# 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.

# `hdrChart` post-process shader The synthetic HDR chart: a picture whose every pixel holds light its properties and its position state, drawn in place of the scene. Registered first in the chain (`postMetrics.chart.show`, priority -1000), it is the input the display transform and every effect after it read, so they are measured against known light with no lighting, geometry or material in between. `@builtin::modules.postMetrics` computes the same light for any pixel on the CPU (`chart.light`) and builds the picture a display curve should present for it (`chart.reference`). | Property | Meaning | |---|---| | `pattern` | 0 ramp, 1 grey wedge, 2 ColorChecker, 3 colour wedge over its grey. | | `low`, `high` | The ramp's light at the left and right edges. | | `evMin`, `evMax` | The wedges' leftmost and rightmost stops; each column is middle grey (0.18) at a whole stop. | | `gain` | The ColorChecker's light, as a multiple of its reflectance. | | `color` | The ramp's tint, and the colour wedge's saturated patch (scaled to its column's grey luminance). | | `dither` | Triangular noise of that many code values either way, added in display-encoded sRGB. | The effect declares `space: light`.

# Camera Manages viewport priority, render-to-texture, and capture. State is stored in the native `Camera` ECS component; the Rust camera system handles render scheduling and render targets. Public fields: `fov`, `near`, `far`, `priority`, `textureHandle` (the guid of the texture the camera renders into; empty = main viewport), `renderLayers` (which render layers this camera draws — a space-separated spec of names, e.g. `"all"`, `"all !ui"`, or `"default sky"`; `ui`/`sky`/`debug`/`EditorUI` are built-in layers), `postProcessing` (whether this camera runs the post-process chain), `debugChannel`, plus the behavior slot below. Methods: `:lookAt(target)` (entity id string OR `{x, y, z}` table), `:render()`, `:capture()`, `:setTargetTexture(tex?)` (a `renderer.texture.create` handle to render into, or nil for the viewport). ```luau entity(id).component.add("Camera", { fov = 90, priority = 10 }) entity(id).component.get("Camera"):capture() ``` The scene's play-mode camera is reached as `layers.active.camera`, a handle that reads and writes the fields above on whichever entity currently carries them. `layers.active.camera.entity` is the entity ref for that camera and `layers.active.camera.entityId` its id string, so a script that needs to attach something to the camera — an `AudioListener`, a child entity — goes through the ref: ```luau local cam = layers.active.camera cam.fov = 70 -- the camera's settings cam.entity.component.add("AudioListener") -- the entity carrying them ``` ## How the camera moves: `behavior` and `follow` A `Camera` does not move itself. `behavior` names a component that does, and setting it attaches that component to this entity. Clearing it detaches whatever was attached. ```luau local cam = entity(id).component.get("Camera") cam.behavior = asset.ref("@builtin::controller.orbital_follow", "component") cam.follow = playerBody ``` The attached behavior is an ordinary component on the camera's entity, so it is tuned the way any component is: read it with `component.get` and set its fields there. A `component.add` of the same type configures the instance the slot attached instead of adding a second one: the values it passes are written onto that instance and its proxy is returned. That add is the form a scene `build.luau` tunes the behavior with, because its values are saved with the scene and the loaded Camera's behavior takes them back. A key the component reads only as it is created (one of its `initKeys`, a private field) refuses the add and names the key. ```luau cam.behavior = asset.ref("@builtin::controller.third_person_follow", "component") local rig = entity(id).component.get("third_person_follow") rig.cameraDistance = 6 -- the same, as an add of the type the slot attached entity(id).component.add("third_person_follow", { cameraDistance = 6 }) ``` `follow` is the standard slot every shipped behavior reads. Set the follow target on the **Camera**, not on the behavior, so swapping behaviors keeps it. A behavior that finds its own `follow` field empty falls back to this one, which is what lets a rig keep tracking the player across a behavior swap. `followResolves` answers whether that slot names an entity that is live — `true` while it names a live one or names nothing at all, `false` once the target is despawned or the id names no entity. A rig whose target does not resolve holds its last pose, and this is the field that tells it from a rig posed correctly on a subject that has not moved. `camera.get` carries the same value beside `follow`, and a write naming an id with no entity behind it draws a warning where it lands. ```luau cam.followResolves -- false once the followed entity is gone tools.use("camera", "get", id).followResolves -- the same answer off the tool ``` The shipped behaviors live under `@builtin::controller.*`: `orbital_follow`, `third_person_follow`, `first_person`, `free`, `orbit`, `chase`, `isometric`, `rts`, `birds_eye`, `side_scroller`, `cinematic`, `menu`. ## Writing your own Any component can be a camera behavior. Write one that moves its own entity and attach it the same way: ```luau cam.behavior = asset.ref("MyChaseCam", "component") ``` `follow` lives on the Camera, so a behavior gets no property notification of its own when the target changes. Declare `onFollowChanged(newFollow, oldFollow)` to be told the moment it does — the Camera calls it on the component it attached, which is what lets a rig re-pose on the new subject at once. A behavior that reads `Camera.follow` on its own schedule declares nothing and is attached the same way. ```luau typed function public:onFollowChanged(newFollow: any, oldFollow: any) -- pose this entity against the new target end ``` To make it appear in the discovery catalog alongside the shipped ones, declare the `cameraBehavior` tag in the component's `.metadata`: ```json { "tags": ["cameraBehavior"] } ``` The tag governs **discovery**, not attachment. A tagged component is listed by `layers.active.camera.behaviors` and is what tooling offers when something asks "which camera behaviors exist"; an untagged component attaches just as well and simply stays out of that list. Tag the ones you want other people (and agents) to find. ```luau for name, ref in pairs(layers.active.camera.behaviors) do print(name, ref.identity) end ``` ## Texture colour space `textureColorSpace = "display"` applies the display transform when rendering into a texture. `"linear"` writes scene-linear values instead. `postProcessing` independently controls the effects chain in either mode. Floating-point targets retain values above one; normalized targets clamp to their representable range. The main viewport uses display encoding.

# PostProcess Component Applies a **stack of post-process effects** to the scene, declaratively, from a single entity. Each effect references a `.shader` asset (`@domain: post-process`) and carries its own **configurable property values** — tuned like material properties, with no shader edit required. This is the load-time **reproducer** for post-processing: where an agent's live `postprocess.add(...)` + `postprocess.setProperty(...)` calls produce effects that vanish on reload, a `PostProcess` component re-registers the exact same stack — with the exact same tuning — every time the scene loads. The persist freeze converts live execute-origin effects into `.shader` assets + one entity carrying this component, so **what you see is what you get** across save/reload. ## Properties | Field | Type | Description | |---|---|---| | `effects` | array | The effect stack. Each entry: `{ shader, priority?, enabled?, layer?, values?, textures? }`. | | `shape` | `"global"` \| `"box"` \| `"sphere"` | Where the stack applies. Default `"global"` (unbounded). | | `extents` | vec3 | Box region half-extents, world units. Default `{5, 5, 5}`. | | `radius` | number | Sphere region radius, world units. Default `5`. | | `falloff` | number | Soft-edge distance outside the volume the stack fades over. Default `0`. | | `priority` | number | Order of this region against other `PostProcess` regions, added to each effect's own priority. Default `0`. | | `display` | struct `{ curve, exposure }` | The display transform this region sets while it is live — `curve` (0 linear, 1 Reinhard, 2 ACES, 3 Khronos PBR Neutral, default `3`) and `exposure` (multiplier on the scene's light before the curve, default `1`). Takes effect only when `setsDisplay` is `true` and `shape` is `"global"`. | | `setsDisplay` | boolean | Whether this region writes `display` to the chain's `__display__` transform while it is live. Default `false`. | Each effect entry: | Key | Type | Description | |---|---|---| | `shader` | asset reference | The `.shader` asset (a `@domain: post-process` shader) this effect runs. Builtin shaders (`@builtin::shaders.post.vignette`, …) or scene-authored custom shaders both work. | | `priority` | number | Chain order within this region — lower runs earlier. Default `100`. | | `enabled` | boolean | Per-effect toggle. Default `true`. | | `layer` | `"all"` \| `"scene"` | Which composited image this effect grades: `"scene"` is the rendered picture before the UI reaches it, in the scene's own light; `"all"` is the picture fitted to the screen with every widget on it. Left empty, the entry follows its shader's `space` — a `light` shader grades `"scene"`, a `display` shader grades `"all"`. | | `values` | table | Named property overrides `{ [prop] = value }`, applied via `postprocess.setProperty` after the effect is added — the configurable tuning. | | `textures` | table | Texture bindings `{ [prop] = path }`, applied via `postprocess.setTexture` after the effect is added. | The component-level `enabled` flag (engine-managed, not declared here) toggles the **whole stack**: disabling the component removes every effect (and restores the chain's own display transform if this region set one); enabling it re-registers them (`onEnable` / `onDisable`). ## Usage ```lua entity.find("fx").component.add("PostProcess", { effects = { { shader = "@builtin::shaders.post.vignette", priority = 0, values = { intensity = 0.6 } }, { shader = "@builtin::shaders.post.grayscale", priority = 10, values = { intensity = 1.0 } }, }, }) ``` Setting the display transform from a `global` region: ```lua entity.find("look").component.add("PostProcess", { setsDisplay = true, display = { curve = 2, exposure = 1.5 }, -- ACES }) ``` Two `global` regions with `setsDisplay = true` both write `__display__` — whichever registers last wins the frame. The regions setting it share one ordered record of who is live, so they come off in any order: removing the newer of two leaves the older one's display standing, removing the older leaves the newer one's, and removing the last leaves whatever stood before any of them wrote. The exposure package drives `__display__.exposure` on its own, from a GPU readback each tick it meters. A region arriving or leaving sets the exposure and the package's next readback sets it again, so with auto-exposure running the exposure a region asks for holds for a frame while its curve holds for as long as the region does. ## Methods - `pp:getEffectNames()` — the live effect names currently registered, in stack order. - `pp:setProperty(index, prop, value)` — tune a property of one effect at runtime (forwards to `postprocess.setProperty`), like editing a material property.

# scene runtime What a `.scene` folder does when it is loaded, saved, built, or swapped. A `<name>.scene/` carries `scene.json` (the entity arrangement), an optional `build.luau` (the code author's half), an optional `entrypoint.luau`, and a `scene_dirty/` overlay of unsaved edits. Reading, composing and writing all four is the scene type's own behaviour, so it lives in the type. ## Sub-modules | Module | Responsibility | |---|---| | `loader.module` | Reads scene.json v6 and v7, refuses versions it does not know, composes canonical + dirty overlay, spawns the entities, and runs the entrypoint. | | `saver.module` | Persists scene state as a delta overlay against the canonical file, promotes that overlay on save, and answers which edits are still pending. | | `build.module` | Runs a `build.luau` inside an entity capture scope and composes what it spawned into scene records. | | `observe.module` | The read side — the per-scene counts and costs `layers` and `loader` write. | | `swapOrchestrator.module` | Drives multiplayer room transitions and the scene-swap gate, so a local swap does not leak despawns to peers in the old room. | ## Reaching it ```luau local rt = require("@builtin::assetTypes.scene.shared") rt.saver.hasPendingSceneEdits(layers.active.name) ``` Fields resolve lazily. The prelude installs `swapOrchestrator` and starts `saver`'s dirty writer in a fixed order, which a table that required all five on load would take away from it.

# 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.

# Shader (asset type) A shader is a WGSL program that runs on the GPU. Materials reference shaders and supply property values; renderable entities reference materials, not shaders directly. This README is the canonical reference for writing **every** kind of shader — it covers all domains, the surface authoring contract, the material property schema, the engine library functions you can call, and how a shader registers and compiles. > New to how shaders, materials, meshes, and textures relate as assets and live > GPU resources? Read `core/resource-model` first. ## Folder shape A `.shader` is a folder asset: ``` <name>.shader/ shader.wgsl # the WGSL body (required) properties.yaml # the material property schema (optional; surface shaders) README.md # a one-paragraph description of THIS shader (required) .metadata # asset metadata ``` Each file carries a committed `.meta` sidecar pinning its stable guid. The identity is `<name>` (the `.shader` suffix strips). Materials and other assets reference a shader by **AssetRef** (a typed, guid-backed handle), never by a raw string. ## Domains The first line of `shader.wgsl` declares the domain: ```wgsl // @domain: surface ``` | Domain | What it is | You write | |---|---|---| | `surface` | A material on a mesh (the common case). | `fragment()` (+ optional `vertex()`/`vertex_clip()`). The engine generates everything else. | | `post-process` | A full-screen pass over the rendered frame, in the space it declares (bloom, vignette, grade). | `fragment(in: PostInput) -> vec4` only. The engine generates the fullscreen `vs_main`/`fs_main` and the group(1) interface from `properties.yaml`. | | `screen` | A standalone full-screen visual (UI background, procedural). | `fragment(in: ScreenInput) -> vec4` only. The engine generates the fullscreen `vs_main`/`fs_main` and the group(1) interface from `properties.yaml`. | | `sky` | The sky background (a fullscreen material). | `fragment(in: SkyInput) -> vec4` only. The engine generates the fullscreen `vs_main`/`fs_main` and the group(1) interface from `properties.yaml`. | | `compute` | GPU data processing, no rasterization. | *(legacy)* An `@compute @workgroup_size(...)` entry over storage buffers — you write the `@group/@binding` lines yourself. **The canonical path is now the separate `.computeShader` assetType** (see below); `.shader` + `// @domain: compute` still compiles for back-compat. | `// @domain:` resolves the names above and `postprocess` / `screenspace` / `ui` as further spellings of `post-process` and `screen`. A body carrying no `@domain:` line is `surface`. `shaderRef:domain()` answers the domain a body declares, a further spelling as the domain it names. Any other name is refused where the shader registers, with an error naming the spellings that resolve, so a shader reaches the renderer only under a domain the compiler scaffolds. Particles are drawn and simulated through these domains like anything else: the particle package's `particle_sprite` and `particle_mesh` are `surface` shaders, and its simulation, culling and sorting steps are `.computeShader` assets. ## Texture coordinate space A shader that samples a texture through a coordinate it builds itself declares which space that coordinate lives in, on a line beside `@domain:`: ```wgsl // @domain: surface // @uv_space: world ``` | Value | The coordinate | A material's `uv_scale` means | |---|---|---| | `mesh` (the default) | The mesh's own UV attribute, `input.uv`. | How many times the texture repeats across a surface. | | `world` | The fragment's world position, as a triplanar projection samples. | How many times the texture repeats per world unit, so a larger surface carries more. | Texture residency reads the declaration to work out how finely a frame samples each texture: a material laying eight copies of its texture across a surface samples each copy at an eighth of the surface's size, and the mip level that serves it is three levels coarser than the surface's own footprint implies. Leaving the line out puts the shader in mesh space, which is what sampling `input.uv` is. `renderer.textureStreaming().textures` reads back the span each texture was measured at and the level that span asked for. **Compute shaders are now their own assetType.** A `.computeShader/` folder gives compute the same zero-scaffolding contract surface/sky/post/screen get: you write only `@compute fn main` (+ helper fns/structs, **no `@group/@binding` lines**) and declare bindings in a sibling `bindings.yaml` (storage buffers, textures, samplers, storage textures, plus a `params:` uniform); the engine generates the `@group(0)/@binding(N)` declarations. Dispatch it through a resolved reference (`asset.resolve("name", "computeShader"):dispatch(...)`). See the `.computeShader` assetType README and `man compute`. The `.shader` compute domain above remains only for back-compat. **Surface**, **sky**, **post-process**, and **screen** shaders all get engine-generated scaffolding — you write only `fragment()` and declare properties in `properties.yaml`; the engine generates the entry points and the group(1) material interface. (Each domain's `fragment` takes a domain-specific input instead of `FragmentData`: `SkyInput`, `PostInput`, or `ScreenInput` — see "Sky shaders" and "Post-process & screen shaders" below.) Compute shaders get the same treatment via the separate `.computeShader` assetType (write only `@compute fn main`, declare bindings in `bindings.yaml`). The legacy `compute` domain here writes its own entry points directly — see `man compute`. ## Surface shaders A surface shader writes **only** the parts that are unique to it. The engine owns all the scaffolding — the vertex stage, every render-mode entry point (`vs_main` / `fs_forward` / `fs_gbuffer`), group(0) (camera, transforms, lights, shadows, and the material rows), and the material interface generated from `properties.yaml` (`material` and your texture slots). Adding a render path never touches your shader. Inside `fragment()` you have access to exactly four things — nothing is hidden: 1. **`input: FragmentData`** — the interpolated per-fragment surface data the engine hands you: world position, world normal, uv, view direction, vertex colour, and more. Every field is in the `FragmentData` table below. 2. **`material.*` and your textures** — the material inputs **you** declare in `properties.yaml`. The mapping is mechanical: a scalar property named `foo` becomes `material.foo`; a texture property named `bar` becomes `bar` (the texture) and `bar_sampler` (its sampler). `material` has **exactly** the fields your `properties.yaml` declares and no others — to add an input, add a property. List what a shader exposes with `shaderRef:getProperties()` or `asset.inspect("<name>")`. 3. **Engine state** — the scene's camera, lights, time, and shadows that the renderer binds for every surface shader. `uniforms.*` (sun direction/colour, ambient, `camera_pos`, `time`) and the punctual lights (`zero_point_light(i)`) are always in scope; the shadow functions come from `#include "@builtin::shaderModules.shadows"`. This is how you light a surface **without** the prebuilt PBR — see "Engine state" and "Writing your own shading" below. 4. **Library functions** you `#include` (see "Library includes"). A shader and its property schema go together. The two files below are a complete surface shader: `properties.yaml` — declares the material inputs: ```yaml properties: - { name: base_color, type: color, default: [1, 1, 1, 1] } - { name: roughness, type: float, default: 0.5, min: 0, max: 1 } - { name: metallic, type: float, default: 0.0, min: 0, max: 1 } - { name: base_color_texture, type: texture, default: white } ``` `shader.wgsl` — those declarations are now `material.base_color`, `material.roughness`, `material.metallic`, and the `base_color_texture` / `base_color_texture_sampler` pair: ```wgsl // @domain: surface #include "@builtin::shaderModules.pbr_shading" // the PBR helpers — see "Library includes" fn fragment(input: FragmentData) -> vec4<f32> { var s = zero_pbr_default_surface(input); s.albedo = material.base_color.rgb * textureSample(base_color_texture, base_color_texture_sampler, input.uv).rgb; s.perceptual_roughness = material.roughness; s.metallic = material.metallic; return vec4<f32>(zero_pbr_shade(input, s), material.base_color.a); } ``` `fragment()` returns the final colour. The engine forces no lighting model on you — flat, toon, PS1, dithered, or PBR are all just different `fragment()` bodies. Calling `zero_pbr_shade` is opt-in. ### The two surface bodies, and what each gives up A surface shader exposes one of two entry points, and which one decides how much of the shader the engine can see: | Body | The engine gets | PBR debug passes read | |---|---|---| | `fn fragment(input: FragmentData) -> vec4<f32>` | the finished pixel, and the `PbrSurface` too when the body hands one to `zero_pbr_shade` | the real channel where a surface was handed over; magenta, the "no data here" marker, where the body shades by its own math | | `fn surface(input: FragmentData) -> PbrSurface` | the surface (albedo, roughness, metallic, emissive, normal, occlusion), which the engine then lights | the real channel | Both are first-class: `fragment()` is what you want when the shader owns its own look, `surface()` when you want engine lighting. `capture { pass = "albedo" }` (and `roughness` / `metallic` / `ao` / `emissive`) answers about your material for either body wherever the engine has the surface — writing the same `PbrSurface` behind `surface()` or behind `fragment()` + `zero_pbr_shade` gives one answer per channel. A body that lights itself by its own math draws those channels magenta. `pbr.shader` exposes `surface()`. `capture { pass = "normal" }` is a geometry read rather than a material one, so it answers for every shader: the normal of the surface where one was handed over, and the interpolated normal of the triangle where none was. It is the same normal the frame's normal buffer carries, which is what a screen-space pass reading `@scene.normal` sees. `shaderRef:shadingModel()` reports which one a shader ended up with — `"engine-lit"` for `surface()`, `"self-shading"` for `fragment()`. ### Optional vertex hooks ```wgsl // Displace geometry in OBJECT space. Runs on skinned meshes too (it sees the // already-skinned, morph-applied local position). Return the modified vertex. // The `v` parameter is immutable (WGSL function params are), so copy it into a // `var` first and modify that. fn vertex(v: VertexData) -> VertexData { var out = v; out.position += out.normal * sin(out.time) * 0.1; return out; } // Post-transform vertex hook (runs AFTER the engine's world/skin/projection). Two // things you can do here, separately or together: // * move `clip_position` — vertex jitter, PS1 snapping, render-resolution lowering; // * write `color` — PER-VERTEX (Gouraud) shading: light the vertex from its // world_normal + the light context and the engine forwards the result into the // interpolated `vertex_color` the fragment reads. fn vertex_clip(v: ClipVertex) -> ClipVertex { var out = v; // Gouraud: Lambert sun + ambient, evaluated once per vertex (flat-banded shading). let n_dot_l = max(dot(v.world_normal, -normalize(v.light_direction)), 0.0); let lit = v.ambient_color * v.ambient_intensity + v.light_color * v.light_intensity * n_dot_l; out.color = vec4<f32>(v.color.rgb * lit, v.color.a); out.clip_position = round(out.clip_position * 80.0) / 80.0; // PS1 snap return out; } ``` #### Declaring how far a hook moves geometry: `vertexBoundsDilation` Static geometry is culled per cluster against its bounds as authored. A hook that moves vertices — wind sway, an outline hull, a vertex wave — can move them outside those bounds, and the cull then drops clusters whose displaced triangles are still on screen. Declare the farthest the hook moves any vertex, in world units, as a `vertexBoundsDilation` float property, with a default that covers the shader's own properties across their ranges: ```yaml properties: - { name: sway, type: float, default: 0.5, min: 0, max: 4 } # 0.4 x sway, at sway's largest value. - { name: vertexBoundsDilation, type: float, default: 1.6, min: 0, max: 100 } ``` Each material sets its own value — a material that sways less can set less, one moved farther sets more — and a material that sets none takes the default. The cull adds the material's value to every bound in its frustum and occlusion tests (not to the level-of-detail cut). A shader with a hook and no `vertexBoundsDilation` property is named once in the engine log when it compiles; its geometry is culled against its undisplaced bounds. ### Structs the engine passes you `FragmentData` (input to `fragment()`): | Field | Type | Meaning | |---|---|---| | `world_position` | `vec3<f32>` | fragment world-space position | | `world_normal` | `vec3<f32>` | interpolated geometric normal (normalized) | | `world_tangent` | `vec4<f32>` | xyz = world tangent, w = handedness (mikktspace) | | `uv` | `vec2<f32>` | primary texture coordinates (perspective-correct) | | `affine_uv` | `vec2<f32>` | the same UVs interpolated **without** perspective correction — the PS1 texture "swim". Always available; sample with it instead of `uv` for affine texture mapping | | `vertex_color` | `vec4<f32>` | interpolated per-vertex colour (white if unset; carries per-vertex lighting if `vertex_clip()` wrote it — see Gouraud below) | | `view_position` | `vec3<f32>` | camera world position | | `view_direction` | `vec3<f32>` | normalized world-space direction to the camera | | `light_direction` | `vec3<f32>` | directional (sun) travel direction, unit length; surface→sun is `-light_direction`. Where no sun reaches the camera it points straight down | | `light_color` | `vec3<f32>` | sun colour | | `light_intensity` | `f32` | sun intensity; 0 where no sun reaches the camera | | `ambient_color` | `vec3<f32>` | ambient colour | | `ambient_intensity` | `f32` | ambient intensity | | `frag_coord` | `vec4<f32>` | framebuffer pixel coords (xy) + depth (z) — for screen-space dither | | `receives_shadows` | `f32` | per-instance: > 0.5 if this surface receives shadows | | `material_index` | `u32` | per-instance: the index standing for the material this surface draws with — the number `renderer.materialIdentity()` maps to a name | | `shader_data` | `array<vec4<f32>, 4>` | per-instance: this entity's own four `vec4` lanes — its `ecs.ShaderData` component's `lane0`..`lane3`, or what `renderer.instanceData.set` put in them (zero until something does). A procedural graph's elements set them through the `data0`..`data3` attributes | | `front_facing` | `bool` | true for front faces (double-sided shading) | | `time` | `f32` | gameplay seconds: advances with the world at `engine.timeScale` and stands still while gameplay is paused (edit mode starts paused), so an effect slows and stops with the world | `shader_data` is the per-instance channel, and it is what lets ONE material serve many entities that differ in a value — a dissolve at its own progress per subject, a hit flash at its own age, a fill level per instance. The alternative is a material per entity, which is a separate pipeline binding and a separate row in the material table for every one of them. ```wgsl const DISSOLVE_LANE: u32 = 0u; fn fragment(input: FragmentData) -> vec4<f32> { let progress = input.shader_data[DISSOLVE_LANE].x; ... } ``` ```lua -- one material on twenty entities, each at its own progress renderer.instanceData.set(subject, 0, progress) renderer.instanceData.clear(subject) -- back to zero lanes ``` The engine attaches no meaning to a lane: a shader and whatever writes it agree what each one carries. Name the indices in the module that writes them. `renderer.instanceData.laneCount()` is how many there are. The same lanes reach a hardware-instanced population through `renderer.mesh.drawInstanced`'s `instanceDataBuffer`, on slots no entity owns. `VertexData` (in/out of `vertex()`): `position` (object-local, model-scale + morph applied), `normal`, `uv`, `color`, `time`. `ClipVertex` (in/out of `vertex_clip()`) — the post-transform vertex. Read context: `clip_position`, `world_position`, `world_normal`, `uv`, `view_position`, `view_direction`, `light_direction`, `light_color`, `light_intensity`, `ambient_color`, `ambient_intensity`, `time`, `view_proj` (the view-projection of the frame being evaluated), and where the vertex stands on its instance: `local_position` (its position in the mesh, after `vertex()` and before the instance's world transform), `object_origin` (the world position of the instance's origin), `object_scale` (the world length of the instance's x, y and z axes) and `object_axes` (`mat3x3<f32>`, the world direction of those axes, unit length) — what a camera-facing card, a shard grown about its own base, or anything placed per instance is built from. **Writable:** `clip_position` (snap / jitter) and `color` (write a lit colour here for per-vertex Gouraud shading; the engine forwards it to the interpolated `vertex_color` — left untouched, the mesh's own vertex colour passes through). ### Each hook runs twice: this frame and the one before it A vertex hook decides where the surface IS, so it also decides where the surface WAS. The engine runs every hook a shader declares a second time, over the same vertex standing one frame back — the previous-frame position stream, with `time` = the clock that frame was drawn at and (for `vertex_clip()`) `view_proj` = the view-projection it was drawn with. The motion vector the renderer publishes is taken between the two results, so a displacement that moves with time reports the velocity of the displaced surface, and a displacement that does not move reports the motion of the transform alone because the identical offset appears on both evaluations and cancels. What that asks of a hook: - **Take the frame from the argument.** `v.time` is the clock of the evaluation being run; `uniforms.time` is always this frame's. A displacement built on `uniforms.time` is identical on both evaluations, so its motion vector cancels to exactly zero. The same holds for `v.view_proj` against `uniforms.view_proj`: a clip hook that rebuilds its position from world space through `uniforms.view_proj` reprojects the previous frame with this frame's camera, and reports no camera motion at all. The wind helpers come in both shapes for this reason — `zero_wind_sway_at_time(world_pos, stiffness, v.time)` inside a hook, `zero_wind_sway(world_pos, stiffness)` outside one. - **Anchor a wrap to `uniforms.time`.** A displacement that jumps discontinuously — a falling drop that restarts at the top, a looping offset — differences its jump as velocity on whichever frame it wraps. Compute the wrap COUNT from `uniforms.time` and the position within the cycle from `v.time`, and both evaluations share the same cycle, so the surface reports the speed it fell at. `@builtin::shaders.rain_material` and `snow_material` do exactly that. The per-vertex attributes (`world_normal`, `uv`, `color`) and the lighting and camera-position context are this frame's on both evaluations, so a hook that displaces along its normal reports the motion of the transform plus this frame's displacement. ## Engine state — point lights & shadows The common lighting state — the sun (`input.light_direction` / `light_color` / `light_intensity`), the ambient (`input.ambient_color` / `ambient_intensity`), the camera (`input.view_position` / `view_direction`), and `input.time` — is already on `FragmentData`, so most shaders never touch the raw engine state. The one thing not on `FragmentData` is the punctual-light array (its length varies), which is always in scope: | Expression | Type | Meaning | |---|---|---| | `uniforms.point_light_count` | `u32` | number of active point/spot lights | | `zero_point_light(i)` | `PointLightData` | one point or spot light (fields below) | | `zero_punctual_shadow(i)` | `PunctualShadowEntry` | that light's shadow record (its projected map or cube) | `PointLightData`: `position`, `radius`, `color`, `intensity`, `direction`, `cone_outer_cos`, `cone_inner_cos`, `kind` (0 = point, 1 = spot). Shadows come from `#include "@builtin::shaderModules.shadows"`: - `compute_directional_shadow_factor(world_pos, normal, light_dir) -> f32` — 1.0 lit, 0.0 fully shadowed. - `compute_spot_shadow_factor(...)` / `compute_point_shadow_factor(...)` / `compute_area_shadow_factor(...)` — one shadow shape each. - `compute_punctual_shadow_factor(light_index, world_pos, normal) -> f32` — the row's own shape, read off its `kind`, for a loop that walks the punctual lights and does not want the switch. - `zshadow_light_reach(light_index, world_pos, normal, object_channels) -> f32` — how much direct light that row puts on a surface on those light channels: the channel mask, falloff, cone or rect orientation, and the cosine, times intensity. Zero exactly where the light contributes nothing. ## Writing your own shading The engine forces no lighting model — `zero_pbr_shade` is just one option. You can light a surface yourself from the state above. Here is a complete custom-lit (Lambert diffuse) surface with no PBR: ```wgsl // @domain: surface #include "@builtin::shaderModules.shadows" // exposes compute_directional_shadow_factor fn fragment(input: FragmentData) -> vec4<f32> { let n = normalize(input.world_normal); let albedo = material.base_color.rgb; // Directional (sun) light: Lambert N·L, attenuated by its shadow. let sun = normalize(-input.light_direction); // surface -> sun let sun_shadow = compute_directional_shadow_factor(input.world_position, n, input.light_direction); var lit = input.light_color * input.light_intensity * max(dot(n, sun), 0.0) * sun_shadow; // Point + spot lights (the punctual-light array, varying length). for (var i = 0u; i < uniforms.point_light_count; i = i + 1u) { let pl = zero_point_light(i); let to_light = pl.position - input.world_position; let dist = length(to_light); let l = to_light / max(dist, 1e-4); let atten = max(1.0 - dist / max(pl.radius, 1e-4), 0.0); lit += pl.color * pl.intensity * max(dot(n, l), 0.0) * atten; } // Ambient fill. lit += input.ambient_color * input.ambient_intensity; return vec4<f32>(albedo * lit, material.base_color.a); } ``` - **Unlit:** skip the lights and return your colour directly. - **Toon / PS1 / custom:** start from the loop above and band, quantize, or warp it however you like. - **PBR:** build a `PbrSurface` and call `zero_pbr_shade` (see "Library includes") instead of writing the BRDF by hand. ## Material properties — `properties.yaml` A surface shader declares its material properties in a sibling `properties.yaml`. The engine GENERATES the entire group(1) interface from it — the uniform struct (`material.<name>`) plus a texture/sampler pair per declared texture. You write no `@group`/`@binding` lines. ```yaml properties: - { name: base_color, type: color, default: [1, 1, 1, 1] } - { name: roughness, type: float, default: 0.5, min: 0, max: 1 } - { name: metallic, type: float, default: 0.0, min: 0, max: 1 } - { name: emissive, type: color, default: [0, 0, 0, 1] } - { name: base_color_texture, type: texture, default: white } - { name: normal_texture, type: texture, default: flat_normal } ``` | `type` | WGSL field type | Notes | |---|---|---| | `float` | `f32` | optional `min`/`max` for editor sliders | | `float2`/`float3`/`float4` | `vec2/3/4<f32>` | | | `color` | `vec4<f32>` | sRGB colour, default is `[r,g,b,a]` | | `int` | `i32` | | | `bool` | `u32` | | | `texture` | `texture_2d<f32>` + `sampler` | `default:` is a built-in texture name (`white`, `black`, `flat_normal`) | In the shader you read scalars as `material.<name>` and sample textures as `textureSample(<name>, <name>_sampler, uv)`. A texture slot with no bound texture samples its default, so a shader can always sample — no presence flag needed. `vertex()` reads the same material interface, so a height or deformation map drives displacement from the slot it was bound to. A vertex stage has no implicit derivatives, so sample it at an explicit mip there: `textureSampleLevel(<name>, <name>_sampler, uv, 0.0)`. ## Sky shaders A `// @domain: sky` shader draws the sky as a fullscreen pass. You write **only** `fn fragment(in: SkyInput) -> vec4<f32>` — the colour along the view ray for each pixel — and declare tunables in `properties.yaml` exactly like a surface shader (read as `material.<name>`, textures via `textureSample(<name>, <name>_sampler, uv)`). The engine generates the fullscreen `vs_main`/`fs_main`, the group(1) interface, and reconstructs the world-space ray; there is no separate sky renderer — a sky material runs through the same material pipeline, just on a fullscreen triangle. `SkyInput` (the only argument) carries: | Field | Type | Meaning | |---|---|---| | `ray_dir` | `vec3<f32>` | normalized world-space ray through this pixel | | `ndc` | `vec2<f32>` | screen position in NDC `[-1, 1]` | | `sun_direction` | `vec3<f32>` | unit vector TOWARD the sun (from the directional light) | | `camera_pos` | `vec3<f32>` | world-space camera position | | `time` | `f32` | gameplay seconds: advances with the world at `engine.timeScale` and stands still while gameplay is paused (edit mode starts paused), so an effect slows and stops with the world | ```wgsl // @domain: sky fn fragment(in: SkyInput) -> vec4<f32> { let up = max(in.ray_dir.y, 0.0); let col = mix(material.horizon_color.rgb, material.zenith_color.rgb, up); return vec4<f32>(col * material.exposure, 1.0); } ``` Day/night comes from `sun_direction.y` (the directional light's elevation), so a sky shader never needs a time-of-day uniform — orient the light and the sky follows. The builtin sky shaders (`procedural_sky`, `solid_sky`, `cubemap_sky`, `equirect_sky`) are all authored this way; author a custom sky material and point a `Skybox` component at it. ## Post-process & screen shaders `// @domain: post-process` and `// @domain: screen` shaders are authored exactly like surface and sky — you write **only** `fn fragment(in: PostInput) -> vec4<f32>` (post) or `fn fragment(in: ScreenInput) -> vec4<f32>` (screen) and declare tunables in `properties.yaml` (read as `material.<name>`, textures via `textureSample(<name>, <name>_sampler, uv)`). The engine generates the fullscreen `vs_main`/`fs_main` and the group(1) material interface. **There are no `uniforms.params[i]` slots** — that convention is retired; every input is a named property. A **post-process** shader's `properties.yaml` carries one further, top-level key beside `properties:` — `space`, either `light` (the default) or `display`: ```yaml space: display properties: - { name: amount, type: float, default: 1.0, min: 0, max: 1 } ``` `light` is the scene's linear radiance — what every surface, the sky and every `afterLighting` feature write, unbounded above 1.0. `display` is the code values the `__display__` pass leaves behind after applying exposure and its tone curve — the 0-1 range a colourist's tool and a dithered or quantized effect expect. `postprocess.add`'s `opts.space` overrides what the asset declares for one registration. The chain converts at both ends of an effect that runs on a segment in the other space, so a light-space vignette still darkens a frame graded after `__display__`, and a lookup table built from a `.cube` export always sees the code values it was authored against, wherever the chain runs it. `space` also decides which layer a registration that names none lands on: a `light` shader grades `scene`, the segment holding the scene's own light, and a `display` shader grades `all`, the picture after `__display__` with the UI on it. So `postprocess.add("glow", asset.resolve("~.shaders.bloom", "shader"))` thresholds highlights that still stand above 1.0, and a lookup table registered the same way reads the code values it was built for. `opts.layer` names one explicitly — `"all"` is what an effect that must grade the interface says. A **post-process** shader's `properties.yaml` carries a further, optional top-level key — `passes:`, the pass list the frame draws through, in order: ```yaml space: light passes: - { name: bright, entry: bright, scale: 0.5, inputs: [scene] } - { name: down1, entry: downsample, scale: 0.25, inputs: [bright] } - { name: up0, entry: upsample, scale: 0.5, inputs: [down1, bright] } - { name: composite, entry: composite, inputs: [scene, up0] } ``` Every pass's entry — `fn <entry>(in: PostInput) -> vec4<f32>` — lives in the one `shader.wgsl` the assetType recompiles on. `scale` is the fraction of the view a pass draws at; the LAST pass takes none, since it draws at the view's size and writes the chain's output. `inputs` names what a pass reads — `"scene"`, the chain's input for this effect, or the name of an EARLIER pass — and `inputs[0]` is what `zero_sample_scene(uv)` reads inside that pass's body; every input, `inputs[0]` included, is also reachable by index through `zero_pass_input(i, uv)` and `zero_pass_input_size(i)`, below. The one place the two reads of `inputs[0]` disagree: in an effect whose declared space differs from the segment it draws on, `zero_sample_scene` converts a `scene` input into that space while `zero_pass_input(0, uv)` hands back the segment's own, unconverted value. A shader declaring no `passes:` is one pass whose entry is `fragment`, and its generated WGSL is byte-identical to what it is without the key. A pass that is not the last writes a scratch target the effect owns — in the space the shader declared, view-sized times its own `scale` — allocated on the first draw and replaced whenever the size changes. `engine.params`, below, carries the drawing pass's own index, its scale, and its first input's texel size, so one shader body serves every level of a chain built this way. The worked example is the bloom: `@builtin::shaders.post.bloom` declares twelve passes — a threshold pass, five downsamples, five tent upsamples and a composite — out of four entries, since the five downsamples share one and the five upsamples share another, each level reading the one below it through `zero_pass_input` and telling itself apart by `engine.params`. Its own README walks the declaration. A declaration is refused at compile time — reported through `compileStatus()`, `postprocess.add`'s second return value, or a live effect's `status()[i].error` — for: an entry `passes:` names that `shader.wgsl` does not define; an input naming a later pass, or naming neither `scene` nor an earlier pass; a `scale` outside `(0, 1]`; a `scale` declared on the last pass; a `buffer` property (group(2) carries the pass inputs now); or a shader whose group(0) plus declared texture slots plus widest pass's inputs ask for more than the 16 FRAGMENT sampled textures one shader stage has. A **post-process** shader runs as a full-screen pass over the already-rendered frame. Its `fragment` argument and framework helpers: `PostInput`: | Field | Type | Meaning | |---|---|---| | `frag_coord` | `vec4<f32>` | framebuffer pixel coords (`@builtin(position)`) | | `uv` | `vec2<f32>` | screen UV, `(0,0)` top-left … `(1,1)` bottom-right | Framework helpers (always in scope — no include needed): | Call | Returns | Meaning | |---|---|---| | `zero_sample_scene(uv)` | `vec4<f32>` | the rendered scene colour at `uv`, converted into the space this effect declared (`zero_scene_light` is the same call, for content that reads it by that name) | | `zero_scene_depth(uv: vec2<f32>)` | `f32` | scene depth at `uv` — a screen UV here, where the surface domain's `zero::scene_depth` module takes a pixel coordinate under the same name (exact texel — an R32Float copy). Reversed: 1.0 is the near plane, 0.0 the far plane and empty sky, so a nearer surface reads GREATER and `d > 0.0` means "a surface was drawn here" | | `zero_linear_depth(d, near, far)` | `f32` | that sample as a distance in metres — the one inversion of the reversed range | | `zero_scene_motion(uv)` | `vec2<f32>` | per-pixel screen-space motion vector at `uv` | | `zero_pass_input(i, uv)` | `vec4<f32>` | the pass's declared input `i`, at `uv`. Input 0 is what `zero_sample_scene` reads | | `zero_pass_input_size(i)` | `vec2<f32>` | that input's size in texels, so one entry serves every level of a chain | Engine data uniform `engine` (a `PostEngineData`): | Field | Type | Meaning | |---|---|---| | `resolution` | `vec4<f32>` | `x`=width, `y`=height, `z`=1/width, `w`=1/height | | `time` | `vec4<f32>` | `x`=elapsed seconds, `y`=dt, `z`=frame index | | `view_proj` | `mat4x4<f32>` | this frame's view-projection | | `prev_view_proj` | `mat4x4<f32>` | last frame's view-projection (motion) | | `inv_view_proj` | `mat4x4<f32>` | inverse view-projection (world-space reconstruction) | | `params` | `vec4<f32>` | `x`=this pass's own index, `y`=the scale it draws at, `zw`=1/size of its first input — for a pass the post-process chain draws. A pass a `renderFeature` fragment pass draws carries that feature's `spec.params` here instead; a shader declaring `passes:` is always drawn by the chain, so the two never meet in one shader. | The engine fills all of it **per render target**. A registered effect runs over the live viewport's frame AND over every offscreen one — a `capture` from a world-space station or orbiting an entity, a capture of a named camera, a render-to-texture camera — and in each of those, `view_proj`, `prev_view_proj` and `inv_view_proj` are the camera THAT render was drawn from, while `resolution` is that target's own pixel size. So a pass reconstructing world space from `zero_scene_depth(uv)` reconstructs against the station and lens the capture asked for, and an offscreen frame is a picture of the effect as it stands at that station. (A render feature's passes reach an offscreen render the same way, against the same camera — the `renderFeature` assetType README carries that half, including `@frame.camera`, its own per-target camera input.) An offscreen render keeps no view history of its own, so `prev_view_proj` there holds that same matrix rather than the frame before it, and a pass taking camera motion from the two reads none. On the viewport the pair is a frame apart, so camera motion is the one reading a capture answers differently from the screen. `postProcessing = false` on a capture is the one control that takes the chain off the frame it returns; it names the camera property the ephemeral capture camera is built with, so it scopes to that one capture. What a capture opts out of is the registered effects; `__display__` still runs on it, so the exposure and tone curve that turn the scene's light into a picture are on what a capture returns. A diagnostic capture (`albedo`, `normal`, `motion_vectors`, …) bypasses `__display__` itself, since a channel like that is a reading of the scene rather than a graded picture of it. The environment-cube capture bypasses it too, and for the same reason: a probe face carries radiance into the cube array, and `__display__` would fit that radiance to a display's code values — a picture of it rather than the value the PBR indirect term multiplies into its lighting. A complete post-process effect — a vignette via `fragment()` + `properties.yaml`: `properties.yaml`: ```yaml properties: - { name: intensity, type: float, default: 0.5, min: 0, max: 1 } - { name: radius, type: float, default: 0.75, min: 0, max: 1 } - { name: softness, type: float, default: 0.45, min: 0, max: 1 } ``` `shader.wgsl`: ```wgsl // @domain: post-process fn fragment(in: PostInput) -> vec4<f32> { let color = zero_sample_scene(in.uv); let intensity = max(material.intensity, 0.01); let radius = max(material.radius, 0.01); let softness = max(material.softness, 0.01); let center = in.uv - vec2<f32>(0.5); let dist = length(center); let vignette = smoothstep(radius, radius - softness, dist); let darkened = color.rgb * mix(vec3<f32>(1.0), vec3<f32>(vignette), intensity); return vec4<f32>(darkened, color.a); } ``` The asset above **defines** the effect. It enters the frame when something registers it: ```luau postprocess.add("vignette", asset.resolve("~.shaders.vignette", "shader"), { priority = 200 }) ``` The registration names no layer, so the effect grades the layer its `space` belongs to: this vignette reads light, so it runs on `scene`, over the picture before the UI reaches it. Registering it is the one step that makes it render, so a world's chain holds exactly the passes its content asked for. Editing the shader body afterwards recompiles every effect registered from it, in place — the pass keeps its enabled state, priority, layer, tuned property values and bound textures, and draws the new pixels on the next frame. `postprocess.remove(name)` takes it back out of the chain and leaves the asset alone. Drive the named properties at runtime with `postprocess.setProperty(name, prop, value)` and bind texture properties with `postprocess.setTexture(name, prop, path)` (both keyed by the **property name**, never a slot index — see the post-process section of `man shaders` / the `postprocess.*` API). Read them back with `postprocess.describe(name)`: it carries the chain state `postprocess.status()` lists for that effect, the `properties` schema it was registered with, and the `values` each of those properties currently holds. Before the effect exists, `shaderRef:getProperties()` on the asset names the same schema, so what a pass takes is answerable either side of the registration. A **screen** shader is a standalone full-screen visual (UI background, procedural pattern). `ScreenInput` mirrors `PostInput` (`frag_coord` + `uv`); there is no scene to sample, so it has no `zero_sample_scene` helpers. Its `engine` uniform is a `ScreenEngineData`: | Field | Type | Meaning | |---|---|---| | `time` | `f32` | gameplay seconds: advances with the world at `engine.timeScale` and stands still while gameplay is paused (edit mode starts paused), so an effect slows and stops with the world | | `scroll` | `f32` | UI scroll offset | | `resolution` | `vec2<f32>` | render-target size in pixels | | `mouse` | `vec2<f32>` | mouse position | | `velocity` | `f32` | scroll velocity | ```wgsl // @domain: screen fn fragment(in: ScreenInput) -> vec4<f32> { let t = engine.time * 0.5; let col = vec3<f32>( sin(in.uv.x * 3.14159 + t) * 0.5 + 0.5, sin(in.uv.y * 3.14159 + t * 0.7) * 0.5 + 0.5, material.brightness ); return vec4<f32>(col, 1.0); } ``` ## Library includes A library module is a **`.shaderModule` asset**: it only EXPOSES functions and structs and does nothing on its own (exactly like a Unity `.cginc`). You must call what you include. Include one by its identity, the same string you would hand `asset.resolve`: | Include | Exposes | |---|---| | `@builtin::shaderModules.pbr_shading` | `struct PbrSurface { albedo, normal (world), metallic, perceptual_roughness, emissive, occlusion }`; `zero_pbr_default_surface(FragmentData) -> PbrSurface`; `zero_pbr_shade(FragmentData, PbrSurface) -> vec3<f32>` (the full forward PBR lighting) | | `@builtin::shaderModules.shadows` | `compute_directional_shadow_factor(...)`, `compute_spot_shadow_factor(...)`, `compute_point_shadow_factor(...)`, `compute_area_shadow_factor(...)`, `compute_punctual_shadow_factor(...)`, `zshadow_light_reach(...)` | | `@builtin::shaderModules.engine_bindings` | the group(0) declarations (camera, transforms, lights, shadow maps) — surface shaders get this implicitly; include it directly only for advanced raw access | | `@builtin::shaderModules.shadow_bias` | `zshadow_offset_receiver(...)`, `zshadow_directional_depth_bias(...)` and the rest of the bias math, as pure functions | | `@builtin::shaderModules.texturing` | `ztex_stochastic(...)` (tile without a visible repeat grid), `ztex_blend_normals(...)` (reoriented normal blending) | | `@builtin::shaderModules.depth` | `zero_linear_depth(depth, near, far)` — the one reading of a stored depth | | `@builtin::shaderModules.gbuffer_material` (`zero::gbuffer_material`) | `struct ZeroGbufferMaterial { base_color, metallic, perceptual_roughness }`; `zero_gbuffer_unpack_material(texel: vec4<u32>) -> ZeroGbufferMaterial`; `zero_gbuffer_material(t: texture_2d<u32>, coord: vec2<i32>) -> ZeroGbufferMaterial`, `zero_gbuffer_base_color`/`zero_gbuffer_metallic`/`zero_gbuffer_roughness(t, coord)` — the one unpacking of `@scene.material`'s `Rgba8Uint` texel into what a surface reflects | | `zero::scene_depth` | `zero_scene_depth(px: vec2<f32>)`, `zero_scene_depth_uv(uv: vec2<f32>)`, `zero_scene_depth_texel(px: vec2<i32>)`, `zero_scene_depth_size()`, `zero_scene_depth_is_sky(d: f32)`, `zero_scene_world_position(px: vec2<f32>)`, `zero_scene_world_normal(px: vec2<f32>)`, `zero_scene_depth_fade(px: vec2<f32>, world_position: vec3<f32>, fade_distance: f32)` — every `px` is a pixel coordinate in two components, so a surface fragment passes `input.frag_coord.xy`, not the `vec4<f32>` `FragmentData.frag_coord` holds. The depth already drawn UNDER a surface fragment, and the world position and geometric normal of the surface standing there. What a decal projector box, a soft particle, a forcefield or water intersection foam shades against. Surface domain; the depth belongs to the view being drawn | | `zero::scene_color` | `zero_scene_color(px: vec2<f32>)`, `zero_scene_color_uv(uv: vec2<f32>)`, `zero_scene_color_texel(px: vec2<i32>)`, `zero_scene_color_size()`, `zero_scene_color_refract(px: vec2<f32>, offset_px: vec2<f32>)`, `zero_scene_color_refract_uv(px: vec2<f32>, offset_fraction: vec2<f32>)` — every `px` is a pixel coordinate in two components, so a surface fragment passes `input.frag_coord.xy`, not the `vec4<f32>` `FragmentData.frag_coord` holds. The scene colour already composed BEHIND a surface fragment, and the displaced read that bends it. What heat haze, a refraction shockwave, a cloaking or shield warp, glass and ice shade with. Surface domain; the colour belongs to the view being drawn, and is the lit opaque scene as it stood immediately before the transparent pass — so a `blend`-queue surface reads this frame's, an opaque one reads the previous frame's, and two overlapping blended surfaces both read the same picture and do not bend each other | `asset.list("shaderModule")` enumerates the `.shaderModule` assets in this engine, builtin and world-authored alike, and each one's README says what it exposes. Those are the `@builtin::shaderModules.*` rows above; a module you write is included exactly the same way, by its own identity or by the package-relative `~.name` form. The `zero::`-named rows come from the renderer itself. Their WGSL is baked into the engine binary and registered under those names before any asset exists, so they answer an `#include` in every engine and appear in no asset index. A shader that includes one records no dependency on it: the engine reading the shader is the engine that already holds the module. Two spellings reach the same `.shaderModule`: an earlier name is kept working through the module's declared alias, so a shader written against `zero::pbr` still compiles and still pins the asset that name resolves to. Newly written shaders should use the identity — it says which asset travels with the content. Whichever punctuation an include is written with — `#include "name"`, `#include 'name'` or `#include <name>` — names the same module and records the same dependency. The engine's own scaffolding — `zero::surface`, `zero::sky`, `zero::post`, `zero::screen` — is injected by the compiler around the matching domain and is never written by hand. The surface framework puts `safe_normalize`, `mat3_from_mat4` and `apply_normal_map(FragmentData, tangent_normal)` in scope for every surface shader. ## Shader features — compile-time variants A **property** is runtime uniform data (a colour, a float, a texture): set per material, read as `material.<name>`, no recompile. A **feature** decides which code is in the program at all. Use a property when the value changes at runtime, a feature when it changes what the shader is. Declare features in `properties.yaml`, alongside the properties: ```yaml properties: - { name: base_color, type: color, default: [1, 1, 1, 1] } features: - { name: PARALLAX, default: false, description: silhouette parallax march } - { name: DETAIL, default: true, description: detail-normal overlay } ``` Guard the code each feature owns with `#ifdef`: ```wgsl fn surface(input: FragmentData) -> PbrSurface { var s = zero_pbr_default_surface(input); #ifdef PARALLAX s.normal = parallax_normal(input); // absent when PARALLAX is off #else s.normal = input.world_normal; #endif return s; } ``` `#ifdef` / `#ifndef` / `#else` / `#endif`, one per line, and they nest. The directives resolve before the WGSL reaches the compiler, so the program holds exactly the lines its feature set selected and every other line is an empty one, which keeps a compiler message on the line number the file shows. An unbalanced block is a compile error naming its line. A material is what chooses a feature set, so `features:` shapes the shaders a material draws with — the surface, sky and screen-space domains. A material names the features it wants in its `mat.yaml`: ```yaml name: worn_rock shader: "@builtin::shaders.pbr_layered" features: PARALLAX: true # on, over the shader's default DETAIL: false # off, against the shader's default ``` or through `asset.create`: ```lua asset.create("material", "worn_rock", { shader = "@builtin::shaders.pbr_layered", features = { PARALLAX = true, DETAIL = false }, }) ``` The engine compiles one program per feature set its materials ask for, named `<shader>#<features>`. Materials sharing a set share that program. A feature the shader does not declare selects nothing, so a stray name cannot make the engine compile anything, and the compile names both halves of a mismatch: a guard on a name `features:` does not declare, and a declared name no guard tests. **Permutations are the cost.** A shader with n features can express 2^n programs, each its own compile and pipeline. One shader holds at most 32 variants; a material asking for a set past that draws with the shader's default features and the engine logs which shader ran out. Read what a scene is spending: ```lua for _, s in renderer.shaderVariants() do print(s.shader, #s.variants, "of", s.budget) print(renderer.variantSource(s.base.program)) -- what it ships as for _, v in s.variants do print(v.program, renderer.variantSource(v.program)) -- what one asked for end end ``` A shader registers under every key it answers to — its identity, its guid, each alias — and each key is a row. A variant lands on the row for the key the material named, which for authored content is the guid, so take a program name from the report rather than composing one. ## Materials reference shaders A `.material` applies a shader to entities. Its `mat.yaml` references the shader by its identity string and supplies property values: ```yaml name: my_material shader: "@builtin::shaders.pbr" render: blend: alphaBlend cull: back depth_write: false floats: roughness: 0.5 colors: base_color: { r: 1.0, g: 1.0, b: 1.0, a: 1.0 } textures: base_color_texture: { ref: "default:white" } ``` `shader:` is a plain identity string, and each `colors:` entry is an `{ r, g, b, a }` map — the two forms `mat.yaml` accepts for those keys. A key's value is the rest of its line, so every value above stands alone on one. ### The render block Render behaviour that used to be material "flags" — the blend equation, alpha cutout, which faces are drawn — lives in the `render:` block and drives the pipeline, not the fragment. These are the keys that reach the pipeline from both authoring routes, and the values each one takes: | Key | Values | Sets | |-----|--------|------| | `blend` | `opaque` `transparent` `alpha` `alphaBlend` `additive` `add` `cutout` `alphaCutout` `premultiplied` `premultipliedAlpha` `multiply` | the equation the fragment composites with | | `cull` | `back` `front` `none` `off` `disabled` | which faces the rasterizer keeps | | `depth_write` | `true` `false` | whether the draw writes depth | | `depth_compare` | `less` `lessEqual` `lequal` `equal` `greater` `greaterEqual` `gequal` `always` `never` | the test a fragment's depth passes | | `topology` | `triangleList` `lineList` `lines` `line` | what consecutive vertices assemble into | `blend` is also spelled `type`, and the two name one key. Its equations, over the fragment the shader returned (`src`) and the value already in the target (`dst`): `opaque` is `src`; `transparent`, `alpha` and `alphaBlend` are `src * src.a + dst * (1 - src.a)`; `additive` and `add` are `src + dst`, the mode a glow, a light shaft or a spark card is written for; `premultiplied` and `premultipliedAlpha` are `src + dst * (1 - src.a)`, taking a source that already carries its own coverage; `multiply` is `src * dst`, which is how a soot, grime or shadow card darkens what stands behind it. `cutout` and `alphaCutout` keep the fragment or discard it on its alpha and go on writing depth. The same block is what `asset.create`'s `render` argument takes, key for key and value for value, so one material named in Luau and the same material standing on disk ask for their pipeline with the same words. `depth_write` is the one key whose value takes the shape of its route: the word `false` on a `mat.yaml` line, the boolean `false` in the Luau table. ```lua asset.create("material", "heat_plume", { shader = "@builtin::shaders.pbr", render = { blend = "alphaBlend", cull = "none", depth_write = false }, }) ``` Where a value outside a key's set is reported is what the two routes differ on. `asset.create` refuses the call on any of these keys and names the set it measured the value against. A `mat.yaml` standing on disk registers either way, each key falling back to a value of its own: `blend` to `opaque`, `cull` to `back`, `depth_write` to `true`, `depth_compare` to `less` and `topology` to `triangleList`. The engine log carries the blend fallback, naming the value and the set it was measured against, so a `mat.yaml` value is worth putting through `asset.create` once — that is where every key answers with its set. ## Registration & hot reload A `.shader` is compiled by the asset system, not by the renderer: writing `shader.wgsl` or `properties.yaml` fires the `.shader` assetType's `onChange`, which calls `shader.compile` — that reads the body + the property schema, generates the group(1) interface and (for surface) every render-mode entry point, expands `#include`s, **validates the result with naga**, and registers it. Validation happens at this compile step — the whole point of "compile". A shader with invalid WGSL (an unknown field, a type mismatch, an undefined function) **fails to compile** with the real reason — readable directly from Luau via `shaderRef:compileStatus()` (`{ status = "compiled" | "failed" | "pending", error?, pending? }`), and also in the author log and `asset.inspect`; it is **not** registered. This fires on create and on every edit, so saving a `.wgsl` recompiles with no world reload; the change is visible on the next frame. Compilation is async, so a `compileStatus()` of `"pending"` immediately after a write means check again next frame. A surface shader is also checked for the material resolve, the pass that shades each pixel of the visibility buffer through the shader's own code. That check reaches its verdict a few frames after the raster compile. Until it does, `compileStatus()` reads `"pending"` with `pending` saying so, and the shader already draws. A shader the check refuses reads `"failed"`, and `error` names the construct the resolve cannot evaluate and where it sits; its pixels resolve through the error shader until it changes. The stage the compile checks comes from one of two places: the hook the engine scaffolds entry points around (`fragment()`, or `surface()` for an engine-lit surface), or the `vs_main` / `fs_main` pair the body writes itself. The pair is a pair: a body that writes its own entry points owes both stages. A body carrying neither route — a hook whose name is a letter off, say, or half a pair — holds no stage the rasterizer can enter, so the compile **refuses it** and names both the entry point it looked for and what the body carries, in the same `compileStatus()` error every other compile failure reads back through. ### Reading a compile error against the text it is about What the compiler reads is not the file you wrote. The engine generates the group(1) material interface from `properties.yaml`, wraps the body in its domain's framework and every entry point that domain needs, expands every `#include`, and resolves every `#ifdef` — so a 100-line body reaches naga as tens of thousands of lines. **Every line number in a compile error, and every `[N]` handle index naga prints where it has no name to print, is a position in that composed module.** A fault at module scope (`no definition in scope for identifier: 'zero_scene_depth'`) reads fine without it; a fault inside a function body does not. `renderer.compiledSource(name)` returns that composed module, and `shaderRef:compiledWgsl()` returns it for a ref you already hold. Both answer for a shader that declares no features, needs no material, entity or draw, and — the case they exist for — **answer for a shader whose compile failed**, holding the text the compiler was refused over for as long as `compileStatus()` reports that failure. `renderer.compiledShaders()` lists every name they answer for. ```lua local ref = asset.resolve("myShader", "shader") local status = ref:compileStatus() if status.status == "failed" then print(status.error) -- the line, the caret, and the cause local wgsl = ref:compiledWgsl() -- the text those positions are in local line = tonumber(string.match(status.error, "wgsl:(%d+):")) print(string.split(wgsl, "\n")[line]) end ``` The composed text carries every `zero::*` module the shader included, so the signature a call was rejected against is in the same text as the rejection — which is the whole of what a "wrong argument type" error needs to be actionable. A material bound to a broken (or missing) shader renders with the **magenta error shader** — never invisibly — so a shader problem is impossible to miss on screen as well as in the log. **Fixing the shader and re-saving recovers it live**, with no engine restart: the recompile clears the failed-shader state and the object returns to normal on the next frame. ## Discovery - `asset.list("shader")` — every registered shader. - `asset.inspect("<name>")` — domain, status, source, parse errors, this README. - `shaderRef:compileStatus()` — did it compile? `{ status, error?, pending? }`, no log needed. `"pending"` with `pending` set means the material resolve check is still reaching its verdict; a resolve refusal reads as `"failed"`. - `shaderRef:compiledWgsl()` / `renderer.compiledSource("<name>")` — the WGSL the compiler received, which is what a compile error's positions index into. Answers for a failed compile too. - `renderer.compiledShaders()` — every name that call answers for. - `shaderRef:getProperties()` — the parsed `properties.yaml` schema. - `shaderRef:listMaterialsUsing()` — materials bound to this shader. ## Common pitfalls - **A compile error shows up in one of three ways at the draw.** A shader that never compiled has no pipeline, so the renderer binds the magenta placeholder. A shader that compiled once and was then edited into brokenness KEEPS the pipeline that build produced — the surface goes on drawing the last good program, pixel for pixel, and looks entirely intact while the source is broken. A geometry-pass-only shader has no magenta tell either, since it is not on a forward mesh. `shaderRef:compileStatus()` gives the status + error text (as does `asset.inspect("<name>")`), and `renderer.drawDiagnostics()` names which renderables are in which of the three states — a row carries `substituted` for the placeholder, `stale` for a program that no longer compiles, and the cause either way. - **A compile error's line numbers are lines of the composed module, not of your file.** `renderer.compiledSource("<name>")` / `shaderRef:compiledWgsl()` is that module; resolve the position against it rather than counting lines in `shader.wgsl`. The `[N]` a message prints in place of a name is a naga handle index — it moves with the size of the body and is the same value for two unrelated faults in one file, so it is neither a line number nor a way to tell two failures apart. - **Don't declare group(0) or group(1) in a surface shader.** The engine owns group(0) and generates group(1) from `properties.yaml`. Re-declaring them is the fastest way to a layout mismatch. - **`#include` does nothing by itself** — it only exposes functions; you must call them. - **Renaming a property** changes the generated uniform field; materials setting the old name silently fall back to its default. - **Compute shaders don't render** — verify output via a buffer readback or a debug pass. Author them as a `.computeShader` (its own assetType), not a `.shader` — see `man compute`. ## Related types - `.material` — the required wrapper that applies a shader to entities. - `.style` — UI cascade, not GPU shaders. ## In the Inspector Selecting a shader opens its **Shader** section: its domain and shading model (and, for a post-process shader, the space its `fragment()` reads and returns), whether it compiled (and the compiler's error when it did not), a table of its declared properties (type, default, range), its post-process passes when it has any, the bindings it declares, and openers for its source. The **Materials** section (collapsed at first) has a Find materials action that lists, as links, every material drawing with the shader; it scans every material, so it runs only when asked.

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

# modules.api.engine.dirty_hot_reload Picks up dirty-overlay changes from disk while a scene is loaded in edit mode, applies them to the live entities, and keeps the in-memory representation in lockstep with `scene_dirty/` files. Pairs with `scene_saver` (writes deltas) + `scene_loader` (composes canonical + overlay at load time). ## Parents A record's `parent` names the entity it stands under: the entity whose id is that text, else the entity whose display name is exactly that text. A `*` or `?` in it is a character of the name, never a pattern. A record whose parent no entity provides waits. An entity that does not stand yet is not built, one that already stands keeps its state, the layer logs the record once, and `debugState(guid).waiting` maps its id to the parent it names. While a record waits, the scene saver leaves it as it stands rather than writing a standing entity's older state over it, until an author edits that entity, which the saver then records as it stands. When a record builds an entity, the records waiting on that entity's id or display name are built under it, so a child record that arrives before its parent's record lands where a load of both places it. Each waiting record is built as its overlay file states it at that moment, so a record rewritten while it waited, including by this session's own saver, builds from its current bytes. A load gives the same account of a record whose parent stays missing: the loader abandons it with `parentMissing`.

# playerSetupValidation Agent-facing validation for authored player setups. A player-spawn scene is built from PlayerSpawn entities (each naming a PlayerPrototype subtree to instantiate on join) and PlayerPrototype roots (marked PrototypeOnly, carrying a Camera in their subtree and a `body` field naming the entity to adopt). `checkEntity` inspects one such entity and returns human-readable messages that name what is wrong and what to do about it; `checkScene` validates the scene's player intent against its PlayerSpawn / Camera counts; `checkActiveScene` runs both across the live active-layer scene and returns a flat `{ entity, message }` list — the queryable surface an agent reads to see what to fix. `checkActiveScene` answers for the settled scene: it holds while a scene load or a mode-flip transition is rebuilding the live tree, then judges what the rebuild lands on. Each PlayerSpawn's prototype resolves wherever the materialisation holds it — the live entity in edit, and in play, where the loader keeps authored prototype subtrees out of the scene, the captured authored template each joining player is cloned from — so the same rules run over the same authored structure in both modes, and a prototype removed from a scene that materialises prototypes reads as the missing reference it is. Location: `src/lua/lib/modules/api/engine/playerSetupValidation.module`

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

# scene_build Turns builder code into scene records, and scene records into scene entities. `run(builder)` opens an entity capture scope, calls `builder`, and composes every entity it created into records — then despawns them. The builder writes ordinary spawn code; what comes back is data. A builder that raises leaves nothing behind. What a component the builder attached creates while running its own lifecycle belongs to that component: the record names the COMPONENT, and the same lifecycle runs again wherever the record is put back. That is what makes a nested build one build — a placement the builder makes runs its own module and owns what it lands, and the build around it describes the placement. `reconcile(records, target, owner)` applies records to the scene under `target`, writing `owner` and the record's place in the hierarchy onto each entity it places as the `buildOwner` / `buildKey` attributes. A rebuild reads that pair back off the entities under `target` and lands on the same ones, so nothing has to be remembered between two rebuilds — the pair is in the scene, and a reload brings it back with the entity. It returns the ids it landed on, keyed by record identity. A record is identified by its place in the hierarchy — the chain of names from the build root down to it, `base/coin_3` — so dropping a line from the middle of a builder, inserting one, or emitting two entities in the other order leaves every other entity's id where it was. Children of one parent that share a name carry their rank among those, `base/crate#2`, counted in the order the builder created them. Together these are the bake: code in, durable static-id scene content out. ## Who states an entity An entity names the build that placed it, so `ownerOf(id)` answers which build owns it — and answers nil for an entity an author spawned. `sourceOf(owner)` names the file that build is written in, from the `source` the reconcile running it passed. That pair is what makes ownership legible where an author meets it. A build states its entities in full every time it runs, so a value set on one of them holds until the next run. `notePreview(id, values)` records what the entity carries after such a change and `takePreview(id)` reads it back exactly once — in the run that states the entity again, which is where what the author set and what the build says can be named side by side.

# `scene.shared.loader` Luau-side scene loader. Reads `scene.json` v6, dispatches to engine FFIs, runs the sibling `entrypoint.luau`. ## Public surface ```lua local loader = require("@builtin::assetTypes.scene.shared.loader") loader.load(ref, opts?) -- ref: AssetRef<scene> | identity string | VFS path -- opts.layer: layer name (default "main") -- Returns: the Scene proxy (with player_config + camera_config attached). loader.unload(layerName) -- Wrapper around layers.unload(name); symmetric to M.load. -- Cannot unload "main". ``` ## Behavior 1. Resolve `ref` to a VFS path; append `/scene.json` if needed. 2. `vfs.read` + `Json.decode` (from `modules.json`) → body table. 3. Version check — refuse anything but `version: 6`. 4. Attach `body.player` + `body.camera` to the Scene proxy as `player_config` / `camera_config` (consumed by player_spawner + camera_spawner). 5. Activate the target layer via `layers.find(layerName)` (the loader threads the layer through `entity.spawn` opts), spawn `body.entities` in two passes (shells + transforms first, parents + components second), then restore the previous active layer. 6. Apply `body.lighting` via `lights.setup` + `lights.addPointLight`. Field name mapping: `directional` → `sun`, `clear_color` → `clearColor` (both engine API names and v6 field names are accepted). 7. Auto-discover sibling `entrypoint.luau` via `vfs.exists`; if present, compile with `loadstring` + run. ## Performance ~5 ms for a 1000-entity scene (≈5k FFI calls × ~1 µs each). Acceptable for a load-time operation. If a particular call class becomes hot, batch primitives can be added in a narrow follow-up. ## Why pure Luau Per § 10 of the unification integration design, the scene format is data + dispatch — no Rust-only primitives needed. The existing ECS FFI (`entity.spawn`, `entity(id).component.add`, etc.) covers everything. Keeping the loader in Luau means iteration speed, auditability, and hot-reload. ## FFI corrections vs. the original plan The plan was drafted against assumed API names. The actual engine FFIs differ: | Plan assumed | Actual engine API | |---|---| | `json.parse(s)` | `require("..json").decode(s)` (`modules.json`) | | `json.encode(t)` | `require("..json").encode(t)` | | `entity.spawn(n, { layer }).id` | layer activation via `layers.find(layer)` + `entity.spawn(n, opts).id` | | `entity.setParent(id, pid)` | `entity(id).setParent(pid)` | | `unloadLayer(name)` | `layers.unload(name)` | | `lights.setup({ directional })` | `lights.setup({ sun })` | | `lights.setup({ clear_color })` | `lights.setup({ clearColor })` | | `lights.addPointLight(table)` | `lights.addPointLight(name, x, y, z, opts)` | The loader accepts both the v6 field names and the engine API names for the lighting fields so that round-tripping through the scene saver and back works without a conversion step.

# scene_observe The record of what a scene load did, and what each loaded scene costs. Backs `layers.observe`, `layers.lastLoad`, `layers.lastUnload`, `layers.loadHistory`, `layers.problems`, `layers.whyPartial`, `layers.inventory`, `layers.cost` and `layers.resetCostWindow`, and the `scene` toolbox's `observe`, `whyPartial` and `cost` above them. `layers` and `scene_loader` are its writers. ## One record per load A load opens a record; the loader, the lifecycle dispatchers and the scene's own build write their failures and phase timings into it; the load's own completion point closes it with the duration the engine already measured for its `DONE` line. Reading is lazy — nothing here walks the world, and the only writer that runs every frame is `noteUpdate`, which the entrypoint tick calls once per scene that declares one. ```lua local r = layers.lastLoad() print(r.name, r.outcome, r.durationMs) print(r.entities.added, "arrived,", r.entities.removed, "left") print(r.phases.teardown, r.phases.instantiate, r.phases.settle) ``` `outcome` is `"ok"` when everything the scene declared was produced, `"partial"` when the load finished with failures in it, `"failed"` when the load raised and left no layer, and `"unchanged"` when the scene asked for was already the active root — that load rebuilt nothing, so the layer keeps the record of the load that built it and still answers why it is not whole. `reason` names the nearest cause from the closed set — `loaderRaised`, `entrypointCompileFailed`, `entrypointBodyRaised`, `entrypointRaised`, `buildRaised`, `entityFailed`, `parentMissing`, `parentRefused`, `parentAbandoned`, `componentUnresolved`, `componentRefused`, `subscriberRaised`, `updateRaised` — ranked so it names the thing to fix rather than the last thing to break. ## Failures reach the layer they belong to Every write of a failure calls the subscriber `layers` registers through `M.onFailure`, which republishes the record onto that layer's proxy: `ok` false, `failures` the records, and `"partial"` in place of `"ready"` once the layer has settled. A tick that starts raising on frame 400 moves the layer the same way one raised during the load does. A failure identical to one already held raises that one's `count`, so a tick raising every frame keeps one record. `FAILURE_LIMIT` bounds the distinct records a report holds, and `failuresOmitted` states how many arrived past it. ## Cost `noteUpdate` accumulates each layer's entrypoint tick into a per-guid entry — calls, total, last, max, average and how many raised — summed across the window `M.window()` reports. `M.resetWindow()` opens a new one, leaving the load history alone. An unload drops the layer's entry.

# `scene.shared.saver` Luau-side scene saver. Writes `scene.json` v6 — **authored intent only**. No captured runtime state. ## Public surface ```lua local saver = require("@builtin::assetTypes.scene.shared.saver") saver.save(name, opts?) -- name: logical scene name ("main") OR full VFS path -- opts.layer: layer name to read from (default layers.active.name or "main") -- Returns: the absolute VFS path written. ``` ## What is captured | Field | Source | Notes | |---|---|---| | `format`, `version` | constants | Always `"scene"` + `6`. | | `entities` | `entity.findAll()` walk | Excludes `temporary` entities + the spawner-managed Player + primary Camera. | | `entities[].transform` | local position / rotation / scale | NOT world transform — local only. | | `entities[].components` | component.list + component.get | Strips `_`-prefixed runtime fields. | | `entities[].attributes` | `attribute.list` + `attribute.get` | The entity's key/value bag, written as a `{ [key] = value }` map; omitted for an entity that holds none. Holds the authored keys — a `_`-prefixed key is the engine's own session bookkeeping. | | `lighting` | `lights.snapshot()`, filtered | Scene-level `clear_color` + `sky` only. Directional / ambient / point lights persist as `Light` entities in `entities[]`. | | `player` | `sceneProxy.player_config` | Carried forward from load-time, authored only. | | `camera` | `sceneProxy.camera_config` | Carried forward from load-time, authored only. | ## What is NOT captured - Local player's position / rotation. Runtime drift; not authored intent. - Primary camera's transform. Runtime; behavior-driven. - Any entity flagged `temporary = true`. Debug helpers, runtime markers. - Internal component fields prefixed with `_` (e.g. `_velocity` on CharacterController). The spawner-managed entities (Player + primary Camera) are excluded because they're created on load by player_spawner / camera_spawner from the scene's declarative `player` + `camera` blocks. Saving them would double them on the next load. ## When to use `layers.active:save(name)` (Phase 6) routes through this module. Callers that want a state snapshot (save-game systems, undo stacks) should use `world.debugSaveToDisk(...)` instead — that captures runtime state by design.

# @builtin::assetTypes.scene.shared.swapOrchestrator Owns the user-scope orchestration for scene swaps: leaves the prior scene's multiplayer room, gates concurrent loads via the `__scene_load.begin/finish` token, drives `scene_loader.M.load` for the new scene, and joins the new scene's room. Keeps the swap atomic from a multiplayer-sync standpoint (room transition + entity churn happen inside a single barrier).

# Module (asset type) A module is a reusable, stateless (or globally-stateful) Luau library that other code pulls in with `require()`. Modules are the unit of factored-out logic in a world: helpers, math libraries, format parsers, registries, shared algorithms. ## When to use one - You have logic you want to share across multiple components, services, scenes, or tools. - You have a registry, lookup table, or shared cache that callers all read from / write to. - You want a stable API surface (`M.fn`) other code can depend on. If the logic is bound to one entity, use a `.component`. If you want a named UI of fields rather than functions, use a `.preset`. ## Where it lives - Source: `/zero/source/.../<name>.module/` - Identity: the source path with `/` written as `.` and each segment's type suffix dropped — `/zero/source/demo/beats.module` is `demo.beats`, and `/zero/source/kit.package/beats.module` is `kit.beats`, the container's name kept and its `.package` suffix gone. `asset.create` returns this string, `asset.resolve(...).identity` reads it back, and the `require` forms below write it as `<identity>`. - Folder shape: - `init.luau` (or `init.lua`) — module body. **Required.** Returns a table (conventionally named `M`). - `README.md` — instance-level documentation. **Required.** - `.metadata` — agent-editable tags + free-form fields. **Required.** ## How to create one ```luau asset.create("module", "<name>") -- Creates: /zero/source/<name>.module/ -- init.luau (canonical `local M = {} … return M`) -- README.md (instance README template) -- `folder` places it in a subfolder of /source, and that subfolder -- leads the identity: `{ folder = "lib" }` produces `lib.<name>`. -- `into` authors it inside a resolved container (a package, a toolbox), -- whose own identity leads the same way: asset.create("module", "<name>", { folder = "lib" }) asset.create("module", "<name>", { into = asset.resolve("myPkg.package") }) ``` ## How it operates 1. **Registration.** Writing `init.luau` into a `.module/` folder indexes the asset and registers the module path with the resolver. 2. **Loading.** The first `require("<identity>")` runs the file's body and caches the returned table. Subsequent requires from anywhere return the **same table** — this is the shared-state lever for "module-local" registries. 3. **Hot reload.** Editing the file re-runs the module body and folds what it returns into the table already loaded, so that table keeps its identity: a caller that captured it with `require` reads the new source's functions and values through the reference it already holds, and a later `require` returns that same table. A key the new source drops goes away; a key something set at runtime stays. The body's own `local`s start again from their initial values, so state that must outlive an edit lives in `modules.state()` (`guides { path: "core/scripting-and-tasks" }`). 4. **Identity resolution.** A module is reached by its `<identity>`, and where the caller lives decides which spelling of it resolves. For a module in a **world**, from a caller in that same world — another module, a component, a scene entrypoint, or an `execute` chunk: - `require("<identity>")` — the identity on its own, resolved against the caller's own root. It carries every folder segment, so a module created with `{ folder = "demo" }` is `require("demo.beats")`. - `require("@root::<identity>")` — the same root-relative resolution, written out. - `require(".sibling")` — a module in the same folder, by its bare name; `..name` steps up one folder, `...name` two. Logs, stack traces and hot-reload notices name that same module `@local.source.<identity>` — its key under the world source root. The `<identity>` tail of that key is the form above, so a trace reading `@local.source.demo.beats` is `require("demo.beats")`. For a module in a **library** — content under `/zero/source/libs/@<lib>/` — `@<lib>::` addresses that library's root from anywhere: `require("@builtin::modules.transform")`. Mounting a world as a library moves its files under such a root and flips the caller root to `@<lib>::`, which is what keeps the root-relative forms above resolving across the move. ## Discovery - `asset.list("module")` — every registered module. - `asset.inspect("<name>")` — public functions, source path, this type README. - `ls /zero/source/<name>.module` lists the files the folder holds. ## Authoring conventions - Return a single `M` table from `init.luau`. Top-level statements with side effects run on first require — useful for one-time initialization, dangerous if they touch the engine before it's ready. - Write exported functions as `typed function`, not `function`: the argument types are enforced at the call and the checker knows the signature, so a caller's mistake is reported where they made it. - Annotate exported functions with `--!desc` / `--!arg` / `--!return` / `--!example` so the LSP, `tools.list`, and `asset.inspect` surface them. A function with no `--!desc` is reachable only by someone already reading this file. - Declare a VALUE with `Field.<kind>(default, mode, description)`, and a table whose members are reached through a metatable with `--!members <TypeName>` — the latter gives the surface its accepted member set, its type, and its documentation from one table. See `guides { path: "core/authoring" }` for all four rules and `modules/api/engine/entity.module/members.module` for a worked member table. - Keep module state in module-local upvalues or in `modules.state()`. Globals leak across reloads. Module-locals start again from their initial values with each hot reload; the table `modules.state()` returns is the same table on both sides of every reload. - Prefer focused modules over kitchen-sink modules. If two halves of a module have no shared state, split them. ## Common pitfalls - **Cyclic requires.** A `require` chain that loops will return the partial table (the half built before the cycle was detected). Design for one-way dependencies. - **Engine-time side effects.** Don't `entity.spawn` at module top-level — the engine may not be ready. Expose an `M.init` and call it from a scene entrypoint. - **Hot-reload + module-local cache.** A module that caches expensive computation in upvalues loses that cache on reload — fine for dev, but be aware in performance work. - **`init.lua` vs `init.luau`.** Either works, `.luau` is canonical. - **Writing one while play runs.** A `/source` write made while play is running lands on the play shadow, and a guarded play-exit discards it unless it is kept. One `.module` write shadows `init.luau`, the `README.md` and the `.metadata` together. `vfs.write(path, bytes, { durable = true })` skips the shadow, and `vfs.promotePlayShadow` keeps what is already on it — the `core/vfs` guide has the model and what each route costs. ## Related types - `.component` — for entity-bound state + lifecycle hooks. - `.service` — generates content you don't have yet (a mesh, sound, texture, …) via a metered provider. - `.tool` — for a single agent-callable function with a YAML schema. - `.package` — to group several modules + components + scenes into one shippable folder. ## In the Inspector Exports: what the module exports (name, kind, signature), parsed from its source without running it, with **Check** (the LSP's diagnostics for its entry file) and **Open**.

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

# PlayerPrototype Marks the root of a player-setup subtree — the entity and children that define what a joining user becomes (avatar slot, spawn behaviour, controller). On awake it flips the entity to PrototypeOnly participation, so the prototype lives in the editor and drives spawning without being saved as a world entity itself; `kind` and `label` describe it for authoring surfaces. In edit mode it draws a cyan silhouette outline so the prototype root is easy to pick out, and surfaces its own setup-validation messages (missing camera, avatar slot, or wrong participation) on the component's error channel. Location: `src/lua/lib/components/PlayerPrototype.component`

# BoxCollider (component) A box collision shape. Works with or without a `Physics` component: on its own it is static collision geometry, and alongside one it moves with the body. ## Sizing `half` is the box's half-extents in the entity's local space, multiplied by the entity's world scale. Leave it unset and the box derives from the entity's model bounds, so a bare `BoxCollider` matches what is rendered at any scale. ```lua entity.find("crate").component.add("BoxCollider", {}) -- fits the mesh entity.find("wall").component.add("BoxCollider", { half = { 2, 4, 0.2 } }) -- authored ``` ## Fields | Field | Meaning | |-------|---------| | `half` | Half-extents. Unset derives from model bounds. | | `isTrigger` | Report overlaps without blocking. | | `friction` | Surface friction. | | `restitution` | Bounciness. | ## Composing A collider on a child entity attaches to the nearest ancestor carrying a `Physics` component, so a body made of several shapes puts each on its own entity and each keeps its own material and trigger flag. Past a few dozen boxes sharing one material, `CompoundCollider` is cheaper: it is a single broadphase volume where separate components are one each.

# Physics Adds rigid body dynamics to an entity. Body kind is `"dynamic"` (affected by forces), `"static"` (immovable), or `"kinematic"` (moved by script, affects other bodies). Public fields: `kind`, `gravityScale`, `mass`, `linearDamping`, `angularDamping`, `ccd`, `interpolation`, `lockRotationX/Y/Z`, `lockTranslationX/Y/Z`. `ccd` (continuous collision detection) sweeps the body along its motion so it cannot pass through thin geometry between two steps. It is off by default: the sweep runs on every body that travels further than its own thickness in one step — most of a collapsing structure or a debris burst — and it dominates the physics budget when a scene has many such bodies. Turn it on for the individual bodies that would visibly tunnel: bullets, thrown props, a wrecking ball. ```luau entity(id).component.add("Physics", { kind = "dynamic", ccd = true }) ``` `mass` is the body's total mass in kilograms. At its default of 0 the mass comes from the collider volume at 1 kg per cubic metre, so a bigger collider makes a heavier body; a value greater than zero sets the total mass exactly. Methods: `:applyForce(x, y, z)`, `:applyImpulse(x, y, z)`, `:applyTorque(x, y, z)`, `:setVelocity(x, y, z)`, `:addVelocity(dx, dy, dz)`. ```luau entity(id).component.add("Physics", { kind = "dynamic" }) entity(id).component.get("Physics"):applyImpulse(5, 0, 0) ```

# Light Adds a light source to an entity. The entity's world transform determines the light's position (point) or direction (directional). Point light positions are auto-synced from that world transform, so a light on a child entity burns where the entity stands — the position `entity.position` reports. A point light's `intensity` is on one scale with the `SpotLight` component's `intensity`/`brightness`: the same number at the same `radius`/`range` puts the same light on a surface either kind faces from the same place, and a spot spends it on the cone it opens on rather than all around itself. Kinds: `"point"`, `"spot"`, `"directional"` (the scene's sun), `"ambient"`, `"distant"` (a parallel light beside the sun). Public fields: `kind`, `colorR/G/B`, `intensity`, `radius`, `directionX/Y/Z`, `castsShadows`, `lightChannels`, `mobility`. `range`, `color` and `direction` are aliases accepting the composite/renamed forms. Methods: `:setColor(color)` (color: `{r, g, b}` array or `{r=, g=, b=}` map), `:setIntensity(i)`, `:setRadius(r)`, `:setDirection(dir)`, `:setKind(lightKind)`. `kind = "spot"` opens a cone along the entity's forward axis, at the engine's default 30° outer and 20° inner half-angles; the `SpotLight` component is the one that carries the cone angles and the `face` axis as fields. `"directional"` and `"distant"` are parallel lights: they arrive from the same direction at every point in the world and no distance attenuates them, so their `intensity` reads against the sun's rather than against a point light's. The `SpotLight` README carries the rest of how to balance a mixed point-and-spot rig. ```luau entity(id).component.add("Light", { kind = "point", intensity = 2, radius = 10 }) entity(id).component.add("Light", { kind = "directional", direction = {-0.5, -1, -0.3} }) ```

# ProceduralSky The editable atmospheric sky: a day/night gradient with a sun disc, glow, stars and a moon, all derived procedurally from the directional light's elevation. Add it to an entity like a light: ```lua entity.spawn("sky").component.add("ProceduralSky", { timeOfDay = 18.5 }) entity.spawn("sky").component.add("ProceduralSky", { preset = "sunset" }) entity.spawn("sky").component.add("ProceduralSky", { zenithColor = { r = 0.05, g = 0.1, b = 0.3 }, horizonColor = { r = 0.9, g = 0.4, b = 0.2 }, }) ``` A `ProceduralSky` owns its material outright: it registers a **runtime GPU material** of its own over the builtin procedural-sky shader and pushes every visual parameter (colours, sun, stars, moon, turbidity, exposure) straight to that record. The component's fields **are** the material definition — no `.material` asset backs it, so retuning a scene's sky changes that scene's sky and nothing else. The renderer reads the values from the material's group(1) uniform like any other material — there is no sky-specific render path. Those values also travel the native `Sky` bridge into the scene sky config, alongside the time-of-day / auto-cycle / sun-sync controls. That config is what `sky.get()` reports and what a saved scene records, so both name the sky being drawn. With `syncSunToLight` on (the default), the sky's `timeOfDay` is what the scene is lit by: the scene's directional light takes its direction, colour and intensity from the sun's position, so the sun in the sky and the sun the scene is lit by are the same sun through a whole day/night cycle. Turn it off for a light the sky leaves alone. The intensity that arrives is the day/night curve between night and noon, and `sunPeakIntensity` is the noon end of it — `1.0`, the sky's own daylight, unless a scene asks for more. A harder sun on water or snow is stated here; setting the light itself does not survive, because the sky writes over it every time the hour moves. Like the directional light, the sky is conceptually **singular per scene**. A `ProceduralSky` fully defines its material on `awake` (every parameter from its own fields), so switching scenes never inherits a previous scene's overrides. Day/night comes from the sun's elevation, so evening presets render dark — drive the look by `timeOfDay` (which orients the sun). ## Fields | Field | Type | Default | Meaning | |---|---|---|---| | `preset` | string | `""` | Named look applied before explicit fields: `clear_day`, `sunset`, `sunrise`, `overcast`, `night`. | | `timeOfDay` | number | `14.0` | 0..24 hours; orients the sun and the day/night gradient. | | `autoCycle` | bool | `false` | Advance `timeOfDay` each frame. | | `cycleSpeed` | number | `60.0` | Game-seconds per real-second for the auto cycle. | | `syncSunToLight` | bool | `true` | Drive the directional light from the sun. | | `sunPeakIntensity` | number | `1.0` | What the sun's light measures at noon; the day/night curve runs from night up to this. | | `zenithColor` / `horizonColor` / `groundColor` | color | — | Sky gradient colours. | | `sunSize` / `sunIntensity` | number | `0.02` / `20.0` | Sun disc size + brightness. | | `starsIntensity` | number | `1.0` | Night star-field intensity. | | `moonSize` | number | `0.03` | Moon disc size. | | `turbidity` | number | `4.0` | Atmospheric haziness. | | `exposure` | number | `1.0` | Sky exposure multiplier. | ## Methods | Method | Description | |---|---| | `sky:setTimeOfDay(hours)` | Set the time of day (0..24). | | `sky:applyPreset(name)` | Apply a named look. | | `sky:setZenithColor(c)` / `setHorizonColor(c)` / `setGroundColor(c)` | Set a gradient colour (`{r,g,b}` array or map; >1 auto-scales /255). |

# Lit Checkerboard A static, lit checkerboard surface built on `@builtin::shaders.lit_checkerboard` — the default ground material for newly seeded worlds. It uses a neutral light-grey base colour (`0.85, 0.85, 0.85`) with a grey emissive tint (`0.35, 0.35, 0.35`) so the pattern stays readable in dim scenes, high roughness (`0.7`), no metallic, opaque, and instanced. ## Inputs - `colors.base_color` (`0.85, 0.85, 0.85, 1.0`) — neutral grey checker palette. - `colors.dark_color` (`0.35, 0.35, 0.35, 1.0`) — the dark square colour, close enough to the base that the pattern stays readable in low light. - `floats.roughness` (`0.7`) — mostly diffuse surface. - `render.instancing` (`true`) — supports instanced draws.

# Asset Promote the bundle's spawned children from temporary to permanent scene state and remove the Asset component, "baking" the bundle's contents directly into the owning scene. Subsequent saves persist the baked entities verbatim and stop replaying the bundle template. Location: `src/lua/lib/components/Asset.component`

# PlayerSpawn A world entity that spawns players from a prototype. It carries the fields describing how spawning happens: which `prototype` to instantiate, the `team` and `role` assigned to spawned players, a `maxPlayers` cap (0 = unbounded), the `spawnPolicy` (how many players spawn from this point), and the `placement` (where a spawned player is positioned). The entity's own transform is the spawn point when `placement` is `at_spawn_transform`. In edit mode it draws an orange silhouette outline at the spawn point and surfaces its own setup-validation messages (missing or mis-targeted prototype) on the component's error channel. Location: `src/lua/lib/components/PlayerSpawn.component`

# lamp_post (bundle) A lamp post: a slim post, a lit head sitting on top of it, and the point light it casts. Four entities under one root — `post`, `head` and `glow` — built from builtin meshes and materials, so the bundle carries no geometry of its own. Its foot sits at `y = 0` and it stands 2.53 units tall, so placing it at a position on the ground puts it on the ground. ```lua asset.resolve("@builtin::bundles.lamp_post", "bundle"):instantiate(nil, { position = { 4, 0, 2 }, rotation = { 0, 30, 0 }, scale = 1.2, }) ``` ## What it is for It is the prop a starting scene places to show what placing an asset does: one call brings a whole hierarchy in as the scene's own entities, and the `Light` riding along shows that a bundle carries behaviour and not only shape. Reach for it whenever a scene needs a light source that reads as an object rather than as a floating value.

# orbital_follow Three-ring orbit camera. Framing is authored as three rings around the follow target — a bottom, a centre and a top, each with a `height` above the target's origin and a `radius` out from its axis. Vertical look slides the camera along the spline through those rings; horizontal look orbits around them. The shape of the orbit is geometry you can see and edit rather than a pair of pitch limits you cannot. Public fields: `follow`, `ringBottom` / `ringCenter` / `ringTop` (each `{ height, radius }`), `verticalAxis` (0 at the bottom ring, 1 at the top), `horizontalAxis` (the world heading the camera looks along, in radians about +Y from world +Z), `radiusScale`, `aimHeight` (the aim point above the target's origin), `damping` (per-axis time constants in seconds), `cameraRadius` (radius of the pull-in sweep; `0` turns the pull-in off), `cameraIgnore` (entities whose colliders the pull-in passes through), `sensitivity`, `invertY` (off by default: pushing the mouse forward looks UP, drawing the camera toward the bottom ring; on pitches the other way), `zoomSpeed`, `minRadiusScale`, `maxRadiusScale`. The rig owns that heading. Binding a follow target aims it along the subject's facing, so the shot opens from behind whoever the camera is told to follow, and look input turns it from there — the subject's facing is never read again. That is what makes the camera steerable for a character who turns to face where it is walking: hold "forward" and the character walks the line the camera looks down, instead of chasing a heading that moves as it turns. The default rings frame a roughly 1.8 m humanoid standing at its origin: the centre ring sits above head height at the widest radius for a resting shot from behind and slightly above, the bottom ring drops to knee height and pulls in to look up, and the top ring climbs and tightens for a near-overhead look down. Writing any framing field re-poses the rig immediately with damping bypassed, so editing a ring moves the camera to the shot that ring describes. `follow` falls back to the `Camera.follow` slot when it is empty, so a rig selected through `Camera.behavior` tracks whatever that camera already follows. Controls: mouse to orbit and to slide along the rings (play mode requests pointer lock, so no button is held), scroll to scale the ring radii. ```luau local cam = entity(id).component.get("Camera") cam.behavior = asset.ref("@builtin::controller.orbital_follow", "component") entity(id).component.get("controller.orbital_follow").ringCenter = { height = 2.6, radius = 6 } ``` ## The camera pulls in when a collider is in the way Each frame the rig sweeps a sphere of `cameraRadius` from the point it aims at out to where its framing puts the camera, and stands the camera where the sphere first meets a collider. Every collider in the world stops that sweep, whether or not anything draws it: an invisible walk bound (a `BoxCollider` with no `Model`), a trigger volume and a solid wall all pull the camera in alike. The follow subject is the one entity the sweep passes by default. So a camera that snaps in close to the player, or collapses onto it, while nothing visible stands behind the player is meeting a collider nobody can see. Two fields settle it: - `cameraIgnore` lists the entities whose colliders the camera sees through. Name the walk bounds and gameplay volumes there and the sweep passes them as it passes the subject, while walls the player can see still pull the camera in. Each entry is an entity (or its id), and it is the collider's own entity that is listed. - `cameraRadius = 0` turns the pull-in off: the camera stands where its framing puts it, through every collider. ```luau local rig = entity(camId).component.get("controller.orbital_follow") rig.cameraIgnore = { entity.find("NorthBound"), entity.find("SouthBound") } -- or drop the pull-in entirely rig.cameraRadius = 0 ``` ## Attach through `Camera.behavior` The Camera owns the behavior slot, so assigning the rig there is what lets the Camera tell it when `follow` changes. A rig added straight onto the entity with `component.add` still poses, but the Camera does not know about it and a `follow` assigned afterwards will not reach it. ## Player cameras: leave `follow` unset Entering play drops and respawns `PlayerPrototype` subtrees, so the body is recreated with a NEW entity id. A `follow` authored on the rig keeps pointing at the original, which is no longer live, and the camera freezes at its last pose instead of tracking the player. For a player camera, set the target on the **Camera** and leave the rig's own `follow` empty: ```luau entity(rigId).component.get("Camera").follow = body -- PlayerPrototype rebinds this on every spawn ``` `PlayerPrototype` refreshes `Camera.follow` to the live body each time it clones, and the rig reads that slot whenever its own `follow` is empty. Set the rig's `follow` only for a camera that watches a fixed, non-respawning subject.

# Plastic Red A glossy red plastic — a non-metallic PBR surface with a saturated red base colour (`0.8, 0.1, 0.1`) and mid roughness (`0.5`) for a soft dielectric sheen. Built on `@builtin::shaders.pbr`. Opaque, back-face culled, queue `2000`. ## Inputs - `colors.base_color` (`0.8, 0.1, 0.1`) — the red plastic tint. - `floats.roughness` (`0.5`) — soft, semi-glossy highlight. - `floats.metallic` (`0.0`) — dielectric (non-metal) response. - `floats.emissive` (`0.0`) — no self-illumination.

# 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.

# 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.

# assetType runtime The machinery that reads a `<typename>.assetType/behavior.luau` and turns its declarations into live behaviour. A `behavior.luau` is a table of declarations — `ref` methods, `modules` shared code, an `events` schema, a `namePattern`, `refShapes`, and the `onCreate` / `onRegister` / `onChange` / `onDelete` / `validate` / `settingsDefaults` / `settingsCorrections` hooks. None of it runs itself. This is the code that runs it, and it lives here because reading a type's declarations is the **assetType type's own behaviour** — the same way `material.assetType` owns what a `.material` does. ## Sub-modules | Module | Reads | Responsibility | |---|---|---| | `ref.module` | `ref`, `modules` | Builds every `AssetRef` envelope, attaches the shared metatable, and dispatches per-type methods and shared modules onto it. Also owns edit-mode write-behind persistence. | | `create.module` | `onCreate`, `namePattern`, `validate` | Backs `asset.create`: resolves the type, checks the name against its pattern, runs `onCreate` (or clones `template/`), and writes the instance. `validate.module` beside it checks a creation `opts` table against the type's `createSchema`. Before running `onCreate`, resolves the type's settings chain (below) and hands the result to the hook as `opts.settings`. | | `settings.module` | `settings`, `settingsDefaults`, `settingsCorrections` | A type's declared settings schema and where its values live (`type.yaml`'s `settings:` block). `Settings.resolveForCreate` layers the schema's own defaults, the type's own `settingsDefaults(name, opts, asked)` hook (a DEFAULT the schema can't express — a name-derived convention, a fact read off a payload the caller handed it, a value following a field `asked` shows a higher layer naming; any later layer overrides it), the Preset Manager, an importer's settings, the caller's `settings` table, then the type's own `settingsCorrections(values, name, opts)` hook (a CROSS-FIELD CONSTRAINT the schema can't express, applied last over the fully merged values). A correction over a default/preset/importer value lands silently; a correction that would override what the caller's own `settings` table explicitly asked for refuses the creation instead, naming the field and why. Neither hook is ever handed a table to mutate; each returns what it wants changed (`settingsCorrections` may also return a `{ [field]: reason }` table for that refusal message). `Settings.cloneValues` deep-copies a values table — `create.module` hands `onCreate` a copy, never the table it stamps. `Settings.valuesOf` / `writeValues` read and write an asset's own values file. | | `typeYaml.module` | `type.yaml` | The folder a type lives in and its parsed `type.yaml`, decoded once per content version of the file. `settings.module` and `inspector.module` read their blocks through it. `about` / `aboutAt` read a type's `about.yaml` (`intent`, `function`, `usage`), leaving out any key that is empty or still starts with `[[describe]]`; `aboutRows` and `aboutMarkdown` lay the texts out for the Inspector and the `types/<name>` guide. | | `inspector.module` | `type.yaml`'s `inspector:` block | Which inspector a type declares for its assets (`inspector: { type: ... }` or `{ instance: ... }`), and the declaration that file returns — the sections it adds, the generic ones it replaces, and their order — or the problem that kept it from loading. | | `onRegister.module` | `onRegister` | Fires an instance's once-only registration hook — on arrival, on world load, and for `@builtin` library instances. | | `changeDispatch.module` | `onChange`, `onDelete`, `refShapes` | Routes a VFS source write or a folder delete to the enclosing typed asset's type hooks. | | `refShapes.module` | `refShapes`, `ref` | Publishes what every `AssetRef<category>` answers to, so a member read on an asset-typed value is checked against that category's real surface. | | `events.module` | `events` | The per-asset event runtime behind `ref.events`. | | `instantiable.module` | `ref.instantiate` | The instantiation contract an asset type opts into: `root` stands the root entity, `place` applies the base placement opts to one the type adopted, and `result` shapes the `(root, idMap)` every `instantiate` returns. Also registers the `sceneInstantiable` field-constraint validator. | | `declaration.module` | `type.yaml` | The type's decoded declaration, read once and held until a write inside an `.assetType` folder; what every question about a type as a whole reads. | | `previewRecipe.module` | `type.yaml` `preview:` | How an instance's `preview.png` is produced: which of the four recipes (`instantiate`, `image`, `surface`, `custom`) the type declares, and what that recipe needs. | ## Reaching it ```luau local rt = require("@builtin::assetTypes.assetType.shared") rt.ref.loadTypeBehavior("material") ``` Fields resolve lazily. The prelude requires the sub-modules directly, in dependency order (`ref`, then `changeDispatch`, `onRegister.install()`, `refShapes.install()`) — a table that required all six on load would take that ordering away from it.