sphere

# mesh A mesh is renderable geometry — vertices and triangle indices, and, for a skinned mesh, the per-vertex skinning data that binds it to a skeleton. A component that draws geometry references a mesh, and the renderer binds the mesh's GPU resource for that entity. > New to how a mesh exists as an asset, as CPU-side vertex data, and as a live > GPU resource (and how `renderer.mesh.*` moves between them)? Read > `core/resource-model` first. Geometry is stored in `data.zmsh`; the GPU resource is keyed by the asset's guid. ## Create `asset.create("mesh", name, opts)` writes the geometry and registers the mesh. `opts` is raw geometry — flat arrays; `positions` and `indices` are required, `normals` and `uvs` optional: ```luau asset.create("mesh", "tri", { positions = { 0,0,0, 1,0,0, 0,1,0 }, -- [x,y,z, ...] (required) indices = { 0, 1, 2 }, -- [i0,i1,i2, ...] (required, 0-based) normals = { 0,0,1, 0,0,1, 0,0,1 }, -- [x,y,z, ...] (optional) uvs = { 0,0, 1,0, 0,1 }, -- [u,v, ...] (optional) }) ``` The full authorable geometry, all flat arrays unless noted: | Field | Shape | Notes | |---|---|---| | `positions` | `[x,y,z, ...]` | required | | `indices` | `[i0,i1,i2, ...]` | required; 0-based, counter-clockwise for the front face (see Conventions) | | `normals` | `[x,y,z, ...]` | optional; the surface's outward direction | | `uvs` | `[u,v, ...]` | texture UVs, optional; `(0,0)` is the image's top-left | | `colors` | `[r,g,b,a, ...]` | optional | | `tangents` | `[x,y,z,w, ...]` | optional (`w` = handedness) | | `uvs1` | `[u,v, ...]` | the lightmap UV set, optional | | `unwrapUvs` | boolean | generate `uvs1` when it is absent | | `skinning` | `{ joints, weights }` | per-vertex skin binding (four each per vertex) | | `skins` | array of skin tables | the skeleton (see `renderer.mesh.decode` for the shape) | | `morphTargets` | array of `{ name?, positions, normals? }` | the shapes the mesh blends towards, each a per-vertex displacement | `encode` / `decode` round-trip every one of these, so a **skinned** mesh can be built in engine, not only imported. Pass `unwrapUvs = true` to generate a lightmap UV set at creation time. ## Conventions Geometry is read against these whether it arrived through `asset.create`, `renderer.mesh.create`, or an importer. | Convention | How the engine reads the geometry | |---|---| | Index base | `indices` count vertices from **0** — index `0` is the first `positions` triple. The Luau array carrying them is 1-based like any other, so `indices[1]` is the first triangle's first index, and vertex `v` has its x at `positions[v * 3 + 1]`. | | Triangle winding | A triangle's **front** face is the one whose three vertices turn **counter-clockwise** as the viewer sees them. Put another way, `cross(v1 - v0, v2 - v0)` points out of the front face. | | Back faces | A material culls its back faces by default, so a triangle turned away from the camera draws nothing where it stands and whatever is behind it shows through. | | Normals | `normals` give the surface its outward direction and shade the face. Which side of a triangle draws comes from the index order alone, so a normal pointing away from the side the winding draws leaves that face standing and shades it as if the light were behind it. | | UVs | `(0, 0)` samples the first texel of an image — its top-left corner — and `v` grows downward through it. | | Axes | Model space carries the world's basis: `+X` right, `+Y` up, and `-Z` the direction an entity's `transform.forward` points. | Winding is what the author states: the inward faces of a room and a sky shell seen from inside are geometry meant to be wound the other way, and `asset.create` writes the index order it is handed. Two levers turn a face around: ```luau indices = { 0, 2, 1 } -- the same three vertices, reversed asset.create("material", "two_sided", { -- or keep the order and draw both sides shader = "@builtin::shaders.pbr", render = { cull = "none" }, }) ``` `cull = "front"` draws the far side by itself, which is what an inverted-hull outline is built on, and `"back"` is the default. `.shader` documents the whole `render` block a material's `mat.yaml` carries. A mesh states which way its own triangles face, so the question is answerable off the geometry — every triangle whose cross product agrees with the normal it carries is wound to draw the side that normal points at: ```luau local cpu = meshRef:load() local g = cpu:geometry() local function facesOutward(t: number): boolean -- t counts triangles from 0 local i = { g.indices[t * 3 + 1], g.indices[t * 3 + 2], g.indices[t * 3 + 3] } local function p(k: number, c: number): number return g.positions[i[k] * 3 + c] end local ax, ay, az = p(2,1) - p(1,1), p(2,2) - p(1,2), p(2,3) - p(1,3) local bx, by, bz = p(3,1) - p(1,1), p(3,2) - p(1,2), p(3,3) - p(1,3) local cx, cy, cz = ay*bz - az*by, az*bx - ax*bz, ax*by - ay*bx local n = i[1] * 3 return cx * g.normals[n+1] + cy * g.normals[n+2] + cz * g.normals[n+3] > 0 end local inward = 0 for t = 0, #g.indices // 3 - 1 do if not facesOutward(t) then inward += 1 end end cpu:unload() ``` ## Built-in primitive meshes The engine ships blockout geometry every world references by bare name (`{ model = "cube" }`). Each one is centred on its local origin, so an entity's `scale` reads directly as the size the mesh covers in the world: | Mesh | Extent (x, y, z) | Local AABB | |---|---|---| | `cube` | 1 x 1 x 1 | `-0.5, -0.5, -0.5` .. `0.5, 0.5, 0.5` | | `sphere` | 1 x 1 x 1 | `-0.5, -0.5, -0.5` .. `0.5, 0.5, 0.5` | | `cylinder` | 1 x 1 x 1 | `-0.5, -0.5, -0.5` .. `0.5, 0.5, 0.5` | | `cone` | 1 x 1 x 1 | `-0.5, -0.5, -0.5` .. `0.5, 0.5, 0.5` | | `octahedron` | 1 x 1 x 1 | `-0.5, -0.5, -0.5` .. `0.5, 0.5, 0.5` | | `rounded_box` | 1 x 1 x 1 | `-0.5, -0.5, -0.5` .. `0.5, 0.5, 0.5` | | `capsule` | 0.5 x 1 x 0.5 | `-0.25, -0.5, -0.25` .. `0.25, 0.5, 0.25` | | `torus` | 1 x 0.3 x 1 | `-0.5, -0.15, -0.5` .. `0.5, 0.15, 0.5` | | `plane` | 1 x 0 x 1 | `-0.5, 0, -0.5` .. `0.5, 0, 0.5` | | `ground_quad` | 1 x 0.1 x 1 | `-0.5, -0.05, -0.5` .. `0.5, 0.05, 0.5` | | `ground_hex` | 1.732 x 0.1 x 2 | `-0.866, -0.05, -1` .. `0.866, 0.05, 1` | | `shader_ball` | 0.933 x 1 x 0.933 | `-0.467, -0.5, -0.467` .. `0.467, 0.5, 0.467` | `plane` is a flat quad in the XZ plane, so it has no vertical extent at all and scaling it on Y moves nothing. `meshRef:load():getBounds()` reads the same numbers back off any mesh, built-in or authored. ## Put a mesh on an entity A component draws a mesh through a `resource("mesh")` field, which accepts the mesh **by name, by ref, or as a `MeshHandle`** — the component resolves whatever you give it. The builtin `Model` and `SkinnedModel` both expose a `model` field: ```luau entity.find("box").component.add("Model", { model = "tri" }) -- by name entity.find("box").component.add("Model", { model = asset.ref("tri") }) -- by ref entity.find("box").component.add("Model", { model = meshHandle }) -- a MeshHandle (below) ``` ## Runtime mesh — no asset Build geometry straight onto the GPU and render it without creating an asset. The `resource("mesh")` field takes the returned `MeshHandle` directly: ```luau local h = renderer.mesh.create({ positions = {0,0,0, 1,0,0, 0,1,0}, indices = {0,1,2} }) entity.find("box").component.add("Model", { model = h }) ``` Its geometry reads back off the handle. `renderer.mesh.geometry(mesh)` returns the same flat-array `MeshGeometry` `create` takes, carrying every stream the mesh has — so a runtime mesh can be inspected, edited, and rebuilt without ever becoming an asset: ```luau local geom = renderer.mesh.geometry(h) -- { positions, indices, tangents?, ... } geom.positions[1] = 0.5 local h2 = renderer.mesh.create(geom) ``` An optional stream is present only when the mesh carries one, so `geom.tangents` answers whether the mesh has a tangent basis and `geom.uvs1` whether it has a second UV set. ## Read geometry — `meshRef:load()` `:load()` decodes `data.zmsh` into the CPU store and returns a CPU handle carrying `vertexCount` / `indexCount`: | Method | Returns | |---|---| | `cpu:getVertices()` | array of `{ pos = {x,y,z}, normal = {x,y,z}, uv = {u,v} }`, one per vertex | | `cpu:getTriangles()` | array of `{ v1, v2, v3 }`, each a full vertex (the shape above) | | `cpu:getBounds()` | `{ min = {x,y,z}, max = {x,y,z} }` — the local-space AABB | | `cpu:geometry()` | the complete `MeshGeometry` — flat arrays, every stream the mesh carries | | `cpu:encode()` | the `data.zmsh` bytes | | `cpu:unload()` | drop this guid's CPU copy | ```luau local cpu = meshRef:load() local v = cpu:getVertices()[1] -- { pos = {x,y,z}, normal = {x,y,z}, uv = {u,v} } local aabb = cpu:getBounds() cpu:unload() ``` By default the CPU copy is transient (decode → read → `unload`). Set `keepCpu` to keep it resident — see Settings. ## Write geometry back — `meshRef.primary` The inverse of reading: encode a `MeshGeometry` and write it to the asset's primary content file. The assetType picks the write up and re-uploads the live GPU mesh, so the change shows without a reload: ```luau local geom = renderer.mesh.geometry(meshRef) geom.tangents = computeTangents(geom) -- add a stream it did not carry vfs.write(meshRef.primary, renderer.mesh.encode(geom), { overwrite = true }) ``` `meshRef.primary` is the asset's `data.zmsh` path. This is the route for a stream with no setting of its own; `keepCpu` + `meshRef:setVertices` moves positions in place, and `lightmapUvs` regenerates the second UV set (both below). ## GPU handle — `meshRef:handle()` `:handle()` uploads the geometry (Disk → CPU → GPU) and returns a `MeshHandle`, cached on the asset so every consumer shares ONE GPU entry. A component does this for you when you pass it the mesh; call it directly only for the runtime/low-level path. ## Settings — `meshRef:settings()` / `meshRef:setSettings(patch)` A mesh's settings are declared in `settings.luau` and live in `settings.yaml`. `:settings()` returns them with every declared default filled in. `:setSettings(patch)` writes any subset — sibling settings are preserved, and a patch that fails the schema is refused, naming the field and why. | Setting | Type | Default | Meaning | |---|---|---|---| | `keepCpu` | boolean | `false` | Keep the CPU geometry copy resident — for an in-use mesh — so geometry can be read repeatedly without re-loading. | | `lightmapUvs` | string | `"keep"` | The mesh's second (lightmap) UV set. `"keep"` leaves the stored geometry's set as-is; `"generate"` unwraps a fresh non-overlapping set; `"none"` strips it. See below. | | `clusterLod` | boolean | `true` | How deep the cluster set is built. Every static mesh draws through clusters, from the frame it materialises (its `lod0` set) until its bake lands. `true` (default) builds the LOD hierarchy; `false` builds one level, drawn at full detail. | ```luau local s = meshRef:settings() -- { keepCpu = false } meshRef:setSettings({ keepCpu = true }) ``` `keepCpu` is an active lifecycle control, and only ever holds geometry for a mesh that is **in use** (GPU-resident): - Setting it **on** while the mesh is in use loads the CPU copy immediately. - Setting it **on** for a mesh that is **not** in use loads nothing — the copy is retained the next time the mesh is materialised, so an unused mesh is never pinned in memory. - Setting it **off** drops a resident CPU copy (the renderer keeps drawing from the GPU). `clusterLod` is the same kind of lifecycle control, for the depth of the cluster set rather than the CPU copy: - Setting it **off** on a mesh in use rebakes it as one level of clusters (`single`), drawn at full detail. - Setting it **on** on a mesh in use rebakes the LOD hierarchy (`dag`). - A mesh that is not in use bakes at the depth the setting asks for when it next materialises. Acting on either setting for a mesh in use can read the mesh's stored geometry, and where the geometry is fetched on first read that read spans frames. `meshRef:settingsPending()` answers whether one is still in flight; once it answers `false`, every settings change made so far has reached the mesh. ### Second UV set (`lightmapUvs`) A mesh can carry a **second**, independent UV set (`uv1`) alongside its texture UVs (`uv`) — a distinct per-vertex channel, non-overlapping where the texture UVs tile and reuse charts. `lightmapUvs` controls whether the stored geometry keeps one, generates one, or drops it: | Value | Effect | |---|---| | `"keep"` | Leave the stored geometry's `uv1` as-is (the default). | | `"generate"` | Unwrap a fresh non-overlapping `uv1` (near-planar charts packed into `[0,1]` with gutters). | | `"none"` | Strip the `uv1` set. | ```luau meshRef:setSettings({ lightmapUvs = "generate" }) ``` Changing the setting reprocesses the asset's geometry in **edit** mode; a change in play mode never rewrites the source. The reprocess round-trips the geometry through the codec, so positions, normals, tangents, skinning, and the skeleton are preserved — only the `uv1` set changes. A runtime mesh carries `uv1` the same way: pass `uvs1` (or `unwrapUvs = true`) to `renderer.mesh.create`. ## Read vertices — `meshRef:getVertices()` With `keepCpu` on for an in-use mesh, read its vertices straight from the resident CPU copy: ```luau meshRef:setSettings({ keepCpu = true }) -- on an in-use mesh local verts = meshRef:getVertices() -- { { pos = {x,y,z}, normal = {x,y,z}, uv = {u,v} }, ... } ``` If the CPU copy isn't resident — `keepCpu` is off, or the mesh isn't in use — it errors loudly, naming the reason and the remedy, rather than silently loading a throwaway copy: ``` mesh:getVertices: cannot read vertices — keepCpu is off, so no CPU copy is kept. Turn on CPU retention for an in-use mesh first: meshRef:setSettings({ keepCpu = true }). ``` ## Morph targets — `meshRef:morphTargets()` A mesh can carry morph targets: shapes it blends towards, each a per-vertex displacement from the base geometry. Every target carries the name it was authored under, and an imported model keeps the one its source file gave its blend shapes, so content addresses a shape as the thing it means rather than as the ordinal it happened to import at. ```luau for i, name in meshRef:morphTargets() do print(i, name) end -- 1 Eyes_Blink ``` An entity blends them with `ecs.MorphWeights`, weight `i` driving target `i`. `renderer.mesh.morphWeights(mesh, { Eyes_Blink = 1 })` builds that ordered array from weights named by shape — shapes left out sit at 0, and an unknown name errors listing the ones the mesh carries. ## Discovery | Call | Shows | |---|---| | `asset.list("mesh")` | every registered mesh | | `asset.inspect("<name>")` | a text report about the mesh (metadata, source, status) | | `meshRef:settings()` | the resolved settings | | `meshRef:settingsPending()` | whether a settings change is still reading the stored geometry | | `meshRef:morphTargets()` | the shapes it blends towards, named, in target order | For the on-disk shape of a mesh asset, run `asset.inspect("<name>")` or read the type's `type.yaml` — those are the live source of truth. ## Related - `renderer.mesh.*` — the GPU/CPU resource layer (`create` a runtime GPU mesh, `encode`/`decode` the `ZMSH` payload, `readback` GPU → CPU). `:load`/`:handle` wrap it; see `man renderer`. - `.material` + `.shader` — what shades the geometry. - `.bundle` — container assets that carry `.mesh` interiors. ## In the Inspector Selecting a mesh opens its **Geometry** section, after the asset's identity and before its Settings. It reports what `data.zmsh` holds, decoded once per payload version: vertices, triangles, the bounds and their size, the vertex streams beyond positions (normals, uvs, uvs1, colors, tangents, skinning), and, when the mesh has them, its skin joints and morph targets. While the renderer holds the mesh's cluster hierarchy, the section also reports its cluster and level counts. A payload is one index stream, so the section names no submeshes. A mesh folder with no `data.zmsh` says so.

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

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

# scene_instantiable (module) The instantiation contract's shared implementation. An asset type opts into scene instantiation by defining `instantiate(self, target?, opts?)` on its behaviour `ref` table; this module carries the parts that mean the same thing for every type, so a caller writes ONE piece of code against all of them. ```lua local root, idMap = ref:instantiate(target?, opts?) ``` ## The contract **IN — the base opts.** `target` is an owning entity ref: the instance lands under (or, for a hierarchy type like a bundle, onto) that owner. With no target the type spawns a fresh root. `position`, `rotation`, `scale`, `name` and `temporary` place that root and mean the same for every type. `rotation` takes three numbers as pitch/yaw/roll in DEGREES, or four as a quaternion. A type may honour more opts of its own — `params` for a type built from declared inputs, `idMap` / `diff` / `sourceTag` for the bundle override contract — and says so in its own `instantiate` docs. **OUT — the two returned values.** Every type returns the same pair: - **`root`** — the composed root, as an `EntityRef`. Composition is **synchronous**: the root and everything the type built under it are live the moment the call returns, so a caller can parent to it, read its components and hand it on in the same statement. There is no frame to wait for and no callback. - **`idMap`** — the `originalId -> runtimeId` map naming what the composition spawned, `{}` for a type with no addressable children. **Never nil.** A component that re-composes the asset on every load (`Asset`) keeps this map and passes it back in, which is how a cross-entity reference into the composition — `SkinnedModel.skeletonRoot` pointing at a bone — survives a reload. The return is enforced, not merely described: `AssetRef` dispatches every `ref:instantiate(...)` through `result` on the way out, whether or not the type called it. A type that returns something else fails at its own call rather than handing its caller a nil root or a map that is sometimes absent. ## Exports - `M.root(self, target?, opts?) -> root` — stand the root entity for a type that spawns one: parented to `target`, born temporary when `opts.temporary`, named `opts.name` else the asset's own name, placed. - `M.place(root, opts?) -> root` — apply the placement opts to a root the type already has (the adopt path: a bundle exploding onto its target, a sceneModule reconciling under one). - `M.result(self, root, idMap?) -> (root, idMap)` — return through the contract. Checks `root` is a live entity ref, normalises a missing map to `{}`, and errors naming the asset type when either is something else. - `M.isOwned(opts?) -> boolean` — whether a component drives this call. The `Asset` / `SceneModule` components tag their own calls with `sourceTag`; they hold the reference and re-compose on every load. An untagged call came straight from `ref:instantiate(...)` and has no such owner. - `M.own(root, self, idMap?) -> root` — hand an already-composed root to an `Asset` component pointing at `self`, so the reference and its map persist and the composition is rebuilt on the next load. The component adopts the live composition rather than building a second one. - `M.check(value, constraint) -> ok, reason?` — the `sceneInstantiable` field-constraint validator, also registered under that kind on load. ## The field constraint `Field.instantiableRef` emits `constraint = { kind = "sceneInstantiable" }`, and this module registers the validator for it on load. Given a written value: 1. `nil` passes — the field is optional (no asset assigned). 2. Reads the value's identity — a bare string, or a table's `__ref` / `guid` / `identity` / `name`. 3. Resolves it (`asset.resolve(identity)` — any category) and asks the resolved ref `ref:canInstantiate()`: true iff the asset's type defines an `instantiate` method. This is what lets `Field.instantiableRef` accept by CAPABILITY rather than a hardcoded type list — a new scene-instantiable asset type is accepted the moment it defines the hook, with no edit to the field or its consumers.

# proc Code-authored, graph-backed procedural generation for the Zero engine. A graph is one function of `g`: `proc.define(function(g) ... end)`. Nodes are called by family and name (`g.<family>.<name>({ ... })`), inputs are declared with `g:input(name, default, opts)`, the returned table is the graph's outputs, and `io.output` is how the graph stands in the world. `builder.module/README.md` holds every rule of that form. This module owns the whole procedural model: the graph builder + data model, the operation registry, the type system, the lazy cached evaluator, deterministic scoped hashing, and the node-family op implementations. Authored `.procGraph` graphs are persisted via `procGraph.assetType`; the `procgen.preview` / `procgen.spawn` operations live in `procgen.toolbox` and are invoked as tools: `tools.use("procgen", "preview", args)` from a script or an agent's `tool_exec` script, or `zero procgen preview` in the shell. Generated meshes/materials/textures/bundles are persisted through their own `.assetType`. An op family can also come from outside this package: a `.procPack` asset registers its ops in the same registry, called as `g.op.<id>(...)` exactly like the ones shipped here (`proc.registerPack(name, ops)` is what it registers through, and what a test or a tool calls to hold a family for the life of one VM). `terrain.*` is one such pack, shipped in `terrainSystem.package/procPacks/` and covering a whole landscape; `guides { path = "systems/terrainSystem/documentation/terrain" }` is its guide. To find out what the registry holds, use the `procgen` toolbox: `searchNodes` searches it and `describeNode` describes one node or op. `proc.search_ops(query)` and `proc.schema(id)` are the same answers in-process, for a graph builder looking something up while it runs.

# 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.