / render-to-texture, each against its own camera. The `capture` tool's > `source = "position"` / `"entity"` therefore run the pass queue too; using > `@frame.camera` is what keeps those captures matching the live viewport. ### The environment A compute pass reads the scene's captured surroundings — the reflection-probe cube array, its sampler and the environment buffer (the probe blend data, then the irradiance light-probe volumes) — through three reserved inputs, bound to bindings of the shapes group(0) binds them in: ```yaml bindings: - { name: environment_map, kind: textureCubeArray } - { name: environment_sampler, kind: sampler } - { name: zero_environment, kind: buffer, access: read, element: ZeroEnvironment, array: false } ``` ```luau inputs = { environment_map = "@scene.environment", environment_sampler = "@scene.environmentSampler", zero_environment = "@scene.reflectionProbes", } ``` Named like that, `#include "zero::environment"` in the shader resolves the environment at a world point along a direction — `zpbr_sample_environment(world_pos, dir, lod)`, the probes whose radius reaches the point blended by rank and proximity, each through its proxy volume, and the sky under them — exactly as a material's environment term does, so a reflection a pass draws and one a material draws agree about the room they are in. The three bind at the scene phases; a post or UI phase carries none. A `textureCubeArray` binding takes `@scene.environment` alone, and a fragment pass has no slot of that shape. ## Pass kinds `enqueue` runs one of three kinds (the `kind` field; default `"fragment"`): - **`"fragment"`** — a full-screen shader over input textures. The program is a GPU **material** (or `shader`) the feature constructed; `inputs` bind live textures (`@scene.*` or RT guids), `output` is the target RT (omit = the phase's default scene target). Post-process, blur, edge effects. **Writing named G-buffer channels (`outputs`).** Instead of the single `output` RT, a fragment pass may declare an `outputs` array — one or more targets, each a named engine channel (`@scene.shaded` / `@scene.normal` / `@scene.emissive` / `@scene.color`) or an RT guid — each with its own blend mode: ```luau ctx.enqueue { kind = "fragment", shader = myShaderKey, outputs = { { target = "@scene.shaded", blend = "under" }, -- premultiplied dst-over-src { target = "@scene.emissive", blend = "additive" }, -- one fullscreen pass, two targets (MRT) }, phase = "afterOpaque", -- deferred: G-buffer filled, before the lighting composite } ``` Blend modes: `"replace"` (overwrite), `"alpha"` (source-over), `"additive"` (sum), `"under"` (premultiplied dst-over-src — accumulates coverage-weighted contributions). A `@scene.*` channel resolves only where it exists (the deferred G-buffer at a pre-composite phase); a pass whose targets are all unavailable at its phase is skipped (logged). `output` + `blend = true` remains the shorthand for a single alpha-blended target. The shader's returned colour is written to every target in the set. A fragment shader returns `vec4<f32>`, so the channels it can target are the float ones. `@scene.material` (and its earlier spelling `@scene.mr`) is `Rgba8Uint`, which binds as `uint` — naming it as an output is refused by name, with the channel's format and class in the log, and the rest of the frame draws. A fragment pass's `inputs` reads through the same fixed float slot, so naming `@scene.material` there is refused the same way; a compute pass reads that channel through a `sample: uint` slot instead. **What a pass with no `inputs` samples.** A fragment pass that declares no `inputs` reads `@scene.color` — the shape of an effect that filters the scene image. A pass that names `@scene.color` among its own `outputs` samples a 1x1 transparent texel instead, because the scene colour is that pass's render target and one texture is a colour attachment or a sampled resource in a render pass, never both. Declare `inputs = { src = "@scene.color" }` and write an RT to read the scene image and write somewhere else in one pass. - **`"compute"`** — a workgroup dispatch (`shader`, `storage`, `buffers`, `dispatch`; see "Compute passes"). - **`"geometry"`** — draw scene geometry with a constructed pipeline. The program is a **material** the feature built (`renderer.material.create`); the engine draws the scene's render-objects with that material's pipeline + uniforms. - **`"draw"`** — rasterize the feature's OWN geometry: `geometry` names a buffer created with `usage = { "vertex" }`, `storage.index` one created with `usage = { "index" }`, and `select` the one entity whose transform and material the draw lands through. `params[0]` is how many indices to submit — or name a buffer under `storage.indirect` (created with `usage = { "indirect" }`, holding a `DrawIndexedIndirectArgs` block: index count, instance count, first index, base vertex, first instance) and the count comes from the GPU instead, so a compute pass that compacts geometry pays only for what it kept and nothing waits on a read-back. `first_instance` must be 0; the engine resolves the entity's per-instance data another way, because a non-zero one needs a device feature WebGPU does not guarantee. - **`"splat"`** — rasterize a compute buffer of particle records as instanced camera-facing billboards into feature RTs (see "Splat passes"). ### Geometry passes A geometry pass re-draws the scene's meshes with a material you supply — the generic primitive for mesh-space effects (the engine names none of them): ```luau ctx.enqueue { kind = "geometry", material = myMaterial, -- the HANDLE renderer.material.create -- returned (or its registry-key string) geometry = "@geometry.opaque", -- which drawables: "@geometry.opaque" | -- "@geometry.transparent" | "@geometry.all" select = { entityA, entityC }, -- OPTIONAL: restrict to these entities -- (entity refs); omit = every matching mesh phase = "afterLighting", -- afterLighting = lit scene + valid depth } ``` `select` restricts the draw to the given entities — the per-instance signal that turns a whole-scene pass into a chosen-meshes effect. The **material** decides how those meshes are drawn; you control three things: - **Pipeline render-state.** `renderer.material.create` takes a `render` block — `cull` (`back`/`front`/`none`), `depthWrite` (bool), `blend` (`opaque`/`alpha`/`additive`) — so the pass can rasterize differently from the surface pass: ```luau local myMaterial = renderer.material.create({ shader = myShaderKey, -- a .shader you authored (identity, not guid) render = { cull = "none", depthWrite = false }, properties = { outline_color = { 1, 0.4, 0, 1 } }, -- seed the shader's uniforms }, "my_pass_mat") -- pass `myMaterial` (or "my_pass_mat") as the pass `material` ``` - **The shader.** A geometry `.shader` is a surface shader: author `fn vertex(v: VertexData) -> VertexData` to move vertices (object-local `v.position` / `v.normal`) and `fn fragment(input: FragmentData) -> vec4<f32>` for the colour. - **Its properties.** A shader reads ONLY the uniforms IT declares in `properties.yaml`, via `material.<yourProp>`. Referencing a field it didn't declare (e.g. a StandardMaterial `material.base_color`) fails to compile and the mesh renders **magenta** — declare the property or use a constant. What effect those three produce (outline, x-ray, wireframe, highlight, …) is yours to design — the engine just draws the selected geometry with your pipeline. ### Compute passes A compute pass dispatches a `.shader` compute program over a workgroup grid: ```luau ctx.enqueue { kind = "compute", shader = myComputeShaderKey, storage = { outTex = myStorageRtGuid }, -- slot -> storage-texture RT guid buffers = { particles = "my_particle_buf" },-- slot -> named compute buffer inputs = { camera = "@frame.camera" }, -- slot -> @frame.*/@scene.* buffer dispatch = { x = 64, y = 1, z = 1 }, } ``` **`dispatch` is optional.** Omit it and the pass is dispatched over what it WRITES: a grid covering its first `storage` texture, at the `@workgroup_size` the shader's entry point declares. With a screen-sized storage target that grid tracks the render target being drawn, so a screen-space effect covers the live viewport, an offscreen capture and an RTT camera without the feature knowing any of their resolutions: ```luau ctx.enqueue { kind = "compute", shader = myComputeShaderKey, inputs = { scene_color = "@scene.color", cam = "@frame.camera" }, storage = { outTex = myScreenSizedRt.guid }, -- screen = true phase = "afterLighting", } ``` State an explicit `dispatch` for a grid that is not one thread per output texel (a reduction, a particle sim), or when the shader's `@workgroup_size` is an override/const expression the engine cannot read. Each WGSL storage-buffer binding in the shader resolves its bound slot in this order: an explicit `buffers` mapping (the handle a buffer's owner holds, or a name), then `inputs` (`@frame.camera` / `@scene.lights` / `@scene.reflectionProbes`), then — when a slot has neither — a buffer whose engine-side name equals the slot's own name. `buffers` is the seam a pass binds through: the buffers a shader works over are the ones handed to it, whatever each is called. `storage` binds storage TEXTURES (RT guids) the same way, one map per resource kind. ### Splat passes A splat pass draws every record of an f32 buffer as a camera-facing billboard — the raster primitive behind screen-space particle surfaces (the `fluidSurface` system is built entirely on it): ```luau ctx.enqueue { kind = "splat", phase = "afterLighting", output = depthRt.guid, -- or `outputs` for the thickness+color MRT splat = { buffer = "my_particles", -- compute-buffer name stride = 12, -- floats per record posOffset = 0, -- float offset of the position count = 200000, -- records to draw radius = 0.3, -- world particle radius channel = "depth", -- "depth" | "thickness" | "sprite" | "gaussian" velOffset = 4, -- optional: velocity → screen-space stretch stretch = 0.04, -- seconds of motion elongating the billboard colorOffset = 8, -- optional (thickness): + per-particle RGB → MRT weightOffset = 7, -- optional (sprite): per-particle intensity minY = -60.0, -- records below this y collapse (parked/dead) maxRadiusPx = 120, -- optional: cap on the projected pixel radius }, } ``` The `"gaussian"` channel draws the engine's packed splat records — what `renderer.splat.components` decodes a `.spz` or `.ply` capture into — as elliptical-weighted-average Gaussians, and takes fields of its own: ```luau splat = { buffer = "cloud_records", stride = 6, -- the packed record is six u32 words posOffset = 0, count = 1200000, radius = 1.0, -- multiplies each splat's stored scale channel = "gaussian", orderBuffer = "cloud_order", -- back-to-front permutation; "over" needs one shBuffer = "cloud_sh", -- optional: quantized higher-order SH shStride = 24, -- u32 words of SH per record shDegree = 3, transform = model, -- object -> world, column-major, 16 floats prevTransform = prevModel, -- where `transform` stood last frame opacityScale = 1.0, } ``` `transform` places the cloud: each Gaussian's covariance is conjugated by its upper-left 3×3, so a non-uniform scale shears the cloud the way it shears a mesh. `prevTransform` plus a second entry in `outputs` makes the channel write an MRT pair — the colour into the first target, and the screen-space displacement each splat underwent between the two placements into the second, premultiplied by the same alpha the colour composites under. That second target therefore resolves to `(coverage-weighted mean displacement, coverage)`, which is what folds a moving cloud into `@scene.motion`. Naming one target, or leaving `prevTransform` out, renders the colour alone. The other three channels write different fragments: `"depth"` writes nearest-surface linear view depth (R32Float, hardware-depth-tested on the target's own depth buffer), `"thickness"` accumulates additive optical thickness (with `colorOffset` and a two-entry `outputs` list it also accumulates thickness-weighted color into the second target), and `"sprite"` accumulates a soft additive disc scaled by `weightOffset`. Every channel discards fragments behind opaque scene geometry by sampling the scene depth at the fragment's own NDC. `maxRadiusPx` scales down billboards whose projected major radius would exceed that many pixels, so particles crossing the near plane stay droplet-sized instead of filling the screen. Targets clear at the pass; `blend = true` on the spec loads them instead to accumulate over a prior splat pass. `renderer.feature.create(featureRef)` instantiates a feature and returns a live handle (`featureRef` may be an `AssetRef<renderFeature>` or its identity string). The handle appears under `/zero/runtime/generated_features/<guid>/`. Re-creating the SAME feature asset replaces the live one (hot-reload after editing `init.luau`) rather than stacking a duplicate. - `renderer.feature.list()` → `{ {guid, identity} }` for every live feature. - `renderer.feature.destroy(handleOrGuid)` (or `renderer.destroy(handle)`) tears one down — by handle OR by guid string, so you can stop a feature even after losing its handle (e.g. across separate `execute` calls). ## In the Inspector Selecting a render feature opens its **Feature** section: whether the feature runs in this session, an Enable or Disable action, and its settings as typed controls. While it runs, the controls hold its live values and an edit reconfigures the running feature (`renderer.feature.configure` checks it against the schema first). Those edits are session state: they change the running feature only, they are not undoable (Ctrl+Z never reaches them), and Disable or a restart ends them; the feature's declared defaults are what the next Enable starts from. While it does not run, the controls show the declared defaults, read-only, and a write reaching it then is refused. A feature enabled, disabled or reconfigured from a script shows in the section as it happens. A feature that declares no settings says so.

# fluidSurface Screen-space fluid surfaces for GPU particle sims. Attach a named compute buffer of particle records (`fluidSurface.attach`) and the engine renders it as a continuous liquid every frame: splat passes rasterize every particle as a velocity-stretched billboard into depth / thickness / color buffers, a separable narrow-range filter fuses particles into a smooth surface while keeping silhouettes crisp, and a post-process composite shades the result with scene-color refraction, Beer–Lambert absorption from the per-pixel liquid color, Fresnel sky pickup, sun specular, and a foam layer — depth-tested against the scene. Everything runs at a configurable fraction of the screen resolution and the particle data never leaves the GPU, so hundreds of thousands of particles render as fluid in a few milliseconds. `update` patches count/radius/sun/shading live; `detach` frees every resource the surface owns.

# 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.

# 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**.

# fluidSurface A GPU particle simulation, rendered as a continuous liquid. Water made of particles has a problem: the particles are spheres, and a pile of spheres looks like a pile of spheres. Turning them into a mesh every frame is expensive and the mesh is thrown away immediately. This package skips the mesh — it renders the particles into screen-space fields and shades those, so the particle data never leaves the GPU and the cost scales with screen pixels rather than with the surface's geometric complexity. ## What it does ```lua local fluidSurface = require("@builtin::systems.fluidSurface.modules.fluidSurface") local rts = fluidSurface.attach("lake", { particles = { buffer = sim, stride = 16, posOffset = 0, count = 400000, velOffset = 4 }, radius = 0.35, }) ``` `particles` describes the record layout of the buffer the caller's simulation writes: how wide a record is, where the position sits in it, and how many are live. Pass the handle a compute shader's `createBuffer` answered. Everything after that happens per frame until `detach`. `update` moves the live knobs — the particle count as a sim grows, the sun direction as the day turns, any composite property: ```lua fluidSurface.update("lake", { count = active, sunDir = { 0.3, 0.8, 0.2 } }) ``` ## The chain 1. **Splat** (engine raster). Every particle draws as a velocity-stretched billboard: nearest-surface depth, hardware z-tested; additive thickness and thickness-weighted colour; and, when the records carry a foam weight, an additive foam sprite layer. 2. **Narrow-range filter** (`fluid_narrow_x` → `fluid_narrow_y`, ping-ponged `iterations` times). Neighbour depths are clamped into a band around the centre before averaging, so particles fuse into a surface while silhouettes stay crisp. The body is the `fluid_narrow_filter` shader module, included by both axes. 3. **Resolve** (one of `fluid_resolve`, `fluid_resolve_col`, `fluid_resolve_foam`, `fluid_resolve_col_foam`). Packs smoothed depth, blurred thickness and the foam fraction into `data`, and the mean liquid colour along each ray into `liq`. Which one runs is decided by whether the records carry a colour and a foam weight, because that changes which textures the pass binds. 4. **Composite** (`fluid_surface_composite`, a post-process shader). Refracts the already-rendered scene through the surface normals, absorbs along the view ray by Beer–Lambert, marches the reflected ray against scene depth so the water mirrors what is above it, adds sun specular, and lays foam on the thin edges. Depth-tested against the scene, so fluid behind geometry stays hidden. Every stage runs at `resolutionScale` of the screen (half by default). ## Sharing The passes are compiled once and shared by every surface. What a surface owns is its render targets, its own filter-parameter buffer, and its own composite — which is why two lakes at different particle radii filter at different widths without interfering.

# assetType.shared.settings Resolves four questions about an asset's typed settings, all answered from its type's `type.yaml` — nothing here is found by convention. ```lua local Settings = require("@builtin::assetTypes.assetType.shared.settings") -- or, from inside the assetType runtime: local Settings = require("@builtin::assetTypes.assetType.shared").settings ``` ## Where does a type's schema live? `type.yaml` names it in a `settings:` block: ```yaml settings: values: "settings.yaml" # where an instance's own values live schema: { type: "settings.luau" } # one schema for every asset of this type ``` or, for a type whose settings differ per instance (an importer): ```yaml settings: values: "settings.yaml" schema: { instance: "settings.luau" } ``` or, for a type whose schema is a table its instance's own source declares and whose values live elsewhere (a component: its `public` fields, valued on each entity it is on): ```yaml settings: schema: { instance: "init.luau", export: "public" } ``` Whether an instance may lack its schema file is what the type's `files:` block says of that file. Listed under `files.optional`, it may be absent, and an instance without it declares no settings — the importer type lists it there, since most importers take none. Listed under `files.required`, or not listed at all, it must load, and an instance missing it is a broken declaration and is logged. `schema.type` is required at the folder relative to the TYPE's own `.assetType/` directory (one schema shared by every instance). `schema.instance` is required relative to each INSTANCE's own folder (`init` resolves the instance's own identity; anything else is a sibling module under it). Without `schema.export`, the file is required as a module and its return value IS the schema. With `schema.export`, the file is run in an environment of its own and `export` is read from a returned table carrying it, or else from the globals the file assigned — a component's `public` is such a global. That environment reads through to `_G` and takes every write itself; its own `_G` is itself, its `declare` and `computed` record into it, and its `task` records spawned, deferred and delayed work instead of starting it. Every other global is the real one, so a call the file makes through one runs as it does anywhere. The schema is the declared table's Field descriptors. A schema that resolves to nothing says why through `Settings.schemaProblemOf(ref)`: the file could not be read, compiled or run, or declared no such table. An instance schema is read again when its file, its type's `type.yaml`, or the entry file of any module the asset `require`s changes. `Settings.blockFor(typeName)` returns the raw block; `Settings.schemaForType(typeName)` and `Settings.schemaOfInstance(ref)` resolve the two schema shapes respectively; `Settings.schemaFor(ref)` tries the type-level schema first, falling back to the instance-level one. `ref` naming an assetType asset itself — e.g. `asset.resolve("texture", "assetType")`, rather than an instance of it — reports that type's own declared schema, the same one every instance of it reports. ## Where do an asset's values live? `settings.values` names a file living beside the asset's own content — `Settings.valuesPathOf(ref)` joins it onto the asset's path. `Settings.valuesOf(ref)` / `Settings.writeValues(ref, values)` read and write it; this module only names where it is. A type that declares its schema with no `settings.values` keeps no values in the asset — a component's live on each entity it is on — so `valuesOf` answers nil for it, `asset.create` refuses a `settings` table for it, and `asset.setSettings` refuses a write. `Settings.recordedWrite(path, text)` writes a file the way every values file is written, and an editor uses it for any other file it writes. It writes the whole contents, records the write into the open undo operation when one is open (so undoing it restores what the file held), and raises when the write does not land. ## In what order are a schema's fields declared? Every `Field.*` constructor stamps its descriptor with `declaredOrder`, one more than the last. Luau evaluates a table constructor's entries in the order they are written, so `Settings.orderedNames(schema)` lists a schema's fields — and a struct's subfields — in the order the source writes them. A values file, or a legacy `.metadata` settings block, may hold an older spelling — a renamed field, an older enum member. Every read passes what is stored through the type's `normalizeSettings` (`Settings.normalizeFor`), so it answers in the fields the schema declares today, and writes nothing. The next local edit of that asset rewrites the file in the declared spelling (`Settings.healLegacyIfNeeded`). `asset.setSettings(ref, patch)` writes a partial patch: `Settings.resolvePatch(ref, patch)` normalises it, merges it over the current values and applies the type's derived defaults for the fields it changed, and `Settings.writeValues(ref, values, patch)` applies the corrections, checks the schema and writes the file. ## How is a new asset's settings resolved at creation? `asset.create` calls `Settings.resolveForCreate(typeName, name, destPath, creationOpts, callerSettings, importerSettings)` before running the type's `onCreate`, checks the result against the schema, writes it to the values file, and hands `onCreate` a COPY of it as `opts.settings` (`Settings. cloneValues`) — never the same table the values file gets, so nothing `onCreate` does to its own copy can reach what was stamped. `onCreate` reads settings from `opts.settings` and never writes to it. `asset.create` also seeds the change baseline with the stamped values (`Settings.seedChangeBaseline`), so the values file's own first dispatch reports nothing changed and the payload `onCreate` encoded is the only encode a create runs. The layers, lowest priority first, each overriding the ones before it field by field: 1. The schema's own declared defaults (`Settings.defaultsOf`). 2. The type's own `settingsDefaults(name, opts, asked)` hook, when its `behavior.luau` exports one. `asked` holds what layers 3 to 5 name, so a default can follow a field one of them sets. 3. The Preset Manager's matching row (`Settings.presetLayerFor`). 4. The creating importer's settings for this type. 5. The `settings` table the caller passed to `asset.create`. 6. The type's own `settingsDerivedDefaults(values, explicit, changed)` hook, when its `behavior.luau` exports one — a field whose default follows another field, set only when no layer from 2 to 5 named it. 7. The type's own `settingsCorrections(values, name, opts)` hook, when its `behavior.luau` exports one — applied last, once every other layer has merged. Layers 2 to 5 are each read through the type's `normalizeSettings`, so a layer naming a field in an older spelling sets the field it names today. `asset.create`'s top-level settings alias accepts those older names too (`Settings.acceptedFieldNames`). Layer 7 is `Settings.applyCorrections(typeName, values, explicit, context)`, the one corrections path every settings write takes — this create chain, and `Settings.writeValues` for every later write (`asset.setSettings`, a type's first-encode seed, the legacy heal). `explicit` names the fields the writer asked for: the caller's `settings` table here, the patch for `asset.setSettings`. A correction lands SILENTLY on a field the writer did not name — nobody asked for that value, so overriding it just states a fact. A correction that contradicts a field the writer named REFUSES the write, naming the field, the value asked for, and why it cannot hold — the same as every other place this codebase refuses an explicit request it cannot satisfy (a `Field.checkSchema` violation, a BC7 alignment error) rather than silently rewriting it into something else. So `asset.setSettings(tex, { compression = "rgba16" })` on a mipped texture stores `generateMipmaps = false` beside it, while `asset.setSettings(tex, { compression = "rgba16", generateMipmaps = true })` is refused. `Field.checkSchema` runs once, over the result AFTER the corrections hook has applied — a bad value nothing corrects refuses the creation. ### Four hooks, four different jobs Every hook is an optional export on a type's `behavior.luau`, alongside `onCreate` / `onChange`. **None is ever handed a table to mutate** — each reads what it's given and RETURNS a table of what it wants changed (or nil); `resolveForCreate`, `resolvePatch`, `applyDerivedDefaults` and `applyCorrections` are the only places that write to the values, by merging what a hook returns the same way every other layer merges. - **`normalizeSettings(values) -> values`** maps every older spelling a stored file or a write may carry to the field and member the schema declares now, returning a new table; a table naming both an older field and its replacement keeps the replacement. The companion export **`normalizedSettingNames = { ... }`** lists the older field names it accepts beyond the schema, so a write naming one is not refused as an undeclared field. `texture.assetType`'s maps the fields its earlier schema stored to `colorSpace` + `compression`, and the older `filter` keywords to `linear` / `nearest`. - **`settingsDerivedDefaults(values, explicit, changed) -> partial?`** answers the values of fields whose default follows another field. At creation `changed` holds every field; on a write it holds the fields the write moved. A returned field applies only where `explicit` — the fields the writer named — does not name it. - **`settingsDefaults(name, opts, asked) -> partial?`** supplies a DEFAULT the schema itself has no syntax for — something only knowable at creation time, like a naming convention, a fact read off a payload the caller handed in, or a value that follows a field a higher layer sets (`asked` holds what the Preset Manager, the importer and the caller name, the higher one's value where two name a field). It runs early (layer 2 above), so any later layer — Preset Manager, importer, caller — freely overrides it. `texture.assetType`'s returns the `textureType` the name suggests (a `_normal`-suffixed name is a `normalMap`), `compression = "uastc"` and `maxDimension = 4096`, with `rgba8` for a `textureType` of `sprite` that a higher layer names; for a pre-encoded ZTEX payload it returns the colour space, compression and sampler the payload's own header carries. Either way, an explicit `settings = { ... }` from the caller still wins. - **`settingsCorrections(values, name, opts) -> (partial?, reasons?)`** enforces a CROSS-FIELD CONSTRAINT the schema itself has no syntax for — a fact about one field that depends on another field's resolved value, true regardless of which layer produced that value. It runs last (layer 7 above), over the fully merged `values`, and again on every later write of the values file. Nothing is left unmet in what gets validated and stamped — but a value the caller explicitly asked for is never silently rewritten to satisfy it; `applyCorrections` refuses instead (see above). The optional second return, `{ [field]: reason }`, supplies the "why" for that refusal message; a field with no reason falls back to a generic one. `texture.assetType`'s returns `{ generateMipmaps = false, maxDimension = 8192, colorSpace = "linear" }` whenever the RESOLVED `compression` is high-precision (the encoder stores one verbatim, linear, and refuses a mip chain or a downsample for it outright), paired with a reason naming the compression, and `nil` otherwise. ## What does a declarer declare? `Field.settingsOf(identity, mode)` embeds another declarer's schema as a struct field without restating it. The identity names one of two kinds of declarer, and `Settings.schemaOfDeclarer(identity)` tells them apart by what `identity` resolves to: - **An assetType** (e.g. `"@builtin::assetTypes.texture"`) — embeds the schema every instance of that type carries, resolved via `schemaForType`. This is the type-level shared schema from the section above, not a per-instance one — an assetType has no settings of its own to declare per instance. - **Anything else** (an importer, or any other asset that declares settings of its own) — embeds that asset's own schema, resolved via `schemaOfInstance`. Every schema this module serves has already run its `Field.settingsOf` fields through this resolution — a caller reading `schema.someField.fields` never sees an unresolved `declarer` with no `fields`. Resolution descends into an already-literal struct's `fields` and a list's `element` the same way, so a declarer embedded several fields deep is still reached. A declarer that embeds itself, directly or through another declarer, stops one level short of the loop instead of recursing forever. ## What are the defaults? `Settings.defaultsOf(schema)` reads every field's declared `default` into a plain table — a field declared without one is absent from the result rather than holding a `nil` value.

# edui.inspector.parts The building blocks a type's `inspector.luau` composes its sections from. Every Context carries this module as `ctx.parts`, so an inspector file requires nothing from `@builtin::editor`: ```luau return { sections = { { id = "summary", title = "Summary", build = function(ctx) local rows = ctx.parts.facts(ctx, { { label = "Vertices", value = 24 }, { label = "Size", value = ctx.parts.bytes(1536) }, }) local n = #rows for _, node in ipairs(ctx.parts.action(ctx, "rebuild", "Rebuild", function() ctx.ref:rebuild() end)) do n += 1 rows[n] = node end return rows end, } } } ``` Every function takes the section's Context first and returns a list of edui nodes, unless stated. | Part | What it shows | Callback key | |---|---|---| | `format(v)` | a value as text: integers plain, other numbers to 4 significant digits, booleans yes/no, a list as its length, a map as its entry count (returns a string) | — | | `bytes(n)` | a byte count as text: `84 B`, `1.5 KiB`, `2.00 MiB` (returns a string) | — | | `facts(ctx, rows, empty?)` | label/value rows (`{ label, value, mono? }`); the value takes the width its label leaves and wraps within it; a row whose value is nil shows "—", so a value that could not be read is seen to be missing. A row that does not apply to the subject is left out of `rows` by the section; with no rows `empty` shows | — | | `list(ctx, items, { max?, empty?, mono? })` | one text row per item, at most `max` (40), then "… and N more" | — | | `table(ctx, key, columns, rows, empty?)` | a table of records, each cell through `format` | `<keyPrefix>:tbl:<key>` (widget id) | | `links(ctx, refs, { max?, empty? })` | one button per asset (an AssetRef, a `{ __ref = guid }` envelope, or a guid or name), named and typed; clicking selects it. An item that does not resolve is listed as text | `<keyPrefix>:link:<guid>` | | `entityLinks(ctx, ids, { max?, empty? })` | one button per entity, by name; clicking selects it. An id whose entity no longer exists is listed as text, marked despawned | `<keyPrefix>:ent:<id>` | | `action(ctx, id, label, run, { primary? })` | a button running `run`; a run that raises shows its message beneath the button until the next run | `<keyPrefix>:act:<id>` | | `openFile(ctx, path, label?)` | an action opening `path` in the Code panel; nothing when the file is absent | `<keyPrefix>:act:open:<path>`, the path relative to the subject's folder | | `problems(ctx, problems, clean?)` | one notice per `{ message, code?, severity?, line? }` (error tone, or info for a warning, info or hint), or `clean` ("No problems.") | — | | `swatch(ctx, color, label)` | a colour square (`{ r, g, b }` in 0..1) beside its label and hex (returns one node) | — | | `cached(key, paths, compute)` | `compute()`'s value, computed again only when the content version of one of `paths` moves (returns the value). Read through `ctx.parts`, it is held while a Context that read it stays open; read through the module itself, until the next `Inspector.release` | — | | `state(ctx)` | the table a Context's sections keep state in between builds (a picked zoom, a chosen tab), forgotten when the Context is released (returns the table) | — | | `check(ctx, path)` | a "Check" action running `lsp.check(path)`, then the counts and diagnostics of the last check of the file's current content | `<keyPrefix>:act:check:<path>`, the path relative to the subject's folder | | `values(ctx, { subject, schema?, values?, write?, readOnly? })` | typed controls over any values: one control per schema field, each edit checked with `Field.check` and written through `write` inside one undoable operation; `readOnly` shows the values with no control that writes. The same subject shown by two Contexts keeps two states | `<keyPrefix>:val:<subject>:set:<field>` | ## Rules a section keeps - **No write in `build`.** A build only reads; writes happen in an action's `run`, in `ctx.setSettings`, or in a `values` part's `write`. - **Expensive reads are once per content version.** A build that decodes a payload, walks a file or asks the LSP goes through `cached` (keyed on the files the value comes from) or runs behind an action. `check` holds each file's last result for as long as the file's content is unchanged. - **Every callback key starts with `ctx.keyPrefix`**, so two subjects — the panel's asset and an inline editor of the same asset — never share one. - **What the parts hold goes with the Context.** `ctx.parts` is the parts as that Context reads them. `Inspector.release(keyPrefix)` forgets the Context's action failures, file checks and state, and every cached value no other open Context read.

# contactShadows Runtime control of the scene contact shadows — `.set` / `.get` / `.clear` / `.active`, with `.lights` reading back the lights this frame's traces aim at and `.refresh` re-reading the scene's lighting. `set` takes any subset; omitted fields keep their value, and a `strength` of 0 releases the render pass. For contact shadows a scene should simply have, author the `ContactShadows` component instead. The full description of the knobs and the pass is in the package readme: `guides { path = "systems/contactShadows" }`.

# debugViz render feature Draws the batched geometry buffer that `@builtin::modules.debugViz` rebuilds every edit-mode tick from every registered provider — bounds boxes, camera frustums, and any further gizmo the debugViz core gains. One Draw pass over the core-owned vertex/index buffer pair, rasterized as GPU lines through the shared vertex-colour unlit material (`@builtin::shaders.debugGeometry`). An empty state (no providers with geometry yet, or the driving `DebugViz` component not yet awake) enqueues nothing.

# 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.