# 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**.

# prefab (nodebox) Prefabs: the entity records a spawned hierarchy is made of, as record and list values. prefab.empty makes a root, prefab.entity, prefab.parent, prefab.add_component and prefab.link shape the hierarchy (each calls prefab.edit, which holds the record-list edits and the name lookup that prefab.find answers), and prefab.from_geometry, prefab.from_geometries, prefab.from_instances, prefab.from_population and prefab.from_asset make prefabs from what a graph built. The output node shows a prefab and the export node saves it as a bundle. prefab.record and prefab.find are the parts the others are built from: one entity record, and a lookup of an entity by name.

# field.distance (procNode) How far each element's position is from a target, as a Float field. It makes the target the wired `b` field or, when `b` is left unwired, the fixed `point` as a constant field (`value.fallback`, `field.constant`), then measures with `field.vector_math` in `distance` mode from `a` to that target. The result compiles to the device with the rest of the field chain. ## Inputs - `a` (`Field<Vec3> | Vec3`): the positions being measured, one per element. - `b` (`Field<Vec3> | Vec3`): what each element is measured to, per element, so the target can move with the element. Wired, it stands in for `point`. - `point` (`Vec3`, default `{ 0, 0, 0 }`): one fixed position every element is measured to when `b` is unwired. It is how a radial falloff around a place is built. ## Outputs - `field`: the distance, a Float field.

# instances (nodebox) Instances: pack a geometry into a piece (instances.pack), place a piece set on target points (instances.to_points) and take a population or piece set apart (instances.unpack). A piece is one point whose `Mesh` holds a geometry whole; `geometry.merge` with `pack` puts several together into a piece set. The copies `instances.to_points` makes are a population, which the output node draws as instanced draws, one per piece and material, and export saves as a population asset; any other points stand as one entity each. instances.pack, instances.to_points and instances.unpack are the nodes of that chain, with `points.pose` composing the instance attributes (`P`, `orient`, `scale`, `N`, `v`, `up`, `pscale`, `rot`, `trans`, `pivot`) the copies stand at. Earlier nodes of the nodebox stand a source on points (instances.on_points), deal one of several sources to each point (instances.pick_random, instances.pick_by_attribute), vary and move the copies (instances.randomize_transform, instances.transform, instances.set_material) and merge them into one geometry (instances.realize). The points they make carry a `Mesh` and stand as entities through the output node. instances.place, instances.variants, instances.turn and instances.sources are the parts the others are built from: a transform written onto points, a variant index written onto points, the product of two rotations, and the geometries a population stands (the ones given, else the ones its points carry).

# asset_on_register Drives the optional `onRegister(self)` assetType lifecycle hook — the surface that lets an asset instance run code exactly once when it first registers, operating on the per-instance ref (`self`). This is what makes "write an asset into the world → it takes effect live, no restart" work for content that registers into a runtime registry (editor panels, and anything else that opts in). A type opts in by exporting `onRegister` from its `behavior.luau`. The hook fires exactly once per instance: - On `engine.onWorldLoaded` — a batched sweep over every world instance of every type that implements `onRegister`, yielding every 32 instances so a large instance count never stalls a frame. The @builtin library (`/zero/source/libs/`) is excluded. - On live `asset.create` — the create path calls `M.fireFor(ref)` on the freshly-created instance. A per-VM once-guard keyed by the instance's VFS path ensures the two triggers can't double-register the same instance. ## Exports - `M.fireFor(ref, onRegisterFn?) -> boolean` — fire one instance's `onRegister(self)` hook exactly once. Resolves the type's hook from `ref.type` when `onRegisterFn` isn't supplied. Idempotent: a second call on the same instance is a no-op. Returns true if the hook fired this call. - `M.sweep()` — batched sweep: fire `onRegister` once for every world instance of every registered type that implements it. Yields, so it must run inside a task. Safe to call repeatedly. - `M.install()` — install the world-loaded sweep. Idempotent. Runs the sweep on a system task so it ticks through pause and never blocks the caller.

# part (nodebox) part.merge packs several values into one part, each piece keeping what it is; part.unpack gives one piece back by its name.

# math One node per operator and function of the authoring surface: add, sub, mul, div, mod, pow, neg, abs, min, max, floor, ceil, sqrt, sin, cos, tan, acos, atan, log, sign, deg, rad, clamp, lerp, smoothstep, length, normalize, dot, cross, vec2, vec3, vec4, the comparisons (lt, le, gt, ge, eq, ne, and `compare` over them), `where`, the integer functions (to_int, to_float, bor, bxor, shl, floordiv), and `concat` for text. Operators and `math.*` over sockets resolve to these nodes. Each calls an operation of `proc.fieldc.operators`: over plain numbers and vectors it answers the plain result, over a Column or a Field it answers a Field (a fieldc template), so a chain of math nodes is one expression that the node consuming it evaluates in a single dispatch (`fieldc.evaluate`).

# core The parts the other procgen nodes are built from: connectivity (edges, boundary, adjacency, islands, owner, corners), normals, weld, select, stitch, curve measure and resample, sampling, neighbours, realize, the raster set (`raster.new`, `raster.read`, `raster.stencil`, `raster.sample`, `raster.add_layer`, `raster.remove_layer`, `raster.reduce`, `raster.column`, `raster.resolve`, `raster.blend`, and `raster.cells` under them), `column`, and `entity.read`, which brings scene entities in (assets come in through `io.import`). Each is a graph of the four ops, the kernels of `kernels/` and other core nodes. `join` holds the module that places the parts of a join, called by `concat` and `realize`. A graph calls them as `g.core.<name>`, for instance `g.core.edges`. A node with several outputs answers a record: `local faces = g.core.normals.face(...)` then `faces.geometry`, `faces.scaled`. Every node's README states its inputs and outputs.

# Scatter (node) A scattering node: its `init.luau` holds the graph that does the work, so the declared inputs are this node's inputs and the declared output is this node's output. The node is its pipeline, in one self-contained asset. It makes points on the surface (`points.on_surface`, area-weighted), gives every point its own random yaw, lean and scale (`instances.randomize_transform`), and places the source on those points (`instances.on_points`). The transform is read from the same point cloud the instances sit on, so each copy takes the pose of its own point. A node is findable by what it does: the `procgen` toolbox's `ops` with the query `scatter` lists it beside `points.on_surface` and `instances.on_points`. Editing this node's `init.luau` cooks again every graph that calls it. ## Inputs - `surface` (Geometry): what the copies land on. - `source` (Geometry): the shape being copied. - `count` (Int, default 200): how many. - `seed` (Int, default 1): changes the arrangement. - `scaleMin` / `scaleMax` (Float, defaults 0.8 and 1.4): per-copy size range. - `tilt` (Float, default 0.15): radians of random lean. ## Output - `instances`: a population, the points each carrying the source as its `Mesh`. ## Authoring a node A node is a graph returned from a `.procNode`'s `init.luau` (`proc.define`). `asset.create("procNode", name)` scaffolds that shape, and `procNode.assetType/README.md` describes what a node states and how graphs call it.

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

# field.ramp (procNode) A ramp read at every element by a value it carries: a particle's colour, size or opacity following its age. It takes the value each element reads by (the wired `t`, else the element's own `by` attribute, through `value.fallback` and `field.attribute`), maps it from `range` onto 0..1 (`field.map_range`, the ends read off `range` by `value.get`), and reads the ramp there with `ramp.sample`, compiled into the element's dispatch. A value past either end of `range` reads that end of the ramp. ## Inputs - `ramp` (`Ramp`): the ramp to read. - `t` (`Field<Float> | Float`): where along the ramp each element reads. Unwired, it is the element's own `by` attribute. - `by` (`String`, default `"life"`): the Float attribute each element reads the ramp by when `t` is unwired. A particle solver's particles carry `life`, 0 at birth to 1 at death. - `range` (`Vec2`, default `{ 0, 1 }`): the values of `t` that land at 0 and at 1 on the ramp, so a speed from 0 to 20 or a temperature from 300 to 3000 reads the whole ramp. ## Outputs - `field`: the ramp's value at each element.

# debug (nodebox) debug.dump summarizes any graph value into a record; debug.validate checks a Geometry's structure and reports every issue it finds.

# geometry.recalculate_normals (procNode) Every vertex's normal averaged, by area, over the faces meeting it. The node is `geometry.smooth_normals` with a crease angle of 180 degrees and area weighting, so no vertex splits: a vertex shared by two faces is smooth across them, and one already split between two copies stays a hard edge. ## Inputs - `geometry` (`Geometry`): whose surface the normals are read off. Attributes and material carry to the result. ## Outputs - `geometry`: the geometry with recomputed per-vertex normals.

# material (nodebox) Materials as records: material.pbrMat is the standard metallic-roughness material made from its PBR maps (base colour, metallic-roughness, normal, occlusion, emissive) and their factors, and material.shader a material of any surface shader, holding every property and slot to what the shader declares. Each answers one element holding the record of the material kind (`records/material.procRecord`), which geometry.set_material, instances.set_material and the other inputs that take a material put on what draws; the output node shows it and the export node saves it as a `.material`.

# instances.cull (procNode) Keeps the instances a test says to. An instance survives when the value it is judged by is strictly above `threshold`; `invert` keeps the rest instead. The value is the `mask` field when it is wired, else the named point `attribute` (`field.attribute`). `elements.keep` on the points carries every attribute onto the instances that stay, so a culled set realizes as the whole one would have. With nothing to judge by, every instance stays, and inverted, none does. ## Inputs - `instances` (`Points`): the set to thin out, points carrying a Mesh. - `mask` (`Field`): the value each instance is judged by. Wired, it outranks `attribute`. - `threshold` (`Float`, default 0.5): an instance survives when its value reads strictly above this. Raising it thins the set, lowering it fills it back in. - `attribute` (`String`): a point attribute on the set to judge by, read while `mask` is unwired. A name the points do not carry is refused. - `invert` (`Bool`, default false): true keeps the complement, every instance the test dropped. ## Outputs - `instances`: the surviving instances.

# points.box (procNode) A 3D lattice of points filling a box centred on the origin. Each count is at least 1, and the extent the lattice spans is the counts times `spacing` (`value.math`). `grid.box` lays out the cells, x fastest, then y, then z, on the device, and each cell's centre is one point. `attribute.remove` takes the cell layout off the detail so the lattice reads as Points, and each point carries its own number as `id`. ## Inputs - `countX` (`Int`, default 3): how many points along X. The lattice holds countX x countY x countZ points and stays centred on the origin on every axis. Below 1 reads as 1. - `countY` (`Int`, default 3): how many points along Y, the layers the lattice is stacked in. 1 collapses it to a single flat sheet at y = 0. Below 1 reads as 1. - `countZ` (`Int`, default 3): how many points along Z. Below 1 reads as 1. - `spacing` (`Float`, default 1.0): distance between neighbouring points, the same on all three axes. The lattice spans (count - 1) x spacing per axis. ## Outputs - `points`: the lattice, with `id` numbering each point.

# component (nodebox) component.set gives every element of a class a component with the fields given.

# texture (nodebox) Textures: images drawn on the device as Texture values, a width, a height and one colour per texel. texture.noise and texture.gradient draw from a formula, texture.from_shader from an author's compute shader and texture.from_raster from the layers of a raster. A material takes a Texture in a slot, and the output node shows one. texture.cells is the part the first two are built from: one point per texel carrying its column and row.

# geometry Nodes that move, join, cut, round, thicken and sample meshes. A graph transforms a geometry (`geometry.transform`, `geometry.set_position`, `geometry.merge`), welds and shades it (`geometry.weld`, `geometry.smooth_normals`), models it (`geometry.extrude`, `geometry.solidify`, `geometry.bevel`, `geometry.subdivide`, `geometry.decimate`), builds surfaces from outlines (`geometry.sweep`, `geometry.revolve`, `geometry.loft`, `geometry.ribbon`) and reads it into volumes (`geometry.voxelize`, `geometry.to_sdf`). Each is built from the core nodes and the kernels of the library. ## Nodes - `geometry.transform`, `geometry.set_position`, `geometry.set_material`, `geometry.merge`, `geometry.triangulate`, `geometry.measure`: the basic edits and the measurement of a geometry. - `geometry.weld` (with `match = "position+normal"` it keeps hard edges), `geometry.smooth_normals`: merging points and shading normals. - `geometry.extrude`, `geometry.solidify`, `geometry.bevel`, `geometry.subdivide`, `geometry.decimate`: modelling. - `geometry.sweep`, `geometry.revolve`, `geometry.loft`, `geometry.ribbon`: surfaces from outlines and paths. - `geometry.voxelize`, `geometry.to_sdf`: a mesh as cells and as a distance field. - `geometry.boolean`: union, subtract or intersect of two closed meshes, over the `intersect` kernels. - `geometry.selected`, `geometry.flip`, `geometry.profile`, `geometry.tangents`, `geometry.sides`, `geometry.shared`, `geometry.bvh`, `geometry.rings`, `geometry.first`: the parts the nodes above are built from, each usable on its own. - `geometry.unit`, `geometry.perpendicular`, `geometry.rotate`, `geometry.transport`: vector arithmetic over sockets that the nodes which orient points and normals share. ## Conventions - Each node's folder name is its call name inside the box: `geometry.<folder>`. - Inputs and outputs carry the names of the op each node replaces. - A node that answers a Data table from numbers read back off the device holds the Luau for it in a `readings.module` inside its own folder. - A node with one output answers that output's value; a node with several answers a record by output name. - A fold's index runs from 1: the first pass is 1, so a pass that works on level, chunk or step `n` reads `index - 1` when it counts from 0 (`geometry.bvh`, `geometry.to_sdf`, `geometry.sweep`, `geometry.loft`). - A field bound to a kernel takes the length of that dispatch, so a node writes a value out as a column (a gather with an explicit `count`) before it binds one whose length differs from the dispatch's.

# assetType.shared.ref Builds the metatable every `AssetRef` (the `{ __ref, type, name, guid, identity, path }` envelope returned by `asset.resolve` / `asset.ref`) carries. Replaces the per-call C metatable that used to live in `crates/zero_scripting/src/ffi/bindings/asset.rs::attach_asset_ref_metatable`. ## Public API ```lua local assetRef = require("@builtin::assetTypes.assetType.shared.ref") -- Called by the Rust factory (push_asset_ref_handle) via -- _G.__build_asset_ref_proxy after the envelope fields are set. assetRef.build(envelope) -- attaches AssetRefMT, returns the table ``` The module exposes no invalidation surface — discovery is registry-driven and hot-reload is transparent (see "Discovery and hot-reload" below). ## Method dispatch order `ref.foo` is resolved in this order: 1. **Default methods** — `getSource` / `getBytes` / `getText` / `exists` / `inspect` and the lazy `meta` property. Per-type definitions cannot override these (engine contract from gh#1889). 2. **Per-type `ref` table** — discovered through `asset.resolve(<typename>, "assetType")` + `require(<identity>.behavior)`. The lookup resolves to whichever `<typename>.assetType/` folder is currently registered for the typename (built-in, user, or library-vendored) and pulls its `ref` methods. 3. **Nil** — unknown key, same shape as the original C metatable. ## Adding methods for a new asset type Drop a `behavior.luau` into the type folder: ``` src/lua/lib/assetTypes/<typename>.assetType/ ├── type.yaml -- structural spec (existing) ├── behavior.luau -- ref + global behaviour (new) └── template/ -- placeholder body (existing) ``` `behavior.luau` returns: ```lua return { ref = { --!desc Per-instance method on every `<typename>` AssetRef. myMethod = function(self, ...) ... end, }, global = { -- Reserved for the asset.<typename>.* surface — not consumed -- yet; included so the contract from gh#1889 lands cleanly. }, } ``` Within `ref` methods, `self` is the AssetRef envelope: `self.path`, `self.identity`, `self.guid`, `self.type`, `self.name` are available. Engine-required fields (`guid`, `path`, `identity`, `type`) must not be redefined. ## Discovery and hot-reload Type discovery uses the asset registry, so it doesn't matter where a `<typename>.assetType/` folder lives — engine built-ins under `@builtin::assetTypes.<X>`, user types dropped under `/zero/source/<X>.assetType/`, or types vendored inside an imported library all resolve identically. The dispatcher walks `asset.resolve(<typename>, "assetType")` → canonical identity → `require <identity>.behavior` on every miss; the asset registry is the cache for the resolve half and Luau's `_LOADED` is the cache for the require half. Hot-reload is transparent. When a `<typename>.assetType/behavior.luau` is rewritten through VFS, the engine's `invalidate_require_cache_for_state` re-runs the module and mutates the cached `_LOADED[<identity>.behavior]` table in place. Dispatch reads `mod.ref` on every access (rather than caching a sub-pointer), so existing AssetRefs see the new methods on the very next access — no Rust-side hook into this module is needed, and no invalidation API is exposed for callers to call. The same registry-driven path also handles type **registration** correctness: dropping a new `<typename>.assetType/behavior.luau` updates the asset registry, the next `asset.resolve(<typename>, "assetType")` returns the new ref, and AssetRefs of that type immediately gain the new methods. ## Why Luau, not Rust The asset surface needed per-category behaviour (`material:getProperties()`, `bundle:instantiate(entityId)`, `tool:run(args)`) and the old shape couldn't grow without an FFI change per method. Owning the proxy in Luau means: - Type-specific methods ship as content (the `<typename>.assetType/` folder), not engine code. - Adding a new asset type drops in a new folder; no Rust rebuild. - Methods can call any other Luau global (`vfs`, `asset`, `Material`, `entity`, etc.) directly, instead of going through narrow FFI primitives. ## Consumers - `crates/zero_scripting/src/ffi/bindings/asset.rs::attach_asset_ref_metatable` — the Rust factory that pushes envelopes invokes `_G.__build_asset_ref_proxy` once per push. - Every Luau call site of `asset.resolve` / `asset.ref` / `entity(id).component.X.material` / any binding declared `AssetRef<...>` — they all receive envelopes built through this module.

# proc.types The procgen type system: core type tags + socket assignability for graph validation. Part of `@builtin::systems.procgen.proc`.

# sdf (nodebox) Signed distance field nodes: shapes, smooth combines, round and shell, space warps (transform, twist, bend, taper, elongate, mirror, repeat), displacement, grids and fields in and out, and sdf.mesh, which contours a shape into a closed mesh.

# Scatter Strews copies of one shape over the surface of another, each with its own turn, lean and size. Both the surface and the thing scattered are inputs, so this covers rocks on a hillside, crates on a deck, bushes along a bank or rubble across a floor: wire it a different `source` and it is a different field. It makes points on the surface (`points.on_surface`, area-weighted), gives every point its own random yaw, lean and scale (`instances.randomize_transform`), and places the source on those points (`instances.on_points`). The transform is read from the same point cloud the instances sit on, so each copy takes the pose of its own point. ## Inputs | Input | Type | Default | What it does | |-------|------|---------|--------------| | `surface` | Geometry | none | What the copies land on. Points are area-weighted, so a bigger face gets proportionally more. | | `source` | Geometry | none | The shape being copied. | | `count` | Int | 200 | How many copies. | | `seed` | Int | 1 | Changes the arrangement. The same seed always gives the same field. | | `scaleMin` | Float | 0.8 | Smallest per-copy size multiplier. | | `scaleMax` | Float | 1.4 | Largest per-copy size multiplier. Equal to `scaleMin` means uniform. | | `tilt` | Float | 0.15 | Radians of random lean off vertical. `0` stands every copy upright. | ## Output `instances`: a population, the points each carrying the source as its `Mesh`. A Generator draws it as one hardware-instanced draw call per source; `instances.realize` merges it into a single Geometry. ## Calling it Another graph calls a `.procGraph` as it calls a node, by its path or identity, naming the inputs in a table; the call answers what the graph outputs (`instances`). Its declared inputs are the call's inputs.

# points.grid (procNode) A flat lattice of points in the XZ plane, centred on the origin. Each count is at least 1, and the extent the lattice spans is the counts times `spacing` (`value.math`). `grid.box`, one cell thick at height `y`, lays out the cells, x fastest, then z, on the device, and each cell's centre is one point. `attribute.remove` takes the cell layout off the detail so the lattice reads as Points, and each point carries its own number as `id`. ## Inputs - `countX` (`Int`, default 4): how many points along X. The grid holds countX x countZ points and stays centred on the origin, so each one added widens it by `spacing`, half of that to either side. Below 1 reads as 1. - `countZ` (`Int`, default 4): how many points along Z. A count of 1 leaves a single row running along X. Below 1 reads as 1. - `spacing` (`Float`, default 1.0): distance between neighbouring points, the same on both axes. The grid spans (countX - 1) x spacing by (countZ - 1) x spacing. - `y` (`Float`, default 0.0): the height the whole lattice sits at. Every point takes this as its y. ## Outputs - `points`: the lattice, with `id` numbering each point.

# points.filter (procNode) Keeps the points a test says to. The value each point is tested by is the `mask` field when it is wired, else the named `attribute`'s values (`attribute.labels`). The test is a comparison (`field.compare`): above `threshold`, or, when `equals` is given, equal to the index that value or label names. `elements.keep` on the points carries every attribute and the detail onto the points that stay, counted on the device. Given neither a mask nor an attribute, the points come back as they are. ## Inputs - `points` (`Geometry`): the cloud to thin. Every point attribute and every detail value is carried onto the survivors, so a colour or an index still belongs to the point it started on. - `mask` (`Field`): the per-point value tested; a point stays when it is above `threshold`. Wired, it decides, and `attribute` is read only when this is empty. - `threshold` (`Float`, default 0.5): a point stays when its value is strictly above this. Raising it keeps fewer points. - `attribute` (`String`): a point attribute to test instead of wiring `mask`. A name the points do not carry is refused, naming the ones they do. - `equals` (`String | Float`): keeps the points whose `attribute` equals this instead of testing it against `threshold`. It is a number, or a label: one of the texts a text attribute holds, or one of the names the points' detail `labels` gives a numeric one (how one solver's particles are split back by the `stream` their source named). ## Outputs - `points`: the points that stay.

# geometry.delete (procNode) Deletes the triangles a test selects. A triangle is selected when its value is strictly above `threshold`. The value each triangle is tested by is the `mask` field when it is wired, else the named primitive `attribute` (`field.attribute`), else 0. `invert` deletes the triangles the test did not select. `elements.keep` on the primitives does the removal: every point stays, and the triangles that remain keep their corners and attributes, counted on the device. ## Inputs - `geometry` (`Curves | Surface`): whose triangles are thinned. Point and detail attributes carry over as they are; primitive and vertex attributes stay with the triangles that survive. - `mask` (`Field`): read once per triangle for whether it goes. Wired, it is what the selection reads, and `attribute` is read only when this is empty. - `threshold` (`Float`, default 0.5): a triangle is selected when its value is strictly above this. Raising it deletes less. - `attribute` (`String`): a primitive attribute on the geometry to read the selection from, instead of a wired mask. A name the triangles do not carry is refused. - `invert` (`Bool`, default false): true deletes every triangle the test did not select, so a mask naming what to keep cuts away the rest. ## Outputs - `geometry`: the geometry with the selected triangles removed.

# shader (nodebox) An author's own compute shaders as nodes. shader.compute runs a .computeShader over the elements of a geometry through the device.kernel op: each buffer binding is a column of the geometry, each param a knob of the node, and what the shader writes comes out as columns.

# scene (nodebox) scene.query finds entity ids by name, component and hierarchy, scene.fetch brings entities in as points carrying their pose and components, scene.input is the entity the graph stands on, and scene.water is the water the scene holds.

# geometry.separate (procNode) Splits a geometry's triangles in two by a test. The value each triangle is tested by is the `mask` field when it is wired, else the named primitive `attribute` (`field.attribute`), else 0. Two comparisons against `threshold` follow (`field.compare`): strictly above, and at or below. `elements.keep` on the primitives runs once for each, so `a` holds the triangles above and `b` the rest. Both keep every point, and between them they hold every triangle once. ## Inputs - `geometry` (`Curves | Surface`): whose triangles are divided. Point and detail attributes carry to both halves as they are; primitive and vertex attributes stay with each half's own triangles. - `mask` (`Field`): read once per triangle for which half it joins. Wired, it is what the split reads, and `attribute` is read only when this is empty. - `threshold` (`Float`, default 0.5): a triangle goes to `a` when its value is strictly above this, and to `b` otherwise. - `attribute` (`String`): a primitive attribute on the geometry to read the split from, instead of a wired mask. A name the triangles do not carry is refused. ## Outputs - `a`: the triangles whose value is strictly above `threshold`. - `b`: the rest. A call answers both as a record by output name.

# sim (nodebox) Simulation nodes: sim.spawn, sim.force, sim.collider, sim.scene_colliders, sim.particles and sim.shader, built on the runtime's g:state and g:step.

# abiBox A node for the procgenAbi suite: it is called through the builder and written out in a graph.

# mesh The primitive solids and sheets a graph starts from: `mesh.box`, `mesh.sphere`, `mesh.cylinder`, `mesh.cone`, `mesh.capsule`, `mesh.octahedron`, `mesh.torus`, `mesh.rounded_box`, `mesh.plane` and `mesh.grid`. Each is made on the device from lattices and fans of the `make` kernel, with positions, normals and texture coordinates written as formulas over the lattice, and answers triangles centred on the origin that fill the box its parameters name. ## Conventions - Each node's folder name is its call name inside the box: `mesh.<folder>`. - Parameters keep the names and defaults of the op each node replaces. - `mesh.lattice` makes the lattices and fans the presets share, `mesh.spherical` the point of a sphere and `mesh.cube_faces` the faces of a cube; a preset writes its positions, normals and texture coordinates as formulas over the lattice.

# io The ways in and out of a graph: `luau` runs a function of a Luau module on the CPU, `output` shows a value in the world and answers a Handle, `export` saves a value as an asset, and `engine` calls the engine bridge the core reading nodes and `export` use. `output` holds `show.module` and `engine` holds `engine.module`, the functions they call.

# entity (nodebox) entity.transform and entity.bounds read one entity's pose and bounds as values, entity.points reads a set of entities as points, and entity.geometry reads the mesh an entity's Model draws as a Geometry.

# 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.

# Nodebox (asset type) A nodebox is a namespace folder that groups related `.procNode/` children, the way a toolbox groups `.tool/` children. A node's name is its folder name inside its box: `points.nodebox/disc.procNode` is called `points.disc`, and nothing inside the node states that name. Moving or renaming a node is a VFS move that keeps its guid. ## Where it lives - Source: `<anywhere>/<family>.nodebox/`, usually inside a `.package`, an effect or a world's content. - Identity: `<family>` (the `.nodebox` suffix strips). - Folder shape (open child set): - `README.md`: what the family is for. Required. - `.metadata`: description and tags. Required. - `<node>.procNode/`: any number of nodes. ## How a graph reaches a node `g.<family>.<node>(args)` resolves the node by its asset identity: the box and the folder name together (`g.points.disc`), a path (`g["/zero/source/fx/ring.procNode"]`), `~` (the nearest enclosing package, effect or world root: `g["~/ring"]`) or a short name the asset system resolves (`g.disc`). A name that matches two nodes is an error naming both; a name that matches none is an error naming the closest nodes. Each call is recorded in the graph's reference table by the node's guid. ## How to create one ```luau asset.create("nodebox", "points", { folder = "fx" }) local box = asset.resolve("points.nodebox") asset.create("procNode", "disc", { into = box }) ``` ## Discovery - `asset.list("nodebox")`: every box. - `asset.inspect("points")`: the nodes in it and what each does. - `asset.list("procNode")`: every node, in or out of a box. ## In the Inspector Nodes: how many nodes the box holds, each node's full name and what it does, and a link to each.

# grid.box (procNode) The cell centres are `min + (coords + 0.5) * cellSize`, computed on the device from each element's index. The layout (`cells`, `min`, `max`) is stored on the detail as `grid`, which is what makes the value a Grid. Built from: `core.points`, `field.index`, `math.*`, `vector.*`. ```luau local air = g.grid.box({ size = vector.create(4, 3, 4), cells = vector.create(32, 24, 32) }) ```

# grid.cell_index (procNode) `floor((p - min) / cellSize)` per axis, flattened `x + nx * (y + ny * z)`; any axis outside `[0, n)` gives -1. Built from: `field.position`, `math.*`, `vector.floor`, `g.where`, `g.compare`.

# grid.neighbor_index (procNode) Each cell's coordinates plus the rounded `offset`, clamped to `[0, n - 1]` per axis and flattened. Gathering a channel through the result is a shift of the channel by one cell. Built from: `field.index`, `math.*`, `vector.*`.

# grid.sample (procNode) The `grid` kernel in sample mode (trilinear) reads the channel at each position: `u = clamp((p - min) / cell - 0.5, 0, n - 1)` and a blend of the eight cells around it, over the grid as one tile with no apron. Built from: `op.device.kernel` (grid), `core.points`.

# points.axis_basis (procNode) Outputs `axis`, `u` and `w`. `points.cone` and `points.cylinder` build their directions in this basis, and `curve.branch` turns a growing direction about an axis perpendicular to it. Built from: `vector.*` and `g.where` over sockets.

# points.box (procNode) The centres of a `grid.box` whose cells are `spacing` apart, as Points numbered by `id`. Built from: `grid.box`, `points.from_grid`, `math.*`.

# points.cone (procNode) The direction is drawn evenly over the spherical cap the angle bounds: `ct = 1 - draw0 * (1 - cos(angle))`, then an angle around the axis from draw 1, and the distance from the apex is `length * draw2 ^ (1/3)`. Built from: `rand.unit`, `points.axis_basis`, `core.points`, `math.*`.

# points.count_neighbors (procNode) The coordinates are rounded to cells and laid in as positions of a fresh point set; every cell's neighbours at lattice distance 1 (the 6 faces) or up to the cube's corner at 1.732 (the 26 cells) fall inside a search radius of 1.01 or 1.74, so `core.neighbours` counts them. The tally is written to the original points. Built from: `core.points`, `core.neighbours`, `vector.floor`, `math.*`.

# points.cylinder (procNode) Draws on channels 0 to 2 of the `emit` scope: the angle around the axis, the radial share, and the height. Built from: `rand.unit`, `points.axis_basis`, `points.shell_radius`, `core.points`, `math.*`.

# points.disc (procNode) Draws on channels 0 to 3 of the `points` scope: radius, angle, dome height and jitter. Built from: `rand.unit`, `core.points`, `math.*`. ```luau local pile = g.points.disc({ count = 200, radius = 3, height = 1.2 }) ```

# points.filter (procNode) The value each point is tested by is the `mask` field or the named attribute's values; the test is `> threshold` or, with `equals`, `== equals` (a label read through its index). `core.select` keeps the elements and renumbers the linkage. Asked for no test the points are returned as they are. Built from: `attribute.labels`, `g.compare`, `core.select`.

# points.from_grid (procNode) `points.box` and `points.grid` end here: the cell layout leaves the detail so the value reads as Points, and the element index is written as `id`. Built from: member writes on the detail and point domains, `g.element.id`.

# points.from_vertices (procNode) Reads the point column `P` (and `N` when the geometry's point names list it) and makes Points of that count in the same order. Built from: `core.points`.

# points.grid (procNode) The centres of a `grid.box` one cell thick at height `y`, as Points numbered by `id`. Built from: `grid.box`, `points.from_grid`, `math.*`.

# points.neighbors (procNode) `core.neighbours` in measure mode, which finds each point's neighbours through a spatial hash and writes `neighbors`, `nearest`, `centroid` and, when `mean` names an attribute, `neighbor_<name>`. Built from: `core.neighbours`.

# points.on_curve (procNode) Per curve the count is `count`, or at a spacing `floor(length / spacing + 0.5)` plus one for an open curve, at least 1, held to `maxPoints` in all. `curve.lay_points` gives each laid point its curve and its index along it; the arc-length fraction is `index / count` around a closed curve (wrapping with `offset`) and `index / (count - 1)` along an open one (clamped). `core.sample_curve` finds the position and tangent there and `core.interpolate` carries the curve's attributes. A point that falls exactly on a vertex takes the direction of either segment that meets there. The point number `id` is an Int. Built from: `core.arclength`, `curve.lay_points`, `field.gather`, `core.sample_curve`, `core.interpolate`, `core.points`, `math.*`.

# points.on_mesh (procNode) `points.surface_samples` on the `emit` scope: a face is picked by its share of the total area and a place inside it from draws 0, 1 and 2, and every attribute of the mesh is carried onto the sample. Built from: `points.surface_samples`.

# points.on_surface (procNode) `points.surface_samples` on the `points` scope, reduced to `P` and the unit normal under each point as `normal`. Built from: `points.surface_samples`, `core.points`.

# points.poisson (procNode) All the candidates of all `maxTries` rounds are thrown at once, about `(radius / minDist)^2` for each round, round after round, uniformly over the disc. Each round of a fold lets the candidates of that round stand where no point already standing and no other candidate of the round lies within `minDist`. Every point carries a tag, 1 when it stands and 1000 when it is a candidate of the round, and `core.neighbours` averages the tags of the points around each one, so a single query answers both counts. The points that stand are kept at the end by `core.select`, in round order. Later rounds fill the gaps earlier ones left, because a candidate near a standing point is dropped. Invariants (the parity test checks these, not the old op's exact points): no two points closer than `minDist`, every point inside the disc at height `y`, and the disc covered: a probe anywhere in it finds a point within twice `minDist`. Built from: `rand.unit`, `core.points`, `core.neighbours`, `core.select`, `g:fold`.

# points.relax (procNode) Each pass asks `core.neighbours` (mode `repel`) for every point's push: the mean over the points within `radius` of the unit vector away from each, weighted `(radius - d) / radius`. The point then steps `strength * radius` along it. `g:fold` repeats the pass `iterations` times. Built from: `core.reduce`, `core.neighbours`, `g:fold`, `math.*`.

# points.shell_radius (procNode) `radius = (lo + (1 - lo) * draw) ^ (1 / dims)` with `lo = (1 - clamp(shell, 0, 1)) ^ dims`. Used by `points.sphere` (dims 3) and `points.cylinder` (dims 2). Built from: `math.*` over fields.

# points.sphere (procNode) Draws on channels 0 to 2 of the `emit` scope: `u` is the height on the unit sphere, then the angle around it, then the radial share `points.shell_radius` turns into a radius. Built from: `rand.unit`, `points.shell_radius`, `core.points`, `math.*`. ```luau local burst = g.points.sphere({ count = 500, radius = 0.2, shell = 0 }) ```

# points.surface_samples (procNode) `core.sample_surface` picks a face by its share of the total area and a place inside it from the draws of the named scope; `core.interpolate` carries each attribute of the mesh onto the samples; the normal is made a unit vector and the sampler's face and corner columns are dropped. `points.on_mesh` and `points.on_surface` end here. Built from: `core.sample_surface`, `core.interpolate`, `vector.normalize`.

# procNode: one reusable step of procedural generation A `.procNode` is a node authored as content: a folder whose `init.luau` is the node. It returns `proc.define(function(g) ... end)`, the same function-of-`g` form a `.procGraph` is written in, so a node is a small graph that other graphs call. Its `g:describe` text says what it makes and when to use it, its `g:input` declarations are what a call passes, and what it returns (or declares with `g:output`) is what the call gives back. ``` MyNode.procNode/ init.luau -- the node README.md -- what it produces, its inputs, its outputs .metadata -- description and tags ``` ## What a node states - **`g:describe(text)`**: what the node produces and when to use it. It is the text search, the node catalogue and the Inspector show. - **`g:input(name, default, opts)`**: one input of the node. The default types it (`Float`, `String`, `Bool`, `Vec3`, `Color`, `List<T>`, `Record`); `opts` adds `type` (for a default that does not state one, or none), `description`, `options`, `min`, `max` and `optional`. A call names inputs in a table, or passes them in declaration order. - **Outputs**: the returned table names them (`return { geometry = geometry }`), and `g:output(name, value)` declares one as the node builds. A node with one output answers that value to its caller; a node with several answers a record by output name; a node with none answers nothing. - **Written as literals.** What a node takes and gives is read from its source without running it, the way search and description read it here and the way ZeroMind reads it, so each declaration states its values as written: `g:describe` and each `g:input` once, at the top level of the function, with a literal name, default and options (a file constant holding a literal, or `asset.resolve("<identity>", "<type>")`, reads as one); outputs named by the table the function returns, or by `g:output`, the same names on every branch of a condition and never inside a loop. `asset.interface(node)` answers what the source declares, with each part it cannot read as a problem, and a push refuses a node with such a problem (`interface.unreadable`). - **The body** is the node's work: calls to other nodes, arithmetic over sockets, `for`, folds, steps and state, as the builder README (`proc.module/builder.module/README.md`) describes. A node that uses another node is recorded in the graph that calls it, so a node can be built from nodes. ## How a graph calls a node A node inside a `<family>.nodebox` is called by its box and folder name: `points.nodebox/disc.procNode` is `g.points.disc({ ... })`, and nothing inside the node states that name. A node is also reached by: - its path (`g["/zero/source/fx/ring.procNode"]`), - `~`, the nearest enclosing package, effect or world root (`g["~/ring"]`), - its guid, - a short name only one node answers to (`g.disc`). A name that matches two nodes and a name that matches none are errors that name the candidates. Each call is recorded in the calling graph by the node's guid, so the node travels with every graph that uses it, and a rename or a move keeps the reference. A `.procGraph` is called the same way and answers what it returns. ## Nodeboxes A nodebox is the family a node lives in: a namespace folder grouping related nodes (`points`, `mesh`, `field`, `terrain`). `nodebox.assetType` describes it. A node placed in a box takes the box's name as its prefix; a node outside any box is reached by path, `~` or guid. `asset.create("nodebox", family)` makes a box and `asset.create("procNode", name, { into = box })` makes a node in it. ## Finding nodes `asset.list("procNode")` lists every node. The `procgen` toolbox's `searchNodes` finds them by keyword and by meaning and lists them grouped by family, and its `describeNode` answers one node's inputs, their types and defaults, and its outputs. Both read what each node's source declares and run no node. The type's `indexing` recipe embeds a node's README and its source, so a search by meaning finds it by its description and by its inputs. ## Registration Every node the asset index lists is known to the procgen registry by what its source declares, read when it is asked for and read again when the source changes; nothing runs a node to list it. Its code loads the first time a build runs it. After that, the lifecycle hooks keep it current: `onChange` loads it again and hot-reloads on an edit, `onDelete` removes it. Editing `init.luau` cooks again every graph that reaches the node, and only the nodes downstream of the change do work. `init.luau` is compiled from its current source on each load, so a module it pulls in uses an absolute require (`require("@builtin::systems.procgen.proc")`). A graph that references a node which is not registered errors at load, naming the missing guid. A graph that reaches itself, directly or through other nodes, errors at cook. ## Content requirements `README.md` carries real text: what the node produces, its inputs and its outputs. `.metadata` carries a `description` (what the node computes and the value type it answers) and `tags` (the family, so search finds it). ## In the Inspector Operation: the node's id and what it does, its cost and caching when it declares them, and its inputs and outputs, from the procgen registry's schema for it. A node that did not register says so.

# topology.adjacency Answer a neighbour relation over a geometry: the faces, points or edges around a point, the faces across an edge, the faces across a face. A neighbour table (offsets into values, 0-based starts) plus a per-element neighbour count written as an attribute. A `group` limits the answer to the faces it selects: the table and the geometry then describe the geometry of those faces, whose faces and edges are numbered from 0 in their order and whose points keep their numbers. ## Inputs - `geometry`: The geometry whose neighbours are listed. - `query` (one of: edge_faces, edge_points, face_edges, face_faces, face_points, point_edges, point_faces, point_points): The neighbour relation to answer, named `<source>_<target>`: "point_points" is the points an edge joins a point to, "point_faces" the faces using a point, "face_faces" the faces sharing an edge with a face. The source half also decides what the table and the count attribute are indexed by. - `element`: One source element id to report the neighbour list of directly, in `adjacency.neighbours`; negative, only the whole table comes back. An id outside the source class's element count is an error. - `attribute`: Name of the per-source-element neighbour count written onto the geometry. - `group`: Names a 0/1 attribute on `class` restricting which faces take part in the answer; empty, the whole mesh takes part. - `class` (one of: edge, point, primitive, vertex): The component class `group` lives on. - `promote` (one of: all, any): How a group on a class other than "primitive" becomes a face set.

# topology.borders For every edge of the geometry's edge table, how many of the faces that take part border it: 1 is an open edge of the participating faces, 2 a shared one. The faces taking part are all of them when no group is named. What `topology.edges` and `topology.boundary` read their open edges from. ## Inputs - `geometry`: The geometry whose edges are measured. - `group`: Names a 0/1 attribute on `class` restricting which faces take part; empty, the whole mesh takes part. - `class` (one of: edge, point, primitive, vertex): The component class `group` lives on. - `promote` (one of: all, any): How a group on a class other than "primitive" becomes a face set. ## Outputs - `borders`: Per edge of the `core.edges` table, the number of participating faces that border it.

# topology.boundary Find the open boundary of a surface: the edges exactly one face borders, as a 0/1 group on the edge and point classes, plus the ordered boundary loops. ## Inputs - `geometry`: The geometry whose open edges are traced. - `group`: Names a 0/1 attribute on `class` restricting which faces take part; empty, the whole mesh takes part. - `class` (one of: edge, point, primitive, vertex): The component class `group` lives on. - `promote` (one of: all, any): How a group on a class other than "primitive" becomes a face set. - `output`: Name the boundary is written under: a 0/1 group on the edge class for the open edges, the same name on the point class for their endpoints, and a detail attribute `<output>EdgeCount`.

# topology.convert Convert a component group between classes: points to the faces that use them, faces to their points, edges to their points, and back. `mode` = "any" selects a target element when any of its incident source elements is in the group, "all" when every one is; an element with no incident source element is selected under neither. ## Inputs - `geometry`: The geometry carrying the group converted. - `group`: The 0/1 attribute on `from` to convert. - `from` (one of: edge, point, primitive, vertex): The class the group is read from. - `to` (one of: edge, point, primitive, vertex): The class the converted group is written to. - `mode` (one of: all, any): How a target element reads the source elements incident to it: "any" selects it when at least one of them is in the group; "all" only when every one is. - `output`: Name the converted group is written under on `to`. Left empty it is `group`.

# topology.edges Derive a geometry's unique edge set with face adjacency: the `edge` attribute class (points, faces, faceCount, length) plus the edge table. An edge is the unordered point pair it joins; its index is its position in the list sorted by (low point, high point), stable for a mesh. ## Inputs - `geometry`: The geometry whose edges are listed. - `group`: Names a 0/1 attribute on `class` restricting which faces take part in the answer. Restricting it changes what is measured: an edge between a participating face and a left-out one is bordered by one face here. - `class` (one of: edge, point, primitive, vertex): The component class `group` lives on. - `promote` (one of: all, any): How a group on a class other than "primitive" becomes a face set. - `output`: Name of the 0/1 edge group written for the edges the participating faces border. Written only when `group` names a selection.

# topology.islands Label a geometry's connected components: a per-primitive island id, and for each point the lowest island id among the faces using it. `connectivity` joins faces across a shared edge or a shared point. Ids run from 0 in order of the first face that carries them. Faces a `group` leaves out carry -1. ## Inputs - `geometry`: The geometry whose connected pieces are labelled. - `group`: Names a 0/1 attribute on `class` restricting which faces take part; empty, the whole mesh takes part. - `class` (one of: edge, point, primitive, vertex): The component class `group` lives on. - `promote` (one of: all, any): How a group on a class other than "primitive" becomes a face set. - `connectivity` (one of: edge, point): What joins two faces into one island: a shared edge, or a shared point. - `attribute`: Name the island id is written under, per primitive and per point, plus a detail attribute `<attribute>Count` holding how many islands there were.

# topology.participation The faces a group selects, as a 0/1 column over the primitives: all of them when no group is named. A group on another class selects the faces every one of whose elements is in it (`promote` = "all") or at least one is ("any"). The selection every topology node restricts its answer by. ## Inputs - `geometry`: The geometry carrying the group. - `group`: Names a 0/1 attribute on `class` restricting which faces take part; empty, the whole mesh takes part. - `class` (one of: edge, point, primitive, vertex): The component class `group` lives on. - `promote` (one of: all, any): How a group on a class other than "primitive" becomes a face set: the faces every one of whose elements of that class is in the group, or the faces at least one is.

# 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.

# value.compare Two values compared, answering 1 when the comparison holds and 0 when it does not. Numbers compare by any op; text and true/false compare by `equal` and `not_equal` and must be the same kind. In a graph, `g.compare(a, op, b)` is the same comparison; this node is for an op picked by a parameter.

# value.expr A number that follows one Luau expression over the graph's clock: `t` (seconds), `frame`, `fps`, `duration`, the math functions by bare name, `clamp`, `lerp`, `smoothstep`, `noise(x)` and the names `variables` gives. The expression is run once with those names bound to sockets, so it becomes arithmetic in the graph: it follows the clock on every present and re-cooks nothing.

# value.fallback The value wired into `value`, or `fallback` when nothing is: how a graph used as a node takes an input its caller may leave unwired. `fallback` is built only when it is the one taken. A device value passes through as it stands.

# value.get One field of a record value, by a dotted path: `vertexCount`, `bounds.max.y`, `centroid.x`. Each name is a member read; a name the value does not have is an error naming where the walk stopped.

# value.math `a <op> b` for two numbers, the op chosen by name. Either side can be an animated value or a live input, and the result follows it. In a graph written with operators, `a * b` is the same node: this one is for an operation picked by a parameter.

# value.present Whether anything is wired into `value`, as a Bool: what a graph used as a node asks of an input its caller may leave unwired, to decide what it does. The answer is known when the graph is planned.

# value.switch `ifTrue` when `when` is true, `ifFalse` otherwise. Only the branch taken cooks, so a branch that would refuse its inputs is never asked.

# math.abs (procNode) The magnitude of a value, element by element. The `abs` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.acos (procNode) The angle whose cosine is the value, in radians, from 0 to pi, element by element. A value past -1 or 1 reads as the nearest of the two. The `acos` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.add (procNode) The sum of two values, element by element. The `add` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.atan (procNode) The angle of the point (`x`, `y`) from the x axis, in radians, element by element: arctangent of `y` over `x`, quadrant aware. The `atan` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.bor (procNode) The bitwise or of two whole numbers. The `bor` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.bxor (procNode) The bitwise exclusive or of two whole numbers. The `bxor` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.ceil (procNode) The least whole number not below the value, element by element. The `ceil` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.clamp (procNode) The value held between a lower and an upper bound, element by element. The `clamp` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.compare (procNode) Compare two values with a named operator: 1 where the comparison holds, 0 where it does not, element by element. Built from `math.lt`, `math.le`, `math.gt`, `math.ge`, `math.eq` and `math.ne`, one of which cooks, chosen by `op`. The operator is written as a name (`lt`, `le`, `gt`, `ge`, `eq`, `ne`, also `neq`) or as a symbol (`<`, `<=`, `>`, `>=`, `==`, `~=`, `!=`). `g.compare(a, op, b)` of the authoring surface resolves here.

# math.concat (procNode) Two texts joined end to end; the `..` operator over text values. Built from the Luau node (`io.luau`) calling `concat` of the counts module. The texts are plan values (attribute names, labels), not per-element data.

# math.cos (procNode) The cosine of an angle in radians, element by element. The `cos` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.cross (procNode) The cross product of two Vec3 values: the vector perpendicular to both, per element. The `cross` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.deg (procNode) Radians as degrees. The `deg` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.div (procNode) The quotient of two values: `a` divided by `b`, element by element. The `div` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.dot (procNode) The dot product of two vectors: a number per element. The `dot` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.eq (procNode) Whether `a` equals `b`: 1 where it does, 0 where it does not. The `eq` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.floor (procNode) The greatest whole number not above the value, element by element. The `floor` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.floordiv (procNode) The quotient of two values rounded down: the `//` operator. Built from `math.div` and `math.floor`.

# math.ge (procNode) Whether `a` is greater than or equal to `b`: 1 where it is, 0 where it is not. The `ge` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.gt (procNode) Whether `a` is greater than `b`: 1 where it is, 0 where it is not. The `gt` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.le (procNode) Whether `a` is less than or equal to `b`: 1 where it is, 0 where it is not. The `le` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.length (procNode) The length of a vector: a number per element, from the vector's components. The `length` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.lerp (procNode) The blend from `a` to `b` by `t`: `a` at 0, `b` at 1, element by element. The `lerp` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.log (procNode) The natural logarithm of a value, element by element. A value at or below 0 answers 0. The `log` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.lt (procNode) Whether `a` is less than `b`: 1 where it is, 0 where it is not, element by element. The `lt` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.max (procNode) The greater of two values, element by element. The `max` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.min (procNode) The lesser of two values, element by element. The `min` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.mod (procNode) The remainder of `a` divided by `b` that keeps the sign of `b`, so a repeating pattern wraps the same way on both sides of zero. The `mod` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.mul (procNode) The product of two values, element by element; a vector scaled by a number scales every component. The `mul` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.ne (procNode) Whether `a` differs from `b`: 1 where it does, 0 where it does not. The `ne` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.neg (procNode) The value with its sign flipped. The `neg` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.normalize (procNode) A vector scaled to length 1; the zero vector stays zero. The `normalize` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.pow (procNode) `a` raised to the power `b`, element by element. The `pow` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.rad (procNode) Degrees as radians. The `rad` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.shl (procNode) A whole number shifted left by a count of bits. The `shl` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.sign (procNode) The sign of a value: -1, 0 or 1, element by element. The `sign` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.sin (procNode) The sine of an angle in radians, element by element. The `sin` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.smoothstep (procNode) A smooth blend from 0 to 1 as `x` goes from `edge0` to `edge1`, flat outside, element by element. The `smoothstep` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.sqrt (procNode) The square root of a value, element by element. The `sqrt` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.sub (procNode) The difference of two values: `a` minus `b`, element by element. The `sub` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.tan (procNode) The tangent of an angle in radians, element by element. The `tan` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.to_float (procNode) A whole number held as a decimal. The `to_float` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.to_int (procNode) A value truncated to a whole number held as an integer. The `to_int` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.vec2 (procNode) A vector of two components from its parts: numbers, or vectors and runs whose components fill it in order. A part left out reads 0, so `vec2(x)` is (x, 0). The `vec2` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.vec3 (procNode) A vector of three components from its parts: numbers, or vectors and runs whose components fill it in order. A part left out reads 0, so `vec3(x, y)` is (x, y, 0). The `vec3` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.vec4 (procNode) A vector of four components from its parts: numbers, or vectors and runs whose components fill it in order. The `vec4` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# math.where (procNode) Choose between two values by a condition: `a` where `cond` is not 0, `b` where it is. The `where` operation of the authoring surface, called through the Luau node on `proc.fieldc.operators`. Operands are numbers, vectors, Columns or Fields. When every operand is a plain number or vector the answer is the plain result, folded where the node cooks; otherwise the answer is a Field: a template over its operands that whatever reads it evaluates in one dispatch together with the chain around it. Nothing dispatches for this node alone.

# core.adjacency (procNode) Answer a neighbour relation over a geometry as a table of offsets and items: the points around a point, the primitives that use a point, the primitives across an edge, the edges and points of a primitive, and the rest of eight relations. Relations (`<owner>_<listed>`): `point_points`, `point_faces`, `point_edges`, `face_points`, `face_edges`, `face_faces`, `edge_points`, `edge_faces`. Built from `core.owner`, `core.edges`, the `expand` kernel (a side or an end per edge; the two faces of each edge that has two are laid out over the live total of those pairs, which one read-back states), `sort` of the owner keys, `scatter` for each owner's count, `scan` for the offsets and `gather`. Outputs: `offsets` (where each owner's list starts in `items`), `counts` (the length of each list) and `items`. The relation's owners are numbered as its first word says: points, primitives or edges. ## Inputs - `geometry` (Geometry). The geometry whose neighbours are listed. - `relation` (one of point_points, point_faces, point_edges, face_points, face_edges, face_faces, edge_points, edge_faces). Default `"point_points"`. Which relation: the owner's kind, then the listed kind. "point_faces" lists, for each point, the primitives that use it. ## Outputs - `offsets`: where each owner's list starts in `items`. - `counts`: the length of each owner's list. - `items`: the listed elements, owner after owner.

# core.arclength (procNode) The length along every curve: each point's distance from the start of its curve as `s`, and each curve's total as `length`. Built from `core.owner`, `attribute.promote` (positions to vertices), `gather` of each vertex's next position, `math.length`, a segmented `scan` for the distance so far and a segmented `reduce` for the total. A closed curve counts its closing segment in `length`; an open curve has none. Written as `s` on the point class and `length` on the primitive class. ## Inputs - `curve` (Curves). The curves measured. ## Outputs - `curve`: the curves with `s` (distance along the curve) on the point class and `length` (the curve total) on the primitive class.

# core.boundary (procNode) The open edges of a geometry and the rings (or chains) they form, each ordered along its walk. Built from `core.edges`, `compact` of the open edges, the `loops` kernel (the edge that follows each one), `jump` rounds (the smallest edge in reach, then the distance to the end of each list; the rounds are `ceil(log2(edges))`), `loops_cut` and `loops_place`, and `scan` of the ring lengths (`segments = 0`). ## Inputs - `geometry` (Geometry). The geometry whose boundary is walked. ## Outputs - `edges`: Record `a`, `b`, `from`, `to`, `source`, `count` of the open edges. - `rings`: Record `ring`, `position`, `order`, `starts`, `count` of the rings.

# core.column (procNode) Make a column from a list of numbers, one element each: the values a graph computed one by one gathered into a run the device can read, such as the births of each source before a scan. Built from `op.transfer.upload`. ## Inputs - `values` (List<Number>). The numbers, in order. - `type` (one of Int, Float). Default `"Int"`. Whether the elements are whole numbers or floats. ## Outputs - `column`: the Column of the numbers.

# core.concat (procNode) Join several geometries into one: points, vertices and primitives end to end, links renumbered, every column any geometry holds. Built from the `concat` kernel, one run per column any geometry holds in each class (the `concat` module lists them, the structure columns and stored numbers such as `id`, `N` and `uv` included). `core.join` answers where each part starts. The `concat` module in this node's folder decides every column of a class in one call: the type it takes (the type the first part with elements holds it as; a part that holds it at another width is refused by name, one that holds it as another type of the same width is cast by value), the part that decides it, its description words, and whether the parts bind as they stand. A column every part holds as that type, with elements, in a run of its own, costs two dispatches whatever the number of parts: the typed destination and the join. Any other column first casts each part by value to the joined type, and the elements of a part that holds no such column stand at zero for it. The link columns shift by what comes before: `vertex.pt` by the points of earlier parts, `primitive.vstart` by their vertices. A column of a type the device cannot hold (text, a record) is laid end to end by the `concat` module in this node's folder, as a column of values; a part that holds no such column leaves its elements without a value. ## Ids The point `id` of each part moves past the ids of the parts before it, so every id of the result is unique. A part spans the larger of its next id and its point count. A part without an `id` column is numbered in order after them. A column carries no statement of what its values mean, so the join keeps a list of the point columns that hold the `id` of another point, in the `concat` module of this node: `parent`. Where some part holds ids, each part's `parent` values move by the amount its ids move, a negative value (no parent) stays, and a part without a `parent` column parents nothing (-1). Where no part holds ids, `parent` values refer to nothing the join renumbers and join as they are. A hierarchy built in two parts, each numbered from 0, keeps its parenting through the join. ## Inputs - `geometries` (List<Geometry>). The geometries joined, in order. ## Outputs - `geometry`: the joined geometry.

# core.corners (procNode) For every vertex, the vertex after it and the vertex before it in its primitive (a cycle), and the primitive it belongs to. Built from `core.owner` and the `gather` kernel. A primitive's run of `vcount` vertices starting at `vstart` is read as a cycle: the vertex after the last is the first. Outputs `owner`, `next` and `previous`, vertex indices. ## Inputs - `geometry` (Geometry). The geometry whose vertices are read. ## Outputs - `owner`: the primitive of each vertex. - `next`: the vertex after it in its primitive. - `previous`: the vertex before it.

# core.edges (procNode) The edge table of a geometry: every distinct side of its primitives as a point pair (a < b), the primitives along each side, whether the side is open (one primitive) or manifold (at most two), and the edge each vertex slot's side belongs to. Built from the `edges` kernel (the sides of every primitive), two stable `sort` passes (by the higher point, then the lower), `gather`, the `edges_runs` kernel (run heads, then the table), `compact` of the heads, an inclusive `scan` of the heads (the edge of each sorted place) and `scatter` through the slot order to give `sideEdge`, the edge id of every vertex slot. ## Inputs - `geometry` (Geometry). The geometry whose sides are listed. - `faces` (Bool). Default `true`. True for a geometry of faces, whose primitives wrap from their last vertex to their first; false for curves, which wrap only where their `closed` attribute says. ## Outputs - `edges`: Record `a`, `b`, `faceStart`, `faceCount`, `faces`, `open`, `manifold`, `reversed`, `sideEdge` (the edge each vertex slot's side belongs to, -1 for a slot with no side) and `count`.

# core.entity.read (procNode) Read live entities as columns, one element per entity, with the number read as `count`. Built from `io.engine` with `readEntities`, then `op.transfer.upload` of the columns it answers. The result is one Record: a column for each field read, and `count`; `core.points` makes points of it. The query names the entities by `ids` (a list of entity ids), `name` (a Name or glob), `component`, or `colliders` (with `sensors`); `fields` is `{ pose = true, space = "world" }` for `P`, `orient` and `scale`, or a list of `position`, `rotation`, `scale`, `id`, `shapeType`, `params` and `Component.field` names. ## Inputs - `query` (Record). Which entities: `ids` (entity ids), `name` (a Name or a glob), `component`, or `colliders = true` with `sensors`. - `fields` (Record, optional). What to read: `{ pose = true, space = "world" | "local" }`, or a list of `position`, `rotation`, `scale`, `id`, `shapeType`, `params`, or `Component.field`. - `space` (one of world, local). Default `"world"`. The space the pose fields of a list are read in. ## Outputs - `read`: Record of one column per field read, and `count`.

# core.interpolate (procNode) Carry a geometry's attributes to sample points: point and vertex values blended by the barycentric weights, primitive values taken from the sample's primitive, values that cannot blend taken from the nearest corner. Built from `gather` at the sample's corners and `math` operators for the blend, over the names `geometry.names[class]` lists for each class. A column of floats blends by `bary`; a column of integers takes the corner with the largest weight. ## Inputs - `geometry` (Geometry). The geometry sampled. - `samples` (Points). The samples: points with `prim`, `ia`, `ib`, `ic` (corner vertices) and `bary` (their weights), as `core.sample.surface` and `core.sample_curve` make them. ## Outputs - `points`: the samples with the geometry's attributes.