globalIllumination

# BakedLighting Keeps the scene's baked lighting in step with the scene. Watches the engine's authored-change feed and reacts the moment an edit reaches the bake: the artifacts that described the old scene are dropped, the withheld lights come back, and (with `autoBake` on) the scene re-bakes itself once the edits settle. The bake attaches this automatically — a scene that has been baked is a scene that maintains its bake. ## Fields | Field | Default | Purpose | |---|---|---| | `autoBake` | true | Re-bake once the edits settle. | | `settleSeconds` | 1.5 | Quiet time after the last edit before re-baking. | | `resolution` | 0 | Lightmap resolution for the re-bake; 0 uses the bake's default. | | `samples` | 0 | Sample count for the re-bake; 0 uses the bake's default. | With `autoBake` off the stale bake is still dropped — the scene shows honest realtime light rather than a stale photograph — and re-baking becomes an explicit `baking.all`. ## Cost Nothing until something is baked, and nothing at all in play mode. Authored edits are an edit-mode concern and static geometry does not move at runtime, so the engine's change feed is inert while the game runs. Dragging a wall across the room drops the bake once, on the first frame of the drag, and re-bakes once after `settleSeconds` of quiet — not once per frame. ## Usage ```luau -- opt out of automatic re-baking, keep automatic invalidation entity.find("scene").component.add("BakedLighting", { autoBake = false }) ```

# LightingScenario Cross-fades a probe volume between two baked lighting states. Sits beside a `VolumeProbe`. ```lua local scenarios = require("@builtin::systems.globalIllumination.scenarios") -- light the scene for noon, bake, then: scenarios.capture(volId, "noon") -- light it for dusk, bake again, then: scenarios.capture(volId, "dusk") entity(volId).component.add("LightingScenario", { from = "noon", to = "dusk", blend = 0, }) ``` | field | meaning | |---|---| | `from` | the captured scenario at `blend = 0` | | `to` | the captured scenario at `blend = 1` | | `blend` | where between them the volume's indirect light sits | Both names must already name a capture; until they do, nothing is published and the volume keeps whatever field it last had. A weight that has not moved republishes nothing, so holding a scenario costs no per-frame work. For more than two states, or a schedule of your own, drive `@builtin::systems.globalIllumination.scenarios` directly.

# SkyResponse The volume's sky term, evaluated when the sky changes instead of baked in. Sits beside a `VolumeProbe`. ```lua local sky = entity(volId).component.add("SkyResponse", { skyR = 0.4, skyG = 0.6, skyB = 1.0, }) sky:calibrate() -- two bakes, once sky.skyB = 0.2 -- no bake ``` | field | meaning | |---|---| | `skyR` / `skyG` / `skyB` | the sky colour the volume's indirect light is lit by | | method | | |---|---| | `:calibrate()` | bake twice and keep the two terms; returns `{ probes, floats }` | | `:isCalibrated()` | whether those terms are held | Until it is calibrated, moving the sky colour publishes nothing and the volume keeps whatever field its own bake gave it. Calibrating restores the `VolumeProbe`'s authored sky before it returns, so what that component holds is unchanged by calibrating.

# VolumeProbe Defines a 3D grid of irradiance probes covering a region of world space. The baked field publishes into the renderer's irradiance-volume set: every standard-PBR fragment inside the bounds (movers, avatars, freshly spawned props) samples it — no per-entity setup. The entity's world position is the volume centre; `sizeX/Y/Z` are the extents along each axis; `resX/Y/Z` controls how many probes are packed into the volume along each axis. ## Fields | Field | Default | Purpose | |---|---|---| | `sizeX/Y/Z` | (10, 4, 10) | World-space size of the volume. | | `resX/Y/Z` | (8, 4, 8) | Probe grid resolution along each axis. | | `samples` | 64 | Sphere samples per probe (Hammersley sequence). | | `bounces` | 3 | Surface interactions each sample path follows. | | `intensity` | 1.0 | Multiplier on the stored radiance at sample time. | | `rayMax` | 100.0 | World-space max distance for sample rays. | | `skyR/G/B` | (0, 0, 0) | Sky radiance seen by rays that escape geometry. | Bake bookkeeping lives in private fields, reachable through the reflection triad (`:fields()` / `:getField(name)` / `:setField(name, value)`): | Private field | Default | Purpose | |---|---|---| | `fieldId` | "" | Stable publish/persist key, minted on first bake. | | `lightmapData` | nil | Baked-lighting container holding this volume's field entry. | A 12×4×12 volume = 576 probes. Each probe stores 9 vec4 (36 floats) of SH L2 coefficients = ~81 KB per volume. Bake time on the GPU scales roughly linearly with `probeCount * samples * log(triangleCount)`. ## Persistence A bake writes the SH field into the scene's baked-lighting container (`lightmapData` asset) keyed by `fieldId` and points the `lightmapData` ref at it. On a fresh boot, awake restores the SH buffer and republishes the field from the container — no re-bake. `baking.clear` retires the field (retract + buffer + container entry). ## Usage ```luau local VolumeProbe = require("@builtin::systems.globalIllumination.volumeProbe") local probe = entity.spawn("level_probes") probe.localPosition = { 0, 0, 0 } probe.component.add("VolumeProbe", { sizeX = 30, sizeY = 6, sizeZ = 30, resX = 12, resY = 4, resZ = 12, samples = 128, }) VolumeProbe.bake(probe.id) ``` Re-bake whenever scene geometry or lighting changes. `bakeAll()` processes every volume in the scene using a shared BVH so the amortised cost stays low.

# bakeScene The scene-reading layer the bake stands on. Before any lightmap or probe field is computed, the bake has to answer one question about the scene as it currently stands: what is bakeable, and where. This module is that answer, read the same way by the `baking` toolbox, by the probe auto-placement in `volumeProbe`, and by component code driving a bake of its own. ## What it reads - **Scope** — `resolveScope` turns a name, id, entity proxy, an array of those, or `nil` (the whole scene) into the flat set of entity ids a pass considers. A scope that names nothing raises rather than silently baking the wrong set. - **Lights** — `gatherSpatialLights` collects the placed lights whose reach defines where indirect light matters. Directional and ambient light is global and carries no position, so it never anchors a volume. - **Renderables** — `collectStatic` finds the static `Model` receivers a lightmap is baked onto; `renderableBounds` bounds everything that renders. Mobility is the axis: static geometry takes lightmaps, movers sample probe volumes. ## How it places `clusterLights` groups lights by influence overlap (two lights join when their influence spheres touch, transitively), so two separated rooms yield two volumes rather than one box spanning the dead space between them. `mergeClustersTo` caps the volume count by fusing the nearest clusters, and `gridForBounds` sizes each volume's probe grid to a target spacing while holding a hard total-probe budget — a large volume gets coarser probes instead of a runaway count. `padBounds`, `boundsCenterSize`, and `lightInfluenceBounds` are the small bounds arithmetic the rest builds on.

# bakeState Keeps the scene's baked lighting honest about the scene it was baked from. A bake is a photograph of a moment: move a wall, edit a static light, or delete a prop and every lightmap and probe field taken before that moment describes geometry that is no longer there. `BakedLighting.component` drives this module off the engine's authored change feed (`layers.onEntityChanged`). The bake attaches that component itself, so producing baked artifacts and maintaining them are one act. ## Invalidation is scene-wide Indirect light is global. One moved wall changes the bounce reaching every surface around it, so invalidating only the wall would leave its neighbours holding light that wall no longer casts. `invalidate` drops every lightmap, retires every probe field, and reinstates every withheld light row. That is also what makes the invalidation visible: the viewport goes from baked to realtime light the moment the edit lands, instead of continuing to show a stale photograph. ## What reaches a bake `affects(entityId)` answers it: | Edit | Reaches the bake | Reason | |---|---|---| | Static geometry moved / changed | yes | `geometry` | | Static light edited | yes | `light` | | A tracked receiver or light despawned | yes | `removed` | | Movable geometry, dynamic light | no | realtime, never baked | A despawned entity can no longer be read, so `dependents()` — refreshed after every bake and every invalidation — is the record of what the bake depended on. ## API - `BakeState.affects(entityId) -> (boolean, reason?)` - `BakeState.isBaked(entityId) -> boolean` - `BakeState.dependents() -> { string }` - `BakeState.hasBake() -> boolean` - `BakeState.refresh()` - `BakeState.hasMaintainer() -> boolean` - `BakeState.ensureMaintainer() -> boolean` - `BakeState.setLightsBaked(ids, baked) -> number` - `BakeState.invalidate(reason?) -> InvalidateReport` - `BakeState.rebake(opts?) -> RebakeReport` `rebake` recomputes the volumes already placed and the static receivers already there. Placing new volumes is an authoring decision the `baking` tools own.

# baking Shared utilities for the globalIllumination package's lightmap and probe bakers — light gathering, surface-attribute gathering (albedo + emissive per instance), transform helpers, and the scene-geometry gather that feeds `compute.buildBvh`. The lowest layer of the package; both bakers consume the same primitives so the lighting model stays consistent across the lightmap and probe pipelines. ## Exports Constants: - `Baking.SH_COEFFS = 9` — number of L2 SH basis functions per probe. - `Baking.SH_FLOATS_PER_PROBE = 36` — std430-padded SH stride. - `Baking.TRI_FLOATS = 72` — std430-padded triangle stride (matches the BVH builder). - `Baking.BVH_NODE_FLOATS = 8` — floats per BVH node on the GPU. - `Baking.LIGHT_FLOATS = 16` — GPU light record stride. Functions: - `Baking.vec3 / add / sub / scale / dot / cross / length / normalize` — vec3 helpers used everywhere downstream. - `Baking.gatherLights() -> { Light }` — enumerate every `Light` component in the scene. - `Baking.packLights(lights) -> FloatArray` — pack lights for compute upload. - `Baking.transformPoint / transformNormal / makeMatrix / entityWorldMatrix` — 4x4 matrix helpers. - `Baking.surfaceAttributes(entityId, cache) -> { albedo, emissive }` — the entity's bake-facing surface description: linear albedo (base_color factor × average base-color texture color, clamped below 1) and emissive (color × strength). - `Baking.gatherMeshInstances(excludeIds?) -> { instances, release }` — every mesh-bearing entity as a `{ guid, transform, attributes }` record for `compute.buildBvh`, CPU mesh items materialised; `release()` drops them again. - `Baking.getEntityTriangles(entityId) -> { Triangle }` — one entity's mesh triangles in local space (used by the UV rasterizer). Types: - `Vec3 = { x: number, y: number, z: number }` - `ColorRGB = { r: number, g: number, b: number }` - `UV = { x: number, y: number }` - `Mat4 = { number }` — 16-float row-major. - `Light = { id, kind, position, direction, color, intensity, radius }` - `Triangle = { v0, v1, v2, n0, n1, n2, uv0, uv1, uv2 }` ## Usage ```luau local Baking = require("@builtin::systems.globalIllumination.baking") local lights = Baking.gatherLights() local gather = Baking.gatherMeshInstances({ entityId }) local bvh = compute.buildBvh(gather.instances) gather.release() ``` ## Notes - All vec3 helpers return new tables — none mutate their arguments. Safe to call in hot paths but allocates per call. - `gatherMeshInstances` walks `entity.findAll` and materialises each mesh-bearing entity's CPU item (`ecs.Mesh` guid → mesh asset → `ref:load()`), so the engine-side BVH build can read the geometry — triangles never enter the Luau heap. Call `release()` after the build; assets whose `keepCpu` setting holds them stay resident. - `surfaceAttributes` deduplicates the texture averaging through the `cache` table — pass one table per gather so entities sharing a material average its texture once. Albedo lanes are clamped to 0.96 so multi-bounce transport converges.

# lightmap Bakes full global illumination (shadowed direct light plus multi-bounce indirect gathered by path tracing through the scene BVH) into per-entity lightmaps: the bake output is read back, dilated across UV seams, and copied into the receiver's region of ONE shared atlas that the PBR module samples through the receiver's per-instance lanes — the receiver keeps the material it was authored with. Each texel traces `samples` cosine-weighted chains of up to `bounces` surface interactions, so color bleed, emissive surfaces, and sky occlusion all land in the map. Receiver selection is the `Model.mobility` axis: only static-mobility world entities bake. Movable geometry samples the published probe fields instead. Set `Model.mobility = "static"` to override a wrong derivation. Every bake persists: the dilated texels land in the scene's baked-lighting container (`lightmapData` asset) keyed by the entity, and the receiver's `Model.lightmapData` ref points at it. A fresh boot restores the lightmap from the asset (`applyFromAsset`, called by the Model component's awake) with zero re-baking. ## Exports - `Lightmap.bake(entityId: string, opts: BakeOpts?) -> BakeReport` — bake one static entity's lightmap into the shared atlas and point the receiver at it. Yields while the GPU bake + read-back complete. - `Lightmap.bakeAll(opts: BakeOpts?) -> { BakeAllEntry }` — bake every static receiver in the world, reusing a single light + BVH cache across them. - `Lightmap.applyFromAsset(entityId: string) -> (boolean, string?)` — restore a receiver's baked lightmap from its persisted container entry (the boot path; no re-bake). - `Lightmap.clear(entityId: string)` — destroy the bake buffer, the runtime lightmap texture, and the per-entity material, restore the entity's original material, and remove the container entry. - `Lightmap.bufferName(entityId: string) -> string` — stable per-entity bake-output buffer name (`"gi_lightmap_<sanitized id>"`). - `Lightmap.materialName(entityId: string) -> string` — stable per-entity material name produced by `bake`. Types: - `ColorRGB = { r: number, g: number, b: number }` - `BakeOpts = { resolution?, texelsPerMeter?, samples?, bounces?, intensity?, rayMax?, shadowSoftness?, sky?, lightsCache?, bvhCache?, rastCache?, containerCache? }` - `BakeReport = { ok, resolution, texelCount, validTexels, ms, bufferName, materialName, textureGuid }` - `BakeAllEntry = { id: string, report: BakeReport }` ## Usage ```luau local Lightmap = require("@builtin::systems.globalIllumination.lightmap") local report = Lightmap.bake(entityId, { resolution = 64, samples = 16, bounces = 3 }) print(report.ms, "ms") -- Bake every static receiver in the world: local reports = Lightmap.bakeAll({ samples = 32 }) -- Tear down: Lightmap.clear(entityId) ``` ## Notes - `bake` refuses non-static receivers with an error naming the mobility rule — the published probe fields are the movable-geometry counterpart. - `bakeAll` builds a single BVH and gathers lights once, threading the caches through every per-entity bake. Add/move lights between invocations to invalidate. - The lightmap texture is a runtime GPU resource under a stable per-entity guid (`BakeReport.textureGuid`); re-bakes update it in place, so the material keeps rendering the latest bake with no re-binding. - Texel coverage rides in the texture's alpha; the upload dilates covered texels over uncovered neighbours so bilinear filtering never bleeds black across UV island seams. - `clear` is a no-op when the entity is missing or never baked.

# lightmap_bake Bakes a lightmap on the GPU — one thread per lightmap texel. Each thread reads its world position + normal, evaluates the shadowed direct irradiance (every scene light, visibility via a BVH shadow ray), then gathers indirect irradiance by tracing `indirectSamples` cosine-weighted path chains of up to `bounces` surface interactions. Every path vertex contributes its emissive plus its albedo (carried on the triangle records by `compute.buildBvh`) times the shadowed direct light there; a segment that escapes contributes the sky. Direct + indirect accumulate as RGBA into `output` (A = coverage). Bindings (see bindings.yaml): `output` (read_write), `texel_positions`, `texel_normals`, `bvh_nodes`, `triangles`, `lights`, `params` — all `array<vec4<f32>>`. Usage: dispatch by identity with `compute.dispatch("@builtin::systems.globalIllumination.lightmap_bake", ...)` (buffers in bindings order) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# lightmap_blur Edge-aware à-trous denoise pass over the indirect half of a lightmap bake. Dispatched by the `lightmap` module between the bake and the read-back: four 3x3 passes with doubling tap stride ping-pong the indirect texels through a scratch buffer, smoothing Monte-Carlo variance over a wide world-space radius. Per-tap weights from the bake's position and normal buffers keep the smoothing on the local surface — taps across a UV chart seam or on different geometry weigh ~zero. The direct half never passes through this kernel, so baked shadow edges keep their full sharpness.

# probe_bake Bakes irradiance-volume probes on the GPU — one thread per probe. Each thread casts N uniform-sphere rays and path-traces each one through up to `bounces` surface interactions: every path vertex contributes its emissive plus its albedo (carried on the triangle records by `compute.buildBvh`) times the shadowed direct light there, and a segment that escapes contributes the sky. The resulting incoming radiance is projected into 9 SH L2 coefficients (Monte Carlo weighted) and written as 9 RGBA `vec4`s into `output`. Mirrors `lightmap_bake`'s traversal + light model. Bindings (see bindings.yaml): `output` (read_write), `probe_positions`, `bvh_nodes`, `triangles`, `lights`, `params` — all `array<vec4<f32>>`. Usage: dispatch by identity with `compute.dispatch("@builtin::systems.globalIllumination.probe_bake", ...)` (buffers in bindings order) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# scenarios.module Several baked lighting states per probe volume, blended at runtime. A volume holds one bake, so a scene lit for noon cannot become a scene lit for dusk without baking again — which takes far longer than a transition is allowed to. Capturing each bake under a name turns that into an interpolation the frame can afford. ```lua local scenarios = require("@builtin::systems.globalIllumination.scenarios") scenarios.capture(volId, "noon") -- after baking under one lighting setup scenarios.capture(volId, "dusk") -- after baking under another scenarios.blend(volId, { noon = 0.25, dusk = 0.75 }) ``` Weights are normalised, so any positive scale expresses the same blend. A name with no capture is an error rather than a silent omission, so a typo does not quietly become a blend of everything else. `mix(fields, weights)` is the blend itself and is pure — the same fields and weights give the same array, so what a blend does to a field can be checked without a volume or a GPU. `field(volId, name)` hands back a capture for inspection or a blend of your own. `list` / `forget` / `clear` manage what a volume carries, and `stats()` reports how many volumes hold scenarios and how much they hold between them. ## What gets blended Irradiance adds, so blending the spherical-harmonic coefficients is the same as blending the light that produced them. Each coefficient's **fourth lane** is not light: it carries the probe's per-axis visibility reach and the markers the sampler reads. Those describe the geometry the volume sits in, which every scenario shares, so they are carried from the heaviest-weighted scenario rather than averaged — the mean of two distances describes no wall that exists. Carrying them from the heaviest contributor also makes the ends of a transition exact: a blend naming one scenario at full weight reproduces that scenario's field lane for lane.

# skyResponse.module A probe volume's sky term, evaluated at publish time instead of baked in. A probe bake follows each path until it escapes, and what escapes carries the sky's colour. Baking that in fixes the sky the moment the bake finishes: a scene cannot dim its sky for dusk, or clear an overcast, without paying for the bake again. The sky enters the path integral as `throughput * sky` where a ray escapes, and `throughput` — the product of the albedos the path already passed through — does not depend on the sky. So the field splits exactly, per channel: ``` field(sky) = lights + sky * aperture ``` `lights` is a bake under no sky. `aperture` is what a unit sky adds: how much of it each probe can see, tinted by whatever the light passed through on the way, so sky arriving through a red wall stays red. ```lua local skyResponse = require("@builtin::systems.globalIllumination.skyResponse") skyResponse.calibrate(volId) -- two bakes, once skyResponse.apply(volId, { 0.3, 0.6, 0.9 }) -- no bake ``` `combine(lights, aperture, sky)` is the evaluation itself and is pure, so what a sky colour does to a field can be checked without a volume or a GPU. `calibrated` / `terms` / `clear` manage what a volume holds. ## Why the split is exact Both terms come from real bakes at the same settings, and the bake seeds each path from the probe and sample index alone — no clock, no frame counter. Two runs therefore trace the same paths, and the subtraction that isolates the aperture carries no sampling residual: it is the difference of two identical path sets, not of two noise realisations. Each coefficient's fourth lane carries the probe's per-axis visibility reach rather than light. No sky changes geometry, so that lane is carried from the `lights` term and never differenced.

# uv_rasterizer UV-space scan-line triangle rasteriser for the lightmap bakers. Walks every triangle of an entity's mesh, projects it into UV pixel space, and for each covered texel writes the barycentric-interpolated world-space position and normal. Output is two flat `vec4`-strided float arrays ready for compute upload. ## Exports - `Rast.rasteriseEntity(entityId: string, resolution: number?) -> RasterizeResult` — rasterise one entity into per-texel position + normal buffers. Types: - `FloatArray = { number }` - `RasterizeResult = { positions: FloatArray, normals: FloatArray, texelCount: number, validCount: number }` ## Usage ```luau local Rast = require("@builtin::systems.globalIllumination.uv_rasterizer") local rast = Rast.rasteriseEntity(entityId, 64) -- rast.positions: buffer, 64*64 texels x 4 f32 — (x, y, z, valid) per texel -- rast.normals: buffer, 64*64 texels x 4 f32 — (nx, ny, nz, pad) per texel ``` ## Notes - Texels with no triangle coverage have `positions[i*4+4] == 0`. Bakers honour this `w` flag to skip empty texels; the lightmap shader uses it as a bilinear-filter weight to mask seams. - Triangle coverage is determined via the standard edge-function test with a `1e-6` epsilon to keep adjacent triangles from leaving cracks along shared edges. - Default `resolution` is 64 when the caller passes `nil` or a value less than 1. - Output is in world space — vertex positions are transformed by the entity's world matrix (`Baking.entityWorldMatrix`) before being written; normals get the 3x3 portion of the same matrix.

# volumeProbe Bake a 3D grid of SH L2 irradiance probes and publish it into the renderer's irradiance-volume set: every standard-PBR fragment inside the volume's bounds (movers, avatars, freshly spawned props) takes its ambient term from the field, sampled in fragment via trilinear interpolation across the 8 nearest grid points — no per-receiver setup. The bake path-traces every probe sample through the scene BVH for up to `bounces` surface interactions, so probes capture indirect light, color bleed, emissive surfaces, and sky occlusion. Probe storage is a flat array of SH coefficients — 9 `vec4` per probe (RGB packed in `xyz`, padding in `w`). Re-bake when geometry or lights change. Every bake persists: the SH brick lands in the scene's baked-lighting container (`lightmapData` asset) keyed by the volume's `fieldId`, and the volume's `lightmapData` ref points at it. A fresh boot restores and republishes the field from the asset (`restore`, called by the VolumeProbe component's awake) with zero re-baking. ## Exports - `VolumeProbe.bake(volumeEntityId: string, opts: BakeOpts?) -> BakeReport` — bake a single probe volume, publish its field, and persist it. - `VolumeProbe.bakeAll(opts: BakeOpts?) -> { BakeAllEntry }` — bake every entity with a `VolumeProbe` component, sharing scene-geometry + BVH caches and one container across volumes. - `VolumeProbe.restore(volumeEntityId: string) -> (boolean, string?)` — restore + republish a volume's persisted field (the boot path; no re-bake). - `VolumeProbe.retire(volumeEntityId: string)` — full teardown: retract the published field, destroy the SH buffer, remove the container entry, clear the ref. - `VolumeProbe.fieldLive(volumeEntityId: string) -> boolean` — whether a field is already published under the volume's key this session. - `VolumeProbe.publishKey(volumeEntityId: string) -> string` — the stable key the field publishes and persists under (`fieldId`, falling back to the entity id). - `VolumeProbe.findCovering(position: Vec3) -> (string?, boolean)` — the volume covering a world position, plus whether the point is contained (false = nearest fallback). - `VolumeProbe.readIrradiance(volumeEntityId: string) -> { any }` — read the baked field back (`{ pos, color }` per probe). - `VolumeProbe.bufferName(volumeEntityId: string) -> string` — stable per-volume buffer name. Types: - `Vec3 = { x: number, y: number, z: number }` - `ColorRGB = { r: number, g: number, b: number }` - `BakeOpts = { samples?, bounces?, intensity?, rayMax?, sky?, baseColor?, bvhCache?, containerCache? }` - `BakeReport = { ok, probeCount, resolution, bounds, ms, bufferName }` - `BakeAllEntry = { id: string, report: BakeReport }` ## Usage ```luau local VolumeProbe = require("@builtin::systems.globalIllumination.volumeProbe") local report = VolumeProbe.bake(volumeEntityId, { samples = 64 }) print(report.probeCount, "probes baked in", report.ms, "ms") ``` ## Notes - Volume size + grid resolution come from the `VolumeProbe` component on the volume entity (`sizeX`, `sizeY`, `sizeZ`, `resX`, `resY`, `resZ`). `bake` reads them each call so component edits propagate to the next bake without restart. - `rayMax` bounds every path segment; volumes that span large open scenes may want a larger value than the 100m default. - `bakeAll` builds one BVH and shares it across every volume — adding or moving lights between invocations is fine, but adding new meshes requires a fresh `bakeAll` for the BVH cache to refresh.

# Package (asset type) A package is an asset — a `<Name>.package/` folder that bundles components, modules, scenes, presets, tools, and any other typed sub-assets under one identity, installed into a world as one unit. Packages are how authoring sets get distributed across worlds. A **library** is the addressable root scope content resolves under (`@builtin`, `@<name>`) — a whole world mounted into this one under a namespace, via `zeromind.installLib` / `world.installLibrary`. A package is an asset that lives inside such a root, and one library holds as many packages as its author put there. A package is installed by guid the way every asset is (`zeromind.installAsset`). ## When to use one - You're authoring a coherent feature suite (character controller stack, voxel engine, UI kit, animation library) and want to ship it as one install target. - You want a stable identity worlds can install and resolve sub-assets against (`@<lib>::pkg.sub_module`). - You want versioning + a per-package metadata layer that travels with the contents. If you're authoring inside a single world and don't need a separate install lifecycle, you don't need a package — drop your `.component` / `.module` / etc. directly in `/zero/source/`. Packages are for cross-world distribution. ## Where it lives - Source: `/zero/source/.../<Name>.package/` (or, for legacy packages, a folder containing `package.yaml` at its root). - Identity: `<Name>` (the `.package` suffix collapses in identity — mirrors `.module`). A file at `<Name>.package/<sub>/init.luau` resolves under the same identity it would at `<Name>/<sub>/init.luau`. - Folder shape (container-style — open child set): - `package.yaml`: metadata (name, version, description) and the packages it depends on (`dependencies`). **Required.** - `README.md` — instance documentation. **Required.** - `.metadata` — agent-editable tags + free-form fields. **Required.** - Sub-asset folders: any combination of `.component/`, `.module/`, `.scene/`, `.preset/`, `.tool/`, `.toolbox/`, `.material/`, `.shader/`, etc. The validator permits unlisted children (`allow_unlisted: true`) by design — packages are open containers. ## How to create one ```luau asset.create("package", "<Name>") -- Creates: /zero/source/<Name>.package/ -- package.yaml (metadata scaffold) -- README.md (instance README template) -- `folder` places it in a subfolder of /source instead of the root: asset.create("package", "<Name>", { folder = "systems" }) ``` Then scaffold sub-assets inside it: ```luau local pkg = asset.resolve("<Name>.package") asset.create("component", "Spinner", { into = pkg }) asset.create("module", "util", { into = pkg }) ``` ## `package.yaml` ```yaml name: inkBlocks # optional; the folder stem when absent version: "1.0.3" description: "Ink and paper style blocks" dependencies: - { name: starterBlocks, version: "1.0.8" } - styleKit # a bare name states no version ``` `dependencies` lists the packages this package needs. Each entry's `name` is a reference the package records, the same kind of reference a `require` or an asset name in a data file makes: - **It resolves in the author's world.** Install the dependency here first (`zeromind.installAsset`); the entry then names the copy this world holds. A push refuses a package whose dependency resolves to nothing, naming it. - **An install brings it along.** Installing the package installs every dependency it lists, at the version this world holds when the package is pushed, under `/source/deps/<owner world>/`, deduplicated against what the installing world already holds. `zeromind.preview` lists each one before anything is written, and the install's `deps` lists what it brought. Uninstalling the package leaves a dependency that another installed package still uses. - **`version` is checked, not chosen.** A stated `version` has to equal the `version` the dependency's own `package.yaml` states in this world; `asset.validate` (and so the push) refuses the package naming both when they differ. To depend on another version, install that version here. ## How it operates 1. **Registration.** Writing `package.yaml` indexes the package with the package registry. 2. **Install.** A package is read before it is installed: `zm ls-tree @<guid>` in the shell lists what it contains, and `zm show @<guid>:<path>` and `zm grep <pattern> @<guid>` read it, so candidates are compared by what they do. The one that fits is installed by guid, the way every asset is: `zeromind_install` over the engine's MCP, or `tools.use("zeromind", "installAsset", <guid>)` inside the engine. The install writes the package's files (and the deps its `.refs` record, the packages its `package.yaml` lists under `dependencies` included) into this world's source, so its sub-assets resolve here. `tools.use("zeromind", "preview", <guid>)` reports what an install would write before it writes anything. 3. **Sub-asset resolution.** Because `.package` collapses in identity, sub-asset paths work whether the package folder is suffixed (`<Name>.package/<sub>`) or not (`<Name>/<sub>`). 4. **Updates.** `tools.use("zeromind", "updates")` lists installed content with upstream changes available; re-running the install pulls them. 5. **Metadata.** `package.yaml::name` overrides the folder stem if present (rare); `version` + `description` are surfaced in the package index. 6. **Hot reload.** Edits to sub-assets hot-reload as normal; edits to `package.yaml` reload package metadata. ## Discovery - `asset.list("package")` — every registered package. - `asset.inspect("<name>")` — sub-asset catalog, source, this type README. - `ls /zero/source/<Name>.package` lists the files the folder holds. - `library.list()` — the library assets registered in this world, including the ones packages under an installed library contribute. ## Authoring conventions - Name packages by their feature (`voxels`, `cameraRigs`, `dialogSystem`), not by their owner — the host library is the `@<lib>::` scope prefix. - Cluster cohesive sub-assets together. A "character controller" package should ship the controller component, its preset configs, its supporting modules, and a demo scene — not just the component. - Document the package's surface in `README.md` — what install installs, what each sub-asset does, how they relate. Agents reading `cat /zero/source/<Name>.package/README.md` get the full picture in one shot. - Version conservatively — breaking a package means breaking every world that installed it. Use semantic version bumps. ## Common pitfalls - **Missing `package.yaml`.** Without it the folder isn't recognized as a package even if it has a `.package/` suffix. - **A dependency named only by a string the code builds.** A package whose files reach another package only through a name assembled at runtime records no reference to it, so an install arrives without it. List that package under `dependencies` in `package.yaml`. - **Identity collapse.** Sub-asset paths skip the `.package` suffix. Don't include `.package` in `require` strings. ## Referencing inside a package: the `~` rule `~` means **this package**, resolved structurally from the referring file's own location. It is the only package-specific syntax. It is rename-safe (no package name is ever written) and library-agnostic (it never names the host library, so it survives `@builtin` being renamed or the package being mounted elsewhere). `~.tail` maps to `<pkg>.package/tail` from anywhere inside the package. | Referencing from | Use | Example | |---|---|---| | An asset/module **inside this package** | `~.tail` | `require("~.modules.myThing")`, `shader: "~.shaders.myThingBlend"` | | A **different package** under the same root | root-relative identity | `require("@root::systems.otherPkg.modules.x")` | | A **different library's** public API (a deliberate external dependency) | `@otherlib::…` | `require("@physics::modules.rigidbody")` | **Never write `@builtin::` (or any host-library name) to reference your own package** — that couples the package to the library it currently lives in and breaks if the library is renamed or the files move. Use `~.`. It works from Luau `require()` and from asset-reference strings in data files (a material's `mat.yaml` `shader:` field, a component's default asset ref); the engine resolves it against the referring file's own package. `asset.resolve` takes a `~.` name the same way, against the package of the file that calls it: `asset.resolve("~.materials.myThingStandard", "material")`. `~.` is the package-relative self-reference; `@root::` is the root-relative one (the library root, or the world source tree for non-library content). The `core/requiring-modules` guide covers the root model in full. A package that ships substantial functionality should include a `.guide` asset (a `<name>.guide/guide.md` folder anywhere under the package); the `guides` tool discovers it live, so collaborators find the system the way they find built-in guides. A package's test suite reaches the shared `Test` framework through its enclosing asset: `local Test = asset.containing(__FILE__).modules.shared` (`asset.containing` returns the deepest enclosing typed asset, the `.testSuite`, not the outer `.package`). ## Related types - Any of `.component`, `.module`, `.scene`, `.preset`, `.tool`, `.toolbox`, `.material`, `.shader`, `.style`, `.service`, `.importer` — packages bundle these. ## In the Inspector Package: the name, version and description package.yaml declares, how many things the package holds and what they are, and **Open** for package.yaml. A package.yaml that does not decode is listed under Problems with the decoder's error.

# Component (asset type) A component is a reusable behavior + data unit attached to an entity. The component file declares public fields, methods, and lifecycle callbacks; the engine instantiates one per attachment and drives its hooks every frame. Components are the primary unit of gameplay code — movement, AI, animations, UI panels, network sync, and per-entity state all live here. ## When to use one - You need per-entity state that survives across frames. - You need per-entity behavior driven by engine lifecycle hooks (`start`, `update`, `onDestroy`). - You want to expose configurable fields to designers / `entity.spawn` callers / scenes without code changes. If you need a stateless pure-function library, use a `.module`. If you need to generate content declaratively, use a `.service`; compute work belongs in a `.computeShader`. ## Where it lives - Source: `/zero/source/.../<Name>.component/` - Identity: `<Name>` (the `.component` suffix strips from the identity, but the folder retains the suffix on disk). - Folder shape: - `init.luau` (or `init.lua`) — declares the component. **Required.** - `README.md` — instance-level documentation. **Required.** - `.metadata` — agent-editable tags + free-form fields. **Required.** The structural contract is enforced by `asset.validate` against this type's `type.yaml`. ## How to create one Always start with the scaffold — it guarantees the folder shape matches `type.yaml` from the moment it's on disk: ```luau asset.create("component", "<Name>") -- Creates: /zero/source/<Name>.component/ -- init.luau (canonical declare + public block + hooks stubbed) -- README.md (instance README template) ``` After scaffolding, edit `init.luau` to fill in the actual fields and behaviour. The component registers as soon as the file is written — hot-reload is automatic; no engine restart required. ## How it operates 1. **Registration.** Writing `init.luau` into a `.component/` folder indexes the asset, mints a guid (in the `.meta` sidecar), and surfaces the type to the engine's component registry. Same-frame visible to `entity.component.add`. 2. **Attachment.** `entity(id).component.add(name, data)` (or the batch form `tools.use("entityOps", "addComponents", targets, { [name] = data })`) attaches an instance. The `data` table's fields override the component's declared defaults; omitted fields take the declared default. The `data` values are copied into `public.*` BEFORE `awake()` runs. 3. **Lifecycle.** The hooks run in this order: - `awake()` — same frame as attach, immediately after the data copy. Initialise state, set up native bridges, register with other systems. Other components on the same entity may not have awoken yet. - `start()` — the next frame. Every component on the entity has completed `awake()` by then, so cross-component setup is safe here. - `update(dt)` — same frame as `start()`, then every frame after, for as long as the gameplay clock is running. `fixedUpdate(dt)` runs once per physics step, straight after it, with the step's `dt`, so a frame can run it several times or not at all; `editorUpdate(dt)` runs while the clock is held. Which of them ticks is decided by `engine.mode` AND `engine.paused` together — see **Per-frame hooks and the two axes** below, and `man modes`. - `onDestroy()` — when the component is removed via `component.remove` or when the owning entity is despawned. Release resources, drop native ECS components. For the full list (`onEnable`, `onDisable`, `fixedUpdate`, `editorUpdate`, `onPropertyChanged`, `onAssetReload`, `onModuleReload`, `onBeforeSave`, …) and the timing details, **read `man components` — that is the canonical lifecycle reference. Generic component patterns (declare blocks, public fields, sync, ECS bindings, typed methods) all live there.** 4. **Public surface.** Fields declared in `public` are inspectable, editable in the inspector, and persist with the entity. Methods are declared on that same table with a colon — `typed function public:method(args)` — and every one of them takes the component ref as `self`, so a caller invokes it with a colon too: `entity(id).component.get(name):method(args)`. That is the one calling convention a component ref answers to: the reflection methods `ref:fields()` / `ref:getField(name)` / `ref:setField(name, value)` take the same spelling. A function the chunk declares at file scope (`function helper()`) is the component's own, reachable from its hooks under its bare name; `public` is what the ref carries. 5. **Settings and the Inspector card.** `type.yaml` names the component's settings schema as `settings: { schema: { instance: "init.luau", export: "public" } }`: the `public` table IS the schema, and its values live on each entity the component is on, so `asset.schema(componentRef)` answers the Field descriptors and no values file exists. On an entity the Inspector shows the component as a card whose generic `settings` section edits those fields as typed controls, each edit checked against the schema and written to the live component as one undoable operation. `type.yaml` also names `inspector: { instance: "inspector.luau" }`: a component that ships an `inspector.luau` beside its `init.luau` shapes its card — the file returns `{ sections, replace, order }` (see `assetTypes/README.md`, "`inspector:`"), each section's `build(ctx)` reading `ctx.component` (the live component) and `ctx.selection.id` (the entity). `SceneModule.component/inspector.luau` replaces `settings` with the bound module's declared inputs. 6. **Events.** An `events` block declares typed moments the component fires from inside — `events = { onHit = Event({ dmg = Field.number(0, NoSync) }) }`. The owner fires with `events.onHit:fire({ dmg = 10 })`; outside code subscribes through the proxy's subscribe-only facade, `entity(id).component.get(name).events.onHit:connect(fn)` (`:once` / `:wait` too). Pass `Sync` as the event's second argument to replicate a fire to other peers. Events let one component react to another's moments without polling. Full reference: **`man components`**, Events section. 7. **Hot reload.** Editing `init.luau` reloads the component definition; live instances are reconciled with the new declaration in-place, and each crosses one lifecycle boundary: `onDestroy()` ends the running life, then `awake()` and `start()` construct the one that replaces it, and `update()` resumes on the next frame. `public` and `private` values carry across; module-level `local`s belong to the chunk, so the new life starts with them at their initial values and its `awake`/`start` are what fill them in. Whatever the old life handed elsewhere — a subscription, a shared registration, a spawned entity — is released in `onDestroy`, the call that pairs with the construction about to run. An edit that leaves the source byte-identical crosses no boundary at all. A field carries its value across when something stated it: a key of the `data` table the instance was attached with (a scene record's data is that table), or a write made since. Every other field takes the edited source's declared default, so changing a default reaches every instance that left the field to it. An instance that states its own value for a field whose default the edit changed keeps that value, and the reload logs a `[HotReload]` warning naming the field, the entity, the value kept and both defaults. ## Discovery - `asset.list("component")` — every registered component (engine + world + libraries). - `asset.inspect("<name>")` — identity, scope, public fields, lifecycle methods, source path, and this type README. `detail` carries the component's declared `fields`, `methods`, and `events`, parsed from its source — `tools.use("assets","describe", "<name>")` renders it as markdown, so a component's events are visible without opening its source. - `ls /zero/source/<Name>.component` lists the files the folder holds. - `entity(id).component.list()` — components attached to an entity. ## Per-frame hooks and the two axes `engine.mode` (`"edit"` / `"play"`) and `engine.paused` (the gameplay clock) are independent, and the per-frame hooks read them separately: - `update(dt)` / `fixedUpdate(dt)` tick while **the gameplay clock is running** — whichever mode the engine is in. - `editorUpdate(dt)` ticks while **the clock is held** — because the mode is `edit`, or because play is paused — and also alongside `update` whenever edit is running. Which gives four states, and this table is the contract: | `engine.mode` | `engine.paused` | hooks that tick | |---|---|---| | `edit` | `true` | `editorUpdate` | | `edit` | `false` | `update`, `fixedUpdate`, `editorUpdate` | | `play` | `false` | `update`, `fixedUpdate` | | `play` | `true` | `editorUpdate` | Entering edit sets `paused = true` and entering play sets it back to `false`, so a session that never writes `engine.paused` only ever sees rows 1 and 3 — which is where the shorthand "`update` is the play tick, `editorUpdate` is the edit tick" comes from. It is the two default rows of a four-row table, not the rule. **Row 2 is the one that surprises.** With `engine.paused = false` in edit — set by hand, or by a tool that advances the gameplay clock to sample it, such as a `capture.collage` given a `duration` — `update` and `editorUpdate` both fire, once each, every frame. A component that declares both and routes them to one body therefore runs that body **twice per frame**: ```luau local function drive(dt) ... end function update(dt) drive(dt) end function editorUpdate(dt) drive(dt) end -- twice per frame in row 2 ``` Nothing reports the doubling; it reads as an animation running at twice its intended speed. To get exactly one tick per frame in every row, ask which axis you meant and answer it in the body: ```luau function update(dt) drive(dt) end function editorUpdate(dt) if engine.paused then drive(dt) end end ``` A scene `entrypoint.luau` declaring the same two hook names is dispatched by the scene loader, not by this table: there `update` needs play AND running, `editorUpdate` needs edit, and play-paused ticks neither. Read `man scenes` before carrying a component's rule to an entrypoint. ## Authoring conventions - Annotate public fields with `--!desc` so the inspector + LSP show documentation alongside the field name. - Declare lifecycle hooks (`start`, `update`, `onDestroy`) explicitly rather than relying on engine defaults — readers can see at a glance what runs when. - Keep `update(dt)` cheap — it runs every frame per instance. Move heavy work to `start`, to a `.computeShader`, or behind a job (`man jobs`). - For multi-entity batching, prefer `tools.use("entityOps", "addComponents", targets, components)` over a loop of `entity(id).component.add` — it takes many targets and many components in one call. ## Common pitfalls - **Naming.** The component identity is the folder stem with `.component` stripped (e.g. `<Spinner>.component/` → identity `Spinner`). Don't repeat the suffix in the identity passed to `component.add`. - **`init.lua` vs `init.luau`.** Either is accepted (it's a `one_of_group: "entrypoint"`), but `.luau` is canonical. Mixing both in one folder is invalid. - **`update` in edit mode.** It runs whenever the gameplay clock is running, and entering edit stops that clock — so `update` is idle in a freshly-entered edit session and ticks again the moment anything sets `engine.paused = false`. Use `tools.use("wld", "play")` to test update logic under the mode it ships in; `tools.use("wld", "edit")` to return. See **Per-frame hooks and the two axes** above. - **Renaming.** Renaming the folder changes the identity. References to the component are recorded against the component itself, so renaming or moving it does not break them. ## Related types - `.module` — pure-function library, no per-entity state. - `.service`: a declarative content generator, no per-entity state. - `.preset` — a captured component configuration, replayable into `component.add` without re-typing fields. - `.bundle` — entity hierarchies that may carry component attachments as part of the bundle. ## In the Inspector Fields: its execution order, hooks, and how many methods and events it declares, then the fields its `public` table declares as read-only typed controls holding their defaults, with **Check** and **Open** for its entry file. Instances: a link to every entity carrying it. What its card shows on an entity comes from the component's own `inspector.luau`.

# Module (asset type) A module is a reusable, stateless (or globally-stateful) Luau library that other code pulls in with `require()`. Modules are the unit of factored-out logic in a world: helpers, math libraries, format parsers, registries, shared algorithms. ## When to use one - You have logic you want to share across multiple components, services, scenes, or tools. - You have a registry, lookup table, or shared cache that callers all read from / write to. - You want a stable API surface (`M.fn`) other code can depend on. If the logic is bound to one entity, use a `.component`. If you want a named UI of fields rather than functions, use a `.preset`. ## Where it lives - Source: `/zero/source/.../<name>.module/` - Identity: the source path with `/` written as `.` and each segment's type suffix dropped — `/zero/source/demo/beats.module` is `demo.beats`, and `/zero/source/kit.package/beats.module` is `kit.beats`, the container's name kept and its `.package` suffix gone. `asset.create` returns this string, `asset.resolve(...).identity` reads it back, and the `require` forms below write it as `<identity>`. - Folder shape: - `init.luau` (or `init.lua`) — module body. **Required.** Returns a table (conventionally named `M`). - `README.md` — instance-level documentation. **Required.** - `.metadata` — agent-editable tags + free-form fields. **Required.** ## How to create one ```luau asset.create("module", "<name>") -- Creates: /zero/source/<name>.module/ -- init.luau (canonical `local M = {} … return M`) -- README.md (instance README template) -- `folder` places it in a subfolder of /source, and that subfolder -- leads the identity: `{ folder = "lib" }` produces `lib.<name>`. -- `into` authors it inside a resolved container (a package, a toolbox), -- whose own identity leads the same way: asset.create("module", "<name>", { folder = "lib" }) asset.create("module", "<name>", { into = asset.resolve("myPkg.package") }) ``` ## How it operates 1. **Registration.** Writing `init.luau` into a `.module/` folder indexes the asset and registers the module path with the resolver. 2. **Loading.** The first `require("<identity>")` runs the file's body and caches the returned table. Subsequent requires from anywhere return the **same table** — this is the shared-state lever for "module-local" registries. The body runs in an environment of the module's own: a name it declares without `local` is readable by the module's own functions and by no other script, so an export reaches its callers through the returned table and nothing else. Requiring a component's folder runs its chunk the same way, once, and its `update`, `start` and `public` stay in that environment; a component runs on an entity through `entity(id).component.add(name)`. 3. **Hot reload.** Editing the file re-runs the module body and folds what it returns into the table already loaded, so that table keeps its identity: a caller that captured it with `require` reads the new source's functions and values through the reference it already holds, and a later `require` returns that same table. A key the new source drops goes away; a key something set at runtime stays. The body's own `local`s start again from their initial values, so state that must outlive an edit lives in `modules.state()` (`guides { path: "core/scripting-and-tasks" }`). 4. **Identity resolution.** A module is reached by its `<identity>`, and where the caller lives decides which spelling of it resolves. For a module in a **world**, from a caller in that same world — another module, a component, a scene entrypoint, or an `execute` chunk: - `require("<identity>")` — the identity on its own, resolved against the caller's own root. It carries every folder segment, so a module created with `{ folder = "demo" }` is `require("demo.beats")`. - `require("@root::<identity>")` — the same root-relative resolution, written out. - `require(".sibling")` — a module in the same folder, by its bare name; `..name` steps up one folder, `...name` two. Logs, stack traces and hot-reload notices name that same module `@local.source.<identity>` — its key under the world source root. The `<identity>` tail of that key is the form above, so a trace reading `@local.source.demo.beats` is `require("demo.beats")`. For a module in a **library** — content under `/zero/source/libs/@<lib>/` — `@<lib>::` addresses that library's root from anywhere: `require("@builtin::modules.transform")`. Mounting a world as a library moves its files under such a root and flips the caller root to `@<lib>::`, which is what keeps the root-relative forms above resolving across the move. ## Discovery - `asset.list("module")` — every registered module. - `asset.inspect("<name>")` — public functions, source path, this type README. - `ls /zero/source/<name>.module` lists the files the folder holds. ## Authoring conventions - Return a single `M` table from `init.luau`. Top-level statements with side effects run on first require — useful for one-time initialization, dangerous if they touch the engine before it's ready. - Write exported functions as `typed function`, not `function`: the argument types are enforced at the call and the checker knows the signature, so a caller's mistake is reported where they made it. - Annotate exported functions with `--!desc` / `--!arg` / `--!return` / `--!example` so the LSP, `tools.list`, and `asset.inspect` surface them. A function with no `--!desc` is reachable only by someone already reading this file. - Declare a VALUE with `Field.<kind>(default, mode, description)`, and a table whose members are reached through a metatable with `--!members <TypeName>` — the latter gives the surface its accepted member set, its type, and its documentation from one table. See `guides { path: "core/authoring" }` for all four rules and `modules/api/engine/entity.module/members.module` for a worked member table. - Keep module state in module-local upvalues or in `modules.state()`. A name the body declares without `local` lives in the module's environment, which every run of the module shares: a function the previous run left in place reads what the reload assigned. Module-locals start again from their initial values with each hot reload; the table `modules.state()` returns is the same table on both sides of every reload. - Prefer focused modules over kitchen-sink modules. If two halves of a module have no shared state, split them. ## Common pitfalls - **Cyclic requires.** A `require` chain that loops will return the partial table (the half built before the cycle was detected). Design for one-way dependencies. - **Engine-time side effects.** Don't `entity.spawn` at module top-level — the engine may not be ready. Expose an `M.init` and call it from a scene entrypoint. - **Hot-reload + module-local cache.** A module that caches expensive computation in upvalues loses that cache on reload — fine for dev, but be aware in performance work. - **`init.lua` vs `init.luau`.** Either works, `.luau` is canonical. - **Writing one while play runs.** A `/source` write made while play is running lands on the play shadow, and a guarded play-exit discards it unless it is kept. One `.module` write shadows `init.luau`, the `README.md` and the `.metadata` together. `vfs.write(path, bytes, { durable = true })` skips the shadow, and `vfs.promotePlayShadow` keeps what is already on it — the `core/vfs` guide has the model and what each route costs. ## Related types - `.component` — for entity-bound state + lifecycle hooks. - `.service` — generates content you don't have yet (a mesh, sound, texture, …) via a metered provider. - `.tool` — for a single agent-callable function with a YAML schema. - `.package` — to group several modules + components + scenes into one shippable folder. ## In the Inspector Exports: what the module exports (name, kind, signature), parsed from its source without running it, with **Check** (the LSP's diagnostics for its entry file) and **Open**.

# guide A guide is a single-file documentation asset: a `<name>.guide/` folder whose body is `guide.md`, surfaced through the `guides` MCP tool, the `man` shell builtin and the Docs panel. Drop one anywhere under `/zero/source/`, a `.package` included, and it shows beside the built-in guides. ## Linking guides together A markdown link in a guide is followed when it is clicked in the Docs panel: `[Bindings](controls-guide)` opens another guide by any name `guides read` takes, `[Slots](#save-slots)` a heading of the same guide (its text in lower case, punctuation removed, spaces turned into `-`), `[Slots](save-kit#save-slots)` a heading of another, and `[the module](../saveKit.module)` a file or asset, relative to the guide's own folder. A link the panel cannot follow says why above the guide. ## In the Inspector Guide: the guide's word count, its headings, and **Open in Docs**, which opens it in the Docs panel.

# Compute shader (asset type) A `.computeShader` is a GPU compute (GPGPU) program with a **zero-scaffolding** authoring contract: you write only `@compute fn main(...)` plus a declarative `bindings.yaml`, and the engine GENERATES every `@group/@binding` declaration — storage buffers, textures, samplers, storage textures, and a `params:` uniform — expands `#include`s, naga-validates the result, and registers it. The single source of truth for the binding layout is `bindings.yaml`; there are no hand-written `@binding` lines to keep in sync. > New to how content lives across the CPU and GPU? Read `core/resource-model` > first: it covers the asset / CPU / GPU forms every resource takes, the upload > path, and how compute fits the performance ladder (`core/performance`). ## Folder shape A `.computeShader` is a folder asset: ``` <name>.computeShader/ shader.wgsl # the WGSL body — only `@compute fn main` + helpers (required) bindings.yaml # the binding + params schema (required) README.md # a one-paragraph description of THIS shader (required) .metadata # asset metadata ``` Each file carries a committed `.meta` sidecar pinning its stable guid. The identity is `<name>` (the `.computeShader` suffix strips). Resolve the shader once, then dispatch through the reference: ```lua local carve = asset.resolve("carve", "computeShader") carve:dispatch({ buffers = { heights }, workgroups = { 64 } }) ``` `asset.resolve` is what records your script's dependency on the shader, so the shader travels with the world your script lives in — packed, pulled, or published. It compiles on first dispatch; there is no setup step. ## bindings.yaml One ordered `bindings:` list — the binding index is the list position (0, 1, 2, …) — plus an optional `params:` scalar-uniform block. `kind` defaults to `buffer` when omitted. ```yaml bindings: - { name: clouds, kind: storage3d, format: rgba16f } # texture_storage_3d<rgba16float, write> - { name: occupancy, kind: texture3d } # texture_3d<f32> - { name: smp, kind: sampler } # sampler - { name: out_tex, kind: storage2d, format: rgba16f } # texture_storage_2d<rgba16float, write> - { name: U, kind: buffer, access: read, element: f32 } # var<storage, read> U: array<f32> - { name: Uniforms, kind: buffer, access: read, element: VolumeUniforms, array: false } # var<storage, read> Uniforms: VolumeUniforms params: - { name: scale, type: float, default: 2.0 } - { name: count, type: int, default: 0 } ``` | `kind` | extra keys | generated WGSL declaration | |---|---|---| | `buffer` (default) | `access: read \| read_write` (default `read_write`), `element: <wgsl type>` (default `f32`), `array: true \| false` (default `true`) | `var<storage, ACCESS> NAME: array<ELEMENT>;` (or `… NAME: ELEMENT;` when `array: false`) | | `texture3d` | — | `var NAME: texture_3d<f32>;` | | `texture2d` | `sample: float \| uint \| sint` (default `float`) | `var NAME: texture_2d<f32>;`, or `<u32>` / `<i32>` for the other classes | | `texture_depth` | — | `var NAME: texture_depth_2d;` — the one sampled shape with no `sample:` of its own; a depth-aspect channel (`@scene.depth`) binds here, not through `texture2d` | | `storage3d` | `format`, `access: write \| read \| read_write` (default `write`) | `var NAME: texture_storage_3d<FMT, ACCESS>;` | | `storage2d` | `format`, `access: write \| read \| read_write` (default `write`) | `var NAME: texture_storage_2d<FMT, ACCESS>;` | | `sampler` | — | `var NAME: sampler;` | | `textureCubeArray` | — | `var NAME: texture_cube_array<f32>;` — the environment cube array, bound to `@scene.environment` by a render feature's pass | | `vertices` | `access: read \| read_write` (default `read_write`) | `var<storage, ACCESS> NAME: array<u32>;` plus the mesh's layout uniform and the `zeroVertex*` accessors | | `acceleration_structure` | — | `var NAME: acceleration_structure;` (hardware ray tracing) | - **Eight storage buffers per shader** — the WebGPU guarantee, and what the engine asks every device for. `buffer` and `vertices` bindings spend that budget; textures, samplers, storage textures and `params:` do not. An `acceleration_structure` brings engine-owned buffers with it — **three** where the device has hardware ray query (the tables `zeroHitSurface` / `zeroMaterial` read) and **five** on the software backend (those, plus the scene triangles and the hierarchy over them) — so a traced pass has three slots of its own on the backend web users get. Over budget, the engine refuses the shader and logs which buffers it declared. - A `buffer` defaults to `array<ELEMENT>`. Set `array: false` for a single NON-array storage buffer — a struct binding (e.g. `element: VolumeUniforms`, `array: false` → `var<storage, read> NAME: VolumeUniforms;`). The struct definition itself lives in `shader.wgsl`, not `bindings.yaml`. - **A sampled texture binds under the class its FORMAT puts it in**, so `sample` states that class and the generated `texture_2d<..>` matches it. An integer channel — `@scene.material`, which is `Rgba8Uint` — is `uint`; everything else is the `float` default. Bind an integer channel to a `float` slot and the engine refuses the pass and names both classes, because the device would otherwise reject the bind group and invalidate the pipeline. - A storage texture's `access` decides both the generated declaration and the layout the engine registers, so the two always agree. It defaults to `write`, the access every target grants every storage-compatible format. `read_write` is granted on `r32f` alone; declaring it on any other format is refused at the compile, with the reason on `compute.programState`. A pass that needs to read a wider target reads it through a separate `texture3d` / `texture2d` binding, or through a second storage binding declared `read`. - `format` tags (storage textures): `r8`, `r16f`, `r32f`, `rgba8`, `rgba16f`, `rgba32f`. Storage textures only allow storage-compatible formats (`r32f` / `rgba8` / `rgba16f` / `rgba32f`). - An `acceleration_structure` binding resolves to the scene acceleration structure when the shader runs as a render-pass with ray tracing enabled (`renderer.setRaytrace(true)`). Declaring one makes the engine emit the helper functions the body can call: `zeroTraceClosest(origin, dir, t_min, t_max) -> ZeroHit` (struct: `hit, t, instance, primitive, bary, attr`, where `instance` is the hit object's render slot), `zeroTraceAny(origin, dir, t_min, t_max) -> bool` (terminate-on-first-hit, for shadow/occlusion rays), and `zeroHitSurface(hit) -> ZeroSurface` (`normal, uv, material`) + `zeroMaterial(index) -> ZeroMaterial` (`base_color, emissive, metallic, roughness`) to shade what a hit landed on. The same surface works on both backends — hardware ray query and the software/compute path — so the shader doesn't branch on `renderer.raytraceCapability()`. Bind it from a render-pass, which is where the scene acceleration structure exists. `params:` declares scalar uniforms (`type: float | int`). When non-empty the engine appends a `ZeroComputeParams` uniform as the trailing binding (read it in WGSL as `params.<name>`) and tunes its values at runtime with `shaderRef:setParam(prop, value)`. ## The kernel ABI: `columns`, counted and appended outputs, `specialize`, `determinism` One shader asset can serve many shapes of data. `bindings.yaml` states the shape with these extensions, and the engine's compile path lowers them to the plain bindings and WGSL above (`modules/compute_abi`, whose README has the whole surface): ```yaml workgroup: 64 # the size the body declares (default 64) bindings: - { name: cols, kind: columns, access: read } # a table of columns in one binding - { name: src, kind: buffer, access: read, element: T } - { name: dst, kind: buffer, access: read_write, element: T, count: "len(src)" } - { name: hits, kind: buffer, access: read_write, element: vec4<f32>, capacity: "n * 4", append: true } specialize: - { name: T, options: [f32, i32, vec2<f32>, vec3<f32>, vec4<f32>] } - { name: FOLD, options: [add, min, max] } - { name: BODY, kind: source, default: "0.0" } # text that replaces the identifier determinism: exact # or float_order ``` - A `buffer` of a scalar or vector element gets `NAME_get(i)`, `NAME_len()` and (unless `access: read`) `NAME_set(i, v)`. A `vec3` element is stored as a flat scalar array, so a column of vec3 keeps its 12-byte stride. `zero_n()` is the dispatch size. - `columns` binds a table of columns (`compute_abi.table`) as one storage buffer; `cols_f32(c, i, lane)`, `cols_vec3(c, i)` and the rest read it. - `count` / `capacity` give the size, in elements, of an output the run allocates. `append: true` adds a live counter binding, `NAME_count`, with `NAME_store(slot, v)`, `NAME_set_count(n)` and, under `determinism: float_order`, `NAME_append(v)`. - `specialize` parameters are compile-time: type options become `alias NAME`, named options become `const NAME` and `NAME_<option>`, `kind: source` text replaces the identifier. Each specialization compiles once. - `determinism: exact` refuses `NAME_append`: an exact output is written at ranks the kernel computed. Dispatch such a shader through its program: ```lua local variant = shaderRef:program():variant({ specialize = { T = "vec3<f32>" } }) local run = variant:run({ n = 64, inputs = { src = srcBuffer } }) local values = require("@builtin::modules.compute_abi").read(run.outputs.dst.buffer) ``` `shaderRef:program()` answers the same program, with the variants it has lowered and compiled, for as long as `shader.wgsl` and `bindings.yaml` hold the bytes they held when it was made. A write to either file, from any origin (`vfs.contentVersion` moves), makes the next `program()` a new one, and a dispatch through it runs the new text. The schema `getBindings()` answers is the one the program was made over. ## Writing a mesh's vertices — `kind: vertices` A mesh's vertices are raw bytes on the GPU, and the engine stores a mesh in one of two layouts: 92 bytes a vertex with every attribute a `f32`, or 32 bytes a vertex with normals and tangents quantized to bytes and UVs to shorts. Which one a mesh got depends on the mesh. Declare `kind: vertices` and the shader is handed both the buffer and the layout that mesh is in, plus accessors that address it: ```yaml bindings: - { name: verts, kind: vertices } # the mesh, writable - { name: heights, kind: buffer, access: read, element: f32 } params: - { name: lift, type: float, default: 1.0 } ``` ```wgsl @compute @workgroup_size(64) fn main(@builtin(global_invocation_id) id: vec3<u32>) { if (id.x >= zeroVertexCount()) { return; } var p = zeroVertexPosition(id.x); p.y = p.y + heights[id.x] * params.lift; zeroSetVertexPosition(id.x, p); zeroSetVertexNormal(id.x, vec3<f32>(0.0, 1.0, 0.0)); } ``` ```lua carve:dispatchOnVertices({ model = meshRef:handle().guid, buffers = { heights }, workgroups = { 64 } }) ``` The accessors, over a binding declared `read_write`: | read | write | |---|---| | `zeroVertexCount() -> u32` | — | | `zeroVertexPosition(i) -> vec3<f32>` | `zeroSetVertexPosition(i, vec3<f32>)` | | `zeroVertexNormal(i) -> vec3<f32>` | `zeroSetVertexNormal(i, vec3<f32>)` | | `zeroVertexTangent(i) -> vec4<f32>` | `zeroSetVertexTangent(i, vec4<f32>)` | | `zeroVertexUv(i) -> vec2<f32>` | `zeroSetVertexUv(i, vec2<f32>)` | | `zeroVertexColor(i) -> vec4<f32>` | `zeroSetVertexColor(i, vec4<f32>)` | | `zeroVertexNodeIndex(i) -> u32` | — | | `zeroVertexWord(i, offset) -> u32` | — | `access: read` gives you the readers only — a `var<storage, read>` binding cannot be assigned to, so the writers are left out rather than handed to you broken. Once a pass has written a mesh's vertices, the engine bounds that mesh by what the pass wrote: it reduces the vertices to an AABB every frame and culls against that, so geometry a pass moves across the scene needs no oversized placeholder to survive culling. `renderer.mesh.boundsSource(guid)` reports `"compute"` for such a mesh and `"geometry"` for one still bounded by what it was created with. A shader declares at most one `vertices` binding; the accessors are generated for that mesh. It can be declared anywhere in the list — the mesh is bound by the dispatch, and `buffers` fills the other storage slots in declaration order. The tangent's `w` carries handedness, and quantized normals/tangents come back in -1..1 while quantized UVs and colours come back in 0..1, so the values are the same ones a surface shader sees whichever layout the mesh is in. ## shader.wgsl Write only `@compute fn main` (and any helpers / `#include`s). The names declared in `bindings.yaml` are in scope — `data`, `out_tex`, `params.scale`, … — with no `@group`/`@binding` lines of your own. ```wgsl // @domain: compute // Bindings are declared in bindings.yaml — do NOT write @group/@binding here. @compute @workgroup_size(64) fn main(@builtin(global_invocation_id) id: vec3<u32>) { if (id.x < arrayLength(&data)) { data[id.x] = data[id.x] * 2.0; } } ``` ## Dispatch & runtime Everything a compute shader does, it does through its reference: | method | what it does | |---|---| | `ref:dispatch(opts)` | `{ buffers, workgroups, params? }` — bind one buffer per declared storage binding, in order | | `ref:dispatchOnVertices(opts)` | `{ model, buffers?, workgroups, params? }` — bind the mesh `model` names to the `vertices` binding, `buffers` filling the rest | | `ref:dispatchEx(opts)` | `{ resources, workgroups }` — for shaders mixing textures, samplers and storage textures: one `{ kind, name }` per declared binding, in order | | `ref:setParam(prop, value)` | write one `params:` scalar uniform | | `ref:createBuffer(name, opts)` | `{ type, len, usage? }` — a GPU buffer owned by this shader | | `ref:buffer(name)` | the buffer this shader last made under `name` | | `ref:getBindings()` | the parsed `bindings.yaml` schema, read and parsed again only after the file is written | | `ref:getSource()` / `ref:setSource(wgsl)` | read / overwrite `shader.wgsl` | | `ref:compile()` | compile now instead of on the first dispatch | | `ref:status()` | what the engine did with this shader's dispatches, one record per target | The `params:` uniform is engine-owned and takes no entry in `buffers` or `resources`, and neither does a `vertices` binding's layout. `setParam` writes the uniform every later dispatch reads. A dispatch that passes `params = { name = value }` reads those values instead, in a copy of the uniform only it binds, with every name it leaves out at the value the shader holds — so one shader dispatched twice in a frame over different data reads different values each time: ```lua lift:dispatch({ buffers = { a }, workgroups = { 4 }, params = { height = 1.0 } }) lift:dispatch({ buffers = { b }, workgroups = { 4 }, params = { height = 3.0 } }) ``` A name the shader does not declare fails that dispatch, and the failure names what it does declare. ### `dispatchEx` resources Each `resources` entry fills the binding at its position. Its `kind` says what the resource is, in the words `bindings.yaml` uses, and the binding decides how it is read. A slot takes the kind it is declared with; a `texture2d` slot also reads a storage texture, a side of a history pair or the scene depth, and a `storage2d` slot also writes this frame's side of a history pair: | binding's `bindings.yaml` kind | `resources` entry | `name` | |---|---|---| | `buffer` | `{ kind = "buffer", name = buf }` | a buffer handle from `ref:createBuffer` | | `texture3d` | `{ kind = "texture3d", name = vol }` | a 3D texture handle from `ref:createTexture3D` | | `storage3d` | `{ kind = "storage3d", name = vol }` | a 3D texture handle from `ref:createTexture3D` made with `storage = true` | | `storage2d` | `{ kind = "storage2d", name = target }` | a storage texture handle from `ref:createStorageTexture2D` | | `storage2d` | `{ kind = "history_curr", name = history }` | a history pair from `ref:createTextureHistory`: this frame's side | | `texture2d` | `{ kind = "texture2d", name = tex }` | a handle `ref:copyBufferToTexture` returns, or a texture asset's guid once `texRef:handle()` has made it GPU-resident | | `texture2d` | `{ kind = "storage2d", name = target }` | a storage texture handle, read as a texture | | `texture2d` | `{ kind = "history_prev", name = history }` / `{ kind = "history_curr", name = history }` | a history pair: the previous frame's side or this frame's | | `texture2d` | `{ kind = "scene_depth" }` | none: the frame's scene depth | | `sampler` | `{ kind = "sampler", name = smp }` | a sampler handle from `ref:createSampler` | `texture3d` and `storage3d` name the same resource, a 3D texture, so either one fills either slot. The engine's own spellings name the same resources and keep working: `texture_3d` for `texture3d` and `storage3d`, `texture_2d` for `texture2d`, and `storage_2d` for `storage2d`. Any other `kind` is refused at the call, naming every kind it accepts. A `vertices` binding is filled by `ref:dispatchOnVertices`, and `texture_depth`, `textureCubeArray` and `acceleration_structure` bindings by a render feature's pass. ```lua local march = asset.resolve("volume_march", "computeShader") -- bindings.yaml: density (storage3d), out_tex (storage2d), U (buffer) march:dispatchEx({ resources = { { kind = "storage3d", name = density }, { kind = "storage2d", name = target }, { kind = "buffer", name = uniforms }, }, workgroups = { 8, 8, 8 }, }) ``` `workgroups` is `{ x, y, z }`, `{ x }`, or a bare `x`, and every dimension it leaves out is 1. A zero in any dimension is refused: the dispatch is dropped and recorded as a failure, so it surfaces in `ref:status()` and `compute.failing()` with the reason. A count derived from how much data there is passes through `math.max` first, so an empty set dispatches one workgroup rather than none: ```lua carve:dispatch({ buffers = { heights }, workgroups = { math.max(1, math.ceil(#points / 64)) } }) ``` ### Buffers and readback (the CPU side) A buffer is created through the shader that owns it and comes back as a handle. Pass the handle to a dispatch — including another shader's — to bind it there: ```lua local double = asset.resolve("@builtin::shaders.compute_double", "computeShader") -- `type` is the element the shader declares, `len` how many of them. local data = double:createBuffer("data", { type = "f32", len = 4, usage = { "readback" } }) data:write({ 1.0, 2.0, 3.0, 4.0 }) -- :writeU32 for integer words, :writeBytes for packed bytes double:dispatch({ buffers = { data }, workgroups = { 1, 1, 1 } }) local pending = data:read() -- starts an async GPU->CPU readback -- a frame or two later, drain it (nil until it has arrived): local out = pending:result() -- :resultU32 / :resultBytes read the same bytes another way data:destroy() -- free it when done ``` `type` is one of `"f32"`, `"vec3"`, `"vec4"`, `"quat"`, `"mat4"`, and `usage` adds `"readback"`, `"vertex"`, `"index"` or `"indirect"` on top of the storage a buffer always has. An `"indirect"` buffer holds a draw's arguments where the GPU reads them, so a shader that compacts geometry writes the drawn count into the same dispatch that produced it and a render feature's `kind = "draw"` pass submits exactly that — the `renderFeature` asset type's README documents that pass and the `storage.indirect` name it reads. The handle's key is the shader's guid plus the name you gave it and a serial, so two shaders that both want a buffer called `data` get one each — and so do two callers asking this same shader for one. `ref:buffer(name)` returns the last one made under that name, which is how two callers share one on purpose. A buffer that no shader computes — a vertex or index run that is only ever drawn — is allocated straight from the primitive instead: `substrate.createBuffer({ name = ..., type = ..., len = ..., kind = "gpu", usage = { "vertex" } })`. The first dispatch of a shader compiles it, so the very first readback can still reflect the un-run shader; dispatch again once it is compiled, or `ref:compile()` to pre-warm. This create/write/dispatch/readback loop is the CPU side of the resource model in `core/resource-model`. ### Is it compiled? `ref:compile()` queues the compile; the pipeline is built on the render side frames later, so that call cannot say whether it produced a program. `compute.programState(ref)` is where that lands: ```lua if compute.programState(carve) == "ready" then carve:dispatch(opts) end local state, reason = compute.programState(carve) if state == "failed" then print(reason) end ``` - `"absent"` — the engine holds nothing under this key and nothing is in flight: never asked for, or released. - `"pending"` — a compile was asked for and has not reached the device. A recompile of a resident program reads pending too, because what it produces is a different program from the one bound now — which is what makes this the precondition to wait on after an edit. - `"ready"` — compiled and resident, so a dispatch naming it binds it. - `"failed"` — the most recent compile produced no program, and the second return says why. A dispatch issued while the program is `"pending"` is held behind the compile and dropped if it never lands, so a readback taken before `"ready"` reports the buffer as it was. Wait for `"ready"`, not for a count of frames. ### Did it run? A dispatch is recorded into a command encoder frames after the call that asked for it returned, so that call's `true` means "queued", not "ran". `ref:status()` is where the outcome lands — one record per target, cumulative: ```lua for _, d in ipairs(carve:status()) do print(d.target, d.ok, d.dispatches, d.failures, d.lastError) end ``` `target` is the mesh guid for a `dispatchOnVertices` and the buffers it bound for a dispatch that writes only those, so two systems driving one shader over their own buffers read as the two passes they are. `ok` is the most recent outcome; `lastError` says why the last failure failed and is kept after a recovery. An empty result means nothing has dispatched this shader at all. `compute.failing()` answers the same question across every shader at once. A failing dispatch also posts a notice, so a pass that stops running reports itself rather than waiting to be found. ### Running one every frame A `kind = "compute"` substrate job queues one dispatch per frame: ```lua jobs.register({ phase = "main", executor = { kind = "compute", shader = asset.resolve("carve", "computeShader"), buffers = { "heights" }, workgroups = { 64 }, }, }) ``` ## Registration & hot reload Writing `shader.wgsl` or `bindings.yaml` fires the `.computeShader` assetType's `onChange`, which compiles it: the binding declarations are generated, `#include`s expanded, the WGSL validated, and the shader registered. This happens on create and on every edit, so saving recompiles with no world reload. A shader with invalid WGSL (a type mismatch, an undefined name) **fails to compile** with the reason logged (`[compute] Compile of '<name>' failed: …`) and is **not** registered. You don't need to register a shader before dispatching it — the first dispatch auto-compiles it on use. `ref:compile()` remains as an optional explicit pre-warm, only to avoid the one-frame first-dispatch warm-up in a latency-critical spot. ## What compute is holding, and why a key names nothing Every buffer, volume, storage target, history pair and sampler a dispatch can bind is filed under a key, and `compute.observe()` lists all of them with what each costs: ```lua local r = compute.observe() print(r.totals.count, r.totals.bytes) for _, res in ipairs(r.resources) do print(res.key, res.kind, res.bytes, res.owner.name) end ``` A row carries the key verbatim — the same string a dispatch names it by and a dispatch-failure message prints — plus its `kind`, its `bytes`, its extent and `format` where it has them, the `usage` bits it was created with, and the frame it was created on. `owner` is read back out of the key (`<shader-guid>::<name>#<serial>`), so a resource nothing has ever dispatched over still names the shader that made it. `compute.resources(ref)` narrows to one shader's — including the `<shader-guid>::__params` uniform the compile created for a `params:` block, which the shader owns like any other resource. `r.totals.bytes` is the `compute` figure of `renderer.gpuMemory()` — the two are read off the same registries, so a listing accounts for the category exactly. The same reading is served at `/zero/runtime/compute`. When a key names nothing, `compute.diagnose(key)` says which of the states the inventory distinguishes it is in, from the closed set `compute.absentReasons()` enumerates: | reason | what the inventory read | |---|---| | `resident` | a resource is filed under exactly this key; the row is on `resource` | | `replaced` | the owner holds the same name at a different serial — `current` names the live key | | `nameUnused` | the owner holds resources, none under this name | | `ownerAbsent` | no live resource carries this key's owner | | `unowned` | the key carries no owner segment, and nothing is filed under it | | `notPublished` | no renderer has published an inventory, so no key can be answered for | So a key out of `[compute] dispatch '…' failed` resolves against what exists, and a typo reports which part of it the engine could not match rather than coming back empty. A reason is the inventory at the moment the call read it. The reading is republished on a frame where a registry gained or lost an entry, so a resource created and diagnosed inside one script sees the reading from before it was made; wait a frame and ask again. ## Discovery - `asset.list("computeShader")` — every registered compute shader. - `asset.inspect("<name>")` — status, source, parse errors, this README. - `computeRef:getBindings()` — the parsed `bindings.yaml` schema (`{ bindings, params }`). - `compute.programState(ref)` — whether the program is compiled, still compiling, or failed, and why. - `compute.observe()` — every GPU resource compute holds, and what it costs. - `compute.diagnose(key)` — whether a key names a live resource, and why not. - `profiler.gpuFrame()` — what each dispatch of this shader spends on the GPU. A dispatch is timed under `compute.<identity>` — the same identity `asset.resolve` takes, so a timing row names the shader that produced it. ## Common pitfalls - **Compute shaders don't render** — verify output via a buffer readback or a debug pass, not a screenshot. - **`ref:compile()` returns before the program exists** — the pipeline is built on the render side; `compute.programState(ref)` says when it is `"ready"`. A dispatch issued before that is held behind the compile and dropped only if the compile never lands. - **A dispatch call returning true means queued** — ask `ref:status()` whether it ran. - **A destroyed buffer is refused where it is bound** — a handle outlives its storage, and `buf:alive()` reports which. - **Binding order is the contract** — `buffers` and `resources` bind in `bindings:` list order; reordering the list reorders the bindings. - **Don't write `@group`/`@binding` in `shader.wgsl`** — the engine owns them; re-declaring is the fastest way to a layout mismatch. - **Don't infer a mesh's vertex stride** — declare `kind: vertices` and use the accessors. A wrong stride writes positions correctly and normals into the wrong word, which renders as flat lighting rather than as broken geometry. - **Storage-texture format must be storage-compatible** — `r32f` / `rgba8` / `rgba16f` / `rgba32f`; others are rejected at compile. - **A key that comes back empty is not the same as one that failed** — `compute.diagnose(key)` separates a name never used from a generation that was replaced, and names the live key in the second case. ## Related types - `.shader`: render-domain shaders (surface, sky, post-process, screen). ## In the Inspector Selecting a compute shader opens its **Compute** section: whether its program is ready (and why not), how many dispatches it has run and failed in this session (and the last error), tables of the bindings and params its `bindings.yaml` declares, and openers for `shader.wgsl` and `bindings.yaml`.

# assetType (asset type) An asset type says what a kind of asset is: the files an asset of the kind is made of, the code that gives it behaviour, the interface a person uses to work with it, and how it is found, pictured and checked. A `<typename>.assetType/` folder declares a type called `<typename>`, and every `<name>.<typename>/` folder is an asset of it. `assetType` is itself a type, so a type is an asset like any other: it is created, versioned, installed and contributed the same way. ## Making a type `asset.create("assetType", "<typename>")` scaffolds a type. The type registers the moment its folder is written, anywhere under `/zero/source/`, and from then on `<name>.<typename>/` folders are its assets. An asset of a type that is not registered yet is not an asset, so make the type first. A type folder is a root: `~.x` in any file inside it names the type's own `x`, wherever the type is installed. Keep the type's whole implementation inside its folder and reach it that way. What a type folder must hold is set by this type's own `type.yaml`, the same way every type's `type.yaml` sets what its assets hold. `asset.validate` on a type reports anything missing, and the scaffold produces a folder that passes. ## What sets your type's schema (`type.yaml`) `type.yaml` is the structural contract every asset of the type is checked against. The keys below are the ones the engine reads; a key not listed here is ignored. | Key | What it controls | |---|---| | `suffix` | The folder suffix of the type's assets. Defaults to `.<typename>`. | | `primary` | The file or files that are the asset's content: what the asset resolves to when it is used. | | `entry_files`, `primary_aliases` | Further files that load as the asset or share its identity. | | `is_container` | Whether the suffix stays in the identities of what the asset holds. | | `is_opaque_walker` | Whether a walk of the tree stops at the asset and registers only its primary. | | `plural_dir`, `classify_exts` | Loose files in a folder of this name, or with these extensions, are assets of the type. | | `is_text_default` | Whether the asset's files are text unless stated otherwise. | | `broadcasts_subassets` | Whether assets nested inside an asset of the type are found by their own short name. | | `root` | `true` makes every asset of the type a root, so `~.x` inside one names that asset's own `x`. | | `contract_ref: { field, category }` | A key of the primary file that names another asset the asset is built on. | | `files: { required, optional }` | The files an asset holds (below). | | `allow_unlisted` | `false` reports every file the type does not declare. | | `aliases_from: [{ file, key }]` | Further names an asset answers to, read from its own files. | | `settings:` | Typed per-asset settings (below). | | `inspector:` | The interface people use for the type and its assets (below). | | `preview:` | How an asset is pictured (below). | | `references:` | Names of other assets the type's files carry (below). | | `indexing:` | What search reads for each asset (below). | | `describe:` | How a missing description is generated (below). | ### The files an asset holds Each entry under `files.required` or `files.optional` is `{ path, kind: file | folder, one_of_group?, content? }`. `*` in a path matches within one segment. Entries that share a `one_of_group` are satisfied by any one of them. `content` lists checks on the file's bytes: | Check | Passes when | |---|---| | `non_empty` | the file has content | | `json_field { key, type?, non_empty?, accept? }` | the JSON holds the key (a dotted path) with that shape | | `yaml_field { key, type?, non_empty?, accept? }` | the same for YAML | | `described { keys?, headings?, message? }` | the file says what the asset is (see "Ask your assets to say what they are") | Each check takes a `message`, which is what the author is told when it fails. ### Settings `settings: { values, schema: { type | instance, export? } }` gives every asset typed settings. `values` names the file an asset's values live in; `schema.type` declares one schema for the whole type, and `schema.instance` names a file each asset declares its own in. `asset.create` writes the resolved values, and a write to the values file reaches `onChange` with what changed. ## The human side (`inspector.luau`) A type is used by people through its Inspector, and without one the type is usable only from code. The Inspector is the type's interface for a person: for a procedural graph it is the graph editor, for a kit it is the tracking view of what the kit holds and what is still missing. Writing it is part of writing the type. `inspector: { type, instance? }` in `type.yaml` names the files. `type` is the interface for the type itself and for its assets; `instance` names a file an asset may ship to add its own. Each returns: ```luau return { sections = { { id = "graph", title = "Graph", build = function(ctx) ... end } }, replace = { contents = { ... } }, -- replace a default section by id order = { "graph", "contents" }, -- section order } ``` `build(ctx)` receives the asset and builds the section. A section's `title`, and the text its rows carry, is a string or an `i18n.text` value read from a catalog (`i18n.text("inspectors.mesh.title")`), which follows the editor's language. `asset.create("assetType", ...)` scaffolds a working `inspector.luau` to start from. `asset.validate` on a type that names no inspector, or names one that does not load, reports it. ## Say what your type is for (`about.yaml`) Every type carries an `about.yaml` that says what the type is for, in three plain-language texts: ```yaml intent: "Sets the typeface of the text in your game: UI, labels, signs and 3D lettering." function: "A font, from a TTF, OTF or WOFF file, made available to all of Zero's text, including 3D text." usage: "You choose it by name for your UI or your text, and the text appears in that typeface." ``` - **`intent`** is what the type is for in someone's game, in the words a game maker uses. Up to 800 bytes. - **`function`** is how it works today: what an asset of it is made of and what the engine does with it. Up to 1500 bytes. - **`usage`** is what a person or an agent does with one. Up to 1200 bytes. Write about the type as a whole, not one asset of it, and say what it does now. Agents read these texts to learn when to reach for the type and how; people searching find the type by them. The scaffold starts each text with `[[describe]]` and a note on what to write; a text that still starts that way counts as not written. `services describe` can write them. They show up in `asset.inspect` as `detail.about`, in `assetTypeRef:getAbout()`, at the end of the type's `types/<typename>` guide, and at the top of the type's Inspector. ## Ask your assets to say what they are A type can require each asset to carry a description: a file, written by the author or generated, saying what the asset is and what it is for. Declare it with a `described` check: ```yaml files: required: - path: "README.md" kind: "file" content: - { check: "described", message: "Say what this widget is for and where it goes." } ``` A file that is missing, empty or still has a line starting with `[[describe]]` fails the check, and so does a YAML file whose named `keys` are missing or over their `max_bytes`, or a Markdown file missing a named heading. `asset.validate` names the asset, and a push that carries it is refused with `message`. `services describe` finds such assets and writes their descriptions. `describe:` steers what is generated: ```yaml describe: guidance: "Say what the widget shows, what input it reacts to, and where it fits in a UI." examples: - "<identity of an asset of this type whose description reads well>" ``` An example is an asset of your type whose description is a true, written one, never a placeholder and never the asset being described; with none, leave `examples` empty. A type whose assets the model cannot perceive (a sound, a motion) says so in `guidance`, and the description is drawn only from what the asset's own files state. Start the file unwritten in your `template/`: a heading and one line starting with `[[describe]]`, never example content, which every new asset would carry verbatim. A type whose assets say what they are through their own content (a mesh, a texture) declares no check. ## The type's code (`behavior.luau`) `behavior.luau` returns one table. These are the keys the engine reads from it; anything else on the table is the type's own. ### What the type's assets can do | Key | Shape | What the engine does with it | |---|---|---| | `ref` | `{ [name] = function(self, ...) }` | Every function becomes a method on every asset of the type: `ref:name(...)`. | | `modules` | `{ [name] = require(".x") }` | Code the type's assets reach with `asset.containing(__FILE__).modules.<name>`. | | `events` | an events schema | Events an asset fires. Readers subscribe through `ref.events.<name>:connect(...)`; the type fires them. | | `refShapes` | `{ [method] = function(self) -> (typeExpr, source?) }` | The result type of a `ref` method for one particular asset (below). | | `namePattern` | a Lua pattern | The names `asset.create` accepts for the type's assets. Default `^[A-Za-z][A-Za-z0-9_]*$`. | | `derive` | `{ output, module, compute, fingerprint, matches?, required?, timeout? }` | A file computed from the asset when it is committed; a `required` one holds the commit until it lands. | Some `ref` names mean the same for every type, and the engine calls them: - **`instantiate(self, target?, opts?) -> (root, idMap)`**: puts the asset in a scene. Defining it is what makes the type scene-instantiable. Its return is a contract (below). - **`inspect(self) -> detail`**: what `asset.inspect` reports for the asset beyond the common record (below). - **`preview(self, opts)`**: renders the asset's picture; it wins over the type's `preview:` recipe. - **`previewMaterial(self) -> { material }`**: the material a `surface` preview paints. - **`saveDefinition(self)`**: writes the asset's in-memory edits back to its files in edit mode. Some names are answered for every asset before the type is asked, so a `ref` entry of the same name is never reached: `getSource`, `getBytes`, `getText`, `exists`, `deps`, `canInstantiate`, `canPreview`, `preview` (which calls yours when you define one), `meta`, `runtime`, `events`, `typeRef`, `modules`, and the residency flags `has_backing_asset`, `has_runtime_changes`, `cpu_resident`, `gpu_resident`. ### When the engine calls the type | Hook | Signature | When it runs | |---|---|---| | `onCreate` | `(name, opts) -> { [path] = contents }` | On `asset.create`. Returns the files of the new asset, laid over the type's `template/`. Annotate `opts`: its type is the schema `asset.create` checks the caller's arguments against. A `""` key writes a single loose file. | | `onReplace` | `(dest, files) -> files` | On an `asset.create` over an asset already at `dest`, after `onCreate`, so what the author added can be carried into the replacement. | | `onRegister` | `(self)` | Once per asset, when it first registers: when the world loads, on a live `asset.create`, and when an asset arrives later (installed, pulled, synced). This is what makes an asset take effect the moment it is written. | | `onChange` | `(ref, change)` | On every write to a file inside an asset of the type. `change` is `{ path, asset, type, kind, origin }`, plus `settings` and `settingsChanged` for a write to the settings values file; `kind` is `edited` or `seeded`, `origin` is `local` or `remote`. Filter on `change.path`. Writes to one asset arrive in order, each after the hook for the one before has finished, and the hook may wait on what it reads. A write the hook makes inside its own asset arrives later like any other, so keep the hook convergent. | | `onDependencyChange` | `(ref, change)` | When a module the asset's code requires is re-run, or a name the asset carries starts resolving. `change.kind` is `dependency`. | | `onDelete` | `(ref)` | When an asset of the type leaves the world: deleted, or the world it is in is swapped away. | | `validate` | `(ref) -> { { code, message, severity?, path? } }` | On `asset.validate`, after the `type.yaml` checks, for the type's own rules. `severity` defaults to `error`. Runs on every push, so a type's rules hold at publish. A hook that fails reports `validate.hook_failed`. | ### Settings hooks | Hook | When it runs | |---|---| | `settingsDefaults(name, opts, asked) -> table` | Once per `asset.create`, for values the schema's defaults do not give. | | `settingsCorrections(values, name, opts) -> (corrections?, reasons?)` | On every settings write. A correction to a field the writer named refuses the write, giving the reason. | | `settingsDerivedDefaults(values, explicit, changed)` | On a settings write, for fields derived from others. | | `normalizeSettings(values, stored?)` | On every read and write, to map an earlier spelling of a field to the current one. | | `settingsHealed(values, stored)` | On a read, to repair stored values. | | `settingsSchemaProblem(schema, ref) -> string?` | When an asset's own schema is read; a returned string refuses the schema. | `creationInputs` (`{ [opt] = true | selectorOpt }`) names `asset.create` options that are inputs to the type rather than settings. ### Reloading An edit to `behavior.luau` reaches existing assets with no restart. ## How an asset is pictured (`preview:`) | `kind` | The picture is | The type provides | |---|---|---| | `instantiate` | the asset placed in the preview studio through its `instantiate` | `ref.instantiate` | | `image` | a file the asset holds, fitted to the frame | `source: { files }`, the candidate files in order | | `surface` | the asset painted on a mesh | `mesh`, and `ref.previewMaterial` | | `custom` | whatever `ref.preview` returns | `ref.preview` | ```yaml preview: kind: surface mesh: sphere ``` `angle: [yaw, pitch]` turns the camera. The studio owns the light, the backdrop and the framing, so an asset pictures the same in every world. A type with no `preview:` that defines `instantiate` still answers `ref:preview()`. A picture is rendered when something asks to view it (the editor showing the asset, `ref:preview()`), when previews are generated on request (`assets.generatePreviews`), and when the asset is staged. An edit alone renders nothing. The picture records what it was made from, so a stale one is told from a current one. ## The names your type's assets hold (`references:`) Where your type's own format or API carries the name of another asset, declare it here: ```yaml references: keys: # a top-level key of the type's files that holds a name, or a table of them - { key: "shader", type: "shader" } args: # an argument of a call, counting from 1 - { call: "g:node", position: 2, type: "procNode" } fields: # a field of the options table a call takes - { call: "fx.beam", field: "material", type: "material" } ``` `type` is the category the name resolves in. `asset.declareReferenceKey`, `asset.declareReferenceArg` and `asset.declareReferenceField` declare the same from a script. ## What search reads (`indexing:`) `indexing:` is how assets are found. Search reaches an asset only through what its type's `indexing:` names, and adds nothing of its own. That includes you: an asset indexed badly is one you cannot find later, when you are making something else and need it. A type whose assets are never looked for says `indexing: none`. ```yaml indexing: data: # text, read from the asset's files - role: identity extractor: verbatim source: { file: "README.md" } - role: interface extractor: symbols source: { files: ["init.luau"] } - role: implementation extractor: verbatim source: { files: ["init.luau"] } content: # the picture - role: identity modality: image source: { file: "preview.png" } facets: # what a query filters and re-ranks by file: ".metadata" rigged: { type: bool, from: { components: { contains: SkinnedModel } } } roughness: { type: number, filter: range, from: { file: "mat.yaml", field: "floats.roughness" } } ``` **Roles.** Each `data` and `content` entry has a `role`, and a query matches in two slots: - **`identity`**: what an asset is. For anything you look at, the picture; for anything else, the text that says what it is. - **`capability`**: what it does and how it is made. `interface` (the signatures or shape a caller uses) and `implementation` (the body) both count as capability, and a type with code usually declares both. Ask what a person would recognise an asset of the type by, and what it does, and point each role at the file that says it. For text, that is the asset's description: the file your template starts with a `[[describe]]` block, which the author writes or `services describe` fills in (see "Ask your assets to say what they are"). **`data`.** `extractor: verbatim` embeds a file's text as it is; `symbols` embeds the declared signatures of code. `source` is `{ file }` or `{ files: [...] }`. Never index a file name (`source: { field: name }`): one or two words carry nothing to match. **`content`.** `modality: image` embeds the picture itself, so a text query matches what the asset looks like. A type whose assets are looked at makes the picture its identity. **`facets`.** What a query narrows and re-ranks the matches by. `file` is embedded whole, so keys nobody declared in it are still found. Each further key is computed for every asset and states a value for every one, including `false`: a file can imply "not rigged" but never say it, and a query separates rigged from unrigged only because the unrigged ones say `rigged: false`. A key is `{ type: bool | number | enum, filter?: range, from }`, where `from` is `{ file, field }` (a field of one of the asset's files, dotted for nesting), `{ metadata: key }`, or `{ components: { contains | any_outside } }` (what the asset's entities carry). ## What blocks a push A push checks every asset it carries against its type. These refuse it: - a required file that is missing, a `content` check that fails, a `described` file not written yet; - an error from the type's `validate`. Unlisted files and warnings do not. A `described` file blocks only a push that changes the asset. When a push is refused, the message names each asset and what it lacks. `world.publishBlockers()` and `zm status` read the same list without pushing. ## Typing a result from the asset (`refShapes`) A `ref` method whose result depends on the asset (one entry per child folder, per row of a config, per control a map declares) can only be annotated as `{ [string]: Thing }`, which accepts any key. `refShapes` states the result for each asset instead: a function returning a Luau type expression for that asset, and the module whose types the expression uses. Read the asset; never run it. ```lua -- inputMap.assetType/behavior.luau M.refShapes = { activate = function(self): (string, string) local names = {} for _, control in ipairs(M.ref.controls(self)) do table.insert(names, control.name .. ": Handle") end if #names == 0 then return "", "" end return "{ " .. table.concat(names, ", ") .. " }", "@builtin::modules.zinput.scheme" end, } ``` With it, `map.jump:onPressed(fn)` is checked and `map.noexisting` is reported. A per-asset type applies where the call site names which asset: a component field whose default names it, or an annotation `AssetRef<"inputMap", "<identity>">`. `asset.resolve(name, category)` carries only the category, and a name computed at runtime carries nothing, so calls on those keep the declared return. The type belongs to the call's result: index it there, or bind what you need from it there, and the names stay checked. `require("@builtin::assetTypes.assetType.shared.refShapes").published()` shows what was published: `categories` (each type's method surface) and `returns` (per-asset results by identity, then method). An identity missing from `returns` was never published. Results are recomputed when an asset is written; at most 64 assets of one type are read. ## Putting an asset in a scene (`ref.instantiate`) A caller writes one piece of code against every instantiable type, so what `instantiate` returns is fixed: ```lua local Instantiable = require("@builtin::assetTypes.assetType.shared.instantiable") M.ref = { instantiate = function(self, target, opts) local root = Instantiable.root(self, target, opts) -- compose the asset under `root`, now return Instantiable.result(self, root, idMap) end, } ``` **In.** `target` is the entity the asset lands under, or onto for a hierarchy type; with none, the type spawns a new root. `position`, `rotation` (three numbers in degrees, or a quaternion), `scale`, `name` and `temporary` mean the same for every type: `Instantiable.root` applies them to a root you make, `Instantiable.place` to one you adopt. Document any options of your own in the hook's `--!arg` docs. **Out.** `(root, idMap)`. `root` is the composed root, live when you return: build synchronously, never defer to a component's `awake`. `idMap` maps each original id to the spawned one, so a component that composes the asset again on every load can pass it back in and keep references into the composition. Every call goes through `Instantiable.result`, which refuses a root that is not live and turns a missing `idMap` into `{}`. ## Inspecting an asset (`ref.inspect`) `asset.inspect(ref)` builds a record every asset shares (`identity`, `name`, `guid`, `source`, `typeName`, `typeDefinitionPath`, `scope`, `origin`, `description`, `tags`), then calls `ref.inspect(self)` for the type's own `detail`: ```lua M.ref = { inspect = function(self) -- read the asset's own files, never runtime state: inspect works on an asset -- that has not been compiled, uploaded or registered return { --[[ what makes this asset what it is ]] } end, } ``` Without it, the record is the shared part alone, and an agent inspecting the asset learns nothing of what it is. A hook that raises leaves `detail` empty and sets `record.warning`. ## Discovery - `asset.list("assetType")`: every registered type. - `asset.inspect("<typename>")`: the type, its README and its `about.yaml` texts. - `asset.resolve("<typename>", "assetType")`: the type itself.

# Model Loads and displays a 3D mesh on an entity. Disabling the component hides the mesh. Supports procedural meshes (`cube`, `sphere`, ...), model files, and remote URLs. Tint and outline are shader effects applied to the mesh. **Material lives on this component.** There is no standalone `Material` component — a material only renders where there is a mesh to render it on, so the `material` field is part of Model (and SkinnedModel). Set it at add time or assign the field later; properties are registry-wide. Public fields: `model`, `material` (`AssetRef<material>`), `tintR/G/B`, `tintBlend`, `outlineR/G/B`, `outlineIntensity`. Methods: `:setTint(color, blend?)` (color: `{r, g, b}` array or `{r=, g=, b=}` map), `:clearTint()`, `:setOutline(color, intensity?)`, `:clearOutline()`, `:setMaterialProperty(prop, value)`, `:getMaterialProperty(prop)`, `:getMaterialPropertyNames()`. ```luau entity(id).component.add("Model", { model = "cube", material = "gold" }) entity(id).component.get("Model").material = "checkerboard" -- swap material entity(id).component.get("Model"):setTint({1, 0, 0}, 0.5) entity(id).component.get("Model"):setMaterialProperty("roughness", 0.2) ``` **Tint is synced.** Every `tint*` field replicates, so `:setTint` is the colour every participant sees. A colour that changes every frame on many entities (a stress map, a heat map, a damage flash, per instance colour) belongs in an instance-data lane instead: wear `@builtin::materials.instance_color` (or `instance_color_unlit`) and write `renderer.instanceData.set(id, 2, r, g, b, coverage)`, which replicates nothing and costs about a twentieth of a tint write. `guides { path = "topics/rendering-instance-data" }` has the lane layout.

# SkinnedModel Component that drives skinned model playback and animation graph integration. Like `Model`, it carries the `material` field (`AssetRef<material>`) — material lives on the model that renders it, not as a standalone component. Set it at add time or assign `entity(id).component.get("SkinnedModel").material = "..."` later; `:setMaterialProperty` / `:getMaterialProperty` / `:getMaterialPropertyNames` operate on the assigned material (registry-wide). **Tint is synced.** Every `tint*` field replicates, so `:setTint` is the colour every participant sees. A colour that changes every frame on many characters (a damage flash, a team colour, a heat map) belongs in an instance-data lane instead: wear `@builtin::materials.instance_color` (or `instance_color_unlit`) and write `renderer.instanceData.set(id, 2, r, g, b, coverage)`, which replicates nothing. `guides { path = "topics/rendering-instance-data" }` has the lane layout. ## Blend model `skinning` chooses how the pass combines a vertex's joint influences. - `"linear"` (default) averages the joint matrices themselves. The average of two rotations is not a rotation, so a strongly twisted joint loses volume toward its axis — at a 180° twist a limb collapses onto the axis entirely. - `"dualQuaternion"` averages the joints' rigid motions as unit dual quaternions and renormalises, so the blend is a rotation at every weight and the cross-section is carried through the twist. Non-uniform joint scale rides along as a separately blended stretch. It costs a quaternion extraction per influence, so it is worth setting on characters whose wrists, shoulders or spine twist far, and leaving off elsewhere. ```lua entity.find("hero").component.get("SkinnedModel").skinning = "dualQuaternion" ``` A rig at rest renders identically under either model. ## Render self-check A few frames after its mesh attaches, a SkinnedModel checks that the mesh names something the engine can draw (on the GPU, or held off the device until this display puts it back) and that the pose it is drawn in has not collapsed it: the posed vertices the skinning pass wrote are measured against the mesh's own bind-pose extent, so a 1 cm part of a prop is judged by its own size. A mesh that fails is swapped for the builtin ERROR marker, drawn un-skinned with the error material, and the reason is logged. Setting `model` again takes the marker down and checks the new mesh. `renderCheck()` answers the verdict: `{ state = "pending" | "passed" | "failed" | "skipped", reason }`. ```lua local v = entity.find("prop_part").component.get("SkinnedModel"):renderCheck() if v.state == "failed" then print(v.reason) end ```

# debugViz The shared edit-mode debug-visualization core. Owns the ONE anchor entity, the ONE vertex-colour line material, the ONE batched vertex/index compute-buffer pair, and the ONE render feature that every debug-visualization gizmo draws through. Individual gizmos (bounds boxes, camera frustums, ...) are **providers** — small modules that append their own geometry into the shared batch every tick, instead of each owning their own GPU state. ```lua entity.spawn("DebugViz"):component.add("DebugViz") ``` ## How it fits together - `DebugViz.component` owns the lifecycle: registers the built-in providers and calls `debugViz.update(dt)` every edit-mode tick; `onDisable`/`onDestroy` call `debugViz.teardown()`. - `debugViz.registerProvider(name, fn)` registers `fn(emit)` under `name`. Registering an existing name replaces its function. - `debugViz.update(dt)` calls every registered provider with an `emit` handle, which records what each call asked to draw, then uploads the combined vertex/index buffers (grow-only capacity). The upload follows what changed: a tick that drew the same thing writes nothing, a tick where some draws changed in place (the same commands, the same vertex counts) writes only their vertices, and a tick where a draw appeared, went or changed its vertex count writes the whole batch. - `emit.section(changed, draw)` marks a part of a provider's drawing that changes apart from the rest: `draw(emit)` runs when `changed` is true or the section has not drawn before, and otherwise its last recording is replayed without running `draw`. - `debugViz.state()` returns the latest `{ vtx, idx, anchor, indexCount, uploadedBytes, shapes, icons }` for the render feature to draw. - `@builtin::renderFeatures.debugViz` reads `state()` every frame and draws the batch through one Draw pass, using `@builtin::shaders.debugGeometry` — a solid-colour shader that reads each vertex's baked colour, so every provider can use its own colour in the same draw call. Each instanced shape (below) draws in a Draw pass of its own. The draw needs an anchor entity with an IDENTITY world transform and a render-object (so the Draw pass has a valid instance slot and a material to override) — this module owns one, spawned lazily, internal so it stays out of the inspector and excluded from scene saves. ## Writing a provider ```lua local debugViz = require("@builtin::modules.debugViz") local function tick(emit) emit.box({ x = -1, y = -1, z = -1 }, { x = 1, y = 1, z = 1 }, { 1, 0, 1, 1 }) emit.line({ x = 0, y = 0, z = 0 }, { x = 0, y = 5, z = 0 }, { 1, 0, 1, 1 }) end debugViz.registerProvider("my_gizmo", tick) ``` `emit.box(min, max, color?)` and `emit.line(a, b, color?)` append world-space geometry into the shared batch for this tick; `color` is an `{r, g, b, a}` array baked per-vertex (defaults to amber if omitted). A provider that needs to exclude the shared anchor entity from its own scene queries reads `debugViz.anchorId()`. A provider that hands the same packed geometry back every tick (`emit.rawLineSoup(bytes, vertexCount)`) costs nothing to upload while the geometry stays the same string. ### Instanced shapes `emit.shape(entityId, key, bytes, vertexCount)` draws a line-list blob in the local space of `entityId`. The blob is uploaded once under `key` and drawn once per entity that asks for it, through that entity's own world transform: any number of entities sharing a shape cost one GPU buffer, and moving them costs no per-tick work. A `key` names immutable bytes (geometry that changes takes a new key), the buffer lives for as long as some entity asks for the key each tick, and the entity needs a render object (a Mesh). `debug_wireframe` draws every mesh this way. ## API - `debugViz.registerProvider(name, fn, opts?)` — register (or replace) a provider. `fn(emit)` runs once per edit-mode tick. `opts.label` is the name the Debug menu and the Rendering panel list the overlay under: text as written, or an `i18n.text` value (`i18n.text("hud.my_gizmo")`), which reads in the editor's language. Without one the overlay is listed by `name`. `opts.default` is whether the overlay starts on, and `opts.available()` whether it currently has anything to show. - `debugViz.providers()` — every provider that currently has something to draw, in registration order, as `{ name, label, enabled }` with the label in the editor's language. - `debugViz.anchorId()` — the anchor entity's id, or `nil` before the first tick. - `debugViz.update(dt)` — run every provider and upload what their drawing changed. - `debugViz.state()` — the latest batched draw, or `nil` before the first tick. - `debugViz.teardown()` — tear down the feature, material, buffers, and anchor entity. Registered providers stay registered. - `debugViz.MATERIAL` — the registry key of the shared vertex-colour line material the render feature draws with.

# lighting Scene-lighting base capability: ambient + directional ("sun") light and procedural-sky setup with modify-or-spawn, read-merge-write semantics, plus clear color, and the per-frame reads of the resolved lights. Identity is the component, never the entity name: the sun is the `Light` the renderer's snapshot names as the directional holder, the ambient is the light-role component of kind "ambient", and the sky is the entity carrying a sky-role component. Name-based lookup, word resolution, and sky-material orchestration (presets, material swap) live in the `lighting` toolbox. `sun` and `ambient` configuration patch the scene's resolved sun / ambient light components, spawning a carrying entity when the scene has none. A partial update (e.g. only `intensity`) reads the component's current fields first and merges the given fields on top, so unspecified fields keep their authored values instead of resetting to a default. `sky` writes the sky entity's ProceduralSky component the same way — any of its fields, plus `enabled = false` to remove the sky component. ## Types - `SunOpts` — `{ direction?, color?, intensity?, castsShadows? }`. - `AmbientOpts` — `{ color?, intensity? }`. - `ProceduralSkyOpts` — ProceduralSky component fields, plus `enabled = false` to remove the sky. - `SetupOpts` — `{ sun?, ambient?, sky?, clearColor? }`. - `SetupResult` — `{ sun?, ambient?, sky? }`, the entity ids each provided section resolved to. - `Sun` — `{ direction, color, intensity, castsShadows, entityId? }`. - `Ambient` — `{ color, intensity, entityId? }`. - `LightRow` — one punctual light as the renderer resolved it. ## Exports Writes — each takes the opts above and answers with the entity the light resolved to: - `M.setSun(opts: SunOpts) -> string` — set the scene's sun, returning its entity id. - `M.setAmbient(opts: AmbientOpts) -> string` — set the scene's ambient term, returning its entity id. - `M.applySetup(opts: SetupOpts) -> SetupResult` — apply a lighting setup in one call. All fields optional — only provided fields change. `clearColor` is `{r, g, b}`. - `M.setProbeVolume(key: string, volume)` / `M.removeProbeVolume(key: string)` — publish or retract a baked irradiance probe volume. Reads — each takes no arguments, and answers from the resolved lighting state at a cost independent of scene size: - `M.sun() -> Sun` — the sun the frame is shaded by. - `M.ambient() -> Ambient` — the ambient term the frame is shaded by. - `M.lightRows() -> { LightRow }` — every punctual light the renderer resolved this frame. Identity: - `M.lightKind(componentType: string, component: any?) -> string?` — the kind a light-role component names. - `M.lightOfKind(entityId: string, kind: string) -> any` — the light-role component of that kind on one entity. ## Usage ```luau local lighting = require("@builtin::modules.api.engine.lighting") lighting.setSun({ direction = { 0.3, -1, 0.2 }, intensity = 2.0 }) lighting.setAmbient({ intensity = 0.3 }) lighting.applySetup({ sun = { direction = { 0.3, -1, 0.2 }, intensity = 2.0 }, ambient = { intensity = 0.3 }, sky = { timeOfDay = 14 }, }) local sun = lighting.sun() print(sun.intensity, sun.entityId) ``` A reader takes no arguments and a setter takes the opts table, so `lighting.sun(opts)` is refused with the name of the call that applies it.

# session Session-scoped key-value state. The store lives in the module's environment, which loads once per engine process, so values survive VM reloads (play flips, hot reloads) and die with the process. Use it for state whose lifetime must equal the session's runtime artifacts (GPU resources, runtime materials, bake outputs), which outlive a world save and would leave stale claims otherwise. ```lua local Session = require("modules.session") Session.set("my_system_" .. entityId, handle) local handle = Session.get("my_system_" .. entityId) ```

# yaml.module YAML decode + encode for authored engine content. Pure Luau, no engine dependencies — a general parsing library, not data-system plumbing. ```luau local Yaml = require("@builtin::modules.yaml") local doc = Yaml.decode(vfs.read(path)) vfs.write(path, Yaml.encode(doc)) ``` ## Supported subset - Block mappings (`key: value`) and block sequences (`- item`), nested to any depth. - Compact sequence-of-mapping entries (`- path: x` / ` kind: y`). - Flow collections — `{ a: 1, b: 2 }` and `[1, 2, 3]` — single line. - Plain scalars with type inference: `~` / `null` → nil, `true` / `false` → boolean, numeric literals → number, everything else → string. - Single- and double-quoted strings (`''` escapes a literal quote inside a single-quoted string; `\n` `\t` `\r` `\\` `\"` inside a double-quoted one). A quote opens a quoted scalar where a scalar begins — after `key:`, after a `- ` entry marker, or inside a flow collection — so a plain scalar carries an apostrophe as data (`note: the world's rules`). Quoted keys are read in flow mappings. - `#` comments — honored outside quotes, so a `#` inside a quoted string is kept as data. - Literal (`|`) and folded (`>`) block scalars, with a chomping indicator (`-` strips the final newline, `+` keeps every trailing blank line, none keeps one newline) and an indentation indicator (`1`-`9`: the content's indent past the parent's), in either order (`|-`, `>+`, `|2`, `>1-`). A block scalar's content is literal text: quotes (balanced or not), `#`, `key: value` and `---` inside it are data. - An optional leading `---` document marker. ## Loud-error contract Constructs outside the subset above raise instead of misparsing: anchors/aliases (`&`, `*`), tags (`!`), directives (`%`), multi-document streams (a second `---`), a block-scalar header it cannot read (`|x`, `|-+`, `|0`), tab indentation, and inconsistent indentation (both block structure and block-scalar bodies). Every error carries the offending line number (`yaml: line N: ...`), so a bad config points straight at the line to fix. Tab indentation is rejected everywhere — including block-scalar body lines whose leading whitespace contains a tab. A tab after the first non-space character of a line is content and passes through. ## API - `Yaml.decode(text: string): any` — decode a YAML document into a Luau value (table, scalar, or nil for an empty document). Raises on malformed input or an unsupported construct. - `Yaml.decodeWithComments(text: string): (any, boolean)` — decode as `decode` does, and report whether the text carries a comment by the decoder's own rule: a `#` at a line's start or after whitespace, outside a quoted scalar and outside a block scalar. Re-encoding the value drops such comments, so an editor that writes a document back reads this first. - `Yaml.encode(value: table): string` — encode a Luau table as YAML (block style, two-space indent, alphabetically sorted keys). Raises on values YAML can't represent (functions, userdata, non-string mapping keys). A top-level empty table encodes to an empty document, which decodes back to `nil` (the YAML empty-document ambiguity).

# areaLights system Lights that emit from a surface rather than from a point. Every screen, neon sign, glowing window, ceiling panel and lantern face is an area emitter. Standing a point light in the middle of one gets the brightness roughly right and the character completely wrong: a point puts a pinpoint reflection on the floor and a radial falloff on the wall, where the real thing puts the shape of the emitter and a falloff that follows its extent. ## Using it An emitter that should follow an entity's face is a component: ```lua local id = entity.spawn("tv").id entity(id).component.add("SurfaceLight", { width = 2.0, height = 1.2, face = "front", -- front | back | up | down | left | right intensity = 6.0, range = 12, }) ``` The rectangle turns with the entity, so a tilted screen lights the direction it actually points. Every field is live, and an `intensity` of 0 removes the light. For code placing emitters directly: ```lua local surfaceLight = require("@builtin::systems.areaLights.surfaceLight") surfaceLight.set("strip", { position = { 0, 5, -12 }, right = { 1, 0, 0 }, up = { 0, 1, 0 }, width = 0.6, height = 7, color = { 1, 0.72, 0.35 }, intensity = 5, }) surfaceLight.remove("strip") surfaceLight.configure({ diffuse = 1, specular = 0.5 }) surfaceLight.clear() ``` ## What the knobs do | field | effect | |---|---| | `width` / `height` | Size of the emitting rectangle, world units. The shape of the light is the shape of this. | | `face` | Which way the entity emits. | | `range` | How far the light carries, with a smooth cutoff at the end. | | `intensity` | Brightness. 0 removes the light. | | `colorR` / `colorG` / `colorB` | Emitter colour. | | `offset` | Distance the rectangle sits proud of the entity's origin, along the face's normal. | | `diffuse` / `specular` | Scales on the two terms — the wash across a surface, and the reflected shape of the emitter. | Shape is the point. A wide panel puts a broad pool on the floor; a narrow strip puts a narrow elongated one. That difference is not reachable with a point light at any brightness. At most 32 emitters are held at once, because the shader loops every light for every pixel. ## How it renders `areaLighting.renderFeature` runs one compute pass after lighting. Diffuse is the exact irradiance of the quad — Lambert's formula over its four edges — which matters where a point approximation fails hardest: a wide emitter close to a wall. Specular uses the representative point on the rectangle nearest the reflection ray, with the lobe widened to cover the emitter's solid angle and its peak scaled down to match, so a large emitter reads broader rather than brighter. ## Files ``` areaLights.package/ SurfaceLight.component/ -- an emitter on an entity's face surfaceLight.module/ -- the emitter registry and scales areaLighting.renderFeature/ -- the compute pass ```

# ambientOcclusion system Screen-space ambient occlusion — the contact darkening in corners, creases and where objects meet. Without it, every concave region is lit exactly like a flat one: a box resting on a floor has no seam, a corner is as bright as the wall, and an untextured scene reads as plastic. Occlusion is the cheapest shading cue there is per millisecond, because it needs no extra geometry pass — only the depth and normal the frame already produced. Three techniques are shipped. All three answer the same question — what fraction of the hemisphere above this pixel is visible — and all three cost the same taps to answer it. ## Using it The scene's occlusion is a component — author it once and it persists with the scene: ```lua local id = entity.spawn("ambient_occlusion").id entity(id).component.add("AmbientOcclusion", { technique = "gtao", -- ssao | hbao | gtao intensity = 0.9, -- how far the darkening goes, 0..1 radius = 1.5, -- world-space reach quality = "high", -- low | medium | high | ultra }) ``` Every field is live: edit one in the inspector and the shading follows. Setting `intensity` to 0 turns it off without losing the rest. For code that adjusts occlusion at runtime — a quality slider, a cutscene — reach for the module directly (same options, no component): ```lua local ao = require("@builtin::systems.ambientOcclusion.ao") ao.set({ technique = "hbao", intensity = 0.9 }) -- any subset; the rest is kept ao.get() -- the settings in force ao.techniques() -- the three, each with what it does ao.qualityLevels() -- the sampling shape each level costs ao.active() -- is the pass running ao.clear() -- off, settings kept ``` ## The three techniques | technique | what it measures | |---|---| | `ssao` | Taps scattered over a disk, each weighed on its own: how far the neighbour rises above the tangent plane, over how far away it is. | | `hbao` | One horizon per direction — a ray marched outward until it finds the steepest thing along it — averaged as sines. | | `gtao` | The cosine-weighted arc between the two horizons of a slice, in closed form. This is the visibility the other two estimate. | They are scaled to agree. A point in a right-angle corner sees exactly half the hemisphere, and each technique is normalised so it reads that corner as half: | technique | flat plane | right-angle corner | occlusion | |---|---|---|---| | `ssao` | 1.000 | 0.566 | 0.434 | | `hbao` | 1.000 | 0.592 | 0.408 | | `gtao` | 1.000 | 0.594 | 0.406 | That is what lets `intensity` mean the same thing whichever technique is selected, so switching one for another changes how the estimate is made rather than how dark the scene gets. ## What the knobs do | field | effect | |---|---| | `technique` | Which estimator runs: `ssao` \| `hbao` \| `gtao`. | | `intensity` | How far the darkening goes, in [0, 1]. 0 turns it off and releases the pass. | | `radius` | World-space reach — roughly "how big is a crease worth darkening". Constant in world space, so it does not swell as the camera approaches. | | `power` | Contrast curve on the visibility term. Above 1 deepens the dark end. | | `thickness` | World-space thickness assumed for an occluder, so a thin foreground object stops occluding everything behind it out to the full radius. | | `bias` | How far a neighbour must rise above the surface before it counts as an occluder rather than as the surface itself, in [0, 1]. Raise it if a flat surface shades itself in patches; lower it if fine creases disappear. | | `quality` | Sampling shape. See the table below. | | quality | slices × steps | taps per pixel | resolution | |---|---|---|---| | `low` | 2 × 3 | 12 | half | | `medium` | 3 × 4 | 24 | half | | `high` | 4 × 6 | 48 | full | | `ultra` | 6 × 8 | 96 | full | Every technique spends the same budget: `slices × steps × 2` taps. `gtao` walks each slice both ways, `hbao` treats each of the two directions as its own ray, and `ssao` takes that many independent taps of the disk. The lower two levels compute occlusion on a half-resolution grid — a quarter of the pixels, each still costing its level's taps. Occlusion is low-frequency almost everywhere, and the filter that removes the sampling noise lifts the coarse grid back to the frame in the same pass, weighting each texel by the depth where it sits so silhouettes survive the upsample. What a half-resolution grid loses is the innermost pixel of a sharp crease; everything wider than a couple of pixels comes back the same. ## How it renders One compute pass after lighting writes the per-pixel visibility, a second filters it and multiplies it into the frame, and a blit puts the result on screen. The filter is depth-aware: a plain blur would bleed occlusion across silhouettes, so each tap is weighted by how close its depth is to the centre pixel's. Every technique jitters its sampling by a per-pixel offset, which trades banding for noise; the filter is the half of that trade that removes the noise. Depth, normal and camera come from the render target being drawn (`@scene.depth`, `@scene.normal`, `@frame.camera`), so the result is correct in offscreen captures and render-to-texture cameras at their own resolutions, not only the live viewport. Sky pixels are passed through — there is no surface to occlude. The normal buffer is the deferred G-buffer, so this needs the deferred path (the default). ## Seeing the occlusion on its own While occlusion is running, `ambientOcclusion` is a capture view: the filtered visibility with no scene colour, white where the hemisphere is open and dark where it is closed. ``` capture { pass = "ambientOcclusion" } ``` It is the fastest way to tell a shading problem from an occlusion one, and to compare two techniques or two `radius` values without the lighting in the way. ## Files ``` ambientOcclusion.package/ AmbientOcclusion.component/ -- the scene's occlusion, authored and persisted ao.module/ -- ao.set / .get / .techniques / .qualityLevels / .active / .clear aoShared.module/ -- the prelude, filter and passes the techniques share ssao.renderFeature/ -- taps weighed on their own hbao.renderFeature/ -- one horizon per direction gtao.renderFeature/ -- the arc between two horizons ```

# 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.