# Tool (asset type) A tool is a single agent-callable function whose schema is its `typed function` signature. Tools are the workflow surface — composed Luau operations that bundle multiple engine APIs into one named call, suitable for agents (and for use from `execute`). Each tool has a declared input shape, return shape, and a strict result envelope (`ZmToolResult`). **Every exported tool function is declared `typed function`.** The `typed` keyword is what makes the signature real: it compiles to a runtime dispatch wrapper that checks each argument against its declared type and raises on a mismatch. A plain `function` — even one carrying Luau type annotations — is checked by nothing at call time, so the tool accepts any input and reports success on garbage. See "The typed signature is the schema" below. ## When to use one - You're composing several engine APIs into a workflow that's worth naming and discovering (`tools.list`, `search_tools`). - You want an agent to be able to call this function by name without reading source code — the typed signature is the API contract. - The operation has clear success / failure modes that fit `{ exitCode, data?, stdout?, message? }`. If the function is just a Luau utility called from other code, use a `.module`. If it's stateful background work, use a `.service`. If it's pure GPU compute, use a compute `.shader`. ## Where it lives Tools nest under a `.toolbox/` parent — toolboxes are the namespace. - Source: `/zero/source/.../<Toolbox>.toolbox/<name>.tool/` - Identity: `<Toolbox>.<name>` (dotted form — the toolbox name is part of the tool identity). - Folder shape: - `init.luau` (or `init.lua`) — exports the function, and carries its schema in `--!desc` / `--!arg` / `--!return` / `--!example` annotations above it. The typed signature IS the tool's signature. **Required.** - `README.md` — instance documentation. **Required.** - `.metadata` — tool-level tier and tags. **Required.** ## How to create one Use the workflow tool that scaffolds the right `.tool/` shape under an existing toolbox: ```luau -- The `tools` global authors a tool inside an existing toolbox: tools.create({ name = "<name>", toolbox = "<Toolbox>", description = "What this tool does, agent-facing.", code = "return shared.ok(true)", -- the function body }) -- Or scaffold the folder manually: local box = asset.resolve("<Toolbox>.toolbox") asset.create("tool", "<name>", { into = box }) ``` Always nest under an existing toolbox — if you don't have one yet, call `tools.createToolbox({ name = "<Name>", description = "..." })` first. ## How it operates 1. **Registration.** Writing `init.luau` into a `.tool/` folder registers the tool with the tools registry. It becomes callable as `tools.use("<toolbox>", "<name>", ...)` from Luau, `use_tool { toolbox, tool, args }` over MCP, and `zero <toolbox> <name> [args]` from the engine shell. 2. **Schema validation.** The `typed function` signature declares the parameter shape. Its runtime dispatch wrapper checks each argument before the body runs and raises a message naming the argument, the expected type, and what arrived. 3. **Return envelope.** Tools MUST return `ZmToolResult`: ``` { exitCode = 0|n, data? = any, stdout? = string, message? = string } ``` `exitCode = 0` means success; non-zero means failure, with `message` carrying the human-readable reason. 4. **Discovery.** The tool surfaces in `tools.list()`, `search_tools { query: "..." }`, and `asset.inspect`'s `exposes:` section (parsed from the typed signature and the `--!` annotations). 5. **Hot reload.** Editing `init.luau` re-registers the tool. Subsequent calls see the new behaviour / schema. ## Discovery - `tools.list()` — every registered tool (any toolbox). - `search_tools { query: "..." }` — MCP-side tool search. - `asset.list("tool")` — same set, asset-style listing. - `asset.inspect("<toolbox>.<name>")` — signature, parameters, return shape, this type README. - `ls /zero/source/<Toolbox>.toolbox/<name>.tool` lists the files the folder holds. ## Authoring conventions - **Implementation lives in `init.luau`.** The tool's full function body — argument validation, the call into engine APIs, the return value — goes in `init.luau`. The toolbox's `shared.module/` is for genuinely cross-tool helpers (`ok` / `fail` constructors, shared parsers / validators), not per-tool logic. Do NOT make `init.luau` a one-line forwarder onto a function defined in `shared.module/`. - Use `shared.module/` in the parent toolbox for `ok` / `fail` result constructors. Don't hand-roll the envelope per tool. Pull it in with `local shared = require(".shared")` from any tool that needs the helpers. - Annotate every public function with `--!desc` / `--!arg` / `--!return` / `--!example` directly above the function — the LSP and toolbox surfaces extract these. - **Declare every exported function `typed function M.name(arg: T, opt: U?): R`.** This is not conditional on the signature being "clear" — a loose argument is the case that needs the checked contract most. Give the argument the type it actually accepts (a union, a named table type, a literal enum) instead of dropping to an unchecked `function`. - Keep tools focused. One tool, one named workflow. Split rather than grow. - Tag tools in the sibling `.metadata` (`{ "tags": [...], "tier": "core|content|specialized" }`) so `search_tools` can find them by domain (e.g. `entity`, `scene`, `assets`, `physics`). ## The typed signature is the schema The `typed` keyword compiles the function into a dispatch wrapper that validates arguments at call time. Without it there is no check at all, so the tool runs its body on whatever arrived and returns a success envelope built from garbage. Type each argument as narrowly as the operation actually accepts: ```luau export type Mode = "edit" | "play" export type SpawnOpts = { position: { number }?, parent: EntityRef?, count: number?, } --!desc Spawn a primitive and return the entities it created. --!arg kind Primitive shape to spawn. --!arg opts Placement and repetition options. --!return The spawned entity refs. --!example "cube", { count = 4 } typed function M.spawn(kind: ("cube" | "sphere" | "plane"), opts: SpawnOpts?): { EntityRef } ``` - **A fixed set of accepted words is a literal union**, never `string`. `("cube" | "sphere")` rejects `"Cube"` at the call and lists the accepted values in the error; `kind: string` accepts `"banana"` and fails somewhere deeper, or not at all. - **A structured argument is a named `export type`**, never `{ [string]: any }`. Naming it puts every field and its type on the tool's page and checks them on entry. - **A named type is only as strong as its fields.** `opts: DrawOpts` where `DrawOpts = { value: any }` passes for a table and checks nothing inside it — the same hole, one level down. The argument checker walks nested fields, so type each one; a type name is not a place to put the work off. - **A dispatch table keyed by an `op` string is several tools.** `{ op: string, [string]: any }` is one unchecked entry point wearing N signatures — split it so each operation carries its own checked arguments. - **An entity or asset argument is `EntityRef` / `AssetRef<kind>`**, never `any` and never a bare name string. - `any` is correct only for a value the tool genuinely does not constrain — a passthrough payload, arbitrary user data. It is not a placeholder for a type not yet written down. ## Common pitfalls - **A plain `function` export.** The tool registers and dispatches, so nothing looks wrong — it just never rejects bad input, and every call reports success. Declare it `typed function`. - **Annotations without `typed`.** `function M.f(x: string)` reads as typed and checks nothing at runtime; the annotation only informs the LSP. The keyword is what enforces it. - **Wrong return envelope.** Returning a raw value instead of `{ exitCode = 0, ... }` will be flagged by callers expecting `ZmToolResult`. - **Tool identity.** The fully-qualified identity is `<toolbox>.<name>`, NOT just `<name>`. Toolbox-less tools don't exist by design. - **Missing dependency.** Tools requiring another package / service must declare it; otherwise the call fails at runtime with a missing-module error. ## Related types - `.toolbox` — the required parent namespace for tools. - `.module` — for Luau libraries with no agent-facing schema. - `.service` — for stateful background work, not callable request/response operations. ## In the Inspector Tool: how the tool is called (its signature), what it does, each argument, what it returns, and its examples, with **Open** for its source.

# volumetrics Volumetric (3D-texture) rendering, end to end, in one package. Built entirely on the engine's generic `compute.*` GPU primitives — no Rust changes are needed to author new volumetric content. ## Layout | Asset | Identity | Role | |---|---|---| | `Volume.component` | `@builtin::systems.volumetrics.Volume` | Attach a 3D voxel texture to an entity; raymarches it through the entity's transform AABB. | | `VolumetricSky.component` | `@builtin::systems.volumetrics.VolumetricSky` | Singleton procedural cloud layer with TAA. | | `ParticipatingMedium.component` | `@builtin::systems.volumetrics.ParticipatingMedium` | Mark an entity as fog/smoke/dust that attenuates the light passing through it. | | `mediaTransmittance.module` | `@builtin::systems.volumetrics.mediaTransmittance` | Light-space optical-depth map: the registry, the settings, and the basis the map is built in. | | `mediaShadow.renderFeature` | `@builtin::systems.volumetrics.mediaShadow` | Builds the optical-depth map and attenuates each surface by the density in front of it. | | `volume.module` | `@builtin::systems.volumetrics.volume` | Builders (`noise`/`sphere`/`box`/`wrap`) + the `.zvol` header reader + occupancy + brick paging + the per-entity raymarch dispatch. | | `VolumeSequence.component` | `@builtin::systems.volumetrics.VolumeSequence` | Play an open volume sequence through an entity's transform AABB. | | `volumeSequence.module` | `@builtin::systems.volumetrics.volumeSequence` | A run of `.zvol` frames streamed through a fixed ring of resident volumes. | | `volumeDemos.module` | `@builtin::systems.volumetrics.volumeDemos` | Shared pipeline for the showcase scenes (fill + emissive raymarch + composite). | | `volumetricSky.module` | `@builtin::systems.volumetrics.volumetricSky` | Cloud volume + raymarch + TAA + composite orchestration. | | `shaders/*.shader` | `@builtin::systems.volumetrics.shaders.*` | `volume_raymarch`, `volume_pages`, `volume_pack`, `cloud_noise[_v3/_v5]`, `cloud_raymarch[_v3/_v4/_v5]`, `cloud_taa`. | | `importers/vdb_to_zvol.importer` | (auto-discovered) | `.vdb` → dense `.zvol` via the `openvdb` WASM plugin (procedural fallback when the plugin isn't loaded). | | `presets/cumulus_default.preset` | `@builtin::systems.volumetrics.cumulus_default` | Canonical full `VolumetricSky` weather preset. | | `demo/*.scene` | `@builtin::systems.volumetrics.demo.*` | `sdf_solids`, `smoke_plume`, `nebula`, `godrays`, `zvol_viewer`, `sky`. | ## Path convention — fully-qualified builtin identities Every intra-package reference uses the asset's fully-qualified builtin identity, the same convention every other builtin package follows: ```luau local Volume = require("@builtin::systems.volumetrics.volume") local Sky = require("@builtin::systems.volumetrics.volumetricSky") local V = require("@builtin::systems.volumetrics.volumeDemos") -- shader identities, e.g. asset.resolve("@builtin::systems.volumetrics.shaders.volume_raymarch") ``` Qualified identities are caller-independent: they resolve identically from a module, a scene entrypoint, or a component. Caller-relative (`.sibling`) requires are deliberately avoided here because the component runtime caller identity is `@builtin::components.<Name>`, so a `.sibling` require from a component resolves against the wrong root. (An earlier revision of this package used a `~volumetrics` package-root alias for relocatability; that alias is not resolvable on current main, so the package uses qualified identities throughout.) ## Usage ```luau -- Per-entity volume. The component resolves the name through `Volume.get`, -- so a volume paged into a brick pool renders from the pool under the same -- name: local Volume = require("@builtin::systems.volumetrics.volume") local cloud = Volume.noise({ name = "cloud", size = 64, scale = 4 }) cloud:buildSparse({ brickSize = 8 }) cloud:releaseDense() entity(id).component.add("Volume", { volumeName = "cloud", density = 6.0 }) -- Procedural sky: local sky = entity.spawn("sky") sky.component.add("VolumetricSky", {}) preset.apply("cumulus_default", { entity = sky.id, component = "VolumetricSky" }) -- VDB import: drop a `.vdb` into the VFS; the importer writes a `.zvol` -- alongside it. Load it with the zvol_viewer demo scene. -- Animated run: one `.zvol` per frame, played through a bounded ring. local Seq = require("@builtin::systems.volumetrics.volumeSequence") Seq.open({ name = "plume", frames = framePaths, resident = 3, fps = 24 }) entity(id).component.add("VolumeSequence", { sequenceName = "plume", density = 6.0 }) ``` ## Plugin dependency The VDB importer delegates real OpenVDB parsing to the `openvdb` plugin in the builtin library, `@builtin::plugins.openvdb`. Without the plugin the importer falls back to a deterministic procedural torus so the pipeline stays functional.

# Baseline Visual Validation harness scene for the [player-camera-unification PR](../../../../docs/plans/2026-05-01-player-camera-unification.md). ## Purpose Visual smoke target for Steps 4–9 of the §17 migration plan. Those steps land *before* §17 step 10 (the generic `camera_spawner` / `player_spawner` that auto-populate scenes with a viewport camera). Without this scene, those intermediate commits have no working viewport to validate against and the boot path produces a single bare `Player` entity that renders nothing. `layers.load("@builtin::scenes.baseline_visual")` brings in: - A `Camera`-bearing entity (`baseline_camera`) at a fixed third-person framing of the origin. Renders to viewport. - A static-collider ground plane (`baseline_ground`) so the character controller has something to stand on. - The engine's default `Player` entity (spawned by `ensure_default_player`) with the two canonical tagged bundles applied: - `@builtin::players.humanoid_visual` — mesh + skeleton + `Locomotion` - `@builtin::players.standard_controller` — `MovementState` + `CharacterController` All spawned entities are `temporary` so `layers.active:save()` doesn't bake them into a persisted `.scene/` file. ## Cleanup path | Step that lands | What changes here | |---|---| | §17 step 10 (`camera_spawner` / `player_spawner`) | The hardcoded camera spawn becomes redundant — drop it; the spawner takes over. Bundle application becomes a no-op smoke check. | | §17 step 3 (`.player/` retirement) | No effect — this scene already references the new tagged bundles. | | End of PR | Either kept as the canonical engine smoke target or deleted in Step 16's test-suite extensions. |

# [scene_name] One-paragraph description of what this scene is — the level, screen or area it represents, and when the world loads it. This README describes *this* scene; what a scene is and how loading works live in the scene assetType README. ## Contents - What the entity hierarchy holds — the terrain, props, lights and spawn points a reader should expect to find. - Which player intent `scene.json` declares (`"spawns"` places the local player and its camera on join; `"none"` leaves both to the entrypoint). ## Entry point - `entrypoint.luau` — what it sets up when this scene loads, and anything a caller has to do before loading it.

# UI Templates — main scene The startup scene for the **UI Templates** world. `scene.json` materializes a ground plane, ambient + directional lighting with a procedural sky, and the standard multiplayer player setup (a `PlayerPrototype` with body + `CameraRig` under `PlayerSetups`, and a `PlayerSpawn` under `Spawns`). `entrypoint.luau` holds the lifecycle callbacks (all commented out by default). This world collects reusable, ready-to-read **UI screen templates** authored against the `ui.*` CSS-parity surface. Each template is a self-contained script under `/source/ui/` that registers and shows an `ui` screen. Current templates: - `ui/p5_menu.luau` — a Persona 5 main-menu lockup: a font-family list resolving the bundled **Arial Black** face for the blocky title, clip-path polygons for the torn wedge / octagon badges / row tears, CSS transforms, `-webkit-text-stroke`, text-shadow, and a repeating-linear-gradient halftone field. Run it with `execute { file = "/source/ui/p5_menu.luau" }` to display the screen.

# hdrChart The synthetic HDR chart as a scene: `@builtin::shaders.post.hdrChart` drawn in place of everything, first in the post chain, so the display path is read against known light with no lighting in between. ## Contents - `HdrChart`: a `PostProcess` holding the chart at priority -1000 as its colour wedge (`pattern = 3`): eleven columns from -4 to +6 stops, the top half a saturated blue light at the column's middle-grey luminance and the bottom half that grey. Change the pattern with `postprocess.setProperty` on the effect, or draw the chart from code with `postMetrics.chart.show`. - `ReferenceCamera`: a camera to hold the viewport; the chart covers the whole frame it draws. The scene's `player` intent is `none`. `postMetrics.chart.reference` builds the picture a display curve should present for the chart, which `postMetrics.flip` holds the presented chart against.

# exposureWedge The exposure reference: known light, read at any exposure. ## Contents - `GreyWedge`: 21 patches of middle grey (0.18) at -10..+10 stops, one stop per patch, left to right (`postReference_greyWedge`, unlit). - `ColorChecker`: the 24 ColorChecker Classic patches, each its published sRGB value as linear reflectance (`postReference_colorChecker`, unlit). - `GreySphereLeft` / `GreySphereRight`: two 18% grey spheres lit by `Sun`, a white directional light of intensity 1 from over the camera's left shoulder. - `ReferenceCamera`: the station every reading is taken from, an isolated camera on black with no ambient term, so the light in the frame is the charts' own and the sun's. The scene's `player` intent is `none`. Put the viewport on the camera with `camera.setEditorOverride(entity.find("ReferenceCamera").id)`, or capture it with `capture.fromCamera`. Sweep `__display__`'s `exposure` by powers of two to walk the wedge through the display curve.

# oceans A sea and the ground under it, as one package: the wave simulation, the surface that renders it, the seabed it is seen through, and the answer to "how high is the water here" that gameplay needs to float things on it. ```lua local Ocean = require("@builtin::systems.oceans.modules.ocean") Ocean.create({ preset = "gale" }) ``` That is a whole ocean — waves out to the horizon, foam on the breaking crests, a seabed below, and a surface that follows whoever is looking at it. To float something on it: ```lua local ocean = Ocean.forEntity(oceanEntityId) boat.position = { x, ocean:sampleHeight(x, z), z } ``` It is a building block. The sun the water glitters under, the ambient its foam sits in and the sky it reflects all come from the scene, through the same directional light and reflection probes every other material in the engine reads — so an ocean drops into a world that already has lighting instead of bringing a second set, and changing the scene's light changes the water with it. ## What it does The simulation is **spectral**: instead of animating individual waves, it builds the sea's energy across every wavelength and direction from an oceanographic spectrum, then inverse-transforms that into a height field. A real sea is what comes out — wind speed alone decides wave height, and it rises with wind the way a fully developed sea does, following the Pierson–Moskowitz law. It runs in **cascades** — independent wave fields over different patch sizes, each band-limited to its own range of wavelengths. A tile of roughly two kilometres carries the long waves and one of a few hundred metres the short ones; they sum into a surface with detail at every scale, and because the bands are disjoint no wavelength is synthesised twice. Above them a **Gerstner bank** adds the swell analytically, which no cascade can hold: a wave longer than its own patch has nowhere to live, and swell arrives from a distant storm on its own heading anyway. **Foam** is not painted on. It comes from the Jacobian of the wave displacement: where the surface folds over itself, the wave is breaking. Whitecaps appear where and when the geometry actually breaks, accumulate into a persistent world-space field, and streak behind the crest as they decay. **Colour and transparency are the same mechanism.** Per-channel Beer–Lambert extinction over the distance light travelled through water gives both — red dies within a metre, blue survives tens. That is why shallow water over sand reads turquoise and the open sea reads near-black blue without switching materials. **The seabed** is one noise field read twice: scaled it is the terrain's relief, unscaled it picks between sand and rock, so outcrops stand on the high ground and sand fills the hollows. The sun's caustic web moves over both, bent by the horizontal displacement of the water directly above it. Bodies land on it: the pass that raises the ground writes the same field out as a height patch that travels with the viewer, so what a body stands on is what the frame drew. Nothing here ships an image. Every map the surface and the seabed sample — the foam patterns, the sand, the rock, the caustics — is grown on the GPU at startup. ## The pieces | Asset | What it is | |---|---| | `components/Ocean` | Puts a sea on an entity. Its fields are the sea state; the simulation is rebuilt from them, so an ocean survives a scene reload. | | `modules/ocean` | The substrate: `attach`, `create`, `forEntity`, `sampleHeight`, `sampleDisplacement`. | | `components/Buoyancy` | Floats a rigid body on the sea. Its fields are the hull: how dense it is, how steady, and what box displaces water. | | `modules/buoyancy` | The forces: `attach`, `forEntity`, `columns`, `submergedFraction`, `restingY`. | | `modules/oceanPresets` | Nine named sea states, from `calmClear` through `gale`. | | `modules/oceanQuality` | The four tiers — how finely a sea is resolved, as distinct from what sea it is. | | `modules/oceanClipmap` | The camera-following ring geometry both the surface and the seabed are built on. | | `modules/oceanFloor` | The seabed: terrain, ground materials, caustics and the ground physics collides with. | | `modules/oceanScene` | The seam between the scene capture and the materials that sample it. | | `shaders/oceanSurface` | The water: cascade normals, absorption, exact dielectric Fresnel, subsurface scattering, sun glitter, foam, and the view from below. | | `shaders/oceanFloor` | The seabed: sand and rock blended by terrain noise, under a caustic web. | | `materials/oceanWater`, `materials/oceanSeabed` | The default looks. | | `renderFeatures/oceanScene` | Copies the frame's colour and depth so the surface can refract what is behind it and measure its own water column. | | `computeShaders/ocean_*` | The ten-stage GPU pipeline. | ## Wind is the control Significant wave height goes as the **square** of wind speed, so that one field does most of the work: | Wind | Sea | Wave height | |---|---|---| | 3 m/s | glassy, a mirror | ~0.2 m | | 11 m/s | working sea, occasional whitecap | ~2.5 m | | 24 m/s | gale, breaking and streaked | ~12 m | Everything else shapes character rather than size: `choppiness` pinches crests into peaks, `standingWaveRatio` runs waves both ways instead of only downwind, `jonswapGamma` sharpens a fetch-limited sea, and the foam layers decide how readily a breaking crest whitens and how long it streaks. Read `documentation/oceans.guide` for the full walkthrough, including the seabed, buoyancy, reflections and what each tier costs.

# banding The banding reference: smooth gradients an 8-bit display path quantises. ## Contents - `ReferenceCamera`: an isolated camera on black at `{0, 0, 6}`, framing the two ramps. - `DarkRamp`: light from 0 at the left edge to 0.1 at the right (`postReference_darkRamp`, unlit): an undithered 8-bit encode climbs it in steps several pixels wide. - `SkyRamp`: a sky-blue ramp from 0.02 to 0.6 (`postReference_skyRamp`, unlit), a clear sky's gradient. - `FogCamera`, `FogGround`, `FogLight` and `DarkFog`: a second station, at `{1000, 1, 0}`, looking down a lit grey ground into dark fog (`@builtin::shaders.post.fog`, density 0.03, fog colour 0.01 / 0.012 / 0.02). The fog is a `PostProcess` box around that station, so it grades the frame only while the viewport camera stands there: the dark fog ramp is the ground fading into it toward the horizon. The scene's `player` intent is `none`. Put the viewport on the station to read (`camera.setEditorOverride(id)`); `postMetrics.banding` reads a ramp's longest flat run, and `postMetrics.scopes.zebra` marks the contours.

# Test Suite (asset type) A **test suite** is a registrable asset that bundles one group of automated engine tests. Each `<name>.testSuite/` folder holds an `init.luau` whose body registers a suite (and its tests) against the test framework this **type** ships in its `shared.module/`, reached with `asset.containing(__FILE__).modules.shared`, plus a `README.md` describing what the suite validates. Test suites are the engine's regression net. Every Luau-facing system — FFI bindings, components, the renderer, the VFS, multiplayer, the input stack — ships its coverage as one or more `.testSuite` assets. Because a suite is an ordinary registrable asset, a new system or package adds its own tests by dropping a `.testSuite` folder next to its code; nothing central (the runner, the shell script, CI) has to be edited. ## When to use one - You added or changed a Luau-facing capability and want a permanent regression guard for it. - You fixed a bug — add a test that reproduces it so it can't silently come back (the `bug_regression` suite is the canonical home for one-test-per-issue guards). - A package or system ships behavior that should be validated on every CI run. If you just want to *manually* exercise something once, use `execute` directly — don't author a throwaway suite. ## Where it lives - Built-in engine suites: `src/lua/lib/tests/suites/<name>.testSuite/` (VFS: `/zero/source/libs/@builtin/tests/suites/<name>.testSuite/`). - Package / system suites: anywhere under the package, e.g. `…/voxelEngine.package/tests/voxel_grid.testSuite/`. - Identity: the folder stem (`strip_suffix: true`), e.g. `vfs`. Suite **names must be unique** across the whole tree — the runner and CI key on the stem. ## Folder shape ``` <name>.testSuite/ ├── init.luau # registers the suite via Test.describe / Test.it ├── README.md # what this suite validates + how to run it └── .metadata # agent-editable tags + free-form fields ``` Suites may also ship fixture files (helper `.module` folders, sample data) alongside `init.luau` — `allow_unlisted: true` permits them. ## How to construct a new suite 1. Create `<name>.testSuite/init.luau`. Reach the framework the type ships, then declare the suite with `Test.describe(name, fn)` and each test with `Test.it(name, fn)`. Documentation is authored as doc-comments the engine's doc parser extracts statically: a top-of-file `--!desc` for the suite, and a `--!desc` (what the test checks) plus `--!pass` (the condition that must hold) directly above each `Test.it`. ```lua --!desc Spawn / despawn / exists / find over the entity API. local Test = asset.containing(__FILE__).modules.shared Test.describe("Entity Lifecycle", function() --!desc entity.spawn(name) creates an entity and returns its proxy. --!pass The returned id is a non-empty string and entity.exists(id) is true. Test.it("spawn returns a stable string id", function() local id = entity.spawn("probe").id Test.expect(type(id)).toBe("string") Test.expect(entity.exists(id)).toBe(true) end) end) return true ``` 2. Create `<name>.testSuite/README.md` describing the suite (what system it covers, notable edge cases, how to run just this suite). 3. That's it. No registration step, no runner edit. The next test run discovers the suite via `asset.list("testSuite")`. See `template/` for a copy-ready skeleton (the templater fills in the `[name]` markers). ## How to run tests - **All suites** (writes `/source/tmp/test_results.md` + `.json`; refused in play mode). A bare `run()` covers the world-authored suites; `"*"` adds the baked `@builtin` library: ```lua return tools.use("tests", "run", "*") ``` - **One suite directly** (instance-direct — runs only this suite): ```lua return asset.resolve("vfs", "testSuite"):run() ``` - **From the shell / CI**: `./scripts/run_luau_tests.sh` (all) or `./scripts/run_luau_tests.sh <name>` (one). `--list` prints every discovered suite. - **From inside the engine** (agent loop): the `tests` toolbox — `tools.use("tests", "list")`, `tools.use("tests", "run", { suite = "vfs" })`, `tools.use("tests", "compare", before, after)` to diff two runs and surface NEW failures. See the toolbox README. ## Discovery commands ```lua asset.list("testSuite") -- every registered suite, as AssetRef handles asset.inspect("vfs") -- summary for one suite asset.resolve("vfs", "testSuite") -- handle { guid, identity, path, type } tools.use("tests", "list") -- { count, suites = { { name, identity, path, origin, testCount? } } } ``` ## Authoring conventions - **One suite per asset.** Keep a suite focused on one system; large systems split into multiple `.testSuite` assets (e.g. `zinput_state`, `zinput_events`, `zinput_actions`). - **No `await()` inside `Test.it()`.** The framework runs synchronously; for multi-frame behavior use the per-test context `t.waitFrames(n)` (see the framework README). - **Clean up.** Entities the runner can't attribute are despawned automatically, but prefer `Test.afterEach` for deterministic cleanup. - **Write fixtures via `Test.tmpPath`.** Any file a test writes to the VFS must go under its per-test sandbox: `Test.tmpPath("Foo.component/init.luau")` → `/zero/source/tmp/tests/<suite>/<test>/...`. That root is under `/source/tmp/` (excluded from world saves + multiplayer sync, so it never clogs the synced VFS) and is torn down per-test and again at end-of-run, regardless of pass/fail/crash. Call it INSIDE the test body. For a fixture shared across tests in one block, write under `Test.TMP_ROOT` directly (survives per-test cleanup, still swept at end-of-run). Never hand-roll a bare `/source/<name>` path — it persists and syncs. - **Idempotent.** A suite must produce the same result run twice and must not depend on ordering between suites. - **Never silence the LSP.** No `--!nocheck` / `---@diagnostic disable` in a suite — fix the underlying type/global instead. ## Common pitfalls - **Duplicate stem.** Two `.testSuite` folders with the same stem collide; the runner warns and skips the duplicate, and `--list` fails. Pick a unique name. - **Forgetting `return true`.** Harmless but conventional — every suite ends with `return true`. - **Deferred mutations.** `despawn` / `setParent` / scene clears apply next frame; verify their effects with `t.waitFrames` or a follow-up query, not in the same frame. ## Related types - **`.module`** — reusable Luau library (a suite often requires the system module under test). - **`.tool`** — agent-callable function; the `tests` toolbox tools are `.tool` assets. - **`.component`** — script component; component behavior is frequently what a suite exercises. ## In the Inspector Tests: how many tests the suite declares and their names, parsed without running it, and **Run**, which runs this suite alone in edit mode and reports its passed, failed, skipped and quarantined counts.

# temporalTorture The temporal reference: the content a temporal resolve gets wrong, under temporal antialiasing. ## Contents - `ReferenceCamera`: the station every reading is taken from, at `{0, 1.5, 9}` looking down -Z; `CutCamera` is a second station (`{6, 3, 6}`, turned 40 degrees toward the scene, priority -1). A camera cut is the viewport going from one to the other (`camera.setEditorOverride(id)`), the frame a resolve has to drop its history on. - `TemporalAntiAliasing`: the scene's temporal antialiasing at its defaults. - `SiemensStar`: 36 spokes of 0.9 on 0.02 (`postReference_siemensStar`, unlit); toward its centre the spokes are narrower than a pixel. - `Wire0`..`Wire4`: horizontal wires 0.016 units thick, thinner than a pixel at this distance (`postReference_white`, unlit). - `FencePost0`..`FencePost16` and `FenceRail0` / `FenceRail1`: a fence of thin white posts at a regular pitch, the pattern a jittered resolve shimmers on. - `Fan` with `FanBlade0`..`FanBlade3`: four white blades turning at 8 radians per second (`Mover.spin`). - `FastObject`: a lit grey cube carried round a 2-unit circle at 3 radians per second (`Mover`) in front of `CheckerBackdrop`, a 64-cell checker (`postReference_checker`). - Everything stands on the scene's dark clear colour, so thin geometry is read against a flat field. - `Sun` and `Ambient` light the lit parts. The movers turn while the engine plays (`engine.mode = "play"`); in edit mode the scene holds still. The scene's `player` intent is `none`. Put the viewport on `ReferenceCamera` and read consecutive frames with `renderer.presentedFrames({ frames = n })`; `postMetrics.temporalVariance` reads how much each pixel changes across them.

# [scene_name] One-paragraph description of what this scene is — the level, screen or area it represents, and when the world loads it. This README describes *this* scene; what a scene is and how loading works live in the scene assetType README. ## Contents - What the entity hierarchy holds — the terrain, props, lights and spawn points a reader should expect to find. - Which player intent `scene.json` declares (`"spawns"` places the local player and its camera on join; `"none"` leaves both to the entrypoint). ## Entry point - `entrypoint.luau` — what it sets up when this scene loads, and anything a caller has to do before loading it.

# Tessellation Showcase Every surface in this scene starts as a **flat two-triangle plane**. The `Tessellation` component subdivides each triangle into thousands of GPU micro-triangles and displaces them along their normals from a **height map**, turning flat geometry into rich relief — no authored high-poly meshes. The entrypoint drives the same component with four procedural height maps: | Piece | Height source | What it shows | | --- | --- | --- | | Rocky mountains | 5-octave value-noise fBm | Natural terrain from a flat plane | | Sand dunes | Low-frequency swells | Smooth rolling forms | | Ocean swell | Crossed sine waves | Repeating wave crests | | Before / after | Bold ridge grid | Same box, flat vs. tessellated | ## What it demonstrates `Tessellation` sits next to a `Model` + `Material`. It reads the entity's current mesh, subdivides each triangle into `4^level` micro-triangles, and displaces them from the material's displacement map — the entity's PBR material renders the result. A single flat box + a height map becomes a detailed surface entirely on the GPU. ## Running Load the scene and enter play mode. The height maps are generated procedurally on load, so the showcase is fully self-contained.

# dofChart The depth-of-field reference: four focus charts at known distances under a lens focused on one of them. ## Contents - `ReferenceCamera`: an isolated camera on black at `{0, 1, 0}` looking down -Z. - `Lens`: a `DepthOfField` focused at 4 units, f/1.4, 50 mm. - `FocusChart2m`, `FocusChart4m`, `FocusChart8m`, `FocusChart16m`: the same chart of bar pairs (`postReference_focusBars`: four rows, 8 pairs across the top row, doubling on each row below, 0.8 on 0.03, unlit) at 2, 4, 8 and 16 units, each scaled with its distance so all four subtend the same angle. The 4-unit chart is in focus; the others are as far out of it as the lens puts them. The scene's `player` intent is `none`. A chart's sharpness is how many of its rows still resolve: `postMetrics.profile` along a row reads the bar contrast.

# bloomEnergy The bloom reference: emitters of known size and light on black, and a specular highlight smaller than a pixel that moves. ## Contents - `ReferenceCamera`: orthographic, 25.6 world units tall, on black with no ambient term. Captured at **256 x 256**, one pixel is 0.1 world units and the frame's centre lies on a pixel corner; every size below is in pixels of that frame. - `Emitter1px`: a single-texel emitter, centred on the pixel 48 from the left and 40 from the top (`postReference_emitter`: 16 times the display's white). - `Emitter4px` and `Emitter16px`: emitters 4 and 16 pixels square, their edges on pixel boundaries, at 4.0 world units above the centre (pixel row 88 from the top), centred at x = 0 and x = 8.0. - `MovingSpecular`: a polished metal sphere lit by `Sun` (directional, intensity 6), its highlight a sub-pixel source; a `Mover` carries it round a circle 0.03 units (0.3 pixel) across at 1.5 radians per second. The scene's `player` intent is `none`. Capture it with `capture.fromCamera` at 256 x 256, or put the viewport on `ReferenceCamera` and read `renderer.presentedFrames`. `postMetrics.ringEnergy` reads the light a bloom spreads around an emitter.

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

# assetType (asset type) The `assetType` is the **type of types** — the meta-type that every `<typename>.assetType/` folder is an instance of, including itself. A `<typename>.assetType/` folder declares a new asset type called `<typename>`: its on-disk shape, its identity rule, and the structural contract instances of the type must satisfy. This type is self-hosting. `assetType.assetType/` conforms to its own schema — a `type.yaml` plus a `README.md` — so the type system is defined in terms of itself rather than a hidden engine special-case (the same way a C compiler is written in C). Every asset in the engine, including each `.assetType` definition, now resolves to a registered assetType: a `.material` resolves to `material.assetType`, and `material.assetType` resolves to `assetType.assetType`, which resolves to itself. ## Why it exists Assets used to be mapped to their type *implicitly*, by matching the folder suffix against a name-keyed registry. That match carried no stored link: nothing on a `Foo.material` recorded *which* `material.assetType` it was written against, so two worlds shipping a same-named type could silently disagree. Making `assetType` a real, resolvable asset closes that gap — the link from an asset to its type is now an explicit reference pinned in the asset's `.refs` sidecar (`via: "asset_type"`), exactly like every other dependency. ## Where it lives - Source: `/zero/source/.../<typename>.assetType/` - Identity: `<typename>` (the `.assetType` suffix strips from the identity; the folder retains the suffix on disk). - Folder shape: - `type.yaml` — the structural spec the validator reads. **Required.** - `README.md` — type-level documentation. **Required.** - `about.yaml` — three short plain-language texts saying what the type is for (see "Say what your type is for" below). Every built-in type ships one. - `behavior.luau` — optional behavior/scaffolding module. - `template/` — optional canonical placeholder body the templater copies into a new asset of the type. - `<name>.module/` — optional shared code the type ships to **every instance** of it, conventionally `shared.module/` (see below). ## Shared code its instances reach (`asset.containing` + `.modules`) A type ships code every instance of it uses by declaring the modules in its own `behavior.luau`, as a map of tracked `require`s: ```luau -- inside <typename>.assetType/behavior.luau M.modules = { shared = require(".shared") } -- the sibling shared.module/ ``` An instance reaches it with one location-independent line: ```luau -- inside any foo.<typename>/init.luau local api = asset.containing(__FILE__).modules.shared ``` `__FILE__` is the chunk's own VFS path; `asset.containing` resolves the calling asset, and `.modules.<name>` follows the instance's pinned `typeRef` (the type's **guid**, recorded in the instance's `.refs` as `via = "asset_type"`) to the module its type declares. Because resolution follows that link rather than a category name, the same line in an instance of a different type resolves to that type's module, and identically-named modules in two types never collide. `asset.typeRef(target)` reads that guid for any target; `asset.resolve(asset.typeRef(target))` gives the full `AssetRef<assetType>`. See `assetTypes/README.md` § "Shared code: type-owned modules" for the full mechanism. ## How to create one Authoring a new asset type is just creating a `<typename>.assetType/` folder under `/zero/source/`. The engine registers `<typename>` as a category **the moment the folder is written** — no engine restart, no Rust change, and it works for built-in (`@builtin/assetTypes/`) and user-defined types identically. Once `<typename>` is registered, `<name>.<typename>/` folders are recognised as assets of that type and resolve their `asset_type` link back to this definition. Creating a `<name>.<typename>/` folder *before* its `<typename>.assetType/` exists fails fast: the suffix has no registered type, so the folder can't be a valid asset. Author the type first. ## Say what your type is for (`about.yaml`) Every type carries a small `about.yaml` beside its `type.yaml`, and the README you write for the type documents how to author an asset of it. Both are required, and both are meant to be written as you make the type, while you know what it is for. `about.yaml` answers three questions in plain words, one key each: ```yaml intent: "Sets the typeface of the text in your game: UI, labels, signs and 3D lettering." function: "A font, from a TTF, OTF or WOFF file, made available to all of Zero's text, including 3D text." usage: "You choose it by name for your UI or your text, and the text appears in that typeface." ``` - **`intent`** is what the type is for in someone's game. Name the whole range of things it covers, in the words a game maker would use for them. - **`function`** is how it works today: what an asset of the type is made of and what the engine does with it. - **`usage`** is what a person or an agent does with one: how they pick it, place it, call it, or hand it to something else. A few habits keep it useful. Write about the type as a whole, so the text holds for every asset of it, and leave out any one asset's name. Say what the type does right now. Stay with words a game maker would say, and mention a file name or a call only where a game maker would know it. The limits are in bytes: `intent` 800, `function` 1500, `usage` 1200. Each is generous, and a few sentences usually say it. Why bother: agents working in a world read these three texts to learn what your type is for, so they reach for it when it fits and use it the way you meant. People searching find the type by what they want to make, and the three texts let them tell at a glance whether it is the one they need. `asset.create("assetType", name)` scaffolds the file with all three keys, and a README whose first paragraph is a `[[describe]]` note. Each value starts with `[[describe]]` followed by a note on what to write; replace the whole value with your own words. A value or a README line that still starts with `[[describe]]` counts as not written yet, which the push's check of each asset it carries against its type reports, naming the file. A type you leave as it was is not asked, so older types stand. Many types at once, or one you would rather not write by hand: `services describe` lists the types that lack these texts and what filling them costs, and `{ mode = "all" }` writes them into the same files, where you edit them like anything else you wrote. Where the texts show up: `asset.inspect("<typename>", "assetType")` returns them as `detail.about`, `assetTypeRef:getAbout()` returns them as a table with the keys `intent`, `function` and `usage`, the type's `types/<typename>` guide page ends with an "About this type" section holding them, and the Inspector's Type section lists them at the top. The guide page is this README plus that section, so a README that explains the type well and an `about.yaml` that says what it is for read well together. ## Ask your assets to say what they are A type can ask each of its assets to carry a description: a file, written by the author or generated, that says what that asset is and what it is for. The people and agents who find an asset read it to decide whether it fits, and the author knows what it is for at the moment of making it. **1. Declare the file with a `described` check.** This is the whole requirement: ```yaml files: required: - path: "README.md" # any file name works kind: "file" content: - { check: "described", message: "Say what this widget is for and where it goes." } ``` With that in place: - An asset whose file is missing, empty, or still has a line starting with `[[describe]]` does not meet the type's requirements. `asset.validate` names it, `zm status` and `world.publishBlockers()` list it, and a push that carries it is refused with `message`. - `services describe` finds it (`mode = "find"` lists it and the price) and can write the description for it (`mode = "all"`). It writes only this file. For a YAML file that holds several texts, name the keys and their limits in bytes, the way this type does for `about.yaml`: ```yaml content: - check: "described" keys: - { key: "intent", max_bytes: 800 } - { key: "usage", max_bytes: 1200 } message: "Write intent and usage." ``` `headings` names sections a Markdown file must have. `assetTypes/README.md` has the full check. **2. Optionally, steer what gets generated with a `describe:` block:** ```yaml describe: guidance: "Say what the widget shows, what input it reacts to, and where it fits in a UI." examples: - "<identity of an asset of this type whose description reads well>" ``` `guidance` says what a description of your type covers, and `examples` names assets whose descriptions show the shape you want. Without the block, generation still works from the general describing guide and the check's `message`. An example is an asset of your type in the library whose description is a true, written one, never a scaffold's placeholder, and never the asset being described. When the library has none, leave `examples` empty rather than name one that is not. A type whose assets the model cannot perceive (a sound it cannot hear, a motion it cannot see) says so in `guidance`: the description comes only from what the asset's own files state, such as its name and the `.metadata` where a generation service records the prompt that made it, and when they state nothing the model answers `cannot` with that reason. `services describe` then fails that one asset with the reason and leaves its file as it was. **3. Start the file unwritten in your template.** Put a heading and one line that starts with `[[describe]]` and a short note on what to write, in `template/<file>`, so a new asset starts unwritten rather than with text that only looks written. Do not put example content in it: every new asset carries the template verbatim, and the same text on many assets makes them impossible to tell apart in search. Types whose assets say what they are through their own content (a mesh, a texture, a sound) leave this out: declare nothing and nothing is asked. ## The `behavior.luau` contract `behavior.luau` is the type's code. It returns ONE table, and the keys below are the ones the framework reads off it for EVERY type — the surface you get by declaring them. Anything else on the table is your own: reachable by name through `require("@builtin::assetTypes.assetType.shared.ref").loadTypeModule("<typename>")` for a system that knows your type (`computeShader` publishes `dispatchKey` that way), and never called by the framework. ```luau local M = {} M.ref = { ... } -- methods on every AssetRef of this type M.modules = { ... } -- shared code the instances reach M.global = {} -- reserved key; ship the empty table function M.onCreate(name, opts) ... end return M ``` ### The tables | Key | Shape | What the engine does with it | |-----|-------|------------------------------| | `M.ref` | `{ [name] = function(self, ...) }` | Every function becomes a method on every `AssetRef` of this type: `ref:name(...)`, with `self` the ref. This is how a type gives its instances an API. Two names in here are contracted — see below. | | `M.modules` | `{ [name] = require(".sibling") }` | Shared code the type's instances reach through `asset.containing(__FILE__).modules.<name>`, resolved by the instance's pinned `typeRef` guid. See the section above. | | `M.refShapes` | `{ [method] = "TypeName" }` | Declares the result type of a `M.ref` method so the LSP can check what a call site does with it. See the `M.refShapes` section below. | | `M.events` | an events schema | The events an ASSET of this type fires, declared the way a component declares its own. Readers subscribe through `ref.events.<name>:connect(...)`; firing authority stays with the type. Keyed by the asset's guid, so every resolver of the same asset shares the signals and a re-resolved ref re-attaches to subscriptions already there. | | `M.namePattern` | a Lua pattern string | The name shape `asset.create` enforces for instances of this type, replacing the default `^[A-Za-z][A-Za-z0-9_]*$`. | | `M.global` | `{}` | Reserved. Ship the empty table. | ### The lifecycle hooks Each is optional; a type that omits one costs nothing. The engine calls them: | Hook | Signature | When it fires | |------|-----------|---------------| | `M.onCreate` | `(name, opts) -> { [filename] = contents }` | On `asset.create("<type>", name, opts)`. Returns the files that scaffold the new instance, as a map of relative path to contents; the framework writes them. The `opts` type annotation is the schema `asset.create` validates the caller's arguments against, so annotate it. | | `M.onReplace` | `(dest, files) -> { [filename] = contents }` | On an `asset.create` that writes over an asset already at `dest`, after `onCreate`. Receives the files `onCreate` produced and returns the files to write, so a type that re-derives its content (a rig re-imported from its source file) can carry what an author added to the asset it replaces. Optional. | | `M.onRegister` | `(self)` | Once per instance, the first time it registers: on `engine.onWorldLoaded` for instances already in the world, immediately on a live `asset.create`, and when an instance arrives after that sweep (installed, pulled, or synced from a peer). Guarded by the instance's path, so a double trigger never double-registers. An instance that leaves the runtime releases the guard, so one arriving at the same path again registers. This is what makes "write an asset into the world and it takes effect live" work for content that registers into a runtime registry. The `@builtin` library is excluded from the sweep. | | `M.onChange` | `(ref, change)` | On every VFS write to a file INSIDE one of this type's instances. `change` is `{ path, asset, type, kind, origin }`: `kind` is `"edited"` or `"seeded"`, `origin` is `"local"` or `"remote"` (an importer runs on the originator only). **Filter on `change.path`**: the hook fires for any file under the folder, so act on the one you care about. It runs as its own task and may wait on what it reads: a `vfs.read` of bytes only the blob store holds (a binary file on the web build) fetches them. The writes to one asset reach the hook in the order they were made, each once the hook before it has finished. A re-entrancy guard suppresses writes back into the same asset routed inline from the hook, and a write the hook makes is routed on a later frame like any other, so the hook must be convergent on its own: diff the meaningful state and short-circuit while your own regeneration is in flight. | | `M.onDelete` | `(ref)` | When an instance of this type leaves the runtime: it is deleted, or the engine swaps away from the world binding that held it. Its files are gone from `/zero/source` by then. A removal routed while the instance's `onChange` is waiting reaches `onDelete` once that hook, and every write queued behind it, has finished. On a swap the instance still exists in the world it belongs to, and a VFS write the hook makes reaches the world now bound. | | `M.validate` | `(assetRef) -> { { code, message, severity? } }` | On `asset.validate`, after the structural `type.yaml` check, for the type's own SEMANTIC validation. `severity` defaults to `"error"`; error-severity problems flip `ok` to false, warnings do not. A hook that raises or returns a non-table is itself reported as a `validate.hook_failed` error. `world.push` runs this per user asset, so declaring it enforces your type's rules at publish time with no further wiring. | ### The two contracted `M.ref` names Most `M.ref` methods are your type's own surface: name them what you like, return what you like. Two are read by the engine and mean the same thing for every type, so their shape is fixed: - **`instantiate(self, target?, opts?) -> (root, idMap)`** — makes an instance part of the scene. Defining it is the whole opt-in: `ref:canInstantiate()` is true exactly when it exists. Its **return is a contract** — see the next section. - **`inspect(self) -> detail`** — the type-specific half of `asset.inspect`. See its section below. ### Names a type cannot shadow Some keys resolve on every `AssetRef` before per-type dispatch, so an `M.ref` entry of the same name is never reached: `canInstantiate`, `getSource` / `getBytes` / `getText`, `exists`, `deps`, `meta`, `runtime`, `events`, `modules`, `typeRef`, and the residency flags `has_backing_asset`, `has_runtime_changes`, `cpu_resident`, `gpu_resident`. These are the behaviours every asset must expose identically, which is why they win. ### Reloading A `behavior.luau` edit ripples to existing refs with no restart: dispatch reads `mod.ref` fresh each time and `require`'s cache is re-run in place. A type whose folder appears at runtime is picked up on the next dispatch — negative results are not cached either. ## The names your type's assets hold (`references:`) An asset that names another asset by a string depends on it: the named asset travels with it into a pack or a pull, and a name nothing answers to is an unresolved dependency `worldValidation` reports and the push gate refuses. The engine reads `require(...)` and the asset lookups on its own; a name your type's format or API carries anywhere else is one you declare, in `type.yaml`: ```yaml references: # A top-level key of this type's own files that holds a name (or a table of them). keys: - { key: "shader", type: "shader" } # A call's argument, counting from 1, wherever the call is written. args: - { call: "g:node", position: 2, type: "procNode" } # A field of the options table a call takes. fields: - { call: "fx.beam", field: "material", type: "material" } ``` `type` is the category the name resolves in, one of `asset.categories()`. An argument declared once per category, at the same `call` and `position`, takes the name from whichever category answers. A key or a field holds one category: declared again with another `type`, it takes the later one. The block is declared as the type registers, when the library or the world holding it is laid into the VFS, so every reference table reads it whatever script has or has not run. `asset.declareReferenceKey`, `asset.declareReferenceArg` and `asset.declareReferenceField` declare the same things from a script, for a surface that is no type's. ## What search does with your type (`indexing:`) A type declares what search embeds for its instances. **This is not optional and there is no useful default**: ZeroMind runs your declaration and adds nothing of its own, so anything you do not point at is absent from the index — silently, and for every instance of the type forever. Twenty types once shipped with no `indexing:` block and every instance of them was unfindable. A type whose instances are never searchable (a run record, a log) says so with `indexing: none`; every other type declares a recipe. A type without an `about.yaml` beside its `type.yaml` refuses every push that carries it, whether or not the push edited the type. Texts in it that are not written yet follow the rule every `described` file follows: they refuse the push that edits, stages or commits the type. Two words carry the whole thing, and they are the same two the search tool exposes: - **`identity`** — what an instance IS. For anything you can look at, that is the picture (`content:` + `modality: image`, matched directly by a text query). For everything else it is the authored text that says what it is. - **`capability`** — what it DOES and how it is made. Code, settings, the model-written summary of them. A type with no behaviour has no `capability` entry. A type with nothing to look at has no image. Leaving a slot empty is a statement; filling it with whatever happens to be lying around is not. The one you have to decide when authoring a type is: *for an instance of this, what is the thing a person would recognise it by, and what is the thing it does?* A texture answers "the image" and "its compression settings". A module answers "its README" and "its code". Write those two answers into `indexing:` and the rest follows. Three specifics worth knowing before you write one: - **`derive` is instructed by this type's own `README.md`.** A model reads an instance's source and writes a description; what it embeds is the description, not the source. It follows your README to know what it is looking at, so a type whose README says what its instances are gets good derivations for free. There is no prompt to name. - **`derive` loses detail.** It keeps the main technique and drops secondary ones. If the source is code you want searchable by its own vocabulary, declare the same files a second time as `capability` with `extractor: verbatim`. Two entries, same role, different failure modes. - **Never `source: { field: name }`.** A filename is one or two words with no usable embedding, and a corpus indexed that way answers "language runtime" with `say_runtime_2.soundClip`. `facets:` is the second stage: a `file:` embedded whole (`.metadata`, so keys nobody declared still get indexed) plus computed keys that state a value for every instance including `false` — the raw file can imply "not rigged" and can never say it. The full schema, every extractor and the facet sources are in [`assetTypes/README.md`](../README.md); the scaffolded block with inline guidance is in [`template/type.yaml`](template/type.yaml). ## A container whose contents work together (`system: true`) A type that is a container can say its contents are one working whole by declaring `system: true` at the top level of its `type.yaml`. `package` declares it: the components, modules, scenes and tools a package ships are parts of one system. The declaration is plain data, read from the decoded `type.yaml` (`require("@builtin::assetTypes.assetType.shared.declaration").of("package").system`), and a type that leaves it out is an ordinary type. ## What your type looks like (`preview:`) A type declares how its instances are pictured, and the engine makes the picture when something needs it: staging an instance whose `preview.png` is missing or pictures content it no longer holds queues a render, a view that shows the instance asks for one, and `ref:preview()` renders one on demand. An edit renders nothing on its own. Each `preview.png` records the content it pictured, which is how a stale one is told from a current one. The preview studio owns the light, the backdrop, the framing and the camera, and nothing in the world reaches it, so an instance pictures the same in every world. Declare one of four recipes: | `kind` | The picture is | Your type provides | |---|---|---| | `instantiate` | the asset stood in the studio through its own `instantiate` | `ref.instantiate` | | `image` | a file the instance holds, fitted to the frame, nothing rendered | `source.files`, the candidate files in order | | `surface` | the asset painted on a builtin mesh | `mesh`, and `ref.previewMaterial(self) -> { material }` | | `custom` | whatever `ref.preview(self, opts)` returns | `ref.preview` | ```yaml preview: kind: surface mesh: sphere ``` A scene-instantiable type that declares nothing still answers `ref:preview()` through its `instantiate`, but persists no picture: the declaration is what makes the engine keep one. List `preview.png` among the type's files so an instance may hold it. The picture is findable only when `indexing.content` names it. The two are separate statements, and neither is derived from the other: ```yaml indexing: content: - role: identity modality: image source: { file: "preview.png" } ``` `@builtin::assetTypes.assetType.shared.previewRecipe` reads the declaration; the scaffolded block with inline guidance is in [`template/type.yaml`](template/type.yaml). ## Typing a result from the instance (`M.refShapes`) Every method on `M.ref` is checked against the type its `--!return` names, and every asset of the type gets the same one. That is right for most methods and wrong for the ones whose result is shaped by the ASSET: a method answering one entry per child folder, per row of a config, per binding an input map declares. The widest true annotation for those is `{ [string]: Thing }`, and an indexer accepts every key — so a caller's typo reads as valid and nothing reports. `M.refShapes` lets the type state the result per instance. Each entry is `function(self) -> (typeExpression, source?)`: a Luau type expression for THIS asset, and the module whose type vocabulary the expression uses. Read the asset; never run it — stating a type must not take effect. ```lua -- inputMap.assetType/behavior.luau — the shipped example. -- `activate()` hands back one handle per control the map declares. M.refShapes = { activate = function(self): (string, string) local names = {} for _, control in ipairs(M.ref.controls(self)) do table.insert(names, control.name .. ": Handle") end if #names == 0 then return "", "" end return "{ " .. table.concat(names, ", ") .. " }", "@builtin::modules.zinput.scheme" end, } ``` With it, `map.jump:onPressed(fn)` resolves and `map.noexisting` is reported with the map's real controls. Without it, both pass silently. ### What the call site has to say A per-instance type is matched by the asset's IDENTITY, so it applies only where the reference the method is called on says WHICH asset. Two spellings do: ```lua -- a component field, whose declared default names the asset public = { map = Field.assetRef("inputMap", "@builtin::inputMaps.default", Sync) } local controls = public.map:activate() -- typed for THAT map -- an annotation, naming category and identity local m: AssetRef<"inputMap", "@builtin::inputMaps.default"> ``` `asset.resolve("<identity>", "<category>")` carries the CATEGORY, so the methods the category defines are checked on the result — but not which asset it found, so a per-instance result keeps the category's declared return. A reference that names no asset (`asset.resolve(someVariable)`, a value passed in as a parameter) carries neither, and calls on it are unchecked. That is the same rule everywhere: the checker states what the code states, and a name computed at runtime states nothing. ### The result is a value, not a binding The type belongs to the expression, so it travels the way any inferred type travels. Indexing the call's result is checked; stashing it in a module local and indexing it from another function is not, because the local's declared type is what carries across — and `any` (or no annotation) carries nothing: ```lua -- checked: `d.greting` is reported function awake() local d = public.dialogue:lines() d.greeting:say() end -- NOT checked: `lines` is a module local typed `any` local lines: any = nil function awake() lines = public.dialogue:lines() end function start() lines.greting:say() end ``` Bind what you need at the call site and the names stay checked in both places — the asset-derived type at the boundary, ordinary scoping after it: ```lua local lineGreeting = nil function awake() local d = public.dialogue:lines() lineGreeting = d.greeting -- `d.greting` is reported here end function start() lineGreeting:say() end ``` ### When nothing is reported and you expected something From a call site, a type that is correct and a type that was never published look the same: no diagnostic either way. `require("@builtin::assetTypes.assetType.shared.refShapes").published()` answers which it is. It returns two maps — the category surfaces, and the per-asset results keyed by identity and then by method: ```lua local shapes = require("@builtin::assetTypes.assetType.shared.refShapes").published() shapes.categories.dialogue --> "{ lines: () -> any, lineNames: () -> { string } }" shapes.returns.Shopkeeper.lines --> "{ browsing: Line, farewell: Line, greeting: Line, wares: Line }" ``` An identity absent from `returns` was never published for, which is a different thing from published-and-correct — and the reason to look here rather than at the call site. The answers are recomputed when an instance is written, so a control added to a map reaches the checker with no restart. Only types that declare `refShapes` are read per instance, and at most 64 assets of one type are — past that the type keeps its declared return and the engine log names what was dropped. ## The instantiate hook (`M.ref.instantiate`) — a contracted return A type opts into becoming part of the scene by defining `instantiate` on its `ref` table. That is the whole opt-in: `ref:canInstantiate()` is true exactly when the hook exists, so consumers offer a scene path — an `Asset.source` field, a viewport drop, a tool argument — by CAPABILITY rather than by a list of type names. Unlike `inspect`, this hook's **return is a contract**. A caller writes one piece of code against every instantiable type, so what comes back cannot vary by type: ```lua -- behavior.luau local Instantiable = require("@builtin::assetTypes.assetType.shared.instantiable") local M = {} M.ref = { instantiate = function(self, target, opts) local root = Instantiable.root(self, target, opts) -- IN: the base opts -- ... compose whatever this type is, under `root`, NOW ... return Instantiable.result(self, root, idMap) -- OUT: the contract end, } return M ``` **IN.** `target` is an owning entity ref: the instance lands under (or, for a hierarchy type, onto) that owner. With no target the type spawns a fresh root. `position`, `rotation`, `scale`, `name` and `temporary` mean the same for every type — `Instantiable.root` applies them to a root you mint, `Instantiable.place` to one you adopt, so you never re-read the spec. Honour more opts of your own if your type needs them, and document them in the hook's `--!arg` docs. **OUT.** Return `(root, idMap)` through `Instantiable.result`: - **`root`** — the composed root, as an `EntityRef`. Composition is **synchronous**: everything your type builds is live when you return, so the caller can parent to it and read its components in the same statement. Do not defer the work to a component's `awake` and return an empty shell — a root that is not live is refused. - **`idMap`** — the `originalId -> runtimeId` map naming what you spawned, or nil for a type with no addressable children (`result` normalises it to `{}`). **A caller never receives nil.** A component that re-composes your asset on every load keeps this map and passes it back in, which is how a cross-entity reference into the composition survives a reload. `AssetRef` runs every `instantiate` through `result` on the way out whether or not your type called it, so returning something else fails at your own call rather than handing a caller a nil root. Calling it yourself is still how you say what you return, and running it twice changes nothing. `@builtin::assetTypes.assetType.shared.instantiable`'s README is the full reference for both halves. ## The inspect hook (`M.ref.inspect`) `asset.inspect(ref)` resolves `ref`, builds a common envelope shared by every asset (`identity`, `name`, `guid`, `source`, `typeName`, `typeDefinitionPath`, `scope`, `origin`, `description`, `tags`), then calls the resolved type's own inspect hook — `M.ref.inspect(self)` on `behavior.luau` — for the type-specific `detail`. The hook returns *only* `detail`; the framework fills in everything else: ```lua -- behavior.luau local M = {} M.ref = { inspect = function(self) -- self.path is the asset's own folder. Parse the asset's OWN -- files — source text, a native payload header, its `.metadata` -- — never runtime state (a live component instance, a GPU -- upload, a compiled schema): inspect must work on an asset that -- hasn't been compiled, uploaded, or registered yet. return { -- type-specific fields, whatever this type wants to surface } end, } return M ``` A type that omits `M.ref.inspect` yields the generic record: the envelope alone, `detail = nil`. That's a valid, working state — not an error — but it means agents calling `asset.inspect` / `tools.use("assets","describe", ...)` on an instance of the type see only identity and scope, none of what makes an instance of it meaningful. Declaring the hook is what makes a type's instances inspectable for what they actually are. A hook that raises leaves `detail = nil` and sets `record.warning` to the error text — `asset.inspect` itself never raises for a resolved ref. ## Discovery - `asset.list("assetType")` — every registered asset type. - `asset.inspect("<typename>")` — the type's identity, source path, and this README, plus its `about.yaml` texts as `detail.about`. - `asset.resolve("<typename>", "assetType")` — the `<typename>.assetType` asset itself (used by the validator to find the type's `type.yaml`). ## Related - `assetTypes/README.md` — the full `type.yaml` schema and validator rules. - `@builtin::assetTypes.assetType.shared.instantiable` — the instantiation contract's shared implementation, both halves. - Every other `*.assetType/` here — the concrete types built on this meta-type. ## The Inspector a type ships Every type names the file its Inspector sections come from with `inspector: { type: "inspector.luau" }` in its type.yaml. `asset.create("assetType", name)` scaffolds the block and an `inspector.luau` whose Contents section lists an asset's files, built from `ctx.parts`. `asset.validate` on a type that names none reports `assetType.inspector_required` (an error for a `@builtin` type the engine's library authors; a warning for a world's own, and for one the library carries by reference, which the world that published it answers for), and one whose file does not load `assetType.inspector_invalid`. ## In the Inspector Type: what the type.yaml declares (suffix, container, primary files, the settings and inspector blocks), whether the type ships a behavior, how many instances it has, and **Open** for its files. Schema: the settings every instance carries, as read-only typed controls at their defaults (a type whose schema is per instance says where it is declared). Instances: a link to each of the first 20 assets of the type, and how many there are when there are more.

# Scene (asset type) A scene is a saved, loadable snapshot of an entity scenegraph inside a world: the entity hierarchy, transforms, components, lighting, and a declared `player` intent, plus an auto-discovered startup script. A scene is the unit of "level" or "screen" — a title screen, a lobby, a gameplay area, and an end-of-game summary each get their own scene. Scenes load as **layers**. One root scene is active at a time; additional scenes can load additively as overlays on top of it. Each scene owns its own multiplayer relay room. Switching scenes is a local call: the client that makes it leaves the old scene's room and joins the new scene's room. ## When to use one - You want a savable, re-loadable snapshot of an entity scenegraph plus its lighting and player setup. - You want a runnable starting state for a level or screen. - You want a scenes-as-data flow: `layers.load("lobby")`, edit live, then `layers.active:save()` to publish the edits back to the scene. For a reusable entity assembly (a prop, a vehicle, a UI panel) that many scenes spawn into themselves, use a `.bundle`. A scene is a whole-world snapshot; a bundle is one prefab that lives inside scenes. ## Folder shape A scene asset is a folder ending in `.scene`. Its identity is the folder name with the suffix stripped (`Lobby.scene` → `Lobby`). - `scene.json` — the scenegraph: `entities[]`, lighting, and the top-level `player` intent. **Required.** Written by the engine — a build, a save, a human dragging something in. Not hand-edited. - `build.luau` — what the scene is made of, written as code. Runs while you author; saving bakes its result into `scene.json` (see Building a scene). - `entrypoint.luau` — the startup script. Auto-discovered as a sibling of `scene.json`; define lifecycle callbacks here (see The entrypoint). - `<name>.<type>/` — an asset the build makes, authored here by `build.asset` (see The assets a build makes), alongside `.build.assets`, which records which `build.luau` produced each of them. - `prefabs/` — optional subfolder for scene-local bundles. - `scripts/` — optional subfolder for scene-local Luau helpers, required from `entrypoint.luau`. - `README.md` — optional per-scene notes about THIS scene. Author one only when there is scene-specific detail worth recording; the general scene model lives here, in `guides { path: "types/scene" }`. `scene.json` is version 7. It carries `"format": "scene"`, `"version": 7`, an `entities[]` array, and a top-level `"player"` string intent. ## The `player` intent Every scene declares how it handles players with a top-level `player` field in `scene.json`: - `"spawns"` — the scene carries an authored player setup, and the engine spawns a player for each connecting user from it. This is the default for a freshly created scene. - `"none"` — the scene spawns no player and authors no camera. Author your own Camera entity for the view (menus, UI-only screens, cinematics). ### How `"spawns"` works A `"spawns"` scene authors two things in `scene.json`: 1. A **PlayerPrototype** — an entity carrying the `PlayerPrototype` component, whose `body` field names a child entity (the body). The body carries an avatar (an `Asset` pointing at an avatar, e.g. `@builtin::avatars.humanoid`). A `CameraRig` child carries a `Camera` with a camera behavior (e.g. `orbital_follow`). The prototype root is authored `PrototypeOnly` so it exists as a clonable template. 2. A **PlayerSpawn** — an entity carrying the `PlayerSpawn` component, whose `prototype` field names the PlayerPrototype to instantiate and whose transform is where players appear. The scaffolded scene groups these under two organizing entities, `PlayerSetups` (holding the prototype) and `Spawns` (holding the spawn), so the authoring tree stays legible. On each user join — entering play, and each subsequent connect — the engine runs the spawn for that user: - It clones the PlayerPrototype subtree. - The clone root becomes the user's **internal identity** — a registry-only entity named `user` carrying the `UserIdentity` component. The identity is the anchor for who the player is; it has no world presence. - The body named by `PlayerPrototype.body` is adopted as the user's **avatar** — their visible presence in the world — and placed at the PlayerSpawn's world transform. Move the PlayerSpawn (or drag it in the editor) to set where players appear. - The `CameraRig`'s Camera follows the bound avatar. The player prototype is live in edit mode so you can see and adjust it. In play mode it is deactivated and marked internal — it stays a clonable source while each user gets their own clone. ### Reaching the live player The player surface lives on the root scene's registry, `layers.active.players`: - `players.localPlayer` — this client's player, a curated handle. - `players.localReady` — `true` once the local player's avatar is bound (or the scene opted its avatar out). - `players:list()` / `players:count()` — the players connected in this scene's room. - `players:get(userId)` — a connected player by account id. - `players:ownerOf(avatar)` — the player whose body is a given avatar. A player handle is a data record about who the player is, plus a link to their body: - `player.avatar` — the body's entity ref. Act on the body through it (`player.avatar.position`, raycasts, rig access). - `player.isLocal` — whether this client owns the player. - `player.ready` — whether a live avatar is bound. - `player.userId` / `player.identity` / `player.displayName` — the player's account identity. - `player.avatar = ref` — bind a live body entity as the player's body (assign nil to clear). To use a `.bundle` / `.avatar` asset, spawn it into the world first, then bind the resulting entity. The player's identity entity is the internal anchor; the handle exposes the body (`player.avatar`) and the player's data, and reaching for `.entity` / `.id` / `.component` raises with a redirect to `player.avatar`. ## Building a scene `build.luau` declares what the scene holds. It is ordinary engine code — `entity.spawn`, `component.add`, transform writes, `for` loops, a `require` of a module that computes a layout — and what it creates is what ends up in the scene. ```lua function content() for i = 0, 4 do local crate = entity.spawn("crate") crate.localPosition = { i * 2, 0.5, 0 } crate.component.add("Model", { model = asset.resolve("cube", "mesh") }) end end ``` The build runs while you author, in **edit** mode, and what it created lands in the live scene. Saving the scene bakes it into `scene.json`, which is what makes the entities durable content: a human can select and inspect them, they replicate, and they are there when the world opens without `build.luau` running at all. Play mode never runs it — in play the entities load from `scene.json` like anything else the scene holds. **Editing the file rebuilds the scene in place.** Writing `build.luau` is the signal; there is nothing to reload, and the rebuild saves. An entity keeps the id it had, so a reference to it — a spawn naming a prototype, another entity's component naming this one — survives every rebuild. Add a crate to the loop and the other four do not move. The write returns as soon as the file is on disk and the rebuild finishes behind it, so what it landed comes back as a notice: ``` [info] a write to build.luau rebuilt the scene { content="6", scene="scenes.main", editorOnly="1" } ``` An edit saved while a rebuild is still running is an edit to code that rebuild has already read, so it gets a rebuild of its own once that one finishes, and says which it was: ``` [info] a write to build.luau arrived during a rebuild and was rebuilt after it { content="7", scene="scenes.main", editorOnly="1" } ``` Several edits saved during the same rebuild get the one run after it, which reads the file as it stands then. A scene that declares a build also runs it when it **loads** in edit, so the scene shows what the code says now, including an edit made while the world was closed. A load whose `.build.state` records the current script reads `scene.json` as the build and runs nothing. When the load does run it, a world's own scene saves the result, unless the scene holds unsaved edits: those stay the author's to keep or discard, and the file write waits for their save. A library scene (one under `/libs/`, the `@builtin` library included) is read by its load: the build lands in the live scene and its files stay as the library states them. Play reads `scene.json`, so it comes up without that build until `:build()` saves it. ### The two surfaces - `content()` — the scene's own entities. Present in play. - `editorOnly()` — entities present while authoring and absent in play. They carry the `EditorOnly` participation the runtime deactivates and hides when play begins, and they are baked too, so a collaborator opening the world sees the same ones. Anything an author needs to see and a player does not goes here — an alignment guide, a spacing marker, a debug volume. Both are optional. A scene with neither has no build. ### What a rebuild touches Only the entities the build itself placed. Anything a human dragged in, or a tool placed directly, is invisible to a rebuild and never moved or removed. Within what it owns, the build is authoritative: an entity the code stopped emitting is despawned, a component it stopped adding is removed. The build writes its own name and each entity's place in the hierarchy onto the entity, and `scene.json` records that pair beside the entity's name and transform — which is why a rebuild after a reload, in a later session, lands on exactly the entities it placed the first time without anything having been remembered. ### When the file did not change `:build()` runs the build against what it resolves right now — for the case where something the builder *reads* changed and the file did not: a module it requires, an asset it resolves. After a write it is unnecessary; the write has already run it. ```lua layers.active.asset:build() -- rebuild and save layers.active.asset:build({ save = false }) ``` It answers with how many entities each surface placed — `{ content = 6, editorOnly = 1 }` — and with nil for a scene that has no `build.luau`. Called while a build for that scene is already running, it returns at once with `{ inFlight = true, scene, trigger, startedBy, message }` naming that build instead of starting a second one; `inFlight` is what tells the two answers apart. An operation the bake cannot hold is **refused** rather than applied. A build accepts what its records carry: entity lifecycle, transforms, hierarchy, names, visibility, active state, participation mode, network scope, attributes, and components with their public data. Anything else raises while the build runs, naming the operation and the build it answered to, instead of leaving the scene depending on something no reload brings back. When that happens the previous build stays exactly as it was. A runtime resource a build needs — a mesh it generates, a texture it writes — is made as an asset instead, below. Everything else a refusal names goes outside the builder, or into a component the builder attaches, which runs at play. ### The assets a build makes `build.asset(type, name, produce)` makes an asset the build's content names — a mesh a lathe produces, a texture a pattern writes. `produce` takes nothing and returns the creation parameters `asset.create` takes for that type; the call returns the asset's `AssetRef`, which is what a component field holds. ```lua function content() local tower = build.asset("mesh", "tower", function() local positions, indices = lathe(profile, 16) return { positions = positions, indices = indices } end) entity.spawn("tower").component.add("Model", { model = tower }) end ``` The asset is authored inside the scene's own folder — `Lobby.scene/tower.mesh` — and the scene records which `build.luau` produced it in `.build.assets`. So `produce` runs when the build script changed and never otherwise: a reload re-runs the build and reuses the asset, while editing the profile re-authors `tower.mesh` **in place**, keeping its path and its guid. That is what holds the reference — `scene.json` names assets by guid. For a part of a scene that several scenes place — or that one scene places many times with different settings — see `guides { path: "types/sceneModule" }`, which is the same idea with declared `inputs` a placement sets. `guides { path: "core/scenes-as-code" }` covers both. ## The entrypoint `entrypoint.luau` is the scene's **runtime** — what happens while the game is being played. What the scene *is* comes from `build.luau` above; nothing here has to construct it. `entrypoint.luau` is auto-discovered as a sibling of `scene.json`. The loader runs it in a fresh environment and folds its top-level `function name(...)` declarations into the matching scene lifecycle event. Define the callbacks the scene needs — the recognised set: - `onLoad()` — the scene loaded in **play** mode. Gameplay-start hook, runs on every connected client. - `onHostLoad()` — the scene loaded in **play** mode, on the client that owns the scene's synced content (the relay room creator; offline and single-player count as host). Fires once. Entities spawned here — and anywhere downstream — become synced automatically, so this is where shared world content is spawned: it runs on exactly one peer, and every other peer receives the entities from the relay snapshot. - `onEditLoad()` — the scene loaded in **edit** mode. Custom per-scene authoring tools. Writing this file while the scene is loaded in edit mode reloads its layer, so the new `onEditLoad` runs after the previous load's `onUnload`. - `onUnload()` — before the scene's entities are torn down. Extra cleanup; engine-managed teardown (entity despawn, resource release) runs separately. - `update(dt)` — per frame in play mode, while the gameplay clock runs. - `editorUpdate(dt)` — per frame in edit mode, running or paused. Play-paused ticks neither hook. The scene loader partitions these strictly on mode; a component's hooks of the same name read `engine.paused` instead, so the two rules differ — `man components` has that table. - `localPlayerReady(player)` — once the local player's avatar is ready. Gameplay wiring for the local player: attach state, bind UI, swap the avatar. The avatar is already placed at the PlayerSpawn, so this is for behavior, not positioning. - `playerJoined(player)` — a remote player joined this scene's room. Use for per-player UI (nameplates, greetings). The local player arrives through `localPlayerReady`. - `playerLeft(eid)` — a remote player left this scene's room. Receives the departed entity's id (the entity is already despawned). Each scene's entrypoint runs in its own environment, so two scenes can declare the same top-level names without clashing. Keep each callback short; push per-scene logic into `scripts/` modules and `require` them. ## Layers Scenes load through the `layers` namespace. - `layers.load(ref, opts?)` — load a scene. `ref` is a scene AssetRef or identity string. Without `opts.additive`, this is a **root** load: it replaces the current root scene. `opts`: - `additive` — load as an overlay alongside the current root instead of replacing it. - `persistent` — keep an additive overlay mounted across mode flips and root swaps. - `origin` — a `{x, y, z}` world offset for the overlay's entities. - `deferred` — spread the entity spawn across frames (for thousand-entity scenes); the load signals complete only once the scene has settled. - `layers.active` — the current root scene proxy (nil before any load). - `layers.list()` — every loaded layer (root + additive overlays). - `layers.find(ref)` / `layers.is_loaded(ref)` — look up a loaded layer by ref. - `layers.onLoad(cb)` / `layers.onUnload(cb)` / `layers.onBeforeLoad(cb)` — subscribe to every scene load / unload (distinct from a scene proxy's own `:on_load` / `:on_unload`, which fire only for that scene). A root scene carries the `players`, `camera`, and `settings` surfaces; additive overlays inherit the root's players and lighting and do not carry their own. ### The scene proxy `layers.active` (and `layers.find` / `layers.list` entries) returns a scene proxy: - Fields: `.guid` (canonical identity), `.name`, `.path`, `.asset`, `.additive`, `.visible`, `.state` (`"loading"` → `"loaded"` → `"ready"` → `"unloading"`), `.ready`, `.players`, `.camera`, `.settings`, `.entrypoint`. - `.camera` — a proxy over the scene's primary camera entity; read and write the live Camera component through it, and `.camera.behaviors._list()` enumerates the available camera behaviors. - `:save(opts?)` — publish the live scenegraph to canonical `scene.json` (see Saving). A convenience that forwards to the scene ASSET's `save` (`self.asset:save(opts)`): the proxy is the runtime view and owns nothing on disk, so persistence lives on the asset. - `:reload()`: unload and reload the same scene (a runtime respawn). A scene with a `build.luau` runs its build again and saves the scene, so `scene.json` holds what the reload built and the next play loads it; a library scene's rebuild lands in the live scene alone. - `:clearDirty()` — discard unsaved edits and respawn from canonical. Forwards to the scene asset's `discard` (`self.asset:discard(opts)`). - `:sceneAsset()` — the durable `AssetRef<scene>` this live layer maps to. - `:promoteDirty()` / `:writeDirty()` / `:hasDirty()` — manage the dirty overlay directly. - `:unload()` — despawn the layer and free its slot. - `:onReady(cb)` — fire once the scene reaches `ready` (latched: a late subscriber fires immediately). ## Multiplayer & relay rooms Every scene has its own relay room, keyed by the world guid, the boot profile, the mode, and the scene guid. Switching scenes with `layers.load` runs a room transition — leave the old room, tear down, join the destination scene's room — all on the client that made the call. Teardown of the old scene never leaks to peers in the new one. In play mode connected to a relay, the scene's entities are host-authoritative: only the room creator instantiates them (marked synced), and every joiner receives them from the relay snapshot rather than spawning their own. This is why shared world content belongs in `onHostLoad` — spawning it in `onLoad` would run on every peer and duplicate it. Each player's own avatar spawns per-user from the PlayerSpawn on every client. Edit mode and offline boots spawn locally and never auto-sync. ## Loading and saving **Loading** — `layers.load(ref)` for a root scene: 1. Despawns the current root scene's non-persistent entities. 2. Instantiates the entities from `scene.json` (including the player prototype and spawn for a `"spawns"` scene). 3. Applies lighting and sky. 4. Runs `entrypoint.luau` and fires lifecycle callbacks as their events occur. **Saving** — persistence lives on the scene ASSET. `sceneRef:save()` writes the scene's current state back to canonical `scene.json`; when the scene is loaded it captures the live scenegraph, and when it is not loaded it promotes the pending dirty overlay. `layers.active:save()` is the convenience form — it forwards to the active layer's mapped asset (`layers.active.asset:save()`). Writing canonical is the only path that does so: edit ↔ play cycles never save, so hitting play to test never overwrites the scene. Between saves, live edits accumulate in a per-scene dirty overlay that the loader merges on top of canonical. `sceneRef:discard()` throws the overlay away and restores the saved state — deleting the overlay, and respawning the live layer when the scene is loaded. It works whether or not the scene is loaded, because the overlay belongs to the asset, not the runtime layer. `layers.active:clearDirty()` forwards here. Saves capture entity data, not the entrypoint script — edits to `entrypoint.luau` and `scripts/` are always preserved. `opts.to` on `save`/`discard` targets a different scene ("save as"), taking either a bare name (`"level_2"`) or a full VFS path. **What a record states.** A component's record in `scene.json` holds the fields that instance's configuration states: the keys of the table it was added with (a `build.luau` call's own init table, or the record it was loaded from) and every field written since, through code, a tool or the inspector. A field nothing set stays out of the record and takes the component's declared default each time the scene loads, so changing that default reaches every entity that left the field to it. To have an entity follow the default again, remove the field from its record. A field set on a live entity after its record was made is a change the scene review names (`sceneAuthoring.changes` lists it as `+ Type.field = value`), and accepting it writes the field into the record. A scene saved before records were stated this way holds every field; those values load and save as they are, since a stored value cannot be told apart from one an author chose, and a hot reload that changes a default one of them shadows names it. A stored field the component no longer declares is named by a `[component.add]` warning when the record loads and left out of the next save. ## Lighting Lights are ordinary entities: a directional light, an ambient light, and a sky are entities carrying `Light` / `ProceduralSky` components in `scene.json`. Author, move, and tune them like any other entity. If a scene is missing any of {directional light, ambient light, sky}, the loader adds a temporary default for the absent one so a scene never loads dark or skyless; the defaults are never saved into the scene. Scene-level lighting state that is not an entity — clear color and sky descriptor — lives under `layers.active.settings.lighting` (`clear_color`, `sky`); writing those fields updates the engine live. ## Modes Scenes load in both edit and play mode (see `man modes`). The mode governs behavior: - An entrypoint's `update(dt)` runs in play while the gameplay clock runs, and its `editorUpdate(dt)` runs in edit. A component's hooks of the same name follow the clock rather than the mode — `man components` has the four states that produces. - Player prototypes are live in edit and deactivated + internal in play, where each user instead gets a clone. `EditorOnly` entities follow the same edit-live / play-internal toggle. - `onLoad` / `onHostLoad` fire on a play-mode load; `onEditLoad` fires on an edit-mode load. ## How to create one ```luau asset.create("scene", "<Name>") -- Creates /zero/source/<Name>.scene/ with: -- build.luau where this scene's content is written. A new one starts -- with the sun / ambient / sky lighting and the "spawns" -- player setup, commented for editing — everything else the -- scene comes to hold is written here too. -- scene.json what that code produces, baked. -- entrypoint.luau commented lifecycle-callback stubs. ``` A freshly created scene has a player with a following camera on the first press of play. It carries no ground, so the first thing to author is what the player stands on — a `content()` line away in `build.luau`. ## Discovery - `asset.list("scene")` — every registered scene. - `asset.inspect("<name>")` — entity count, lighting summary, source path, and this type README. ## Authoring conventions - Keep static layout in `scene.json` — geometry, lights, props, the player prototype and spawn. - Keep dynamic setup in `entrypoint.luau` lifecycle callbacks — event listeners, gameplay state, services attached to spawned entities. - Spawn shared, synced world content from `onHostLoad`; spawn each player's own gameplay wiring from `localPlayerReady`. - Set the world's startup scene in `/.world_settings` — that is the scene the world boots into. - Y is up; +Z is forward. - Renaming the folder changes the scene's identity — update every `layers.load` callsite and the world's startup-scene field. ## Related types - `.bundle` — reusable entity hierarchies that scenes spawn into themselves. - `.service` — cross-scene background work that outlives a scene load. - `.world_settings` — picks the startup scene and world-level renderer / physics options. ## In the Inspector Selecting a scene opens its **Scene** section, read from `scene.json` without loading the scene: how many entities it holds, how many of them are roots (and their names), how players join and the file's format version when it states them, and whether the scene has edits not yet saved.

# ScreenSpaceReflections Reflections off the scene's own drawn frame, as a one-feature component. A scene lists its features together, each with its settings, on `RenderFeatures` (`{ feature = "@builtin::systems.reflections.ssr", settings = { ... } }`); this component carries the same knobs as fields for one feature. ```lua local id = entity.spawn("reflections").id entity(id).component.add("ScreenSpaceReflections", { intensity = 1.0, maxDistance = 40, quality = "high", }) ``` Polished floors start reflecting what stands on them, wet ground reflects what is above it, and metal picks up its surroundings — all from geometry the camera can already see, with nothing authored per surface. Roughness decides who gets them. A screen-space ray traces one direction, which is a mirror; `roughnessCutoff` is where that stops being a fair stand-in for a surface's real lobe, and past it the pass leaves the surface alone. Every field is live: edit one in the inspector and the reflections follow. Setting `intensity` to 0 turns them off without losing the rest of the settings. How much a reflection shows through is the surface's own Fresnel term, so metal takes almost all of it and a dielectric floor takes a few percent head-on and more at a grazing angle — the same way a wet road reads dry underfoot and mirror-like down the street. For code that adjusts reflections at runtime, reach for `@builtin::systems.reflections.ssr` — same options, no component. The full description of what each knob does and how the passes work is in the package readme: `guides { path = "systems/reflections" }`.

# Polished floor A polished stone floor with three coloured pillars standing on it, under an afternoon sky, with screen-space reflections listed on the scene's `RenderFeatures` entity — so the floor reflects the pillars, and a player walking across it, rather than the sky alone. Load it with `scene.load("@builtin::systems.reflections.demo.polished_floor")`. Players arrive facing the pillars from floor height, which is the grazing angle a polished dielectric reflects at most strongly. ## What it shows - **The feature on one entity.** `render_features` carries a `RenderFeatures` list with `@builtin::systems.reflections.ssr` at `intensity = 1`, `maxDistance = 60`, `quality = "high"`. Delete the entity and the floor mirrors the sky alone; put it back and the pillars stand in the floor. - **Only what the camera sees.** A pillar's reflection comes from the frame the camera drew, so turning away from a pillar takes its reflection with it, and the reflection fades toward the screen edge rather than cutting off. - **The environment underneath.** Where a ray finds nothing the floor keeps the sky reflection the environment gives it, at the same mip and Fresnel weight, so the seam between the two is a change of content and not of brightness. - **Roughness decides who reflects.** The floor sits at roughness 0.06, the pillars at 0.55 — above the feature's `roughnessCutoff` — so the floor is the one surface tracing reflections in the scene. ## Contents - `floor` — a 60 m slab of `PolishedStone`, a near-black dielectric at roughness 0.06, with a collider. - `pillar_1..3` — 1.6 × 5 × 1.6 m boxes in `PillarRed`, `PillarGreen`, `PillarBlue`, sunk into the slab. - `sun`, `ambient`, `sky` — a side-lit afternoon under a `ProceduralSky`. - `render_features` — the `RenderFeatures` entity this scene exists for. - `PlayerSetups` / `Spawns` — the humanoid player on an orbital-follow camera, spawning in front of the pillars. The scene's player intent is `"spawns"`. ## Entry point - `entrypoint.luau` — nothing to set up: the reflections run from the `RenderFeatures` entity the moment the scene loads.

# ssr Screen-space reflections — polished floors reflect what stands on them, from the frame the engine has already drawn. ```lua local ssr = require("@builtin::systems.reflections.ssr") ssr.set({ intensity = 1, maxDistance = 40, quality = "high" }) ssr.get() --> the settings in force ssr.active() --> are the reflection passes running ssr.clear() --> off, settings kept for the next set() ``` `set` takes any subset — omitted fields keep their current value, so adjusting one knob does not mean restating the rest. An `intensity` of 0 turns reflections off and releases the passes rather than running them at zero strength. `roughnessCutoff` is the field that decides who gets reflections at all. A screen-space ray traces one direction, which describes a mirror; past the cutoff a real surface scatters over a lobe too wide for one ray to stand in for, and the pass leaves those surfaces alone. `maxDistance` and `quality` trade against each other. Quality sets how many steps the march spends, so a long distance at a low quality samples coarsely — reflections thin out at range rather than disappearing, because refinement adapts to the step size on its own. For reflections a scene should simply have, author the `ScreenSpaceReflections` component instead — it carries the same settings, persists with the scene, and edits live in the inspector. This module is for code that changes reflections at runtime: a quality slider, a cutscene, weather turning pavement wet. The full description of what each knob does and how the passes work is in the package readme: `guides { path = "systems/reflections" }`.

# ssr The render feature behind `ScreenSpaceReflections` and `@builtin::systems.reflections.ssr`. One compute pass runs at the `afterDepthPrepass` seam, once the visibility raster has laid the frame's depth and before anything shades: | order | pass | output | |---|---|---| | 60 | `ssr_trace` | reflected colour plus a confidence weight, per pixel, into `@scene.reflection` | That channel is what a material's environment term reads the same frame, at its own pixel: the traced reflection stands in for the probes and the sky to the degree the trace trusts it, and the material's own Fresnel, roughness and tint weigh it into the pixel the way they weigh any environment. Nothing here touches the lit picture. The trace marches against this frame's depth, which the visibility raster has just written, so the reflection stands where the camera is now. What it reads about the surfaces — the reflecting surface's normal and roughness, the hit's normal and its colour — comes from the previous frame: the G-buffer as that frame left it (`readsPrevious`), and `@scene.colorHistory`, the light it ended with, each reprojected through the previous view-projection `@frame.camera` carries in its rows `[5..9)`. A point the previous frame did not show reflects its environment alone. ## The march `ssr_trace` reflects the view ray about the surface normal and walks it through the depth buffer. Steps are uniform in **screen** space, not world space. A ray heading toward the horizon covers enormous world distance across a few pixels, so stepping in world units there means either missing every thin occluder near the camera or spending the whole budget on distance nothing can be seen at. The world parameter is recovered from the screen parameter through `1/w`, which is what interpolates linearly under perspective. At each step the ray's world position is compared against the world position reconstructed from the depth sample under it. Comparing in world space is what lets `thickness` mean a distance in world units rather than a depth-buffer epsilon whose meaning changes with range. The march looks only for the **crossing** — where the ray first passes behind the depth buffer. Thickness is tested after bisecting that crossing, not during the march: one march step covers roughly as much depth as a surface is thick, so a ray tested during the march can jump from in front of a surface to well behind it without ever landing inside it. Bisection runs for whichever is larger, the quality tier's budget or however many halvings bring one march step under `thickness`. A coarse march that stopped bisecting early would leave the crossing bracketed more loosely than a surface is thick, and every hit would then fail the thickness test — long-range reflections would vanish outright instead of thinning. A hit is rejected when the surface it landed on faces along the ray, because what is on screen there is that surface's far side. ## What the channel holds `ssr_out` is `@scene.reflection`: linear radiance in `.rgb`, and in `.a` the confidence — the edge fade, the range fade, how squarely the ray carried on into the scene, and `intensity`, multiplied — so `intensity` is how much of the trace reaches the picture and a miss is a zero the material reads as "the environment alone". The channel is cleared at the top of every scene render this feature does not run for, so such a frame reflects the environment alone too. The trace reads the light the previous frame ended with, so it runs on the lit channel alone (`debugChannel = 0`); a camera drawing a diagnostic pass is drawn lit first, unpresented, so the trace runs for where that camera stands, and the diagnostic reads the channel traced for it. The cutoff exists because a single ray describes a mirror: past it the lobe a rough surface gathers over is wider than one ray can stand in for, and the material keeps the prefiltered environment it already has.

# ssr_common The screen-space reflection passes' shared ground: the view-space reconstruction from depth, and the ray-to-screen projection the march steps along. Included with `#include "@builtin::systems.reflections.ssr_common"`.

# ssr_trace Marches a reflection ray through the depth buffer and reports where it hit. ## Includes - `ssr_common` ## Bindings | name | kind | |------|------| | `scene_color` | `texture2d` | | `scene_depth` | `texture_depth` | | `scene_normal` | `texture2d` | | `scene_material` | `texture2d` (`sample: uint`) | | `frame_cam` | `buffer` | | `ssr_params` | `buffer` | | `ssr_out` | `storage2d (rgba16f)` |

# 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.install`, `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). **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 }) ``` ## How it operates 1. **Registration.** Writing `package.yaml` indexes the package with the package registry. 2. **Install.** A package is installed by guid, the way every asset is: `zeromind.install` from the shared library, or `tools.use("zeromind", "installAsset", <guid>)` inside the engine. The install writes the package's files (and the deps its `.refs` record) 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. - **Dependency installs.** A package that depends on another package must declare it (in `package.yaml::dependencies` once supported) and the parent world must install dependencies in order. - **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.

# ParticipatingMedium Marks its entity as a volume of fog, smoke, dust or steam — something light has to travel through. What is behind the volume comes out dimmer than what is beside it, and overlapping volumes stack. ```luau local id = entity.spawn("fog_bank").id entity(id).component.add("ParticipatingMedium", { sizeX = 30, sizeY = 8, sizeZ = 30, density = 0.15, }) ``` ## Fields | Field | Meaning | |---|---| | `shape` | `"box"` (default) or `"sphere"` | | `density` | Extinction per world unit. `0` releases the medium. | | `sizeX` / `sizeY` / `sizeZ` | Half-extents, for a box | | `radius` | Radius, for a sphere | `density` is the physical knob: a ray crossing `d` world units of a medium of density `k` leaves with `exp(-k * d)` of the light it entered with. A 20-unit bank at `0.15` therefore passes about 5% of the light straight through it. The entity's position places the volume; move the entity and the shadow moves with it. ## Notes - The light-space map is sized to the bounding sphere of everything registered. A small bank sharing a scene with a very large one lands on few texels — set `extent` and `centre` through `mediaTransmittance.set` to bias the map toward the region you care about. - Attenuation applies to surfaces. The sky keeps its own colour. - The attenuated light is the sun's: `sunDirection` sets which way the map's rays travel. See `mediaTransmittance` for the scene-wide settings and the direct API.

# Volume Per-entity attachment that renders a 3D voxel texture (cloud, smoke, nebula, imported VDB grid) into the scene as a volumetric body. The component does NOT own the volume's lifetime — producers (the `volume` module, a custom compute fill, or `compute.writeTexture3D`) build the texture and pass its name in `volumeName`. The entity's world transform defines the AABB the raymarcher samples. `volumeName` is resolved through `Volume.get`, so a volume the `volume` module built is rendered as it stands — at its own dimensions, from its own density channel, through its occupancy grid, and out of its brick pool if it is paged. A name no volume answers to is taken as a bare 3D texture some other system owns, and `occupancyName` / `isRgba` describe it. ## Usage ```luau local Volume = require("@builtin::systems.volumetrics.volume") local cloud = Volume.noise({ name = "cloud", size = 64, scale = 4 }) cloud:buildOccupancy({ brickSize = 8 }) local e = entity.spawn("cloud_entity") e.localScale.set(8, 4, 8) e.component.add("Volume", { volumeName = "cloud", occupancyName = cloud.occupancyName, density = 6.0, }) ``` A paged volume costs what it holds and is named the same way: ```luau local cloud = Volume.noise({ name = "cloud", size = 128, threshold = 0.6 }) cloud:buildSparse({ brickSize = 8, threshold = 0.01 }) cloud:releaseDense() -- the brick pool is now the only copy local e = entity.spawn("cloud_entity") entity(e.id).localScale = { 8, 4, 8 } e.component.add("Volume", { volumeName = "cloud", density = 6.0 }) ``` ## Public fields | Field | Type | Sync | Default | Meaning | |---|---|---|---|---| | `volumeName` | string | Sync | `""` | Required. Name of the volume, or of a bare 3D texture, to render. | | `occupancyName` | string | Sync | `""` | R8 occupancy texture for a bare texture's empty-space skipping. Empty = no occupancy. A volume the module built carries its own, and a name set against one is reported as left aside. | | `density` | number | Sync | `1.0` | Density gain multiplier. | | `absorption` | number | Sync | `1.0` | Beer-Lambert absorption coefficient. | | `emission` | number | Sync | `1.0` | Emission gain. | | `color` | color | Sync | `{1,1,1,0}` | RGB tint + density floor in alpha. | | `stepSize` | number | NoSync | `0` | World units per ray step. `0` = auto-derive from volume extent. | | `maxSteps` | number | NoSync | `256` | Ray-march step cap. | | `target` | string | Sync | `"scene_volume_rt"` | Output render target name (composite key). | | `targetWidth` | number | NoSync | `1280` | Output width (px). | | `targetHeight` | number | NoSync | `720` | Output height (px). | | `useOccupancy` | boolean | NoSync | `true` | Toggle empty-space skipping. | | `isRgba` | boolean | Sync | `true` | `false` reads density from the red channel. Left `true`, a volume the module built is read from the channel it was built with, and a bare texture as RGBA. | All public fields use the `Field.<kind>(default, Sync|NoSync)` schema (PR #3019). Visual params (look, tint, density) propagate Sync; quality knobs (stepSize, maxSteps, target resolution, useOccupancy) are NoSync — each client picks its own perf/quality point. ## Lifecycle - **`awake`** — no-op. The volume texture is owned by the producer and looked up lazily on the first `update`. - **`update(dt)`** — resolves `volumeName` through `Volume.get`, falling back to a wrapper over a bare texture of that name, and dispatches the compute raymarcher into `target`. The resolution runs every frame, so a volume built, paged or destroyed after this component attached is picked up on the next one. - **`onPropertyChanged(key, value, old)`** — drops the resolved volume when `volumeName`, `occupancyName`, or `isRgba` changes, forcing a re-resolve on the next frame. ## Related - `volume` module — texture builders and name lookup (`Volume.noise`, `Volume.get`, `Volume.wrap`, `:buildSparse`, `:render`). - `vdb_to_zvol.importer` — VDB → dense voxel pipeline that produces textures consumable by this component. - `volumeDemos` / `volumetricSky` packages — worked examples.

# VolumeSequence Plays an open volume sequence through an entity's transform AABB. The sequence is opened by a producer and named here — the same split the `Volume` component makes between "what data to render" and "where it appears in the world". Each tick the component advances the playhead and raymarches the frame that is resident into the shared `scene_volume_rt` target, in both play and edit mode, so the run animates while it is being authored. ```luau local Seq = require("@builtin::systems.volumetrics.volumeSequence") Seq.open({ name = "plume", frames = paths, resident = 3, fps = 24 }) local id = entity.spawn("plume_entity").id entity(id).localScale = { 8, 8, 8 } entity(id).component.add("VolumeSequence", { sequenceName = "plume", density = 6.0 }) ``` `fps` and `playing` are pushed into the sequence when they change, so a script calling `seq:setFps()` / `seq:pause()` between two ticks is left standing until the authored value itself moves. The component does not own the sequence: despawning the entity leaves the ring allocated, and `volumeSequence.close(name)` is what frees it. ## Sharing The playhead, the rate and the ring belong to the sequence, so several entities naming one run play the same frame from the same three textures: the playhead advances once per engine frame however many components tick it, and the rate is whichever component's `fps` moved last. Give each entity its own run when they should play independently. `target` is a render target, and a raymarch writes the whole of it — two volumes visible at once (a sequence beside a `Volume`, or two sequences) need a `target` name each, or the later write replaces the earlier one and only one of them appears. Composite each target the way any volume render is composited — see `volume.compositeShaderSource()`.

# VolumetricLighting The air between the camera and the scene, as a component. Add it to an entity and light travelling through that air scatters toward the viewer, so a lamp becomes a glow rather than an invisible point and the sun cuts shafts where something crosses it. ```lua local id = entity.spawn("air").id entity(id).component.add("VolumetricLighting", { density = 0.06, anisotropy = 0.7, }) ``` Every field is live — editing one in the inspector changes the air on the next frame, and the values persist with the scene. Setting `density` to 0 empties the air and releases the passes while keeping the rest authored; removing the component clears it. | field | effect | |---|---| | `density` | How much medium there is per world unit at the reference altitude. 0 is off. | | `heightFalloff` / `heightRef` | How fast density thins with altitude, and the altitude `density` is quoted at. 0 falloff fills the scene evenly. | | `steps` | Samples along each view ray. More resolves a beam's edge more cleanly. | | `colorR/G/B` | What the medium scatters. Warm dust and cold mist differ here. | | `anisotropy` | How forward-biased the scattering is, in (-1, 1). Positive values throw light onward, so haze blooms around a source you look toward. | | `sunIntensity` / `sunColorR/G/B` | The sun's contribution to the medium. | | `lightScale` | The scene lights' contribution to the medium. | | `shadowSteps` / `shadowDistance` | Samples taken back toward the sun to decide whether a point in the air is lit, and how far they reach. **0 leaves the sun's contribution unshadowed**, so the haze glows evenly and no shafts form. | | `maxDistance` | How far along the view ray the march runs. A ray that escapes to sky stops here. | The lights are the scene's own, each scattering on the terms its kind emits on: a point fills the air around it, a spot fills its cone, a rect reaches the air on the side its face emits along, and a parallel light lays an even glow across the whole medium. One added, moved, re-aimed or recoloured at runtime changes the glow it throws with nothing to keep in step here. One body of air fills the scene, so one of these per scene is enough — the last one to push wins. The work runs in `lightScattering.renderFeature`; the settings live in `@builtin::systems.volumetrics.volumetricLighting`, which is also how to drive them from a script.

# VolumetricSky Singleton component that drives the procedural cloud layer. Attach to one entity (usually a sky placeholder), and the component owns the cloud volume + render target lifecycle, bakes the noise field when what it is baked from changes, and dispatches the compute raymarcher every frame into `scene_volumetric_sky`. A composite (post-process or material) blends `scene_volumetric_sky` over the scene — see `demo/sky.scene/` for the full wiring. ## Usage ```luau -- Defaults (the v4-tuned cumulus look — `Sky.defaultPreset()` hands out a -- copy of the same table this field defaults to) local sky = entity.spawn("sky") sky.component.add("VolumetricSky", {}) -- Or apply a captured preset: preset.apply("cumulus_default", { entity = sky.id, component = "VolumetricSky" }) -- Inline tweak. `component.add` writes the `preset` field as it is given, -- so a table handed here carries the whole configuration: local p = require("@builtin::systems.volumetrics.volumetricSky").defaultPreset() p.noiseScale, p.octaves, p.coverage = 9.0, 5, 0.20 p.densityGain = 0.04 -- v5 σ_t sky.component.add("VolumetricSky", { shaderVariant = "v5", preset = p }) ``` `volumetricSky.module`'s `M.spawn` / `M.configure` take the same parameters by name, folding each into the current configuration and leaving the rest where they stand: ```luau local Sky = require("@builtin::systems.volumetrics.volumetricSky") Sky.spawn({ shaderVariant = "v5", noiseScale = 9.0, coverage = 0.20 }) ``` ## Schema (Field<T> / Sync / NoSync) The 28 shaping / weather / lighting params travel as ONE Sync field — `preset = Field.table(DEFAULT_PRESET, Sync)` — so replicating a sky change is **one mutation, not 28**, and copying a sky between scenes is **copying one field, not 28**. Per-client quality knobs sit outside the preset as NoSync fields so each client picks its own tier without disturbing peers. `SkyPreset` and `DEFAULT_PRESET` are declared by `volumetricSky.module`, which this component reads its default from and which routes an option by that same key set — so the shape below and the module's `M.spawn` options are one declaration. | Field | Type | Sync | Default | Meaning | |---|---|---|---|---| | `preset` | `SkyPreset` table | Sync | `DEFAULT_PRESET` (v4 cumulus) | All shaping / weather / lighting (see below). | | `shaderVariant` | string | Sync | `"v4"` | `"v3" \| "v4" (default) \| "v5"`. | | `wind` | vec3 | Sync | `{0,0,0}` | Animated drift offset (advanced per frame from `preset.windSpeed`). | | `cloudSize` | number | NoSync | `256` | Volume W,D resolution. | | `cloudHeight` | number | NoSync | `128` | Volume H resolution. | | `stepSize` | number | NoSync | `4.0` | World units per ray step. | | `maxSteps` | number | NoSync | `224` | Ray-march step cap. | | `shadowSteps` | number | NoSync | `8` | Shadow ray step count. | | `alphaCutoff` | number | NoSync | `0.99` | Early-exit α threshold. | | `jitter` | number | NoSync | `1.0` | Ray-origin jitter strength. | | `taaBlendAlpha` | number | NoSync | `0.1` | TAA current-sample weight. | | `targetWidth` | number | NoSync | `0` | Render target width (`0` = viewport). | | `targetHeight` | number | NoSync | `0` | Render target height. | | `noiseRegenRate` | number | NoSync | `10` | Times per second wind drift re-bakes the cloud volume (`0` = every frame the wind moved). | ### Preset (`SkyPreset`) shape Noise / shaping: `noiseScale, octaves, coverage, densityGain, altitudeLow, altitudeHigh, anvilBias, detailScale, detailOctaves, detailStrength, detailThreshold, baseLowRemap, baseHighRemap, color, windSpeed, seed`. Volume placement: `horizExtent, cloudBaseAltitude, cloudTopAltitude`. Look (visual, not perf): `phaseG`. Sun / sky: `sunDir, sunColor, sunIntensity, sunDiscSize, horizonColor, zenithColor, groundColor, ambient`. v5-only: `cloudType, worleyBlend`. See `presets/cumulus_default.preset/preset.yaml` for the canonical full preset shape, and the `init.luau` `DEFAULT_PRESET` table for the runtime defaults. ## Where the frame time goes Two passes carry the cost, and different fields reach each: - **The bake** (`cloud_noise_*`) fills every voxel of the `cloudSize × cloudHeight × cloudSize` volume with layered noise. It is the most expensive pass the layer has (around 10 ms at 256×128×256 on a desktop GPU), and it runs only when the volume's inputs move: at once for a change to `preset`, `cloudSize`, `cloudHeight`, `shaderVariant` or the render device, once the program it compiles is resident for an edit to the noise shader's own source, and at most `noiseRegenRate` times per second for wind drift. A sky whose `preset.windSpeed` is zero bakes once. `cloudSize` / `cloudHeight` set what one bake costs; `noiseRegenRate` and `windSpeed` set how often it is paid. - **The raymarch** (`cloud_raymarch_*`) runs for every view of every frame. `stepSize`, `maxSteps`, `shadowSteps`, `alphaCutoff` and `targetWidth` / `targetHeight` set its cost. `profiler.gpuFrame()` reports both as `compute.<shader>` spans; a span's `frames` count is how many frames of its window the pass ran in, and `volumetricSky.volumeBakes()` counts the bakes themselves. ## Field-mutation gotcha (and why `update()` reassigns the whole vec3) Under the new Field<T> / Sync / NoSync schema, `public` is not a plain Lua table — it's wrapped in a proxy whose `__newindex` metamethod performs type-checks, marks the field dirty, and queues Sync replication. Writing `public.wind = {x,y,z}` triggers all four steps. Writing `public.wind[1] = x` reads `public.wind` (getter), mutates the returned table directly, and **bypasses the setter** — no Sync replication, no dirty flag, no `onPropertyChanged`. Always assign the whole vec3 / preset / color table; never index-mutate. The same caveat applies to `public.preset`: `public.preset.coverage = 0.2` won't replicate. To change one preset field, copy the table, mutate, reassign: ```luau local p = public.preset local next = {} for k, v in pairs(p) do next[k] = v end next.coverage = 0.2 public.preset = next ``` ## Lifecycle - **`awake`**: starts the sky's clock and creates the render feature that runs the layer's passes. - **`update(dt)`** — advances `wind` (reading `preset.windSpeed`), hands the noise inputs to `volumetricSky.fillClouds`, which bakes the volume when they moved (see "Where the frame time goes"), then queues the raymarch dispatch for the frame's deferred phase. - **`onDespawn`** — releases the volume, the render target and the composite effect via `M.destroy`. ### Why the raymarch is dispatched from `task.defer` The raymarch produces ONE full-screen layer for ONE view, and the frame composites it over everything that frame drew — so it has to be rendered from the view the frame ends up drawn with. Which view that is settles only once the frame's script work is finished: a cutscene walking the camera from a task loop, a camera controller, a component ordered after this one, an editor tool — each writes the camera after `update` has run, while the renderer reads the camera once all of them are done. Taking the camera snapshot in the deferred phase reads what every one of them has already written, and still queues the dispatch ahead of the frame's render. Snapshotting in `update` instead renders the layer for whatever the camera was midway through the frame; on a hard cut that is a different place entirely, and the frame the cut lands on composites a cloud layer belonging to the shot it just left. A caller driving `volumetricSky.dispatchRaymarch` directly owes the same discipline. ## Related - `volumetricSky.module` — orchestration backend. - `presets/cumulus_default.preset` — canonical full preset; copy to author named weather (storm, overcast, dawn, …). - `Volume.component` — per-entity flow for non-cloud volumetric content. - `demo/sky.scene` — worked example.

# godrays_fill Fills a volume with shafted light. One invocation per voxel. ## Bindings | name | kind | what it is | |------|------|------------| | `vol` | `storage3d` (rgba16f) | the volume written — RGB emission, A density | | `U` | `buffer` (read, f32) | the demo's fill parameters |

# nebula_fill Fills a volume with a spiral nebula: RGB carries emission, A carries density. One invocation per voxel at workgroup size 4x4x4. ## Bindings | name | kind | what it is | |------|------|------------| | `vol` | `storage3d` (rgba16f) | the volume written, read-write so a pass can accumulate | | `U` | `buffer` (read, f32) | the demo's fill parameters, in the order the shader reads them | `U` holds: elapsed time, spiral frequency, arm thickness, core brightness, edge brightness, dust density, noise strength.

# sdf_solids_fill Fills a volume with signed-distance solids. One invocation per voxel. ## Bindings | name | kind | what it is | |------|------|------------| | `vol` | `storage3d` (rgba16f) | the volume written — RGB emission, A density | | `U` | `buffer` (read, f32) | the demo's fill parameters |

# smoke_plume_fill Fills a volume with a rising smoke plume. One invocation per voxel. ## Bindings | name | kind | what it is | |------|------|------------| | `vol` | `storage3d` (rgba16f) | the volume written — RGB emission, A density | | `U` | `buffer` (read, f32) | the demo's fill parameters |

# zvol_viewer_fill Leaves the volume as it is. The ZVOL viewer uploads voxels straight into the volume's 3D texture from the CPU, so the fill stage this shader occupies has nothing to compute — it reads one value from each binding so both stay live. ## Bindings | name | kind | what it is | |------|------|------------| | `vol` | `storage3d` (rgba16f) | the volume the viewer writes into from the CPU | | `U` | `buffer` (read, f32) | the fill parameters the spawn API supplies |

# emission_raymarch Marches a camera ray through an emissive volume and writes the result to a 2D target. Emission accumulates along the ray and density attenuates what is behind it, so a volume reads as light rather than as a surface. ## Bindings | name | kind | what it is | |------|------|------------| | `vol` | `texture3d` | the volume marched — RGB emission, A density | | `smp` | `sampler` | how `vol` is filtered along the ray | | `out_tex` | `storage2d` (rgba16f) | the image the march writes | | `U` | `buffer` (read, f32) | camera, volume placement and march settings | `U` carries the inverse view-projection, the volume's world transform, the step count, density and emission gains, and the target's inverse size.

# VDB → ZVOL importer Claims `.vdb` (OpenVDB) writes and produces a sibling `.zvol` — the engine-native dense RGBA8 volumetric format consumed by the volumetrics system. This is a standard `importer` asset: `init.luau` returns a `{ canImport, import }` module that the importer dispatcher (`@builtin::assetTypes.importer`) loads lazily and runs only when a matching file is written. It does **not** execute anything at load time. ## Pipeline 1. **Real parse** — if the `openvdb` plugin in the builtin library (`@builtin::plugins.openvdb`) is loaded, the VDB B-tree is parsed into a dense RGBA8 voxel buffer and wrapped in a 64-byte ZVOL header. 2. **Procedural fallback** — without the plugin, a deterministic noise-modulated torus is synthesised (FNV-1a hash of the first 256 source bytes seeds it) so the importer + demo wiring stays functional. The `produced_by` field in the result distinguishes the two paths. ## ZVOL header (64 bytes) | offset | size | field | |--------|------|-------| | 0 | 4 | magic `ZVOL` | | 4 | 4 | u32 version (1) | | 8 | 4 | u32 width | | 12 | 4 | u32 height | | 16 | 4 | u32 depth | | 20 | 4 | u32 format (1 = rgba8) | | 24 | 12 | f32[3] aabb_min | | 36 | 12 | f32[3] aabb_max | | 48 | 16 | reserved | | 64 | … | voxel data, `w*h*d*4` bytes, XY-major Z-slowest |

# lightScattering The render passes behind the `VolumetricLighting` component and the `volumetricLighting` module. Two compute passes after lighting. **`vol_scatter`** marches each view ray at half resolution, from the camera to the surface the ray hits — or to the medium's reach when it escapes to sky, since an unbounded march would integrate the whole horizon into every sky pixel. At each step it evaluates the medium's density, gathers the light arriving there, and accumulates the fraction sent toward the camera, attenuating by everything already crossed. A surface-only renderer draws the pool of light a lamp throws on the floor but not the beam that carried it there, because nothing between the lamp and the floor is ever shaded. Marching the ray shades that space. The lights are the scene's own. `@scene.lights` is the same buffer the lit passes read, so a light added, moved or recoloured at runtime changes the beam it throws with no bookkeeping here. It holds **twelve vec4s per light** — the light, then its punctual shadow record — read as raw words so no struct declaration has to mirror the engine's layout. A spot's cone gate is evaluated at the sample itself rather than at a surface, which is what makes the cone visible as a volume instead of only where it lands. Attenuation matches the lit passes' windowed falloff, so a beam and the pool of light it lands in agree about how far the source reaches. Area lights are skipped — their contribution to a medium is an integral over the rect rather than a single direction. The sun's contribution is gated by a short march back toward it, tested against the depth buffer. That is what turns uniform haze into shafts: the medium is lit only where the path back to the sun is clear, so an occluder carves a dark volume out of the beam rather than only shading the surface behind it. Because the test reads the depth buffer, an occluder outside the view frustum does not cast into the medium. Scattering follows Henyey-Greenstein, so the medium brightens toward a source you are looking at and stays dim when it is behind you — the difference between haze that reads as air and haze that reads as a grey wash. Each ray's first sample is offset by a per-pixel fraction of a step, trading the banding a fixed step pattern produces for noise. **`vol_composite`** upsamples that result and composites it. The taps are weighted by how closely their depth matches the full-resolution pixel's, which keeps a beam from bleeding across a silhouette — the halo a plain bilinear upsample leaves behind. The camera comes from `@frame.camera`, the camera of the render target being drawn, and the forward matrix is derived by inverting it in the shader rather than passed in from script — so an offscreen capture or an RTT camera marches through its own matrix at its own resolution. Parameters arrive through the `vol_params` buffer, packed by the `volumetricLighting` module.

# mediaShadow The shadow a fog bank casts on what is behind it. Two compute passes run after lighting: | Order | Pass | Work | |---|---|---| | 36 | `media_tau_map` | One ray per texel of a light-space map; accumulate optical depth | | 37 | `media_shadow_apply` | Attenuate each surface by the density in front of it | | 38 | composite | Blit the result | ## Why not a shadow map A depth-based shadow map answers one question per texel: is this point nearer the light than the first thing the light hit? Density has no first thing. What a medium does to light is continuous — a ray crossing `d` units of extinction `k` keeps `exp(-k*d)` of its energy — so what a receiver needs is the optical depth between it and the light, not a depth to compare against. The first pass therefore stores optical depth rather than distance, at four points down each ray. Two consequences fall out of that choice: - **Overlapping media stack.** Optical depth is additive, so two volumes that intersect contribute to the same running total with nothing to resolve. - **Geometry inside a volume is lit correctly.** A receiver looks up its own position along the ray and reads the depth accumulated *up to that point*, so a post standing in the middle of a fog bank is dimmed by the half in front of it rather than by the whole column. ## Inputs `@scene.color`, `@scene.depth`, `@frame.camera`, and the `media_params` / `media_volumes` buffers packed by `@builtin::systems.volumetrics.mediaTransmittance`. Sky pixels are passed through untouched.

# mediaTransmittance Light attenuation through participating media, in a form both media and surfaces can sample. A shadow map stores one depth per texel and answers a yes/no question, so nothing made of density can cast with it. This module owns the other representation: a light-space map holding the **optical depth** accumulated along each light ray, recorded at four points down its length. Optical depth is additive. Every medium a ray crosses contributes to the same texel, so overlapping volumes stack with nothing to resolve between them. And because four points are stored rather than one total, a receiver standing halfway through a fog bank is attenuated by the half in front of it, not by the whole column. ## Direct use ```luau local Media = require("@builtin::systems.volumetrics.mediaTransmittance") Media.set({ sunDirection = { 0.55, 0.55, 0.55 }, steps = 32 }) Media.setMedium("bank", { position = { 0, 8, 0 }, size = { 20, 6, 20 }, density = 0.15, }) ``` Most scenes attach `ParticipatingMedium` to an entity instead and let it drive this module. ## API | Call | Effect | |---|---| | `set(opts)` | Scene-wide settings; omitted fields keep their value | | `setMedium(key, opts)` | Register or move a medium under a stable key | | `removeMedium(key)` | Drop one medium | | `get()` | A copy of the settings in force | | `clear()` | Drop everything and release the passes | | `active()` | Whether the passes are running | ### Settings | Field | Meaning | |---|---| | `sunDirection` | Points **toward** the sun; light travels the other way | | `strength` | How much of the computed attenuation is applied, `[0, 1]` | | `steps` | Samples along each light ray, `[4, 128]` | | `extent` | Half-width of the map in world units; `0` sizes it to the media | | `centre` | Point the map is centred on; omit to centre it on the media | ### Media | Field | Meaning | |---|---| | `position` | World-space centre | | `shape` | `"box"` (default) or `"sphere"` | | `size` | Half-extents, for a box | | `radius` | Radius, for a sphere | | `density` | Extinction per world unit | Up to 32 media are packed into the records buffer. ## Cost and limits The map is 512×512 and is rebuilt each frame; `steps` sets the march length. With nothing registered the passes are released entirely, so a scene with no media pays nothing. The map is sized to the bounding sphere of everything registered, so a small bank sharing a scene with a much larger one lands on few texels — set `extent` and `centre` explicitly to bias the map toward the region that matters. Attenuation applies to surfaces. The sky keeps its own colour.

# media_common The media-shadow passes' shared ground: the volume record layout, the transmittance accumulation along a ray, and the cap on how many volumes one frame carries (`MAX_VOLUMES` = 32). That cap sizes a fixed array, so it is a constant here rather than a param.

# media_shadow_apply Applies the media's transmittance to the lit scene. ## Bindings | name | kind | |------|------| | `source_map` | `texture2d` | | `scene_depth` | `texture_depth` | | `tau_map` | `texture2d` | | `frame_cam` | `buffer` | | `media_params` | `buffer` | | `media_out` | `storage2d (rgba16f)` |

# media_tau_map Builds the transmittance map through the media, so a later pass reads how much light survives to a point instead of marching for it. ## Includes - `media_common` ## Bindings | name | kind | |------|------| | `media_params` | `buffer` | | `media_volumes` | `buffer` | | `media_tau_out` | `storage2d (rgba16f)` |

# cumulus_default Default weather preset for `VolumetricSky.component`. Captures the v4-tuned cumulus look: visible discrete clouds, warm-afternoon sun, moderate coverage. ## Use ```luau local sky = entity.spawn("sky") sky.component.add("VolumetricSky", {}) preset.apply("cumulus_default", { entity = sky.id, component = "VolumetricSky" }) ``` The values set the component's `preset` Field.table as a unit — one Sync replication carries every shaping/lighting parameter to peers. Tweak by reading the values and changing them before the component is added: ```luau local values = preset.values("cumulus_default") values.shaderVariant = "v5" -- swap raymarcher values.preset.coverage = 0.6 -- sparser sky sky.component.add("VolumetricSky", values) ``` ## Authoring more presets Capture a sky you have tuned with `preset.capture({ entity = sky.id, component = "VolumetricSky" }, "<name>")`, or drop another `<name>.preset/` folder next to this one (or anywhere under `/zero/source/`); the asset indexer registers it and `preset.values("<name>")` resolves it. Common alternatives: - `stratocumulus.preset` — broad overcast layer (`coverage ~= 0.15`, `cloudType = 0.5`, `altitudeHigh ~= 0.65`). - `clear.preset` — barely any cloud (`coverage ~= 0.7`, `densityGain ~= 0.2`). - `storm.preset` — dense black anvils (`coverage ~= 0.1`, `densityGain ~= 0.85`, `sunColor ~= [0.6, 0.55, 0.5]`). `preset` is one `Field.table`: applying a preset replaces it whole, so provide every field.

# scattering_common The light-scattering passes' shared ground: the phase function, the shadow lookup along a ray, and the froxel-to-world mapping. Included with `#include "@builtin::systems.volumetrics.scattering_common"`.

# cloud_noise Procedural volumetric-cloud noise fill (Schneider/Hillaire style). A low-frequency FBM gives the base blob silhouette, a high-frequency FBM erodes it near the surface for the fluffy cumulus look, plus altitude shaping (round bottom, full middle, anvil top). Writes the 3D cloud density texture. Bindings (see bindings.yaml): `clouds` (storage3d rgba16f — the cloud volume), `U` (read `array<f32>` uniforms). Usage: dispatch by identity with `compute.dispatchEx("@builtin::systems.volumetrics.shaders.cloud_noise", ...)` (storage texture requires resource binding, not positional buffers) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# cloud_noise_v3 Volumetric-cloud noise fill (Schneider/Hillaire style), v3 variant. Low-frequency FBM base silhouette + high-frequency FBM surface erosion for the billowed cumulus look, with altitude shaping (round bottom, full middle, anvil top). Writes the 3D cloud density texture. Bindings (see bindings.yaml): `clouds` (storage3d rgba16f — the cloud volume), `U` (read `array<f32>` uniforms). Usage: dispatch by identity with `compute.dispatchEx("@builtin::systems.volumetrics.shaders.cloud_noise_v3", ...)` (storage texture requires resource binding, not positional buffers) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# cloud_noise_v5 Volumetric-cloud noise generator, v5 (Nubis/Schneider style). Builds two foundational noises — Perlin-Worley FBM for the lumpy "cauliflower" base shape and Worley FBM for high-frequency detail erosion — under weather-map control. Writes the 3D cloud density texture. Bindings (see bindings.yaml): `clouds` (storage3d rgba16f — the cloud volume), `U` (read `array<f32>` uniforms). Usage: dispatch by identity with `compute.dispatchEx("@builtin::systems.volumetrics.shaders.cloud_noise_v5", ...)` (storage texture requires resource binding, not positional buffers) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# cloud_raymarch Volumetric-sky cloud raymarcher with Frostbite-style lighting: Wrenninge/Hillaire multi-scatter approximation (3 octaves), a 5-sample cone-traced soft self-shadow, and combined Beer-Lambert + Powder so cloud edges glow toward the sun. Reads the cloud volume + occupancy textures and writes the lit raymarch result. Bindings (see bindings.yaml): `clouds` (texture3d), `occupancy` (texture3d), `cloud_smp` (sampler), `out_tex` (storage2d rgba16f), `U` (read `array<f32>` uniforms). Usage: dispatch by identity with `compute.dispatchEx("@builtin::systems.volumetrics.shaders.cloud_raymarch", ...)` (textures/sampler/storage texture require resource binding, not positional buffers) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# cloud_raymarch_v3 Volumetric-sky cloud raymarcher (Frostbite-style lighting), v3 variant: Wrenninge/Hillaire multi-scatter (3 octaves), 5-sample cone-traced soft shadow, and combined Beer-Lambert + Powder edge glow. Reads the cloud volume + occupancy textures and writes the lit raymarch result. Bindings (see bindings.yaml): `clouds` (texture3d), `occupancy` (texture3d), `cloud_smp` (sampler), `out_tex` (storage2d rgba16f), `U` (read `array<f32>` uniforms). Usage: dispatch by identity with `compute.dispatchEx("@builtin::systems.volumetrics.shaders.cloud_raymarch_v3", ...)` (textures/sampler/storage texture require resource binding, not positional buffers) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# cloud_raymarch_v4 Volumetric-sky cloud raymarcher, v4. Adds procedural detail noise computed in-shader on top of the large-scale texture silhouette (removes v3's voxel-grid blockiness) and uses multi-distance shadow sampling (4 geometrically spaced strides) instead of a cone trace. Reads the cloud volume + occupancy textures and writes the lit raymarch result. Bindings (see bindings.yaml): `clouds` (texture3d), `occupancy` (texture3d), `cloud_smp` (sampler), `out_tex` (storage2d rgba16f), `U` (read `array<f32>` uniforms). Usage: dispatch by identity with `compute.dispatchEx("@builtin::systems.volumetrics.shaders.cloud_raymarch_v4", ...)` (textures/sampler/storage texture require resource binding, not positional buffers) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# cloud_raymarch_v5 Production volumetric-cloud raymarcher, v5 (Nubis/Hillaire style): Hillaire multi-scatter octaves (fixes black cloud cores), energy-conserving Beer-Powder-MS lit-edge glow, a 6-offset Wrenninge cone-trace shadow, and a dual-lobe Henyey-Greenstein phase. Reads the cloud volume + occupancy textures and writes the lit raymarch result. Bindings (see bindings.yaml): `clouds` (texture3d), `occupancy` (texture3d), `cloud_smp` (sampler), `out_tex` (storage2d rgba16f), `U` (read `array<f32>` uniforms). Usage: dispatch by identity with `compute.dispatchEx("@builtin::systems.volumetrics.shaders.cloud_raymarch_v5", ...)` (textures/sampler/storage texture require resource binding, not positional buffers) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# cloud_taa Cloud TAA composite — temporal anti-aliasing for the raymarch output. Reprojects last frame's blended output through the previous view-projection, color-clamps the history to the current sample's neighborhood to suppress ghosting, and exponentially blends the two. Writes both the next-frame history slot and the externally-sampled `scene_volumetric_sky` texture the composite path reads. Reprojection runs through the world point named by uniform `[37]`, the NDC z of the range the cloud stands at along the view ray — `volumetricSky.reprojectionDepthNdc` computes it. The weight the history carries falls to zero across the last `REPROJECT_BORDER_TEXELS` of the reprojected frame, so a pixel whose history lies off the previous frame reaches the raymarch's own output down a gradient rather than across a line. Bindings (see bindings.yaml — slot order must match the Luau dispatch): `cur_tex` (texture2d), `hist_prev` (texture2d), `smp` (sampler), `out_hist` (storage2d rgba16f), `out_scene` (storage2d rgba16f), `U` (read `array<f32>` uniforms). Usage: dispatch by identity with `compute.dispatchEx("@builtin::systems.volumetrics.shaders.cloud_taa", ...)` (textures/sampler/storage textures require resource binding, not positional buffers) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# volume_pack Fills the brick pool from the volume `volume_pages` has just paged. One invocation per pool voxel. The pool is a grid of blocks, one block per slot; a block holds a brick plus a one-voxel apron taken from the neighbouring bricks, so a trilinear sample inside a brick reads what the dense volume would have given it rather than whatever brick the pool stores next door. ## Bindings | # | name | what | |---|---|---| | 0 | `source` | the dense volume being paged (sampled 3D texture) | | 1 | `atlas` | the brick pool (`rgba16f` storage) | | 2 | `page_slots` | four words per slot, written by `volume_pages` | | 3 | `K` | `PackParams` — volume dimensions and brick edge | ## Why the pool is always `rgba16f` A pool is written as a storage texture and sampled with filtering. `rgba16f` is the format that is both: the one-channel formats cannot be written as storage textures, and `r32f` cannot be filtered without a device feature the engine does not require. So a scalar volume's density rides in the pool's red channel — which is where the raymarcher reads density from in density mode — and pays `rgba16f` per resident voxel. `Volume:sparseStats()` reports the dense and resident sizes side by side rather than assuming paging is the smaller of the two. The pass writes every voxel of the pool, including blocks whose slot was never handed out: those hold whatever brick their stale slot entry names, and the page table never points at them.

# volume_pages Decides which bricks of a volume are worth storing, and where each one lives. One invocation per brick. It scans the brick's voxels in the source volume, and a brick holding anything over `threshold` claims a slot from an atomic counter. The slot number lands in the page table (`slot + 1`, so 0 keeps meaning "empty"), and the brick's grid coordinates land in the slot list so `volume_pack` knows what to copy into that slot. Nothing is read back to the CPU and no brick waits on another, so the pass can run every frame — which is what makes the page table usable as the acceleration structure for a volume whose contents change while it renders. ## Bindings | # | name | what | |---|---|---| | 0 | `source` | the dense volume being paged (sampled 3D texture) | | 1 | `pages` | page table, one texel per brick (`rgba16f` storage) | | 2 | `page_alloc` | `[0]` slots handed out, `[1]` bricks that found the pool full | | 3 | `page_slots` | four words per slot: the brick's x, y, z, and 1 | | 4 | `P` | `PageParams` — volume dimensions, brick edge, threshold, channel, capacity | `page_alloc` must be zeroed before each run; the counter is what allocates, so a stale count hands out slots past the pool. ## The page value A resident brick's page value is `slot + 1`, split into two digits base 1024 across the texel's red and green channels. The page table is `rgba16f` because that is the format that is both storage-writable and filterable — the raymarcher binds it where a sampled 3D texture is expected — and a half float only carries integers exactly up to 2048, which one digit stays under. A brick holding nothing writes zero in both channels, so "is anything here" is the sum against zero, the same test the older single-channel occupancy grid answers. ## Overflow A brick that arrives after the pool is full is counted in `page_alloc[1]` and written as empty. The volume renders without it rather than sharing a slot. `page_alloc[0]` keeps counting past the capacity, so a caller that reads it back learns the capacity the volume actually needs.

# volume_raymarch Generic volume raymarcher. One invocation per output pixel: builds a world-space ray from the camera inverse view-projection, clips against the volume AABB, and marches front-to-back, using the occupancy grid to skip empty bricks. Output is RGBA16F (premultiplied RGB, accumulated alpha) for the caller to composite. A paged volume marches through the same shader: `volume` is then the brick pool and `occupancy` the page table, whose texel per brick carries the pool slot that brick lives in (0 for a brick holding nothing, which is what the empty-space skip already reads it as). `VolumeUniforms.paged` carries the flag and the volume's own dimensions, which the pool no longer describes. Both the skip and the pool lookup find a point's brick by the voxel it lands on divided by the brick edge — the way the page table and the occupancy grid were written. A volume that is not a whole number of bricks across has a grid wider than `dims / brick`, so dividing the normalized coordinate by the grid instead would name a different brick for the same point. When the dimensions are unknown (a wrapper was never told them) the grid times the brick edge stands in for them. Bindings (see bindings.yaml): `volume` (texture3d), `occupancy` (texture3d), `volume_smp` (sampler), `out_tex` (storage2d rgba16f), `U` (read buffer, a single `VolumeUniforms` struct). Usage: dispatch by identity with `compute.dispatchEx("@builtin::systems.volumetrics.shaders.volume_raymarch", ...)` (textures/samplers/storage texture require resource binding, not positional buffers) — it resolves to the shader's stable guid and auto-compiles on first use (no setup).

# vol_composite Composites the scattered light over the scene, depth-aware so geometry occludes it. ## Includes - `scattering_common` ## Bindings | name | kind | |------|------| | `scene_color` | `texture2d` | | `scene_depth` | `texture_depth` | | `scatter_map` | `texture2d` | | `vol_params` | `buffer` | | `vol_out` | `storage2d (rgba16f)` |

# vol_scatter Accumulates in-scattered light through the volume, one froxel at a time. ## Includes - `scattering_common` ## Bindings | name | kind | |------|------| | `scene_depth` | `texture_depth` | | `frame_cam` | `buffer` | | `lights` | `buffer` | | `vol_params` | `buffer` | | `scatter_out` | `storage2d (rgba16f)` |

# volume High-level Luau API for 3D textures and volumetric rendering. Composes the engine's generic `compute.*` primitives into volume-specific helpers — procedural builders (`sphere`, `box`, `noise`), a sparse NanoVDB-style occupancy grid for empty-space skipping, and a one-call raymarcher that composites a volume through any entity's transform. Pairs with the `Volume` component which attaches a built (or imported) texture to an entity. ## Exports - `M.create({name, width, height, depth, format?, storage?}) -> Volume` — allocate a fresh, zero-filled 3D texture and return a Volume wrapper. - `M.wrap({name, format, occupancyName?, occupancyBrick?}) -> Volume` — wrap an existing named texture without recreating it (used by the .zvol viewer). - `M.get(name) -> Volume?` — the live volume built under that texture name, with its dimensions, channel count, occupancy grid and brick pool. - `M.names() -> {string}` — every name `M.get` answers to, sorted. - `M.register(volume) -> Volume` — publish a wrapped volume under its own texture name. - `M.unregister(name) -> Volume?` — stop answering for a name and hand back the volume that held it, leaving its GPU resources alone. - `M.releaseTarget(name) -> boolean` — destroy a render target this module built for `render` and forget its size. - `M.sphere(opts) -> Volume` — procedural Volume filled with a soft sphere SDF. - `M.box(opts) -> Volume` — procedural Volume filled with a soft box SDF. - `M.noise(opts) -> Volume` — procedural Volume filled with FBM noise. - `M.raymarchShaderIdentity() -> string` — absolute identity of the shared raymarch shader. - `M.compositeShaderSource() -> string` — WGSL source for the post-process composite blending `scene_volume_rt` over the scene. - `M.FORMATS` — table of canonical format strings (`R8`, `R16F`, `R32F`, `RGBA8`, `RGBA16F`, `RGBA32F`). - `volume:destroy()` — release the GPU texture + occupancy. - `volume:writeBytes(bytes) / :writeFloats(floats)` — upload payload to the 3D texture (matches the texture's format). - `volume:fill(fn)` — CPU procedural fill via `fn(x,y,z) -> color`. - `volume:readback() -> bytes` — pull the texture's current contents back to Luau. - `volume:buildOccupancy({brickSize, sampler?})` — build an R8 occupancy companion for empty-space skipping. - `volume:buildSparse({brickSize?, threshold?, headroom?, capacity?, mode?})` — page the volume into bricks, keeping only the ones holding something. Yields while the brick count reads back — twice unless `capacity` says how many slots to take. - `volume:refreshSparse()` — re-page from the volume's current contents; two dispatches and no wait. - `volume:releaseDense()` — free the dense texture and render from the brick pool alone. - `volume:releaseSparse()` — free the brick pool and page table and go back to rendering the dense texture. - `volume:readSparseCounts()` — `{ bricks, wanted, overflow, capacity }` off the GPU; yields. - `volume:sparseStats()` — byte accounting: `denseBytes`, `poolBytes`, `pageBytes`, `residentBytes`, `ratio`. - `volume:fillCompute(shaderName, opts)` — drive a custom fill shader against this volume. - `volume:render(opts)` — dispatch the shared compute raymarcher into a 2D storage target, using `opts.entity` for AABB. A paged volume renders through its pool with no change at the call site. ## Usage ```luau local Volume = require("@builtin::systems.volumetrics.volume") -- Build a procedural noise cloud + occupancy. local cloud = Volume.noise({ name = "cloud", size = 64, scale = 4, octaves = 4, threshold = 0.55, }) cloud:buildOccupancy({ brickSize = 8 }) -- Render through the shared raymarcher; output to scene_volume_rt. cloud:render({ entity = entity(id), target = "scene_volume_rt", targetWidth = 1280, targetHeight = 720, density = 8.0, absorption = 1.2, emission = 0.9, color = { 1.0, 0.9, 0.7 }, maxSteps = 256, mode = "rgba", }) ``` The `Volume.component` is the per-entity wrapper around this module — it resolves the name it carries through `Volume.get` and dispatches `volume:render` from its `update` hook. ## Addressing a volume by name Every volume this module builds answers to its texture name, so anything holding only the name — an entity's `Volume` component, a second script, a tool — reaches the volume itself: ```luau local cloud = Volume.noise({ name = "cloud", size = 128 }) cloud:buildSparse({ brickSize = 8 }) cloud:releaseDense() -- somewhere else entirely Volume.get("cloud"):render({ entity = entity.find("cloud_host") }) ``` What the name alone cannot express is what makes this matter: the voxel dimensions, which channel holds density, and whether the volume is paged into a brick pool. A holder that reconstructs a wrapper from the name gets a dense volume that the paging may already have released. One volume owns a name at a time: the 3D texture, the page table and the brick pool all address it, so `create` over a name a live volume holds releases that volume first and says so in the log. `destroy` clears the entry. A wrapper around a texture another system owns is published with `Volume.register` and dropped with `Volume.unregister`, which hands the volume back so it can still be destroyed. The names live where this module is loaded — one set per Luau VM, alongside the raymarch target registry. `render` builds its `target` on the first call that names one and keeps its size, so repeated renders reuse it; `Volume.releaseTarget(name)` destroys that target and forgets the size, and the next render builds it again. ## Paging a volume into bricks A dense volume costs its bounding box. `buildSparse` splits it into bricks, keeps only the ones holding anything over `threshold`, and stores those in a brick pool; a page table one texel per brick says which slot each resident brick took, and 0 says the brick holds nothing. That page table is also the grid the raymarcher already skips empty space with, so paging and empty-space skipping are the same structure. ```luau local cloud = Volume.noise({ name = "cloud", size = 128, threshold = 0.6 }) local stats = cloud:buildSparse({ brickSize = 8, threshold = 0.01 }) print(stats.bricks, "of", stats.grid[1] * stats.grid[2] * stats.grid[3], "bricks") print(stats.poolBytes, "vs dense", stats.denseBytes) cloud:releaseDense() -- the pool is now the only copy cloud:render({ entity = entity.find("cloud_host") }) ``` Both passes run on the GPU with no readback between them, so a volume a compute shader rewrites keeps a matching page table for the cost of two dispatches: ```luau cloud:fillCompute(myFillShader, { extraResources = { { kind = "buffer", name = fillU } } }) cloud:refreshSparse() ``` The pool is fixed at the size the build measured, so a volume that grows past it loses the surplus bricks. `refreshSparse` asks the GPU for the counts without waiting on them and folds them in on a later call, so `sparseStats()` reports the overflow — and the log carries a warning naming the capacity to page at — a frame or two after the refresh that caused it. `buildSparse`'s `headroom` buys the slots up front for a volume that is expected to grow. What it costs: - A block in the pool is the brick plus a one-voxel apron on every side, so a resident brick costs `(brick + 2)³` voxels. At `brickSize = 8` that is 1.95x per resident brick, at 16 it is 1.42x. The apron is what makes a trilinear sample inside a brick read exactly what the dense volume would have given it. - A pool is always `rgba16f`: it has to be writable as a storage texture and sampled with filtering, and that is the format that is both. A scalar volume therefore spends more per resident voxel than it did dense (its density rides in the pool's red channel), so `sparseStats()` reports `denseBytes` and `residentBytes` side by side rather than assuming paging is the smaller of the two. - `refreshSparse` re-pages from the dense volume, so a volume that will keep changing keeps its dense copy; `releaseDense` is for one that is finished. - Classification reads one channel: alpha for a four-channel volume, red for a scalar one. A four-channel volume that carries density in red — the one `render`'s `mode = "density"` marches — has to say so, with the same word: `buildSparse({ mode = "density" })`. A `render` that names no `mode` marches a paged volume from the channel its pool was filled from, so the two agree without the caller repeating the choice. ## Notes - Volumes are GPU-owned; the Luau wrapper just holds the named handle. `volume:destroy()` releases both the texture and any occupancy companion. - The composite target `scene_volume_rt` is shared across every Volume entity in the scene, so multiple volumes composite into one image. Override `opts.target` if you need separate render targets per volume. - Occupancy grids use a brick size (default 8) — smaller = more precise skipping at the cost of grid memory. - The `vdb_to_zvol.importer` in this package produces dense voxel buffers consumable by `compute.writeFloatsTexture3D`, which can be wrapped via `Volume.wrap` (see the `zvol_viewer.scene/` demo for the full path).

# volumeDemos Shared orchestration backend for the `volumeDemos.package` showcase scenes. Owns the per-demo resource pack (3D texture, 2D render target, two uniform buffers) and the auto-registered composite, exposing a small public surface the demo scenes drive once per frame. ## Exports - `M.spawn({name, size, fillShader, fillUniformBytes}) -> ()` — register a new demo pipeline. Creates the 3D volume, the 2D storage target, registers the per-demo fill shader, ensures the shared raymarcher is registered, and auto-installs the depth-aware composite. - `M.destroy(name) -> ()` — release everything `spawn` created (texture + render target + buffers + composite registration). - `M.dispatchFill(name, fillUniforms) -> ()` — pack `fillUniforms` (Lua array of f32) into the demo's fill UBO and dispatch the fill shader against the volume. - `M.dispatchFrame(name, {camera, aabbMin, aabbMax, width, height, stepSize, maxSteps, alphaCutoff, densityGain, emissionGain}) -> ()` — pack camera + raymarch params into the shared 40-float UBO and dispatch the raymarcher into the demo's render target. - `M.NAMES(name) -> {volume, rt, composite}` — engine-side resource names for the demo (used by the `.zvol` viewer to bypass the helpers and upload voxels via `compute.writeFloatsTexture3D` directly). ## Usage ```luau -- From a demo scene at <pkg>/demo/<name>.scene/entrypoint.luau, -- `...` climbs to the package root, then resolves volumeDemos.module: local V = require("@builtin::systems.volumetrics.volumeDemos") -- onLoad: spin up the pipeline. V.spawn({ name = "smoke_plume", size = { 96, 192, 96 }, fillShader = SMOKE_FBM_WGSL, fillUniformBytes = 64, }) -- update(dt): repaint the volume + raymarch into the RT. V.dispatchFill("smoke_plume", { elapsed, density_amp, spread, ... }) V.dispatchFrame("smoke_plume", { camera = cam.get(), aabbMin = { -40, 0, -40 }, aabbMax = { 40, 160, 40 }, width = 1280, height = 720, stepSize = 0.9, maxSteps = 240, densityGain = 2.5, emissionGain = 1.0, alphaCutoff = 0.995, }) -- onUnload: free GPU resources. V.destroy("smoke_plume") ``` ## Notes - `dispatchFrame` packs 40 f32s into the raymarch UBO: `[0..16)` inv_view_proj (mat4 row-major), `[16..19)` aabb_min, `[19..22)` aabb_max, `[22..23)` step_size, `[23..24)` max_steps, `[24..25)` alpha_cutoff, `[25..26)` density_gain, `[26..30)` target_width/height + inv reciprocals, `[30..31)` emission_gain, `[31..40)` padding. - Pipeline state lives in module-locals keyed by `name` — the same module instance can host many demos in parallel, but two scenes must not pick the same `name`. - Each demo scene supplies its own fill shader; the raymarcher is shared (one shader name, one compiled pipeline). Replacing `fillShader` between frames is supported; replacing the raymarcher isn't (use the volumetrics package for that use case).

# volumeSequence Playback for a run of `.zvol` frames, through a ring of resident volumes. A sequence names its frames as VFS paths in playback order. It allocates `resident` 3D textures — one frame each — and nothing else: the frames the playhead is about to reach are read off the VFS on their own tasks and uploaded into whichever ring slot the playhead has travelled furthest past. So a 240-frame run and a 4-frame run cost the same on the GPU, and what a sequence costs is decided when it is opened rather than by how long it is. ```luau local Seq = require("@builtin::systems.volumetrics.volumeSequence") local frames = {} for i = 0, 239 do frames[#frames + 1] = string.format("/source/sim/plume_%04d.zvol", i) end local seq = Seq.open({ name = "plume", frames = frames, resident = 3, fps = 24 }) local s = seq:stats() print(s.residentBytes, s.allBytes) --> 3145728 251658240 ``` Drive it from a component, which is also what makes it visible: ```luau entity(id).component.add("VolumeSequence", { sequenceName = "plume", density = 6.0 }) ``` or by hand, if the caller already has a tick of its own: ```luau seq:tick(dt) local frame = seq:current() if frame then frame:render({ entity = entity(id), density = 6.0 }) end ``` The playhead advances once per engine frame however many callers tick the sequence — a component and a script, or two entities naming one run, share one playhead rather than each moving it. Every call still promotes the frame that has landed and starts the reads ahead of it. ## Residency Every frame of a run has the dimensions frame 1 declares, so one ring serves the whole run. `stats()` reports both what the ring holds (`residentBytes`) and what holding every frame at once would cost (`allBytes`); `residency()` says which frame each slot holds right now. The ring needs at least two slots for a multi-frame run — one holds the picture on screen while the other takes the read — and `open` raises the count to two if it was asked for less. `prefetch` says how many frames ahead of the playhead reads are started, and defaults to every slot the ring has spare — a slot left empty is a frame that gets waited on later. It is bounded by those same slots, so asking for more than fits reads as far ahead as it can. ## Keeping up A tick that wants a frame no slot holds yet keeps showing the frame it had and counts a `stall`. Playback is therefore never blank and never blocks, and `stats().stalls` is the number that says whether the ring and the prefetch distance are big enough for the rate: a run whose reads keep up shows a stall count that stops rising once the ring has filled. `errors` counts frames that failed to read or whose header disagreed with the ring. Each one is counted and logged once, with the path and what was wrong with it, and the run steps over it from then on rather than re-reading it every tick — so `errors` answers how many frames of the run are broken, and a mistyped path costs one line in the log rather than one per frame. The rate and the playhead are the sequence's, not a caller's: `setFps` keeps the frame the playhead stands on and the fraction of the way through it, and `seek` lands on exactly the frame asked for.

# volumetricLighting The settings behind the `VolumetricLighting` component, and the way to drive the scene's participating medium from a script — fog that rolls in over a cutscene, a quality slider that drops the step count, a room that fills with smoke. ```lua local volumetricLighting = require("@builtin::systems.volumetrics.volumetricLighting") volumetricLighting.set({ density = 0.06, anisotropy = 0.7 }) volumetricLighting.get() -- a copy of the settings in force volumetricLighting.active() -- whether the march is running volumetricLighting.clear() -- empty the air, keep the settings ``` `set` takes any subset of the fields; whatever is omitted keeps its current value. A `density` of 0 releases the render feature rather than marching a medium that scatters nothing, and `clear` is the named way to say the same thing. `sunDirection` tracks the scene's sun on its own. Pin it through `set` when a scene wants the medium lit from somewhere else. The module packs the settings into the `vol_params` buffer the passes read, so a change lands on the next frame without recompiling anything. ## Cost The march is the expensive part, and its cost is `steps` × (`shadowSteps` + the number of live scene lights) per marched pixel. Those are the two knobs to reach for on a budget: `steps` controls how cleanly a beam's edge resolves, and `shadowSteps` controls whether the sun's contribution is shadowed at all. Setting `shadowSteps` to 0 removes the per-sample visibility work entirely, which is the single largest saving available — at the cost of the shafts, since the medium is then lit evenly wherever it reaches.

# volumetricSky Orchestration backend for the `VolumetricSky.component`. Owns the GPU resources the cloud layer needs (cloud volume, raymarch render target, ping-pong TAA history pair, post-process composite) and exposes a small public surface the component drives every frame. ## Exports - `M.spawn(opts?) -> id` — spawn the singleton sky entity, or configure the one already standing, and return its id. Every weather parameter (`coverage`, `sunDir`, `sunColor`, `sunIntensity`, `windSpeed`, …) is settable at the top level or inside a `preset` sub-table; every `VolumetricSky` component field (`shaderVariant`, `cloudSize`, `taaBlendAlpha`, …) by its own name; `name` names the entity. Parameters left out keep their current values. An option that names neither raises, listing both sets, and leaves no entity behind. A weather parameter takes the shape its default carries — a number, or an array of that many numbers — and a value of another shape raises naming the parameter. - `M.configure(opts) -> boolean` — apply those same weather parameters and component fields to the sky already standing. Returns `false` when none has been spawned. - `M.defaultPreset() -> table` — a fresh copy of the weather configuration a sky spawned with no options carries. The copy is the caller's to edit. - `M.destroy() -> ()` — release every resource `spawn` created. - `M.fillClouds(noiseParams) -> boolean`: bake the cloud volume with the active `cloud_noise_*` shader when what it holds is not what `noiseParams` describe, and return whether this call baked. A change to a shaping parameter, the colour, the seed, the size, the variant or the render device bakes at once, and a write to the noise shader's `shader.wgsl` or `bindings.yaml` bakes once the program it compiles is resident; a change to the wind alone bakes at most `noiseParams.noiseRegenRate` times per second (default `M.DEFAULT_NOISE_REGEN_RATE`, `0` = every call the wind moved) on `noiseParams.clock` (default `getTime()`). `noiseParams` is the flat table produced by `VolumetricSky.component`'s `snapshotNoiseParams()`. - `M.volumeBakes() -> number`: how many times the cloud volume has been baked since the module loaded. - `M.dispatchRaymarch(renderParams, viewport) -> ()` — dispatch the active `cloud_raymarch_*` shader, blend with history via the TAA pass, and write into the composite target. `renderParams` is the flat table from `snapshotRenderParams()`. - `M.find() -> id?` — return the id of the active VolumetricSky entity, or `nil` if none has been spawned by `M.spawn`. - `M.despawn() -> ()` — despawn the entity `M.spawn` minted (does NOT free GPU resources — call `M.destroy()` for that). - `M.setCoverage(c) / M.setDensity(g) / M.setSun(dir, color, intensity?) / M.setWind(v)` — convenience setters that route through the active component's `public` fields. - `M.reprojectionDepthNdc(camPos, fwd, aabbMin, aabbMax, near, far) -> number` — the NDC z the TAA pass carries history through, taken from where the cloud stands along the centre view ray. A point at range `d` travels `translation / d` across the screen, so this is what keeps a translating camera's history landing on the part of the picture the cloud moved to. ## Usage ```luau -- The component drives this module automatically. Direct M.* use is -- rare; the canonical entry point is attaching VolumetricSky to an -- entity (or loading a preset and passing it to component.add): local sky = entity.spawn("sky") sky.component.add("VolumetricSky", {}) -- Driving the layer by hand instead, a frame at a time. Each dispatch -- creates the resources it needs at the size its own arguments name — -- the cloud volume from `noiseParams.cloudSize / cloudHeight`, the -- render target and composite from the viewport: local Sky = require("@builtin::systems.volumetrics.volumetricSky") Sky.fillClouds(noiseParams) Sky.dispatchRaymarch(renderParams, { width = 1280, height = 720 }) ``` ## Notes - `shaderVariant` selects which compute shader pair (`cloud_noise_v3 + cloud_raymarch_v3` / `cloud_noise + cloud_raymarch_v4` / `cloud_noise_v5 + cloud_raymarch_v5`). The module resolves the variant strings to absolute identities — relative paths don't work from a module body (the chunkname retains an `.init` segment that throws off the rsplit-to-parent step in `resolve_relative_dot`). - The cloud volume + history pair are RGBA16F — 256×128×256 ≈ 32 MiB VRAM. Drop to 192/96 via `cloudSize` / `cloudHeight` if tight. - The TAA pass is a single compute dispatch blending current sample with the previous frame's RT through the history pair. Set `taaBlendAlpha = 1.0` to disable while still going through the same code path (useful for benchmarking). - All public setters write through to `VolumetricSky.component`'s `public` fields, which means they replicate as Sync if the component is sync-enabled. Tweaks survive scene reloads as long as the same entity is alive. - `SkyPreset` and its defaults are declared here, and the component declares its `preset` field from them. `M.spawn` / `M.configure` read that same key set to tell a weather parameter from a component field, so a parameter added to the preset reaches the schema and the option routing in one edit.

# volumetricSky The cloud layer's render passes. The layer is raymarched for the camera being drawn, copied into the target the composite reads, temporally accumulated where there is a previous frame of that view to accumulate against, and laid over the frame behind whatever the depth buffer holds. Every pass but the accumulation runs for each view the frame draws, an environment cube's six faces included — which is what puts the clouds into reflections. The accumulation blends against the previous frame of the same view, and a cube face is rendered once with no previous frame, so it declares `environmentCapture = false` and the copy before it is what those faces read. `VolumetricSky` creates this feature; it is not meant to be created by hand.

# pathfinding.module Public API for the pathfinding package. Caller-facing entry point lives in `init.luau`; sibling modules implement individual concerns. ## Modules | File | Purpose | |------|---------| | `init.luau` | Public surface (`path`, `addLink`, `addModifier`, registries, costs). | | `astar.luau` | Generic A* over an `adjacent(node) -> { Edge }` callback. Binary-heap frontier, opaque node identity via `nodeKey`. | | `graph.luau` | Two concrete graphs: `grid` (uniform 3D voxel grid) and `waypoint` (hand-authored network). Both expose the same interface. | | `modifiers.luau` | Volumetric cost-zone registry. AABB containment, OBB hooks reserved for future engine OBB primitive. | | `links.luau` | Off-mesh link registry + per-query baking onto a graph. | | `path.luau` | `Waypoint` / `Path` constructors. Mirrors Roblox `PathWaypoint` shape. | ## Algorithm at a glance 1. `nodeAt(start)` / `nodeAt(goal)` — snap world points onto graph nodes. 2. `links.bake(graph, agent)` — snap every enabled, condition-satisfying link's endpoints onto graph node-keys; bucket adjacency lookups by from-key. One pass per `path` call, not per A* expansion. 3. A* expands each node, calls the closure `adjacent(node)`. The closure: - asks the graph for native neighbours, - for each neighbour, queries `modifiers.costAt(midpoint, costs, mode)`, - skips edges with `math.huge` multipliers, - appends link-overlay edges from `linkBuckets[nodeKey]`. 4. On reach: `Path.fromAStar(result, graph, edgeMeta)` produces a list of `{position, action, label, link, payload}` waypoints. Walk edges become `action = "Walk"`; link edges become `action = "Custom"` with `label = link.label`. ## Edge-cost composition Per edge `e: a -> b`: ``` edge_cost = base_cost(a, b) * compose({ modifier.cost-at-mid(a, b) }, mode) ``` Composition mode: - `multiply`: `cost *= Π c_i` (default; composable preferences amplify). - `max`: `cost *= max(c_i)` (worst-zone wins; conservative). - `first`: `cost *= c_first` (registration order; legacy). `math.huge` from any modifier blocks the edge regardless of mode. The per-edge midpoint sample matches Roblox's PathfindingModifier semantics exactly — multiple overlapping modifiers compose. ## Identity & determinism - A* node identity is by string key (`graph.nodeKey(node)`), not table identity, so transient nodes built by `nodeAt` snap onto the same key as graph-internal nodes. - The frontier is a binary min-heap; ties on `f` are broken by insertion order. With identical inputs the same path is returned — important for tests and replay. ## Extension points - `graph.luau` exposes a clear interface (`nodeAt`, `nodeKey`, `position`, `adjacent`, `heuristic`, `edgeMidpoint`). Future navmesh-polygon graphs implement the same shape; nothing in the rest of the package cares. - `modifiers.luau` already exposes a `basis` field for oriented bounding boxes; the AABB-containment fast path is the current default. When an OBB primitive lands (#2677-style attachment basis or a future renderer-side OBB) the basis-aware branch in `modifiers.contains` is the single place to extend. - `links.luau::bake` builds the per-query overlay; if predicate links start showing up in profiles, this is the cache point. ## Boundaries - This module performs no engine I/O: no physics raycasts, no entity spawning, no renderer state, no time. Pure data in, path out. - That means the package never breaks the engine, and tests can exercise it without booting the engine — see `astar.luau::search` + `graph.grid` for the canonical setup. - The components (`PathfindingLink.component`, `PathfindingModifier.component`) own the entity-side wiring and call `_addLinkFromComponent` / `_addModifierFromComponent` in `awake`. They're a thin, optional adapter on top of the module.

# bookshelf Voxel template `bookshelf` (demo asset). Live instances spawned via `Voxel.fromTemplate("bookshelf")` reload automatically when this template's `template.voxbin` payload is rewritten.

# bot_seated Voxel template `bot_seated` (demo asset). Live instances spawned via `Voxel.fromTemplate("bot_seated")` reload automatically when this template's `template.voxbin` payload is rewritten.

# bot_standing Voxel template `bot_standing` (demo asset). Live instances spawned via `Voxel.fromTemplate("bot_standing")` reload automatically when this template's `template.voxbin` payload is rewritten.

# cabinet Voxel template `cabinet` (demo asset). Live instances spawned via `Voxel.fromTemplate("cabinet")` reload automatically when this template's `template.voxbin` payload is rewritten.

# chair Voxel template `chair` (demo asset). Live instances spawned via `Voxel.fromTemplate("chair")` reload automatically when this template's `template.voxbin` payload is rewritten.

# clock Voxel template `clock` (demo asset). Live instances spawned via `Voxel.fromTemplate("clock")` reload automatically when this template's `template.voxbin` payload is rewritten.

# desk Voxel template `desk` (demo asset). Live instances spawned via `Voxel.fromTemplate("desk")` reload automatically when this template's `template.voxbin` payload is rewritten.

# keyboard Voxel template `keyboard` (demo asset). Live instances spawned via `Voxel.fromTemplate("keyboard")` reload automatically when this template's `template.voxbin` payload is rewritten.

# lamp Voxel template `lamp` (demo asset). Live instances spawned via `Voxel.fromTemplate("lamp")` reload automatically when this template's `template.voxbin` payload is rewritten.

# linked_workstation_baked Voxel template `linked_workstation_baked` (demo asset). Live instances spawned via `Voxel.fromTemplate("linked_workstation_baked")` reload automatically when this template's `template.voxbin` payload is rewritten.

# monitor Voxel template `monitor` (demo asset). Live instances spawned via `Voxel.fromTemplate("monitor")` reload automatically when this template's `template.voxbin` payload is rewritten.

# mug Voxel template `mug` (demo asset). Live instances spawned via `Voxel.fromTemplate("mug")` reload automatically when this template's `template.voxbin` payload is rewritten.

# plant Voxel template `plant` (demo asset). Live instances spawned via `Voxel.fromTemplate("plant")` reload automatically when this template's `template.voxbin` payload is rewritten.

# printer Voxel template `printer` (demo asset). Live instances spawned via `Voxel.fromTemplate("printer")` reload automatically when this template's `template.voxbin` payload is rewritten.

# trash Voxel template `trash` (demo asset). Live instances spawned via `Voxel.fromTemplate("trash")` reload automatically when this template's `template.voxbin` payload is rewritten.

# whiteboard Voxel template `whiteboard` (demo asset). Live instances spawned via `Voxel.fromTemplate("whiteboard")` reload automatically when this template's `template.voxbin` payload is rewritten.

# blade Voxel template `blade` (demo asset). Live instances spawned via `Voxel.fromTemplate("blade")` reload automatically when this template's `template.voxbin` payload is rewritten.

# house Voxel template `house` (demo asset). Live instances spawned via `Voxel.fromTemplate("house")` reload automatically when this template's `template.voxbin` payload is rewritten.

# rock Voxel template `rock` (demo asset). Live instances spawned via `Voxel.fromTemplate("rock")` reload automatically when this template's `template.voxbin` payload is rewritten.

# tree Voxel template `tree` (demo asset). Live instances spawned via `Voxel.fromTemplate("tree")` reload automatically when this template's `template.voxbin` payload is rewritten.

# windmill_base Voxel template `windmill_base` (demo asset). Live instances spawned via `Voxel.fromTemplate("windmill_base")` reload automatically when this template's `template.voxbin` payload is rewritten.

# cabin Voxel template `cabin` (demo asset). Live instances spawned via `Voxel.fromTemplate("cabin")` reload automatically when this template's `template.voxbin` payload is rewritten.

# chassis Voxel template `chassis` (demo asset). Live instances spawned via `Voxel.fromTemplate("chassis")` reload automatically when this template's `template.voxbin` payload is rewritten.

# door Voxel template `door` (demo asset). Live instances spawned via `Voxel.fromTemplate("door")` reload automatically when this template's `template.voxbin` payload is rewritten.

# front_bumper Voxel template `front_bumper` (demo asset). Live instances spawned via `Voxel.fromTemplate("front_bumper")` reload automatically when this template's `template.voxbin` payload is rewritten.

# headlight Voxel template `headlight` (demo asset). Live instances spawned via `Voxel.fromTemplate("headlight")` reload automatically when this template's `template.voxbin` payload is rewritten.

# hood Voxel template `hood` (demo asset). Live instances spawned via `Voxel.fromTemplate("hood")` reload automatically when this template's `template.voxbin` payload is rewritten.

# mirror Voxel template `mirror` (demo asset). Live instances spawned via `Voxel.fromTemplate("mirror")` reload automatically when this template's `template.voxbin` payload is rewritten.

# rear_bumper Voxel template `rear_bumper` (demo asset). Live instances spawned via `Voxel.fromTemplate("rear_bumper")` reload automatically when this template's `template.voxbin` payload is rewritten.

# rear_window Voxel template `rear_window` (demo asset). Live instances spawned via `Voxel.fromTemplate("rear_window")` reload automatically when this template's `template.voxbin` payload is rewritten.

# seat Voxel template `seat` (demo asset). Live instances spawned via `Voxel.fromTemplate("seat")` reload automatically when this template's `template.voxbin` payload is rewritten.

# spoiler Voxel template `spoiler` (demo asset). Live instances spawned via `Voxel.fromTemplate("spoiler")` reload automatically when this template's `template.voxbin` payload is rewritten.

# steering_wheel Voxel template `steering_wheel` (demo asset). Live instances spawned via `Voxel.fromTemplate("steering_wheel")` reload automatically when this template's `template.voxbin` payload is rewritten.

# taillight Voxel template `taillight` (demo asset). Live instances spawned via `Voxel.fromTemplate("taillight")` reload automatically when this template's `template.voxbin` payload is rewritten.

# trunk Voxel template `trunk` (demo asset). Live instances spawned via `Voxel.fromTemplate("trunk")` reload automatically when this template's `template.voxbin` payload is rewritten.

# wheel Voxel template `wheel` (demo asset). Live instances spawned via `Voxel.fromTemplate("wheel")` reload automatically when this template's `template.voxbin` payload is rewritten.

# windshield Voxel template `windshield` (demo asset). Live instances spawned via `Voxel.fromTemplate("windshield")` reload automatically when this template's `template.voxbin` payload is rewritten.

# greedy_mesh Turns a voxel chunk into a mesh, merging coplanar faces of one colour into the largest rectangle that covers them so a solid wall costs two triangles instead of two per voxel. One invocation per slice; the vertex and index counts are claimed atomically, so the pass writes both buffers in a single dispatch. ## Bindings | name | kind | what it is | |------|------|------------| | `params` | `buffer` (read, u32) | chunk size, padding and the origin the mesh is built around | | `solid_padded` | `buffer` (read, u32) | the chunk's occupancy bitmask, one voxel of padding on every side so a face test at the edge reads a real neighbour | | `colors` | `buffer` (read, u32) | one packed colour per voxel | | `vertex_buf` | `buffer` (read_write, u32) | the vertices produced, in the engine's vertex layout | | `index_buf` | `buffer` (read_write, u32) | the indices produced | | `counters` | `buffer` (read_write, atomic u32) | how many vertices and indices have been claimed | ## Params | name | type | what it is | |------|------|------------| | `vertStride` | `u32` | one vertex in u32 words, so the writes follow the engine's vertex layout |

# voxelConfig Read and write the voxel engine's configuration — the path defaults and engine knobs the voxel system runs on (chunk size, default block size, default mesher, CPU fallback, play-mode write permission, and the path defaults). Get a value by key, get the whole merged config, set a runtime override, or reset one or all overrides. Values resolve in order: a runtime override wins, then the world's voxel settings, then the built-in defaults.

# voxelEngine Build and edit voxel worlds — spawn worlds and shapes, mutate blocks, query them, transform them, manage palettes, persist them, and kitbash composites. Spawn worlds, shapes, and templates, clone handles, or scatter and stamp templates across regions, and destroy them. Mutate blocks — set, clear, fill boxes, spheres, cylinders, and lines, mirror, translate, and paste regions. Read the world back — a block, its neighbours, a region, counts by name, raycasts, sphere and line queries, region copies, and bounds. Apply entity-level transforms (position, rotation, scale, parent, snap-to-world) and read them. Manage the palette. Persist to voxbin and templates — save, bake, save and copy templates, and capture an area. Kitbash composite props from existing templates — new, add child, save baked or linked, explode, save as a bundle. And read or override the voxel config. A target — a handle, `"world"`, an entity id, or an entity name — is accepted uniformly across the toolbox.

# voxelEngine Public API for the voxel system. Single entry point for creating and editing voxel worlds and shapes. Tools and custom code call into here; nobody touches the `VoxelWorld` / `VoxelShape` components directly. Two top-level concepts: - **World** — singleton entity carrying a chunked `VoxelWorld` grid. Created lazily on the first `createWorld` call, found by name later via `world()` / `hasWorld()`, destroyed with `destroyWorld()`. - **Shapes** — per-entity dense or chunked `VoxelShape` grids. Spawned freely; each carries its own voxbin path on disk under `Config.get("paths.shapes")/<entityId>.voxbin`. Templates are stored under `Config.get("paths.templates")/<name>.voxbin` and instantiated via `fromTemplate`. Captures (snapshots of a world region) land at `Config.get("paths.captures")/<name>.voxbin`. ## Exports Module-level: - `M.world() -> Handle?` — handle to the singleton VoxelWorld, or nil. - `M.createWorld(opts: CreateWorldOpts?) -> Handle` — create or reuse the singleton. - `M.destroyWorld()` — despawn the singleton world if it exists. - `M.hasWorld() -> boolean` — true when the singleton exists. - `M.shape(name_or_id) -> Handle?` — handle to an existing shape entity. - `M.createShape(opts: CreateShapeOpts) -> Handle` — spawn a new shape entity. - `M.destroyShape(name_or_id)` — despawn the shape entity if it exists. - `M.fromTemplate(name: string, opts: FromTemplateOpts?) -> Handle` — instantiate from `paths.templates/<name>.voxbin`. Supports live-link, detached, and memory-only modes. - `M.saveAsTemplate(shape: Handle, name: string, opts: SaveAsTemplateOpts?) -> string` — write a shape's grid as a named template. - `M.listTemplates() -> { string }` — enumerate template names (no extension). - `M.deleteTemplate(name: string)` — remove a template file. - `M.copyTemplate(srcName: string, dstName: string) -> string` — duplicate a template file. - `M.captureArea(opts: CaptureAreaOpts) -> any` — flatten a region of world + shapes into a dense voxbin record (and optionally save it). - `M.scatter(templateName: string, opts: ScatterOpts) -> { Handle }` — bulk-spawn instances across a region. - `M.stamp(templateName: string, opts: StampOpts) -> Handle` — single placement, either as a new entity (`mode = "instance"`, default) or rasterised into the world grid (`mode = "merge"`). - `M.composite` — re-export of the composite-prop module. - `M._resolvePivot(value) -> { number, number, number }?` — internal pivot helper, exposed for composite reuse. Handle methods (returned by `createWorld` / `createShape` / `fromTemplate` / `world` / `shape` / `scatter` / `stamp`): - `h:setBlock(x, y, z, name)` / `h:getBlock(x, y, z)` - `h:fillBox(min, max, name)` / `h:fillSphere(center, radius, name)` - `h:fillCylinder(p1, p2, radius, name)` / `h:fillLine(p1, p2, name)` - `h:clear()` — clear every cell. - `h:setPalette(palette)` / `h:addPaletteEntry(name, color)` - `h:bounds() -> Bounds?` — inclusive bounds of every filled cell. - `h:flush()` — flush pending dirty-chunk remeshes. - `h:save()` — write the grid to the component's dataPath. - `h:dirtyChunks() -> { any }` - `h:isLive() -> boolean` / `h:templatePath() -> string?` - `h:bake() -> Handle` — break the live-link, copy into a private dataPath. Shape-only. - `h:saveAsTemplate(name, opts) -> string` - `h:exists() -> boolean` / `h:destroy()` - `h:setPosition(x, y, z) -> Handle` / `h:getPosition() -> Vec3Map?` - `h:setRotation(r) -> Handle` / `h:getRotation() -> Vec3Map?` (Euler radians, ZYX) - `h:setParent(parentEntityId) -> Handle` - `h:copyRegion(min, max) -> any` / `h:pasteRegion(offset, regionData, opts)` - `h:mirror(axis)` / `h:translate(dx, dy, dz)` - `h:getNeighbors(x, y, z) -> any` - `h:queryRegion(min, max, opts) -> { any }` / `h:countByName(min, max) -> { [string]: number }` - `h:raycast(origin, dir, maxDist) -> any` / `h:sphereQuery(center, radius) -> { any }` / `h:lineQuery(p1, p2) -> { any }` - `h:clone(opts) -> Handle` — shape-only. Detached duplicate. - `h:snapToWorld(opts) -> Handle` — quantise transform or shift voxel data to the world grid. Types: - `Vec3Map = { x: number?, y: number?, z: number? }` - `Vec3Array = { number }` - `Vec3Like = Vec3Map | Vec3Array` - `ColorMap = { r: number?, g: number?, b: number? }` - `ColorArray = { number }` - `ColorLike = ColorMap | ColorArray` - `PaletteEntry = { name: string, color: ColorLike, material: any?, atlas: any?, faces: any? }` - `Palette = { PaletteEntry } | { [string]: ColorLike }` - `Bounds = { min: Vec3Map, max: Vec3Map }` - `Handle = { entityId: any, componentName: string, [string]: any }` - `CreateWorldOpts` / `CreateShapeOpts` / `FromTemplateOpts` / `SaveAsTemplateOpts` - `CaptureAreaOpts` / `CaptureAreaBoxSelector` / `CaptureAreaSphereSelector` - `CloneOpts` / `SnapToWorldOpts` - `RegionSpec` / `ScatterOpts` / `StampOpts` - `QueryRegionOpts` / `PasteRegionOpts` ## Usage ```luau local Voxel = require("@builtin::systems.voxelEngine") -- Create the singleton world, write a couple of cells. local world = Voxel.createWorld({ size = { x = 64, y = 32, z = 64 }, palette = { stone = { r = 0.5, g = 0.5, b = 0.5 } }, }) world:setBlock(0, 0, 0, "stone") world:fillBox({ 1, 0, 0 }, { 3, 0, 3 }, "stone") -- Spawn a shape from a template, live-linked to the template file. local tree = Voxel.fromTemplate("tree", { position = { x = 10, y = 0, z = 5 }, }) -- Scatter 20 copies inside a region. local hs = Voxel.scatter("tree", { region = { box = { min = { 0, 0, 0 }, max = { 50, 0, 50 } } }, count = 20, snap = true, }) -- Capture a region of world + shapes into a dense voxbin record. local rec = Voxel.captureArea({ box = { min = { 0, 0, 0 }, max = { 15, 15, 15 } }, }) ``` ## Notes - Handles are thin wrappers over an `entityId` + a component name. Each method re-resolves the underlying component on every call, so the handle stays usable across hot-reload cycles. - All `h:setBlock` / `h:fillBox` / … calls forward to the component via colon-call (`c:method(...)`) — dot-call would drop `self` and the strict typed-function checker would read args from the wrong slots. - `fromTemplate` defaults to `live = true` + `persist = true` — live-linked instance that auto-bakes private edits to disk. Pass `live = false` for a detached copy with its own dataPath, or `persist = false` for a memory-only instance. - `Voxel.scatter` / `Voxel.stamp` (mode = "merge") obey the play-mode write gate enforced by `assertModeAllowsWrite`. In play mode, callers must toggle `Config.set("allowPlayWrites", true)` (or set the `[voxel].allowPlayWrites` WORLD_SETTINGS override) to unlock voxbin writes. - `Voxel.stamp(mode = "merge")` only supports yaw rotations of 0 / 90 / 180 / 270 degrees — voxel grids require axis-aligned stamps. Non-axis-aligned yaws raise. - The `composite` sub-module is reachable as `Voxel.composite`. It builds kitbashed `.voxcomp` props that re-resolve their children at instantiation time; `fromTemplate` transparently dispatches to it when the named template resolves to a `.voxcomp` manifest.

# Voxel Template (asset type) A voxel template is a reusable, named voxel grid that live instances link to. It is the source of truth for a family of `VoxelShape` instances spawned via `Voxel.fromTemplate(<name>)` — every live instance reloads its grid + rebuilds its mesh automatically when the template's payload is rewritten, and a `Voxel.deleteTemplate(<name>)` flips every live instance's `staleTemplate` flag. ## When to use one - You want a reusable voxel prop (`tree`, `rock`, `barrel`) that many entities share, with edits to the template propagating to every live instance. - You want a stable identity (a guid) for a voxel grid so the engine's asset-reload machinery can drive the live-link instead of a poll loop. If you just need a one-off shape on a single entity, use `Voxel.createShape` — that writes a private `dataPath` voxbin and never becomes a template. ## Where it lives - Source: `Config.get("paths.templates")/<Name>.voxelTemplate/` - Identity: `<Name>` (the `.voxelTemplate` suffix strips). - Folder shape: - `template.voxbin` — the binary grid payload (size, blockSize, palette, flat grid array). Written by `saveAsTemplate` / `copyTemplate`. **Optional** in the structural spec only so the freshly-scaffolded (empty) folder validates; every real template carries it. - `.metadata` — agent-editable tags + free-form fields. **Required.** ## How to create one From a live shape you authored: ```luau local Voxel = require("@builtin::systems.voxelEngine.voxelEngine") local shape = Voxel.createShape({ size = { 8, 8, 8 } }) shape:fillBox({0,0,0}, {7,7,7}, "stone") shape:saveAsTemplate("my_prop") -- Writes: <paths.templates>/my_prop.voxelTemplate/ -- template.voxbin (the grid payload) -- .metadata ``` Or scaffold an empty one to fill in later: ```luau asset.create("voxelTemplate", "MyProp") -- Creates: /zero/source/MyProp.voxelTemplate/ -- .metadata ``` ## How it operates 1. **Live-link.** `Voxel.fromTemplate(<name>)` resolves the template to an `AssetRef<voxelTemplate>` and stores it in `VoxelShape.templateRef`. The engine indexes that subscription by guid, so a write to the template's `template.voxbin` fires `onAssetReload("templateRef")` on every live instance, which re-reads the payload and rebuilds the mesh. 2. **Delete.** `Voxel.deleteTemplate(<name>)` removes the folder and directly flips `staleTemplate = true` on every live instance — deletes do not emit a content-change event, so the engine notifies instances synchronously rather than waiting on a reload hook. 3. **Copy-on-write.** Editing a live instance (`setBlock`, `fillBox`, …) auto-bakes a private `dataPath` copy and clears `templateRef`, detaching the instance from the template. The original template is untouched. ## In the Inspector Selecting a voxel template opens its **Grid** section, decoded from `template.voxbin` once per version of the file: the template's size in voxels, its block size, whether it is chunked (and, when it is, its chunk size and chunk count), how many palette entries it holds, and whether it carries custom data.