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

# 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.

# 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.

# 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.

# Buoyancy Floats the entity's rigid body on the sea. ```lua entity.find("barrel").component.add("Buoyancy", { density = 0.4 }) ``` The entity needs a dynamic `Physics` body. Position and orientation stay the physics world's — this component only adds the forces water exerts, so a floating body still collides, still takes impulses, and still falls when it is lifted clear of the water. | Field | What it does | |---|---| | `density` | Relative to water: the lower it is the higher the hull rides, and a body denser than water sinks. A hull settles a little deeper than the number alone asks for, so trim it until the waterline sits where it should. 0 releases the body. | | `damping` | How hard water resists the hull moving through it, as a fraction of the damping that settles it without overshoot. 1 is that critical value, 0 bobs indefinitely. Applied per column, so it steadies rolling as well as heaving. | | `angularDamping` | The same, for a hull turning. The rigid body carries it as its own angular damping while the hull is in the water, and it is the only thing that damps a spin about the hull's own vertical axis, which the per-column damping cannot see. | | `columns` | Grid resolution per horizontal axis over the footprint. 1 floats but cannot right itself; 2 is the smallest grid that produces a righting moment. | | `sizeX`/`sizeY`/`sizeZ` | The box that displaces water, in the hull's own space. All three at 0 measures it from what the entity draws. | `barrel:submersion()` reads how much of the hull was under water on the last step, and `barrel:waterline()` reads the world Y the surface stood at under it, wave motion included. Forces reach a rigid body only while the scene is playing, so a hull sits where it was placed in edit mode and settles onto the water when play starts.

# Ocean Puts a live sea on an entity. The component's fields ARE the sea state — wind speed and direction, choppiness, swell, foam, extent and detail — and the wave simulation, the GPU surface mesh and the material bound to the simulation are all rebuilt from them whenever the component wakes. That rebuild is what makes the ocean persistable. The simulation lives entirely in GPU buffers and a runtime mesh, none of which survive an engine restart; the component's settings do, and the whole sea is reconstructed from them. A scene with an ocean in it reloads into the same sea. The surface follows the viewer and covers `extent` metres around them, so one ocean is the whole sea however far anyone sails. `sampleHeight(x, z)` and `sampleDisplacement(x, z)` report where the water is — the same waves that are drawn — which is what a boat, a buoy or a swimmer floats on. Start from a `preset` (`calmClear`, `darkChop`, `darkRolling`, `heavySwell`, `whitecapped`, `murkyGrey`, `paleSwell`, `glassyDark` and `gale`) and override whatever the scene needs. Wind speed does most of the work: significant wave height goes as its square.

# ocean_assemble Unpacks one cascade's two transformed fields into the `(dx, height, dz)` displacement field the surface mesh reads, applying the `(-1)^(x+z)` sign alternation that undoes the centred-on-zero wave-vector grid the spectrum was built on. Height and horizontal displacement carry independent gains, so crest pinching (`choppiness`) can be dialled without changing wave height.

# ocean_displace Displaces the ocean surface mesh by one cascade, once per cascade per frame. The first cascade writes each vertex from the rest position stored in its UV and the rest accumulate onto it, so the mesh is rebuilt from a clean grid every frame instead of drifting. Cascades are sampled at the vertex's true world position — the mesh follows the camera, so its rest grid sits at a moving origin. The vertex normal accumulates each cascade's surface gradient (the ratio `n.xz / n.y`), which is how independent wave fields actually combine; per-fragment normal detail comes from the cascade normal maps in the surface shader, since the mesh is far too coarse near the horizon to carry it.

# ocean_evolve Advances one cascade's static spectrum to the current time — `h(k,t) = h0(k) e^{iwt} + conj(h0(-k)) e^{-iwt}` at the deep-water dispersion `w = sqrt(g|k|)` — and emits the two complex fields the inverse FFT consumes. The frequency is quantised to a multiple of `2*pi / loop_period` so the whole sea state repeats seamlessly instead of drifting as elapsed time grows. Field A packs the height and X-displacement spectra into one complex field (`H + i Dx`), which the Hermitian symmetry of both lets a single inverse transform separate again — two FFTs per cascade instead of three.

# ocean_fft Transforms one axis of an ocean cascade's complex field in place, as one dispatch per axis: a workgroup per line runs every Stockham auto-sort radix-2 butterfly stage against workgroup-shared memory, so a 256-wide transform costs one dispatch rather than eight butterfly passes and needs no bit-reversal permutation. Supports grids up to 512 per side. The axis, direction and scale arrive through the bound `plan` buffer rather than a `params:` uniform, because same-frame dispatches are chained into one submission and a uniform rewritten between them would not be seen per-dispatch.

# ocean_floor_displace Raises the seabed's flat grid into terrain: one gradient-noise field over world XZ, written into each vertex's height, with the analytic slope written into its normal. Runs when the mesh recentres rather than every frame. The terrain is still in the world; only the grid under it moves. It is a compute pass rather than the surface shader's `vertex()` hook so that every pass that draws the mesh, and everything that reads its vertex buffer, meets the same displaced geometry. The normal is the derivative of the noise rather than a difference of neighbouring vertices, so it stays correct where the grid is coarse — which, over a clipmap, is nearly everywhere. ## The collision patch The threads past the mesh write a square patch of the same field into `heights` as plain metres, row-major with the column along world X and the row along world Z — the layout a heightfield collider indexes. `plan[2]` gives the patch its world centre, its samples per side and its world span. It is the same call to the same function that raised the vertices. A second evaluation of the noise, in Luau or in a pass of its own, is a copy free to drift from the one that is drawn, and ground stood on a metre from where it is drawn is worse than ground with no collision at all — nothing reports it. ## Bindings | Buffer | Access | Contents | |--------|--------|----------| | `plan` | read | lane 0: `xy` mesh world origin, `z` vertex count, `w` noise period (m). lane 1: amplitude, lacunarity, persistence. lane 2: `xy` patch centre, `z` samples per side, `w` patch span (m). | | `vertices` | read_write | The mesh's vertex buffer, engine 23-word layout. | | `heights` | read_write | The collision patch, `side * side` f32 metres. | Dispatch `vertexCount + side * side` threads.

# ocean_floor_texture Grows the three tiling maps the seabed is built from: sand, rock, and the caustic web the sun draws on both of them. Albedo goes in `rgb` and height in `a`; the caustics map carries two independent phases in `r` and `g`. Generated rather than shipped as images. A stored texture is a binary, content-addressed asset, and a material blocked on a texture reference that never resolves never prepares — which leaves its entire uniform block unwritten and the surface black. Generating keeps the seabed on the same compute-texture path the cascade maps and the foam patterns already use. Run once per map at startup, each with its own seed. Every map tiles: each octave hashes its lattice modulo a period that divides the texture size. The caustics are constructed rather than painted. Sunlight refracting through a wavy surface lands as the light a patch gathers divided by the area it spreads over — the reciprocal Jacobian determinant of the refraction map. Writing the surface as a height field makes that map `p + k grad h`, so the determinant is that of `I + k H`; inverting it produces the sharp filaments and their crossing cusps, which are the places the determinant approaches zero and a finite bundle of light lands on almost nothing.

# ocean_foam The persistent whitecap field: a world-space region, following the viewer, in which foam accumulates where the sea folds and drains everywhere at a fixed half-life. Shading foam directly from the instantaneous fold makes it blink with the wave that caused it. This field is what gives a broken crest a wake of white behind it, and what the surface's `waves` foam layer is actually gated on. Run once per frame, after every cascade's `ocean_normals`. The two history buffers swap roles each frame; the caller binds whichever holds last frame's result as `previous`.

# ocean_foam_texture Grows the tiling greyscale pattern the three foam layers stamp on the water. It is generated rather than shipped as an image. A stored texture is a binary, content-addressed asset, and a material blocked on a texture reference that never resolves never prepares — which leaves its entire uniform block unwritten and the surface black, not merely un-foamed. Generating the pattern keeps foam on the same compute-texture path the cascade maps already use. Run once per layer at startup, each with its own seed. The noise tiles: every octave hashes its lattice modulo a period that divides the texture size.

# ocean_normals Differentiates one cascade's displacement field into a shading normal and a foam mask. Normals come from central differences of the displaced positions (so crest pinching is accounted for, unlike a height-only gradient), with wrap-around neighbours because the cascade tiles. Foam comes from the smaller eigenvalue of the horizontal displacement Jacobian: where it goes negative the surface has folded over itself, which is what a breaking wave is — so whitecaps appear from the same displacement that raised the crest rather than from a painted-on noise threshold. Fresh foam replaces the stored value immediately while old foam fades at `foam_decay` per second, leaving streaks behind broken crests.

# ocean_probe Resamples every cascade onto one small grid that the CPU reads back, so gameplay can ask where the water is without stalling a frame on the full simulation. Dispatched once per cascade: the first overwrites the grid, the rest add to it. `xyz` is the summed displacement in metres and `w` the strongest folding, so a caller can also ask whether the water at a point is breaking. The swell bank is deliberately absent — it is analytic and longer than the tile this grid covers, so `ocean.module` evaluates it directly on the CPU instead.

# ocean_spectrum Builds one ocean cascade's time-independent complex wave amplitude `h0(k)` from a JONSWAP directional spectrum: a Phillips energy core, Donelan–Banner directional spreading around the wind, a JONSWAP peak enhancement, and a `k_min`/`k_max` band limit that keeps each cascade to its own disjoint range of wave numbers. The result is randomised into a complex Gaussian so the same sea state produces a real random surface rather than a deterministic ripple. Runs when the sea state changes, not per frame — `ocean_evolve` animates the field it writes.

# islandLagoon The island the `island_lagoon` demo scene stands in, as a terrain graph. A flat lagoon bed at -14 m with a broad dome rising through sea level at roughly 1:21, carrying two surfaces: sand from the lagoon floor up past the waterline, grass over the dry crown. The gentle slope is the point — it puts a continuous range of water depth in front of the camera, which is what makes the ocean's shoaling, absorption and shoreline wash readable in one shot. ## Inputs None. Every dimension is authored in the graph; edit `init.luau` to move the waterline, widen the beach or change the relief. ## Outputs - `land`: the landscape as one element carrying `Terrain`, which the graph shows through `io.output`: the ground, its colliders and its water, standing in the scene. ## Consumers - `@builtin::systems.oceans.demo.island_lagoon` instantiates it as the demo's terrain and binds the ocean's `ground` to the entity it produces.

# Island lagoon The spectral ocean against a shore: an island rising out of a lagoon at a beach's slope, so one view holds every water depth from the waterline to open blue. Load it with `scene.load("@builtin::systems.oceans.demo.island_lagoon")`, then walk down to the water. ## What it shows - **Depth as colour.** The water column's absorption is per-channel, so the sea reads turquoise where the sand is a metre or two down and turns blue as the bed falls away. The gradient is the ground's own slope seen through the water, not a painted ramp. - **The seabed through the surface.** The bed is refracted, attenuated over the real path the light travelled, and lit by the caustic web the surface focuses onto it. - **Shoaling.** Chop dies as the bottom comes up — geometry and shading together — so the shallows are glassy while the open water stays crisp. - **The shoreline.** Wash along the waterline, foam that clings to breaking crests, and a sea that meets the sand instead of ending at it. - **A sun path over water.** The glitter track is the surface's own slope statistics under this scene's directional light. ## Things to try ```luau local Presets = require("@builtin::systems.oceans.modules.oceanPresets") Presets.names() -- nine sea states, calm to gale entity("lagoonSea").Ocean.preset = "gale" -- the same shore under a gale entity("lagoonSea").Ocean.seaLevel = 2.0 -- flood the beach ``` A preset is a whole sea — spectrum, swell, colour, all three foam layers and the seabed — so swapping one changes the water and leaves the island, the light and the sky exactly where they are. ## What it is made of - `@builtin::systems.oceans.demo.islandLagoon` — the terrain graph the island is baked from. - `Ocean` — the sea, bound to that landscape through its `ground` field. - A directional sun, an ambient fill, a `ProceduralSky` and a `PhysicalAtmosphere`. The ocean carries no light of its own: every reflection, the glitter and the foam's shading come from these.

# oceans guide The walkthrough for building a sea with the oceans package: putting an ocean in a scene, choosing a sea state and understanding which control does what, floating things on the waves, and what the simulation costs.

# oceanSeabed The ground under the sea: one gradient-noise field mixed between sand and rock, lit by the scene's own sun and ambient, with the caustics the waves above focus onto it added on top. The simulation drives the cascade displacement map, the sand and rock maps the compute pass generates, and the terrain's world origin on this material as the clipmap recentres; the blend threshold, the tiling and the caustic strength are authored here. Sea-state presets in `~.modules.oceanPresets` override these values.

# oceanWater The default open-ocean material the `Ocean` component applies: deep blue with per-channel absorption tuned for clear seawater, a near-mirror surface, and breaking-wave foam. The simulation drives the cascade normal maps, the cascade patch sizes and the scene-depth map on this material every frame; everything else is authored here. Sea-state presets in `~.modules.oceanPresets` override these values for paleSwell, gale and the rest.

# buoyancy Floats a rigid body on the sea the simulation is already drawing. ```lua local buoyancy = require("@builtin::systems.oceans.modules.buoyancy") buoyancy.attach(barrel, { density = 0.4 }) ``` Or attach a `Buoyancy` component next to the entity's `Physics` body and author `density` / `damping` / `angularDamping` / `columns` on it — the component calls this module every frame. ## A hull is a bundle of columns A grid is laid over the hull's footprint, and each cell stands for a vertical prism spanning the hull's full height. Every column measures the water above its own base, and carries the share of the displaced volume that implies, applied at its own position. That is what the grid is for. One force at the centre of mass can only push a body up and down; forces spread over the footprint push harder on the side that is deeper, which is what rights a hull that has been tipped over and what makes it pitch as a wave rolls under it. `columns = 1` is a single central column: it floats, but it cannot right itself. ## Density sets the waterline `density` is relative to water: the lower it is, the higher the hull rides, and a body denser than water sinks. `buoyancy.restingY(waterY, height, density)` gives the height at which a hull of that density displaces its own weight. A hull settles somewhat deeper than that height, and how much deeper moves with how long the frames are — a force applied from a script acts over a frame, while gravity is integrated by the physics step, so the two balance a little below where the arithmetic puts them. Densities up to about a half float on every frame time measured; above that a hull rides progressively lower and sinks outright on a long frame. Trim the number until the waterline sits where it should. The body's own mass comes from its rigid body, whether `Physics.mass` sets it or the solver derives it from the collider volume, and the buoyant force is scaled against it, so a hull floats at the same waterline whatever mass it was authored with — mass changes how briskly it gets there, not where it ends up. `mass` and `gravityScale` may be passed to `attach` / `configure` for a body whose rigid body says something else. ## Damping is measured against the hull's own spring Buoyancy is a spring: push a hull under and the water pushes back in proportion to how far, so it has a natural frequency of its own, set by how deep it has to sink to displace its own weight. `damping` is a fraction of the damping that would return it to its waterline without a single overshoot — 1 is that critical value, lower values let it bob on the way, 0 bobs indefinitely. Reading it as a ratio rather than an absolute rate is what keeps a dinghy and a barge equally steady at the same setting. It is applied per column against that column's own velocity, so it steadies rolling as well as heaving; a body spinning about its own vertical axis moves every column but their forces cancel in pairs, so `angularDamping` damps the hull's turning on top of it. That one is handed to the rigid body as its own angular damping rate for as long as the hull is in the water, so the physics step takes the spin down itself and can never overshoot the rest it is bringing the body to. Both scale with how much of the hull is actually in the water, so a body lifted clear of the sea falls freely. ## The hull's box The hull is measured from what the entity draws, in the entity's own space, so it stays the same box however the body is turned. Where that box sits comes with it, so a model drawn off its own pivot — a keel-pivoted boat, an offset child mesh — displaces water where it draws and carries its columns over that footprint. What an entity draws arrives over the frames after it is spawned, so the measurement is retried until it lands and a body keeps its place while it waits. `sizeX`/`sizeY`/`sizeZ` name a box explicitly — for a body whose visible mesh is not what displaces water, or one that draws nothing at all. That box is centred on the entity's origin, and it belongs at the size of the body that is actually there: the water pushes on the rigid body's own inertia, so a footprint much wider than the collider rocks a hull the body has no weight to steady. ## What it reads The water height comes from `ocean:sampleHeight`, the same wave field the surface renders, so a hull rides the waves that are on screen. With no ocean in the scene there is nothing to float on and the body is left to the physics world; pass `ocean` to pick one when a scene has several.

# ocean The oceans package's substrate. One `Ocean.create` call brings up a live sea: the GPU wave simulation, the surface mesh that renders it, the material bound to the simulation's output, and the coarse readback gameplay queries. The simulation is spectral and runs in cascades — independent wave fields over different patch sizes, each band-limited to its own range of wavelengths, summed into one surface. That is what gives detail at every scale (swell, wind waves, chop) while keeping each transform small. The surface is one mesh whose vertices a compute pass rewrites every frame, so no wave data crosses to the CPU for rendering. It is graded radially and follows the viewer, snapped to a wave-patch multiple so the sea stays put in the world while the mesh slides under it. `sampleHeight` / `sampleDisplacement` answer where the water is, from a small grid read back off the GPU a few times a second — enough to float a boat on the same waves that are drawn without stalling a frame on a round-trip. Both invert the horizontal wave displacement, so they return the surface point that actually ended up above the position you asked about. Use the `Ocean` component to place a sea in a scene; use this module directly to drive one from code.

# oceanClipmap Builds the ocean's geometry: concentric rings that double in extent and halve in density outward, the stitch strips that remove the T-junctions between them, and the skirt that carries the water out to the horizon. Returns the vertex and index data as Luau buffers, ready to upload straight into the compute buffers `ocean_displace` rewrites each frame.

# oceanFloor The ground the water is seen through. It spans the same extent as the clipmap, follows the viewer the way the surface does, and is shaded by `~.shaders.oceanFloor`. One noise field is the whole terrain: scaled it is the relief the seabed's vertex stage raises the grid into, and read again unscaled it picks between sand and rock. Over both moves the sun's caustic web, displaced by the horizontal displacement of the water directly above it. The seabed applies no absorption of its own. The water column belongs to the surface shader, which knows the real distance light travelled through water; attenuating here as well would darken the ground twice. Its three tiling maps are grown once by `ocean_floor_texture` — the same compute-texture path the cascade maps take — so the seabed carries no binary asset and no content reference that could fail to resolve. ```luau local Floor = require("@builtin::systems.oceans.modules.oceanFloor") local floor = Floor.create({ config = cfg, -- a resolved ocean config extent = 12800, -- the clipmap's own extent, metres prefix = "ocean1_floor_", name = "Seabed", }) floor:bindWave(cascadeDisplacementTexture, cascadeTile) floor:step(elapsed, viewerX, viewerZ) floor:destroy() ``` `Ocean` creates and drives one of these itself whenever the sea state's `floor` block is enabled, so a scene that uses the `Ocean` component gets a seabed without naming this module at all.

# oceanPresets Named sea states for the oceans package — `calmClear`, `darkChop`, `darkRolling`, `heavySwell`, `whitecapped`, `murkyGrey`, `paleSwell`, `glassyDark` and `gale`. Each name says what the water does, so a sea can be picked off the list without reading its values. A state is an `OceanConfig` fragment applied underneath whatever the caller passes to `Ocean.create`, so any single field can be overridden without giving up the rest. The states are laid out along the Beaufort scale, because wind speed is what determines wave height in a spectral ocean — the remaining fields shape character: how long the swell runs, how readily crests break, and what colour the water body is. `materialProperties` returns the appearance half of a preset, ready to apply to an ocean material.

# oceanQuality The four quality tiers: how finely the sea is resolved, as distinct from what sea it is. A tier owns the FFT grid per cascade, the clipmap's ring density, the swell band count, the whitecap field's resolution and whether screen-space reflections run. It never touches wind, spectrum shape or colour — those come from the preset, so the same named sea looks like itself on any machine.

# oceanScene The seam between the `oceanScene` render feature, which captures the colour and depth behind the water, and the ocean materials that sample them. `renderer.feature.create` hands back a handle rather than the feature module, so a shared module is how the half that fills the textures reaches the half that reads them.

# ocean_copy Copies the ocean's rendered surface into the scene target. ## Bindings | name | kind | |------|------| | `scene_depth` | `texture_depth` | | `scene_color` | `texture2d` | | `depth_out` | `storage2d (r32f)` | | `color_out` | `storage2d (rgba16f)` |

# oceanCalmClear The "Calm Clear" sea state, offered as `calmClear` in the ocean's preset list (slot 1 in the calm-to-gale progression). The lightest wind in the catalogue, at 4 m/s, over the brightest and clearest water it holds, above a shallow shoal. A complete `oceanPreset` configuration: spectrum and swell, colours, fresnel, all three foam layers, the seabed and its caustics, subsurface scattering, screen-space reflections and the sun sparkle.

# oceanDarkChop The "Dark Chop" sea state, offered as `darkChop` in the ocean's preset list (slot 2 in the calm-to-gale progression). A brisk wind chopping the darkest water in the catalogue, with almost no swell running underneath it. A complete `oceanPreset` configuration: spectrum and swell, colours, fresnel, all three foam layers, the seabed and its caustics, subsurface scattering, screen-space reflections and the sun sparkle.

# oceanDarkRolling The "Dark Rolling" sea state, offered as `darkRolling` in the ocean's preset list (slot 3 in the calm-to-gale progression). Dark water rolling under a long swell, on the least choppy surface in the catalogue. A complete `oceanPreset` configuration: spectrum and swell, colours, fresnel, all three foam layers, the seabed and its caustics, subsurface scattering, screen-space reflections and the sun sparkle.

# oceanGale The "Gale" sea state, offered as `gale` in the ocean's preset list (slot 9 in the calm-to-gale progression). The strongest wind in the catalogue, at 38 m/s, raising a fully wind-driven sea under the heaviest surface foam. A complete `oceanPreset` configuration: spectrum and swell, colours, fresnel, all three foam layers, the seabed and its caustics, subsurface scattering, screen-space reflections and the sun sparkle.

# oceanGlassyDark The "Glassy Dark" sea state, offered as `glassyDark` in the ocean's preset list (slot 8 in the calm-to-gale progression). No swell at all and the highest standing-wave ratio in the catalogue: a still, strongly refracting surface over near-black water. A complete `oceanPreset` configuration: spectrum and swell, colours, fresnel, all three foam layers, the seabed and its caustics, subsurface scattering, screen-space reflections and the sun sparkle.

# oceanHeavySwell The "Heavy Swell" sea state, offered as `heavySwell` in the ocean's preset list (slot 4 in the calm-to-gale progression). The largest and longest swell in the catalogue, running through mid teal-green water. A complete `oceanPreset` configuration: spectrum and swell, colours, fresnel, all three foam layers, the seabed and its caustics, subsurface scattering, screen-space reflections and the sun sparkle.

# oceanMurkyGrey The "Murky Grey" sea state, offered as `murkyGrey` in the ocean's preset list (slot 6 in the calm-to-gale progression). Grey, murky water whose reflections fall away close to the eye and which carries no glitter at all. A complete `oceanPreset` configuration: spectrum and swell, colours, fresnel, all three foam layers, the seabed and its caustics, subsurface scattering, screen-space reflections and the sun sparkle.

# oceanPaleSwell The "Pale Swell" sea state, offered as `paleSwell` in the ocean's preset list (slot 7 in the calm-to-gale progression). A big swell under one of the lightest winds in the catalogue, through the palest blue subsurface transmission it holds. A complete `oceanPreset` configuration: spectrum and swell, colours, fresnel, all three foam layers, the seabed and its caustics, subsurface scattering, screen-space reflections and the sun sparkle.

# oceanPreset A complete sea state for the ocean system: everything `ocean.create` needs to stand up a specific sea, from the wave spectrum to the seabed under it. Each `.data` instance is one named preset offered in the ocean's preset list. ## Fields - `key` — the name the preset answers to in `ocean.create({ preset = ... })` and the presets API. Stable; world content refers to it. - `label` — the human-readable name shown in pickers. - `order` — the preset's slot in the calm-to-gale progression the list is offered in (1 = flattest). - `seed` — the spectrum's random seed. - `waves` — the FFT spectrum: wind speed and direction, choppiness, gravity, JONSWAP gamma, spectral sharpness, standing-wave ratio, animation speed, and a global amplitude on top. - `cascades` — the three simulation bands: per-band enable, amplitude and world-space tile scale in metres. - `gerstner` — the analytic long swell layered under the FFT bands: wavelength and its spread, amplitude, wave count, directional spread. - `clipmap` — the surface mesh: base tile size in metres and ring count. - `color` — the water column: absorption rates authored as a hex triple (decoded to per-channel 1/m extinction), transmission and body colours, and the depth assumed where nothing stands behind the water. - `fresnel` — the mirror: distance fade start/power, index-of-refraction ratio, normal strength, screen-space refraction strength. - `foam` — the three layers: `surface` lace, `waves` whitecaps (with persistence, optional `breaking` window and `placement` mask), and the `shoreline` wash. - `floor` — the procedural seabed and its `caustics` web. - `shore` — how deep the bottom starts taking the waves (`shoalDepth`, metres); omitted, the ocean's default shoaling band applies. - `sss` — subsurface scattering through backlit crests. - `ssr` — screen-space reflections. - `sparkle` — the sun's specular glint. Colour-valued fields are authored as `#rrggbb` strings and decoded to linear RGB by `Presets.color` on the way to the GPU — including `absorptionColor`, whose channels are extinction rates rather than a colour.

# oceanWhitecapped The "Whitecapped" sea state, offered as `whitecapped` in the ocean's preset list (slot 5 in the calm-to-gale progression). A hard wind raising the steepest crests in the catalogue, whose foam is the heaviest and the slowest to fade. A complete `oceanPreset` configuration: spectrum and swell, colours, fresnel, all three foam layers, the seabed and its caustics, subsurface scattering, screen-space reflections and the sun sparkle.

# oceanScene Copies the colour and depth of everything drawn behind the water into textures the ocean surface material can sample. A surface shader cannot bind the frame's own depth buffer or colour target while drawing into them, and the water needs both: depth gives the length of the water column, and colour is what refraction bends and what screen-space reflections march through. Both copies run at `afterOpaque` and are published through `~.modules.oceanScene`, which is where the ocean materials pick them up.

# oceanFloor The seabed under the spectral ocean: sand where the ground has settled, rock where it has not, lit through the water by a moving web of focused sunlight. One noise field decides the whole terrain. Scaled, it is the relief the vertex stage raises the mesh into and the normal that shades it; unscaled, the same field picks between sand and rock — so rock outcrops stand on the high ground and sand fills the hollows, because the two are readings of one surface rather than independent patterns laid over each other. Both ground maps carry albedo in `rgb` and height in `a`. The height is differenced into a detail normal that rides on the terrain's own slope as a gradient, so relief accumulates rather than one normal replacing the other. The caustics are two layers of the caustics map scrolling against each other at slightly different scales and in opposite directions, displaced by the horizontal displacement of the water directly overhead — which is what makes the web ripple with the surface instead of sliding across the ground as one rigid sheet. Each colour channel is read at its own small offset, giving the chromatic fringe focused light through a dispersing medium has. The seabed applies NO absorption of its own. The water column above it belongs to the water surface, which knows the real distance the light travelled through water; attenuating here as well would darken the ground twice. The mesh follows the viewer, so `floor_center` carries where it currently sits and every terrain and texture lookup is made in world space. That is what keeps the ground still while the mesh slides beneath it.

# oceanSurface The water surface of the spectral ocean. Geometry arrives already displaced by `ocean_displace`, so this shader only decides what the surface looks like: the normal summed across cascades as gradients (which is what adds when wave fields overlap), a water column shaded by per-channel Beer–Lambert extinction over the distance to whatever lies behind it, Fresnel reflection from the scene's own reflection probes, subsurface scattering through backlit crests lit by the scene's directional light, a sharp sun-glitter lobe, and foam from the simulation's own breaking-wave mask plus a shoreline band. Opacity is the extinction rather than an authored constant, so colour and transparency stay consistent from a turquoise shallow to a near-black deep. Works from below as well as above.

# Package (asset type) A package is an asset — a `<Name>.package/` folder that bundles components, modules, scenes, presets, tools, and any other typed sub-assets under one identity, installed into a world as one unit. Packages are how authoring sets get distributed across worlds. A **library** is the addressable root scope content resolves under (`@builtin`, `@<name>`) — a whole world mounted into this one under a namespace, via `zeromind.installLib` / `world.installLibrary`. A package is an asset that lives inside such a root, and one library holds as many packages as its author put there. A package is installed by guid the way every asset is (`zeromind.install`, `zeromind.installAsset`). ## When to use one - You're authoring a coherent feature suite (character controller stack, voxel engine, UI kit, animation library) and want to ship it as one install target. - You want a stable identity worlds can install and resolve sub-assets against (`@<lib>::pkg.sub_module`). - You want versioning + a per-package metadata layer that travels with the contents. If you're authoring inside a single world and don't need a separate install lifecycle, you don't need a package — drop your `.component` / `.module` / etc. directly in `/zero/source/`. Packages are for cross-world distribution. ## Where it lives - Source: `/zero/source/.../<Name>.package/` (or, for legacy packages, a folder containing `package.yaml` at its root). - Identity: `<Name>` (the `.package` suffix collapses in identity — mirrors `.module`). A file at `<Name>.package/<sub>/init.luau` resolves under the same identity it would at `<Name>/<sub>/init.luau`. - Folder shape (container-style — open child set): - `package.yaml` — metadata (name, version, description). **Required.** - `README.md` — instance documentation. **Required.** - `.metadata` — agent-editable tags + free-form fields. **Required.** - Sub-asset folders: any combination of `.component/`, `.module/`, `.scene/`, `.preset/`, `.tool/`, `.toolbox/`, `.material/`, `.shader/`, etc. The validator permits unlisted children (`allow_unlisted: true`) by design — packages are open containers. ## How to create one ```luau asset.create("package", "<Name>") -- Creates: /zero/source/<Name>.package/ -- package.yaml (metadata scaffold) -- README.md (instance README template) -- `folder` places it in a subfolder of /source instead of the root: asset.create("package", "<Name>", { folder = "systems" }) ``` Then scaffold sub-assets inside it: ```luau local pkg = asset.resolve("<Name>.package") asset.create("component", "Spinner", { into = pkg }) asset.create("module", "util", { into = pkg }) ``` ## How it operates 1. **Registration.** Writing `package.yaml` indexes the package with the package registry. 2. **Install.** A package is installed by guid, the way every asset is: `zeromind.install` from the shared library, or `tools.use("zeromind", "installAsset", <guid>)` inside the engine. The install writes the package's files (and the deps its `.refs` record) into this world's source, so its sub-assets resolve here. `tools.use("zeromind", "preview", <guid>)` reports what an install would write before it writes anything. 3. **Sub-asset resolution.** Because `.package` collapses in identity, sub-asset paths work whether the package folder is suffixed (`<Name>.package/<sub>`) or not (`<Name>/<sub>`). 4. **Updates.** `tools.use("zeromind", "updates")` lists installed content with upstream changes available; re-running the install pulls them. 5. **Metadata.** `package.yaml::name` overrides the folder stem if present (rare); `version` + `description` are surfaced in the package index. 6. **Hot reload.** Edits to sub-assets hot-reload as normal; edits to `package.yaml` reload package metadata. ## Discovery - `asset.list("package")` — every registered package. - `asset.inspect("<name>")` — sub-asset catalog, source, this type README. - `ls /zero/source/<Name>.package` lists the files the folder holds. - `library.list()` — the library assets registered in this world, including the ones packages under an installed library contribute. ## Authoring conventions - Name packages by their feature (`voxels`, `cameraRigs`, `dialogSystem`), not by their owner — the host library is the `@<lib>::` scope prefix. - Cluster cohesive sub-assets together. A "character controller" package should ship the controller component, its preset configs, its supporting modules, and a demo scene — not just the component. - Document the package's surface in `README.md` — what install installs, what each sub-asset does, how they relate. Agents reading `cat /zero/source/<Name>.package/README.md` get the full picture in one shot. - Version conservatively — breaking a package means breaking every world that installed it. Use semantic version bumps. ## Common pitfalls - **Missing `package.yaml`.** Without it the folder isn't recognized as a package even if it has a `.package/` suffix. - **Dependency installs.** A package that depends on another package must declare it (in `package.yaml::dependencies` once supported) and the parent world must install dependencies in order. - **Identity collapse.** Sub-asset paths skip the `.package` suffix. Don't include `.package` in `require` strings. ## Referencing inside a package: the `~` rule `~` means **this package**, resolved structurally from the referring file's own location. It is the only package-specific syntax. It is rename-safe (no package name is ever written) and library-agnostic (it never names the host library, so it survives `@builtin` being renamed or the package being mounted elsewhere). `~.tail` maps to `<pkg>.package/tail` from anywhere inside the package. | Referencing from | Use | Example | |---|---|---| | An asset/module **inside this package** | `~.tail` | `require("~.modules.myThing")`, `shader: "~.shaders.myThingBlend"` | | A **different package** under the same root | root-relative identity | `require("@root::systems.otherPkg.modules.x")` | | A **different library's** public API (a deliberate external dependency) | `@otherlib::…` | `require("@physics::modules.rigidbody")` | **Never write `@builtin::` (or any host-library name) to reference your own package** — that couples the package to the library it currently lives in and breaks if the library is renamed or the files move. Use `~.`. It works from Luau `require()` and from asset-reference strings in data files (a material's `mat.yaml` `shader:` field, a component's default asset ref); the engine resolves it against the referring file's own package. `asset.resolve` takes a `~.` name the same way, against the package of the file that calls it: `asset.resolve("~.materials.myThingStandard", "material")`. `~.` is the package-relative self-reference; `@root::` is the root-relative one (the library root, or the world source tree for non-library content). The `core/requiring-modules` guide covers the root model in full. A package that ships substantial functionality should include a `.guide` asset (a `<name>.guide/guide.md` folder anywhere under the package); the `guides` tool discovers it live, so collaborators find the system the way they find built-in guides. A package's test suite reaches the shared `Test` framework through its enclosing asset: `local Test = asset.containing(__FILE__).modules.shared` (`asset.containing` returns the deepest enclosing typed asset, the `.testSuite`, not the outer `.package`). ## Related types - Any of `.component`, `.module`, `.scene`, `.preset`, `.tool`, `.toolbox`, `.material`, `.shader`, `.style`, `.service`, `.importer` — packages bundle these. ## In the Inspector Package: the name, version and description package.yaml declares, how many things the package holds and what they are, and **Open** for package.yaml. A package.yaml that does not decode is listed under Problems with the decoder's error.

# procGraph (asset type) A `.procGraph` asset is a **procedural graph**: a description of how to make something, written as code, that can be evaluated over and over with different numbers. Its `init.luau` returns `proc.define(...)` — that source IS the asset, the way a `.procNode`'s `init.luau` is. ## Shape A `<name>.procGraph/` folder containing: - `init.luau`: the graph's definition. Returns `proc.define(function(g) … end)`, the graph named by its asset folder. - `graph.json` — the compiled form (`proc.graph.v1`), written by this type from `init.luau`. Generated, never hand-edited. - `README.md`, `.metadata` — the universal asset files. ## Authoring Edit `init.luau`. The type recompiles on the write, rewrites `graph.json`, and every live `Generator` bound to the asset re-cooks from it — there is no build step between saving and seeing the result. A recompile is cheap however large the graph: node results are keyed by content, so recompiling an unchanged node reuses its cooked output, and an edit invalidates only that node and the ones downstream of it. Changing the last step of a landscape does not re-run the erosion above it. Two words worth keeping apart, because both happen here: - **compile** — `init.luau` → `graph.json`. Produces the graph. - **cook** — each node performing its operation to produce a value. Runs the graph. Driven by a `Generator`, reported by `procgen.cooks`. ## Using one Through the ref rather than a path string: `ref:eval("mesh")` evaluates an output, `ref:inputs()` lists the knobs a Generator can override by name, `ref:outputs()` the values it produces, `ref:validate()` type-checks it, and `ref:asOp()` wraps it so another graph can composite it as a node. Generated outputs (meshes, materials, textures, bundles) are persisted through their own asset types. ## Related - `@builtin::systems.procgen.proc` — the authoring + evaluation model. - `procgen.toolbox` — `preview`, `spawn`, `bake`, `validate`, `ops`, `schema` and the wider tool family. ## In the Inspector The Inspector shows the graph as nodes and wires, and edits it there. Every graph input, op, graph used as a node and output is a node; each input port that nothing is wired into carries the value that drives it, and a click on a value edits it where it stands (typing, dragging a number, flipping a switch, choosing from a list). Drag a node to move it, drag from a port to another port to connect, drag a connected input away to take its wire off, Delete removes the selection. A node is added from the op search under the graph, or from the procGraph assets, which stand as nodes that open their own asset on a double click. The graph's inputs and outputs are nodes too: their name, type, default and range, and an output's domain, are values on them, and the Inputs and outputs section declares new ones. Describes is the sentence search finds the graph by. Every edit is written into `init.luau` with `proc.saveSource` and compiled by the type, so a live Generator re-cooks on it; the node positions are kept beside the graph in `layout.json`. The Result section scrubs the timeline of a graph that has one and shows what the selected node makes (`procgen.preview` with the target `node:<id>`), and the Preview section above it shows what the graph makes, live. **Compile** and **Open** for its source stay as they were.

# luau_introspect (module) Parses Luau/asset source TEXT into structured declarations. Pure string/pattern parsing (`string.find` / `string.match` / `string.gmatch`) over the literal source — no compiling, no VM spawn, no runtime state, no engine FFI. Given source text, it extracts what is written in the file. This is the shared parser every per-assetType `M.ref.inspect` hook uses to turn a component/module/tool's own source into the structured record `asset.inspect` returns. ## Exports - `docstrings(src) -> DocMap` — scans `--!desc` / `--!arg` / `--!return` / `--!example` comment runs and binds each run to the name of the declaration on the next non-comment line (the identifier after `function`, `public:`, `local function`, or `M.`). - `publicFields(src) -> { FieldEntry }` — parses `public = { name = Field.<kind>(default, mode), ... }` table-literal entries and module-scope `public.<name> = Field.<kind>(...)` assignments. - `events(src) -> { EventEntry }` — parses `events = { name = Event(payloadSchema?, syncMode?), ... }` table-literal entries. - `methods(src) -> { MethodEntry }` — parses `function public:<name>(...)` / `typed function public:<name>(...)` declarations (params + optional return type). - `lifecycleHooks(src, catalog) -> { string }` — top-level `function <name>(` declarations whose name is in the caller-supplied `catalog` array. - `moduleExports(src) -> { ExportEntry }` — parses `M.<name> = function` assignments, `function M.<name>(...)` declarations, and a trailing `return { foo = foo, ... }` export table. - `forSource(src, computeFn) -> any` — memoises `computeFn(src)` keyed on `src` itself in a module-local table. The same source text returns the cached result without re-running `computeFn`; different source text recomputes. Keyed on the source content (not an asset checksum) because composite/container assets (component folders, scene folders, etc.) all hash to the empty-string checksum — a checksum-keyed cache collapses every such asset's detail onto whichever one was inspected first. ## Usage ```luau local Introspect = require("modules.luau_introspect") local src = self:getInitScript() local detail = Introspect.forSource(src, function(s) return { fields = Introspect.publicFields(s), events = Introspect.events(s), methods = Introspect.methods(s), hooks = Introspect.lifecycleHooks(s, lifecycleCatalog), } end) ``` ## Notes - Every function is a pure string→table transform: same source text in, same structured table out, every time. No reads of live component state, no entity/world queries. - Structural scanning runs over a comment- and string-aware **mask** of the source (a same-length copy where comment bodies and string-literal contents are blanked to spaces, delimiters and newlines preserved). Pattern matches and brace/paren balancing run on the mask — so a brace, `Field.`, `Event(`, or a whole entry that appears inside a comment or a string literal never registers — while captured values are sliced from the original source at the same (aligned) indices. This makes the parser robust to apostrophes in comments, commented-out entries, string defaults containing `}` / `Field.` / `Event(`, and `[[ ]]` long strings. - `default` / `category` are raw trimmed source-text slices (with any trailing comment stripped), not evaluated values. - For a **ref constructor** (`Field.assetRef` / `dataRef` / `resource` / `componentRef`) the FIRST positional argument is the category / contract / componentType selector, captured under `category`; the SECOND argument is captured under `default`. - For every **other** Field kind the first argument is the `default` and `category` is nil. - A trailing `Sync` / `NoSync` identifier is captured as `sync`, tolerating a trailing comma or a trailing comment after the last argument. - Field/Event entries whose key is a computed or indirect expression (`[expr] = Field.number(...)`) are omitted — only literal identifier keys are recognised. - `methods` captures a `...` variadic parameter (as `name = "..."`), with its `: <type>` annotation when present. - A `--!desc` written above a field/event declaration (`<name> = Field.<kind>(...)` / `<name> = Event(...)`) or a `public.<name> =` assignment binds to that name in `docstrings`, and is folded into the corresponding `publicFields` / `events` entry's `desc`. - `lifecycleHooks` never hardcodes the lifecycle-callback catalog; the caller passes the list of names to match against. - `forSource`'s memo is bounded (oldest-key eviction) so a long session touching many distinct asset versions can't grow it without limit.

# 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.

# ik.reach How far a limb can extend, and how far away a point is, in the same units — plus whether that point falls inside the reachable band. Part of `ik.toolbox`; surfaces as `ik.reach`. This is the first thing to check when an IK solve looks inert. A limb reaches as far as its bones are long and no further: a target beyond that has no solution, so the chain extends straight toward it and stops. That is correct behaviour and it is indistinguishable from a broken solver by eye. There is a lower bound too — a two-bone chain cannot fold its tip closer to the root than the difference between its segment lengths. Everything is reported in world units, so the rig's model space never has to be reasoned about. That matters because a limb's `reach` as the component reports it is in model space, where a 0.61 m arm reads as about 61, and the scale factor usually lives on a node inside the imported body rather than on the entity you set `localScale` on. Takes either a canonical limb role (`leftarm`, `rightarm`, `leftleg`, `rightleg`) or a `"rootBone..tipBone"` pair, so it works on rigs that carry no retarget profile at all.

# 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.