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# Module (asset type) A module is a reusable, stateless (or globally-stateful) Luau library that other code pulls in with `require()`. Modules are the unit of factored-out logic in a world: helpers, math libraries, format parsers, registries, shared algorithms. ## When to use one - You have logic you want to share across multiple components, services, scenes, or tools. - You have a registry, lookup table, or shared cache that callers all read from / write to. - You want a stable API surface (`M.fn`) other code can depend on. If the logic is bound to one entity, use a `.component`. If you want a named UI of fields rather than functions, use a `.preset`. ## Where it lives - Source: `/zero/source/.../<name>.module/` - Identity: the source path with `/` written as `.` and each segment's type suffix dropped — `/zero/source/demo/beats.module` is `demo.beats`, and `/zero/source/kit.package/beats.module` is `kit.beats`, the container's name kept and its `.package` suffix gone. `asset.create` returns this string, `asset.resolve(...).identity` reads it back, and the `require` forms below write it as `<identity>`. - Folder shape: - `init.luau` (or `init.lua`) — module body. **Required.** Returns a table (conventionally named `M`). - `README.md` — instance-level documentation. **Required.** - `.metadata` — agent-editable tags + free-form fields. **Required.** ## How to create one ```luau asset.create("module", "<name>") -- Creates: /zero/source/<name>.module/ -- init.luau (canonical `local M = {} … return M`) -- README.md (instance README template) -- `folder` places it in a subfolder of /source, and that subfolder -- leads the identity: `{ folder = "lib" }` produces `lib.<name>`. -- `into` authors it inside a resolved container (a package, a toolbox), -- whose own identity leads the same way: asset.create("module", "<name>", { folder = "lib" }) asset.create("module", "<name>", { into = asset.resolve("myPkg.package") }) ``` ## How it operates 1. **Registration.** Writing `init.luau` into a `.module/` folder indexes the asset and registers the module path with the resolver. 2. **Loading.** The first `require("<identity>")` runs the file's body and caches the returned table. Subsequent requires from anywhere return the **same table** — this is the shared-state lever for "module-local" registries. The body runs in an environment of the module's own: a name it declares without `local` is readable by the module's own functions and by no other script, so an export reaches its callers through the returned table and nothing else. Requiring a component's folder runs its chunk the same way, once, and its `update`, `start` and `public` stay in that environment; a component runs on an entity through `entity(id).component.add(name)`. 3. **Hot reload.** Editing the file re-runs the module body and folds what it returns into the table already loaded, so that table keeps its identity: a caller that captured it with `require` reads the new source's functions and values through the reference it already holds, and a later `require` returns that same table. A key the new source drops goes away; a key something set at runtime stays. The body's own `local`s start again from their initial values, so state that must outlive an edit lives in `modules.state()` (`guides { path: "core/scripting-and-tasks" }`). 4. **Identity resolution.** A module is reached by its `<identity>`, and where the caller lives decides which spelling of it resolves. For a module in a **world**, from a caller in that same world — another module, a component, a scene entrypoint, or an `execute` chunk: - `require("<identity>")` — the identity on its own, resolved against the caller's own root. It carries every folder segment, so a module created with `{ folder = "demo" }` is `require("demo.beats")`. - `require("@root::<identity>")` — the same root-relative resolution, written out. - `require(".sibling")` — a module in the same folder, by its bare name; `..name` steps up one folder, `...name` two. Logs, stack traces and hot-reload notices name that same module `@local.source.<identity>` — its key under the world source root. The `<identity>` tail of that key is the form above, so a trace reading `@local.source.demo.beats` is `require("demo.beats")`. For a module in a **library** — content under `/zero/source/libs/@<lib>/` — `@<lib>::` addresses that library's root from anywhere: `require("@builtin::modules.transform")`. Mounting a world as a library moves its files under such a root and flips the caller root to `@<lib>::`, which is what keeps the root-relative forms above resolving across the move. ## Discovery - `asset.list("module")` — every registered module. - `asset.inspect("<name>")` — public functions, source path, this type README. - `ls /zero/source/<name>.module` lists the files the folder holds. ## Authoring conventions - Return a single `M` table from `init.luau`. Top-level statements with side effects run on first require — useful for one-time initialization, dangerous if they touch the engine before it's ready. - Write exported functions as `typed function`, not `function`: the argument types are enforced at the call and the checker knows the signature, so a caller's mistake is reported where they made it. - Annotate exported functions with `--!desc` / `--!arg` / `--!return` / `--!example` so the LSP, `tools.list`, and `asset.inspect` surface them. A function with no `--!desc` is reachable only by someone already reading this file. - Declare a VALUE with `Field.<kind>(default, mode, description)`, and a table whose members are reached through a metatable with `--!members <TypeName>` — the latter gives the surface its accepted member set, its type, and its documentation from one table. See `guides { path: "core/authoring" }` for all four rules and `modules/api/engine/entity.module/members.module` for a worked member table. - Keep module state in module-local upvalues or in `modules.state()`. A name the body declares without `local` lives in the module's environment, which every run of the module shares: a function the previous run left in place reads what the reload assigned. Module-locals start again from their initial values with each hot reload; the table `modules.state()` returns is the same table on both sides of every reload. - Prefer focused modules over kitchen-sink modules. If two halves of a module have no shared state, split them. ## Common pitfalls - **Cyclic requires.** A `require` chain that loops will return the partial table (the half built before the cycle was detected). Design for one-way dependencies. - **Engine-time side effects.** Don't `entity.spawn` at module top-level — the engine may not be ready. Expose an `M.init` and call it from a scene entrypoint. - **Hot-reload + module-local cache.** A module that caches expensive computation in upvalues loses that cache on reload — fine for dev, but be aware in performance work. - **`init.lua` vs `init.luau`.** Either works, `.luau` is canonical. - **Writing one while play runs.** A `/source` write made while play is running lands on the play shadow, and a guarded play-exit discards it unless it is kept. One `.module` write shadows `init.luau`, the `README.md` and the `.metadata` together. `vfs.write(path, bytes, { durable = true })` skips the shadow, and `vfs.promotePlayShadow` keeps what is already on it — the `core/vfs` guide has the model and what each route costs. ## Related types - `.component` — for entity-bound state + lifecycle hooks. - `.service` — generates content you don't have yet (a mesh, sound, texture, …) via a metered provider. - `.tool` — for a single agent-callable function with a YAML schema. - `.package` — to group several modules + components + scenes into one shippable folder. ## In the Inspector Exports: what the module exports (name, kind, signature), parsed from its source without running it, with **Check** (the LSP's diagnostics for its entry file) and **Open**.

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

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

# proc.builder What a graph builder hands the author, in the call form: `proc.define(function(g) ... end)`. - `g.<name>(args)` adds a node of the node asset the name resolves to, by asset identity: the nodebox and the node's folder name (`g.points.disc`), a path (`g["/zero/source/fx/ring.procNode"]`), `~` (the nearest package, effect or world root: `g["~/ring"]`), a guid, or a short name (`g.disc`). A path, `~` name or identity ending in `.procNode` or `.procGraph` names an asset of that kind alone; one without the suffix names either, so where a node and a part share a name it states the suffix. A name that matches two nodes, and a name that matches none, are errors that name the candidates. Each call is recorded in the graph by the node's guid. Arguments are a table naming inputs or positional values in the node's input order. - What a call answers: a node with one output answers that output's socket, a node with several answers a record of sockets by output name (`local f = g.core.normals.face(geo); f.geometry, f.area`), a node with none answers nothing. The record does not depend on declaration order. The record handed whole to an input that takes one value is refused where it is handed, naming the outputs to read (`.value`, `.report`). - A name is called this way only for a node written in the call form (`builder.callsByName(path)` says which). A name no node answers to is refused naming the nearest names a call resolves. - A node's own source reaches its package's modules and assets with `require("~.<name>")` and `asset.resolve("~.<name>", type)`: `~` there is the nearest `.package` folder, wherever the node sits in it. - `g.op.<name>(args)` (and `proc.op.<name>`) adds a node of an op, for library nodes built on the ops. An op that is a graph built with `g:node` (the `procNodes/` of the procgen package, registered under their graph ids) is refused at the call, naming its folder and the node written in this form that answers to the same name (`'g.op.points.filter' is .../procNodes/pointsFilter.procNode, a graph built with g:node, ...; call g.points.filter`). An id no op carries is refused naming the ops that start the same way. - `g:input(name, default, opts)` is typed by the default: `Float`, `String`, `Bool`, `Vec3`, `Color`, `List<T>`, `Record` with its fields. `opts` takes `min`, `max`, `options`, `description`, `optional`, `plain` and `type` for a default that does not state its type or no default at all. An empty table default with a stated `type` is that type's empty value (`g:input("entities", {}, { type = "List<Entity>" })`). A vector written as a plain table reads its components by name whichever form it was written in, the reading an op's params take: `{ 0, 0, 0, 1 }` answers `.w`, and a pair (`{ a, b }`, `{ x, y }` or `{ x, z }`) answers its second component as `.y` and as `.z`. - An input declared `plain = true`, an input with `options`, and an input of type Bool or String is a plain value while the graph is built: `g:input` answers the value itself, `if`, comparisons and loops over it are allowed, and it passes into calls as a constant. `plain = true` is how a count, a vector, a record or a list that chooses the graph's structure is declared (`g:input("storeys", 5, { type = "Int", plain = true })`, `g:input("edges", { { bays = 3 } }, { plain = true })`): the graph is built again for each value it is given, it is not animated, and it takes no per-element field. Any other number and vector input is a socket, which changes without a build and takes animated values and fields. A table value reaches the build as a frozen copy. The graph records the plain values it was built with in `graph.plain`, and each such declaration in `graph.inputs[name].plain = true`. - Sockets take `+ - * / % ^ // ..` and unary minus, `math.*` and `vector.*` (each a `math.<name>` node; `vector.create` over sockets is `math.vec2`, `math.vec3` or `math.vec4` by its component count), `x.name`, `x.name = v` and `x[name] = v` for a computed name (which rebind `x`), `x[class][name]`, `x[n]`, and `for index, item in list do ... end`. A source loaded through `builder.prepareSource` reads plain `math`, `vector` and `rand` over sockets unchanged; `define` loads a node or graph entry that way when it names them. - `vector.create` has the width of its component count whether its arguments are sockets or numbers: two numbers answer the Vec2 value `{ x, y }` and four the Vec4 value `{ x, y, z, w }` (what `math.vec2` and `math.vec4` make of numbers), and three a Luau vector. `orient = vector.create(0, 0, 0, 1)` writes a Vec4 column. - `g.compare(a, op, b)`, `g.where(cond, a, b)`, `g.pick(choice, alternatives)`, `g:fold(n, init, fn, opts)`, `g:state(name, columns)`, `g:step(dt, substeps, fn)`, `g:check(cond, message)`, `g.has(geometry, class, name)` and `g.copy(socket)` record the constructs the evaluator knows. - `g:state(name, columns)` states the columns a step keeps, `{ [name] = { type, count } }`, as values the plan knows: literals and inputs, records and lists of them, and what constructs and a `pure` `io.luau` call make from them. A pure call's answer stands even when its arguments are cooked (a call reading the attribute names of a source's points), so a `for` over its answer may add a column per name (`schema["s_" .. name] = specs[name]` over `specs.keys`), and a step body writes them by the same names. - `g:check(cond, message)`: a `cond` known while the graph is built refuses the build with the message (a true one records nothing); a `cond` that reads a socket is recorded for the plan or the cook to answer. The build of a node's own defaults, which is what indexes the node, holds such a refusal instead of raising it (`graph.refusals`), and `forInputs` states it where the node is called or cooked as it stands, so a check over a plain input fires when the call gives it the refused value. - A plain Luau table filled inside a `for` body over sockets keeps one element (`rings[#rings + 1] = v`, `table.insert(rings, v)`): the body is one pass for every item. `builder.check` refuses it with the code `socket-loop-append`, naming the form to write: a local declared before the loop and assigned inside it, read after the loop, where it is the list of every pass's value. - `g.copy(value)` of a record or a list written in the graph (`g.copy({ total = 0 })`) is a value of its own that member writes rebind, so a `for` body that fills it carries it from pass to pass. - A class view made with a socket key (`names[i]`) and read as a value is a node of the scope it was made in, whichever loop body first reads it. - A `for` body is one pass that stands for every item. `index` is the item's place (a socket, from 1). A value built outside the body that the body reads or assigns (`geometry[class][name] = v`, `record.name = v`, `record[name] = v`) is carried: each pass starts from what the pass before left, the first from the value as it stood before the loop, and after the loop the value is what the last pass left. The loop records the carries in `scope.carries[id] = { init, result }` and the refs `loop_index`, `loop_carry` (the value at the start of a pass) and `loop_result` (the value after the loop). A value the body only reads reads as it was. The emitter writes a carrying loop as it was authored: a local that starts as `g:copy(value)`, the body's assignments to it, and the loop reading that local after it (`proc.emit`). - `g.clock.placement` (16 numbers, column after column), `g.clock.inverse`, `g.clock.rotation` (`{ x, y, z, w }`) and `g.clock.entity` answer where the graph stands in the scene it is cooked in: each is a `construct.scene` node that reads the scene the cook is handed (a graph standing on no entity has the identity placement and no entity). `g.transform.point(p)`, `g.transform.direction(d)` and `g.transform.rotation(q)` carry a world position, direction or quaternion into the graph's space through the inverse placement; each takes plain values, sockets or Fields. - `g:fold(n, init, fn, { stop = "changed" })` or `{ stop = function(before, after) return <Bool> end }`; `fn` returns the state only. The fold runs `n` passes and ends early at the first pass whose stop holds. - `g.element` is the element a Field evaluates over: `g.element.id` (Int), `g.element.P` (the position leaf that `fieldc.withPosition` substitutes, also written `g.element.point.P`) and `g.element.<class>.<column>` for a column of the domain the field stands in. Each read is a socket, so `g.element.id * 1.0` is a math node. - `rand.unit(seed, ...scope, id)` (a global in a node source, also `builder.rand.unit`) is the Float field of unit draws keyed by the seed, the scope (`graphId, nodeId, channel`, or `graphId, compositePath, nodeId, channel`) and the element `id`, last (`g.element.id`). It adds an `io.luau` node `{ module = "@builtin::systems.procgen.proc.fieldc.leaves", fn = "rand", args = { seed, { ...scope }, id }, returns = { "Any" } }` and answers its `value`. - `geometry.names[class]` lists the attribute names a class holds (a list socket the plan answers); `geometry[class].count = n` assigns the domain count, so `count` is no column's name (a value per element written under it is refused); `geometry.material = m` assigns the material. `names` is read by that name on any socket: what is read off it by a class (`geometry.names.point`) lists the names, and any other read (`record.names[2]`, `record.names`) is the member a record holds under that name, as `count` and `keys` are. `material` is assigned by that name on any socket. - A member, an item, a column or the names of a value built outside a fold, step or stop body that the body reads first is a node of the scope the value was built in: the body and every later fold read the one value, which the plan writes once. A read keyed by a socket of the body (a fold's index) stays in the body. - `g.clock.time`, `.frame`, `.delta` and `.duration` are sockets; `.fps`, `.frames`, `.loop` and `.realTime` are the timeline's values. - Luau's `< <= > >= == ~=` over a socket, and `and`, `or`, `not`, `if` and `while` that test one, have no value while the graph is built. `builder.check(source)` names each one with the `g.*` form to write, and `define` holds a node or graph entry to it. `and` and `or` test their left operand alone, so `plain or socket` passes. The check follows names block by block as Luau scopes them: a local, a loop variable or a function parameter is its block's own, and a parameter of a function that is not a fold, step or stop body is not known to be a socket (a comparison over one is refused when the graph is built). Plain inputs are not sockets to the check. A plain Luau table indexed by a socket (`LANES[values.type]`) answers nil while the graph is built, so the check refuses it with the code `socket-table-index`, which names `g.pick`. - A list of values holds a nil as a value: `{ a, nil, b }` is three, and the second is a constant of nothing. ## Building a graph for other plain values A graph whose plain inputs change structure is built again for the values a cook was given. - `builder.forInputs(graph, inputs)` answers `graph` while its plain inputs hold what the build used, else the graph built again from `graph.source` with the values `inputs` states (an input it leaves out takes its default); values are compared by content, a record or a list included, and the result is cached by the source text and the values, so a node written again is built again. `builder.KEPT_BUILDS_PER_SOURCE` of a source's builds are kept, the ones used last. A build for other values keeps what the cook already made: only the nodes the new values change cook. A plain input given an animated value, a per-element field or a value held on the device is refused by name. It answers `nil, reason` when the source cannot be built again or a value is outside the input's options. - An optional input with no default (`g:input(name, nil, { optional = true })`) is nil while the graph is built for a call that leaves it unwired, and its socket otherwise, so `if input == nil then ... end` in a node source is decided by what the call wired. The declaration states `wiring = true` and the graph records the wiring it was built for in `graph.wiring[name]`; `forInputs` builds the graph again for a cook given no value for such an input (`values[name] == false` states none in `rebuild` and `withInputs`). - `builder.rebuild(graph, values)` builds again unconditionally; `builder.withInputs(values, fn)` runs a function that calls `proc.define` and gives that graph the values. A node asset called with a plain value records it as a constant param; the evaluator reads a node's graph through `forInputs` with those params. ## What a build resolves once A build resolves each name once. The first call of a name `g.<name>(...)` in a build finds the node asset the name answers to; the build keeps the asset, its inputs and outputs, and the envelope its calls record, and every later call of that name in the same build takes them. Each `building` frame (a graph source, or a node source loaded by a call) holds its own, by the graph's source and the name, on the thread that runs the build; the memo ends with the frame, so a node written between two builds is resolved again by the next, and builds on other threads share nothing. The `Info` of a node asset is kept by the node graph it was read from, and the line of each call is kept as a number that `siteOf` states as `path:line` where it is read. `builder.setResolveMemo(false)` switches all three off for the builds after (the answer is the setting before), and `builder.resolveCounts()` answers the calls that resolved a name (`resolved`) and the calls a kept answer served (`hits`). ## What a build is made against A graph source that has a base is built against it. The base of an entry source is the graph the last `proc.takeHandOff` of its folder gave a Generator (`builder.setBase(graph)`, `builder.baseOf(entry)`), held weakly. When the run of a build ends, a pass compares every node the run made with the base's node of the same id (`compareNode` of `proc.eval.replan`, and the node's `op` field by field). A node that is equal is replaced in `graph.nodes` by the base's own table, which is frozen, along with the tables under its inputs and params; a node that differs, or that the base does not hold, is frozen where it is. The scopes are compared and the ones that differ are listed; they stay the build's own tables. The graph states the result in `_diff`: `changed` (the ids of the nodes that differ or are new), `removed` (the ids of the base's nodes the build did not make), `scopes` (the ids of the scopes that differ), `added`, the counts of the nodes and scopes, `against` (the base, held weakly) and the edit counts of both graphs when the pass ran. The planner (`replan.dirty`) reads it while the graph and the base stand as they did then, and compares only the nodes it lists. - A node that keeps the base's table keeps the place the base gave it in the order the nodes were made in. When this build made it elsewhere, the graph states the new place in `_moved`; `builder.seqOf(graph, id)` answers the place a node holds, and `graph:toJSON()` states the nodes with it (`builder.documentNode(graph, id, node)` is one node as the document states it), so a document and an emitted source are those of a build that made every node itself. - A table two graphs share is frozen, so a write into one raises. `proc.edit` replaces a node it writes into by a copy of its own (the node, its `inputs` and its `params`) before it writes, and `builder.againstCounts()` counts those copies beside the passes run (`passes`), the nodes filed from the base (`reused`), the nodes listed (`changed`) and the time the passes took (`ms`). - `builder.setBuildAgainstBase(false)` switches the pass off for the builds after (the answer is the setting before). A build of a source with no base, a build for other plain values (`forInputs`, `rebuild`) and a build of a node asset are the graph their run made. ## What a build reads A node or graph source is compiled with `builder.compile(src, "@" .. entry)` and run as a build with `builder.building(entry, fn, ...)`. While a build runs, the source sees a `vfs` whose `read`, `readAsync` and `readBounded` note each file for that build, and `builder.read` (`proc.read`) notes a file read from a module the build calls into. When the build ends, the files it read are recorded against its entry source, replacing what its earlier builds read: `builder.readsOf(entry)` lists them and `builder.readersOf(file)` the entry sources whose last build read a file. A write of such a file is a `proc.sourceChanged` of each of those sources. `builder.forget(folder)` drops the source text and the built graph the builder holds for a node or graph, so the next build that reaches it runs its source again. The modules a build requires are recorded by the engine, which tells the node or graph type through `onDependencyChange` when one of them re-runs. ## The wiring of each run of `graph.module` `graph.module` binds its wiring into the builder (`builder.bind`) each time its body runs, with the metatable of the graphs that run makes as `helpers.graph`, and the builder keeps that wiring on the metatable. A graph is wired by the run that made it: `builder.run` declares its outputs, a value is wired into its refs, and `rebuild` builds an inline graph again, each through the wiring of the graph's own run. The body runs again whenever the require cache lets go of the module while a module that took its functions keeps them (`proc.define` is `graph.module`'s `define` as `proc` loaded it), as a reset of the scripting state to a mark taken before the module loaded does; the graphs of both runs are then built side by side. ## What a graph records A call-form graph states `surface = "call"`. Each node it makes carries `call = true`, `seq` (the order it was made in, which the emitter writes it back in) and `scope`. A node asset is `op = { __ref, type = "procNode", name }`; an op is its id string; a construct is `op = "construct.<kind>"` with `construct = <kind>`. `graph.scopes` holds each `for`, `fold`, `stop` and `step` body, `graph.states` each `g:state`, `graph.plain` the plain input values. Each call and scope also records the line of the graph's source it was written on, `path:line` (`builder.siteOf(graph, id)`), in a table the graph's document leaves out, so where a call sits moves no hash. The plan carries it onto each call it writes out (`plan.flat.origins[<flat id>].site`, the graph's own calls in `plan.flat.sites`), and a cook's failure is read at it: `describeFailure(flat, err)` of the eval module (`@builtin::systems.procgen.proc.eval`) answers `<path>:<line>: g.<call> failed: <why>`, the line being in the deepest source the person can edit. The `inputs` of a construct node are refs (a constant is `{ kind = "const", value }`); `params` are constants. | construct | inputs | params | answers | |---|---|---|---| | `member` | `value`, `name` | | the member of `value` | | `member_set` | `value`, `name`, `to` | | `value` with the member written | | `item` | `list`, `index` | | the item | | `column` | `geometry`, `class`, `name` | | the column read (a read of `count` is the domain count) | | `column_set` | `geometry`, `class`, `name`, `value` | | the geometry with the column written | | `column_remove` | `geometry`, `class`, `name` | | the geometry without the column | | `count_set` | `geometry`, `class`, `count` | | the geometry with that class's domain count set to `count`; a value per element is refused (no column is named `count`) | | `material_set` | `geometry`, `material` | | the geometry with its material set | | `names` | `geometry`, `class` | | the List of attribute names the class holds, answered at plan | | `has` | `geometry`, `class`, `name` | | a Bool answered at plan: whether the class holds the column | | `check` | `cond` | `message` | nothing; a `cond` that is false when cooked is an error stating `message` | | `compare` | `a`, `b` | `op` (`eq neq lt le gt ge`) | a Bool | | `where` | `cond`, `a`, `b` | | `a` where `cond` holds, else `b` | | `pick` | `choice`, `alternatives` | | the alternative the choice names: by option name, by a list position (a false choice the first, a true one the second), or by `false` and `true` keys | | `step_sample` | `step`, `value` | | the value of an animated `value` at the step's time | | `step_between` | `step`, `index` | | the fraction (0 to 1) of the step's movement that source `index` of the step has covered; the evaluator defines it | A call that has several outputs names them in refs: `{ kind = "node_output", node, output = "<name>" }`; a node with one output has `output = nil`. ### Refs The v1 refs (`const`, `graph_input`, `node_output`, `list`, `record`, `animated`) and: | ref | stands for | |---|---| | `loop_item { loop }`, `loop_collect { loop, ref }` | the item of a `for` scope, and the list of `ref` over every item | | `fold_value { scope }`, `fold_index { scope }`, `fold_result { scope }` | the value and the index (from 1) of a fold pass, and the value after the last pass | | `fold_before { scope }`, `fold_after { scope }` | the state before and after a pass, inside a fold's `stop` function; `scope` is the `stop` scope | | `step_state { scope }`, `step_index { scope }`, `step_result { scope }` | the state record, the step record (`dt time graphTime index first start`, with `step_sample` and `step_between`), and the state the step reached | | `state { name }`, `clock { field }`, `engine` | declared state, the clock's field, the engine API namespace | | `element { field, class? }` | the element a Field evaluates over: `field = "id"` its index, `field = "P"` its position leaf (no class), else the column `field` of the domain `class` | ### Scopes `graph.scopes[id]` is `{ kind, parent, seq, ... }`: - `for`: `list`, `item`. - `fold`: `count`, `init`, `result`, and `stop` when it states one: `"changed"` (the pass ends the fold when the state it produced equals the one it read) or `{ scope = <id of a stop scope> }`. - `stop`: a scope whose `parent` is its fold. Its nodes read `fold_before` and `fold_after`; `result` is the Bool ref the fold stops on. It is evaluated after each pass. - `step`: `dt`, `substeps`, `result`. The `plain` table of a graph and the `plain = true` flag of an input declaration state which inputs are build-time values. Part of `@builtin::systems.procgen.proc`.

# proc.demos Procedural-generation demo recipes — graph builders that showcase the proc system end to end. Part of `@builtin::systems.procgen.proc`. - **`cashPile(proc, opts?)`** — scatters a billboard source over a disc of points and merges it into a single mesh (the scatter → merge showcase).

# proc.eval Lazy topological evaluator of a graph target, with per-eval memoization and cycle detection. Part of `@builtin::systems.procgen.proc`. ## Graphs built in the call form A graph built with `proc.define(function(g) ... end)` has `surface = "call"`. It records nodes (ops and node assets), scopes (`for`, `fold`, `step`), declared state and the refs between them. It has no output the evaluator is asked for: every node nothing reads is cooked from. ```lua local play = eval.play(graph, { inputs = { count = 8 } }) local report = play:present({ time = 0, frame = 0, fps = 30, duration = 0 }) play:release() ``` `eval.play(graph, opts)` plans the graph, cooks from every node nothing reads and keeps what those nodes return. `play:present(clock)` cooks at a clock (`{ time, frame, fps, duration }`; a `duration` above 0 is a timeline with an end, where a seek replays from the start), `play:setInputs(inputs)` gives the graph other inputs, `play:handle(id)` answers what a node cooked from answered last, `play:report()` says what happened and `play:release()` lets go of everything the play holds, the Handles its output nodes answered included. What a play stands in the world goes over to a present all at once. A present opens a stage (`eval.openStage`): every show its cooks make (an `io.output`'s `show`) is prepared and set aside, and once the present's pulls are cooked the stage commits (`eval.commitStage`) and every show stands in that frame. A value that stood and that the present supersedes (a node's Handle cooked again, an output node no plan holds any more) is set aside as well (`opts.standingRetired`) and let go of right after the commit, each release on a task of its own (`eval.releaseStanding`), so the world never holds part of one present beside part of another. A present that raises stands none of its shows, drops the nodes that made them (`eval.forgetValues`), and leaves what stood standing for the next present to replace. A value that stands is never kept per key on a timeline with an end: a key it held before is cooked again, and its show made again, when it comes back. A present cooks with the inputs the play holds when it starts: inputs `setInputs` gives it while it runs are the next present's. A show of an output reconciles onto the entities the last show of that output stood under the same place, by element id. The place is the entity the graph stands on (the scene's `entity`); for a graph that stands on no entity it is the play's own (`play.showPlace`), which a play names on its thread while it presents or moves on the device (`eval.standOn`, read by `eval.standingPlace`) and a play started with `inherit` takes over. Two plays that stand on no entity show beside each other, and releasing one leaves the other standing on its own runs. Every call-form graph cooks through the plan, whoever asks: `proc.eval(graph, target, opts)` of a graph with `surface = "call"` plans it (`opts.inputs`, `opts.clock`), cooks what the plan waits on and then the target through the flat graph, and a node asset used as an op cooks its graph the same way. `output:<name>` names an output of the graph (`flat.outputs` holds each one lowered), and the nodes the eval cooked into its own cache are released apart from what the answer reaches. Each node cooks at `opts.clock`: an animated value it reads, handed straight to an op or through a node asset's input into a field op (`fieldc.pcallSampling`), holds its value at that time; one that becomes a field stays a live field, rewritten for a later time without a cook. `proc.historyKey` and `proc.liveDigest` of a call-form graph are queries of the same plan: the plan is made, read and keyed exactly as a cook makes, reads and keys it (what it waits on is cooked, its leaves are keyed), and only the final read of the flat graph answers the key or the digest. So a key asked before an eval and after it is the same, and a plan a query made is kept keyed for the cooks after it. `eval.plan(graph, opts)` is the plan alone, and `eval.references(graph)` the assets and ops the graph's calls reach, by guid and id, without cooking. ### The document ``` graph.surface "call" graph.nodes[id] { op, inputs = { socket = ref }, params = { name = ref | value }, scope = scopeId? } graph.scopes { [id] = { kind = "for", list = ref } | { kind = "fold", count, init, result } | { kind = "step", dt, substeps, result }, parent = scopeId? } graph.states { [name] = { columns = ref } } graph.inputs { [name] = { type, default, ... } } graph.outputs { [name] = { ref } } -- what a graph used as a node gives ``` `op` is an op id (`"device.kernel"`, or `"op.device.kernel"`), a node asset (`{ __ref = guid, type = "procNode", name }`) or `"construct.<kind>"`. ### The graph's hash `proc.depHash(graph)` (`eval.depHash`) is the hash of two things: the document without its nodes (id, version, metadata, timeline, inputs, outputs, composites, scopes, states, surface, plain values; `graph.documentHeader`) and the sum of the nodes' digests, mod 2^52. A node's digest is the hash of its id and of the node as the document states it (`builder.documentNode`: the node, with the place a build gave it when that is not the one its table holds). The sum does not depend on the order of the nodes, so two documents of the same nodes hash equal however their nodes are held, and a document read back from JSON hashes as the graph it was written from. A graph keeps its sum with the count of edits it was stated at (`eval.depSum`). A graph built against its base (`_diff`, see the builder README) states it as the base's sum less the digests of the base's nodes that the build changed, removed or moved, plus the digests of those nodes in the new graph; the nodes it filed from the base are not read. A graph with no base, one edited since the build, and a document state it from every node (`eval.depHashWhole` is that sum, the definition the patched sum equals). `eval.depHashCounts()` answers the sums patched (`patched`), worked out from every node (`whole`) and found kept (`held`), and the digests made. `eval.setDepHashFromNodes(false)` returns to the hash of the serialized document folded in one pass; the two give different numbers for the same graph, so a key built from a hash (a composite's version, the disk cache) misses once when the setting moves. The refs are the v1 refs (`const`, `graph_input`, `node_output`, `list`, `record`, `animated`) and: | ref | stands for | |---|---| | `loop_item { loop }` | the item of the `for` scope in the copy being written out | | `loop_collect { loop, ref }` | the list of `ref` in every copy of the `for` scope | | `loop_index { loop }` | the place (from 1) of the item in the copy being written out | | `loop_carry { loop, carry }` | a value built outside the `for` scope as a pass begins: the value before the loop for the first copy, what the copy before left for every other | | `loop_result { loop, carry }` | the same value after the last copy | | `fold_value { scope }`, `fold_index { scope }` | the value and the index (from 1) of the pass of a fold | | `fold_result { scope }` | the value after the last pass | | `step_state { scope }`, `step_index { scope }` | the state record and the `step` record of a step body | | `step_result { scope }`, `state { name }` | the state the step has reached | | `clock { field }` | `time`, `frame`, `fps`, `duration` or `delta` of the graph's clock | | `engine` | the engine API namespace | ### The plan - A node asset built in the call form is written out where it is called, its inputs bound to what the call was given. A call nothing reads is cooked from through every output it declares. - A `for` body is written out once per item of its list, a `fold` body n times in a chain, a `pick` takes the one alternative its choice names. A copy is keyed by its content, so reordering, inserting or removing items cooks only what is new. - A count or a list a scope needs is a plan value: a constant, an input, or the answer of a node, which the plan cooks and lists in `report.waits`. A column left on the device is not a plan value; reading it back with `transfer.readback` is, and the wait names the readback. The length a scope was written out for is watched: a cook that answers another length plans the graph again. - A `where` whose condition the plan knows takes one alternative. What only the other alternative stands on is not written out, and a call nothing reads that stands on any of it is not written out either (the nodes a node asset leaves unread are written after every alternative of the plan is decided), so nothing reachable only through the untaken alternative is cooked while the plan is made. A node of the graph itself that nothing reads is always cooked. - A `for` scope's `carries` (`{ [id] = { init, result } }`) chain the copies: copy 1 starts a carried value at `init` and copy n+1 at what copy n's `result` lowered to; a `loop_result` read after the loop is what the last copy left. - A step becomes one solver node. Its state is one record of device Columns per play (`g:state(name, { column = { type, count } })` allocates them zeroed). The columns a state allocates are stated through plan values: a literal record, or a record a fold fills or constructs read off a list or an input (per-source columns, counts from `list.count`, names from `geometry.names`), whose counts the plan cooks and lists in `report.waits`. A `member` or `item` read inside the body of a value the plan knows (a count or a list a fold inside the step is written out for) is answered while the plan is made. The step record carries `dt`, `time`, `graphTime`, `index` and `first`. The body runs `substeps` times in each fixed step of `dt` seconds. Pausing holds the state, a seek back replays from the start on a timeline with an end, and a changed value the step reads begins it again. ### A plan is made once A graph is planned once for the values its plan stands on, and every later cook of it reads that plan. - A plan stands on the registry (`registry.revision()`), on the graph its plain inputs build, on the values of the inputs it read (as keys), on the animated values it read at the clock, on the answers it waited on and the nodes it cooked for a count or a list, and on the modules it required (by what their files hold). A cook reads a kept plan after asking each of those again (`expand.stillStands`); a plan that no longer holds is made again, and a plan that does is read. - The body of a node asset is planned once for each structure its calls give it and kept (`expand.bodyCounts`): a plan made again reads the kept body, and the nodes it writes out are the ones it wrote before. A kept body stands while its asset's source is as it was and every definition it was written out from (the asset's own, and each op and node asset it calls, at any depth) is the one the registry holds. A node registered again lets go of the bodies that reach it and no other, so an edit of a node cooks again what the node reaches and nothing beside it. A call is compared with a kept body by what its leaves hold, without reading them: a plan reads the inputs of the bodies it uses, at any depth of calls, and none that only a body it compared and did not use reads. - A node the plan cooks while it is made is keyed over the flat graph as it stands then. The passes after emission rewrite nodes of that cone (an expression folded, a node read by none taken out), so a made plan lets go of the keys its flat graph holds (`eval.forgetHeldKeys`): the keys held for what the flat graph held while it was made go, and the next eval derives them from what it holds. - A Field that states what it computes (`proc.fieldc`'s `_expr`) is keyed by that statement and the operands it names, not by the closure it samples with: a field written out again keys as it did. - Each answer and node the plan waited on is held by the key of its cone, without a cook. The leaves a cone stands on are named once, when the plan is kept (`expand.keyWatches`): the graph inputs it reads, the animated values, the constants that hold a device value (a Geometry, a Column) or an asset reference, and the nodes that read live state; the ops, their versions, the plain constants and the wiring are fixed by the plan and the registry. A read asks the evaluator for the key of each leaf as it stands now (`opts._leafKeys`: a device value is keyed by the run it stands on and the writes the run has had, an asset reference by what the asset's files hold) and compares them with the keys the watch stood at. A watch whose leaves are unmoved holds and cooks nothing; a watch whose leaf moved is cooked again, only its cone, and holds when it answers what it answered, and the keys it stands at are renewed. A plan that cooked a node reading the clock, a play's input or a live run, or whose cone stands on a solver or an op that always cooks, is not keyed: each of its watches is cooked again on every read. - A plan made against its base, which it took the tables of, takes the base's leaf list, leaf index and the cone of each node (`expand.keyWatches(plan, dynamic, base, reach)`; `expand.setWatchesCarried(false)` walks every cone). The cones of the nodes the edit reached (`reach`, from `eval.moveKeys`) and of the nodes it let go of are dropped, and only the watches whose roots hold no cone are walked; the rest keep the places they stood on. The places keep their numbers: a leaf that no cone and no watch holds any more is a tombstone (`kind = "dead"`, key 0) that no list names, and when the tombstones are at least 64 and outnumber the leaves the next plan walks whole. A registry that moved since the base was keyed, a base that is not keyed and a plan that wrote its own tables are walked whole. `expand.counts()` answers the plans carried and walked whole (with the reasons), the watches kept and walked, the nodes walked, the tombstones and the compactions. - A kept plan also holds the answer of each target it was cooked for (up to four a plan, and sixteen plans at a time), filed by the keys of the target's cone: a cook of `proc.eval` that shares no node cache with its caller, finds the cone unmoved and passes no `stats` or `cookRecord` is answered with a copy of the held answer (a Geometry or a Column is cloned, a list or a record of them rebuilt), and cooks nothing. An answer holding anything else (a Handle, a Field) is not held. The held answers are let go of with the plan. - A plan is kept unless it registered a step solver or wrote a run of the device into itself (a `for` over geometries). A plan that stands on a run of the device holds by the key of its cone, and is made again when the key moves. `eval.planCounts()` answers how many plans were made and read (`made`, `reused`), the milliseconds each took (`madeMs`, `reusedMs`), `notKept`, the plans that could not be kept by what stood in the way, `served`, the cooks answered from a held answer, and `notKeyed`, the kept plans whose watches are cooked again on every read, by why. - `engine` is the engine namespace, a constant. A member read or an item read out of constants, out of a record or a list a call wrote, is the ref written there and costs no node; `engine.require` of a module named by a constant is the module, required while the plan is made and asked for again each time the plan is read. - The plan is made in slices of `budgetMs` (5 ms) when the caller can yield; a cook over the plan hands a frame back after `cookBudgetMs` (100 ms). - A cook that shares no node cache with its caller keeps none: nothing is keyed or filed, what the plan cooked while it was made (or asked again) and what the cook makes stand in one table by node, and all of it is released as the cook ends but what the answer reaches. A Field that is the answer keeps the runs its leaves read; they stand as long as it does. What the answer reaches takes in the values a geometry's columns carry (a packed piece's `Mesh` record and the geometry its `mesh` holds): a value names what it carries and does not own through `__proc_carried`. A value a node of the cook made that the answer reaches only through what it carries is handed to the value carrying it (`substrate.holdCarried`) before the answer is copied or let go of: it stands while any holder of it stands (a copy of a holder is a holder) and goes with the last of them. A column that owns its values (a detail value) owns the geometries and columns in it and lets go of them with itself, so what it carries is what they carry. A node that lists what its passes made (`eval.ownedBy`, a fold or a `for` over geometries) lists the carried values its answer reaches that the values it was handed do not, and none a column owns. A store keeps what its entries carry from the release of a cook (it is among what the store holds), and a store shared by plays counts, among the values an entry lets go of with the last entry holding them, only the values the entry owns: a carried value is its maker's. - A node of a plan that stands is held to the contexts its producers operate in once, takes the label of its refusals from one string, and takes its params prepared once when every one is a constant. ### A cook after a change is run from a list (`cookrun`) A kept plan whose cone stands on numbers (graph inputs holding a number or a Bool) is cooked node by node while those numbers move. The recording wraps the plan's cone re-check and the cook together: the first such cook after the plan was made is recorded as a compute list and the next one is recorded beside it; the words that differ between the two recordings (a dispatch param, a word of a write) must each be the value of one leaf in both, and become the slots of the second list. A cook after that runs the list with the leaves' values in its slots, asks the recorded plan-time read-backs again, runs the watches that are not nodes (modules, animated values, the registry stamp) and answers a device copy of the list's columns (`cookrun.counts()`: `recorded`, `diffed`, `replayed`, `verified`, `mismatched`, `readbackChecks`, `dispatches`, `refused` by why): no node is cooked and no buffer is allocated but the copy. What makes a recording stand, and what ends it: - Two recordings are one cook when they make the same dispatches over the same programs and workgroups, bind buffers one for one, and write the same number of words; a run placed at another offset (`zero_base_*`, a write offset) is a placement. A first cook that uploads a mirror of a CPU column makes the pair differ once, so the comparison is tried again on the next cook (twice at most). A moved leaf that is no word of the list is refused by name, since its value reaches the device by a write the recording did not hear. - A cook that read the clock, a play's input or a live run, and an answer that cannot be copied are not recorded. - A `cpu.call` is first handed the geometries it is given with their columns on the device standing in as columns that answer their type, width, length and run (`substrate.structureOf`): a call that asks for no numbers (the names of the columns a class holds, the types a join decides) moves nothing off the device and records no read-back. A call that asks a stand-in for its numbers, fails, answers a stand-in, declares a return that is no plain value, or is handed a geometry counted on the device or a part is made again over the drained inputs, and its read-back is recorded. - Every node whose cook read back from the device (every `transfer.readback`, whatever the traffic of its thread counted, and a drained `cpu.call`) is recorded as a read-back row: its inputs, whether they were drained, and a digest of its plain outputs. A node that holds nodes of its own is asked again by their rows. After the list has run each row is asked again; one that answers another value than it did ends the recording and the cook is made node by node, answering correctly. A read-back whose outputs are not plain data is not recorded. A graph that reads a figure that moves with its inputs (the bounds of a mesh, a volume) answers another value at every cook; one that reads the whole number or the verdict that figure comes to (a power of two, 0 for a solid) answers the same. - A count the device holds is not a read-back row: a node states the room it is allocated (`device.bound`) and the list runs the count on the device inside that room. A count the cook states no room for is allocated twice what the cook measured, in powers of two, and a room is never smaller than an earlier recording of the entry allocated (`Run:room`). The room a count of a number takes is a decision of the cook: the list is run again for every number that takes the same room, and for a number that takes another the recording is let go of and made again. - A recording holds the guards its nodes state (`Run:guard`, `device.guard`, `device.bound` without a room): words of the device the list writes, which are 0 while the cook's conditions hold. After a replay the words are asked for without waiting (`substrate.deferredReads`, counted apart from `readbacks`), and the cook of the entry that follows reads the answers that have landed (at most eight replays ahead; past that the latest words are read at once). A word other than 0 lets the recording go, so that cook is made node by node and recorded again: it raises the refusal the condition states, or allocates a count that outgrew its room four times the room (`counts().guarded`). - The first replay of a list is held to the cook of the same values made node by node, column for column; a difference ends the recording (`mismatched`). A list that dispatched a kernel declaring `determinism: float_order` (a float sum whose threads arrive in any order) is held to f32 columns that agree to the rounding of a sum taken in another order. - A buffer a cook lets go of while it is recorded stays until the recording goes (`substrate.deferReleases`): the list names it, and a replay writes it. - A changed key of any other leaf (a Geometry input, a constant device value, an animated value), a plan made again and a registry change let go of the recordings; at most six plans hold recordings. - The recordings of two threads do not meet: a dispatch, a write and a release belong to the recording of the thread that made it. - The first replay answers a copy word for word onto runs of its own (`cookrun.deviceCopy`) and is held to the cook. Every replay after it answers a share of the runs the list wrote (`cookrun.handOut`; `counts().shared`): a Geometry clone, the columns of which share the runs, costs the caller nothing to make. The recording names every holder of those runs (a clone of a share is named too); before the list runs again it moves the holders still out onto a copy of the runs, so an answer a caller holds across cooks keeps the values it was handed (`counts().detached`). The held answer of a plan is always a copy. `cookrun.setEnabled(false)` cooks every cook node by node. A `g:fold` of three passes or more over device state is planned as one `construct.fold_run` node (`foldrun`): the body is built once as a flat graph with the inputs `state` and `index`, the first pass is cooked while a compute list records it, and every later pass queues that list over a copy of the state, so a pass after the first cooks no node. `foldrun.counts()` answers how many passes were recorded, replayed and cooked, and how often a body was refused a list, by why. A body cooks each pass on its own when it reads `index`, when the state holds something the list cannot follow (a record, a text, a readback), when a pass makes a state of another shape, or when the fold sits inside another recording. `foldrun.setEnabled(false)` writes the folds of the plans made after out once per pass. The shape of a state names each column it holds; a column carried as values (a record, a text) and a detail value stand by the evaluator's key of what they hold (`eval.keyOf`), under which a geometry or a column a record holds stands as the runs it reads and the writes they have had. ### How a step runs A step solver's definition (`construct.step.<id>`) is registered under the content of its body, and every plan that writes that body runs it. It holds the body's nodes, inputs, outputs and exports; the flat graph the body was written in is read by the plan that writes it, while that plan is made. A step solver plans its body once (`proc.eval.stepplan`), when the state takes its first step. - A node of the body that depends on neither the state, the `step` record, an animated value nor the scene is STATIC: it is cooked once, with the first step, and read as it stands by every later step (`opts.fixed` of the evaluator). The plan reads only the nodes the next state stands on. - What is left is the device work of a step. The first step of each distinct set of `step` values the body reads (its `dt`, `first`, `progress`, ..., and the animated values it reads, as the device sees them: the f32 they round to) is cooked with every dispatch and every write it makes into a device buffer kept as one compute list over buffers the solver holds, and the next state written back into the state's own columns by the last dispatches of the list. Every later step with those values queues the list: the dispatches read the state's columns where they stand and write the next state into them. A step that runs from a list cooks no node and allocates no buffer. - The columns of the state are written in place, so what a step presents is a copy of them made on the device. - Up to six sets of `step` values are kept. A body the plan cannot stand on is cooked a step at a time with its static nodes still read as they stand, and says why in `report.steps[<step id>].reason`: a node of the body reads the clock, a play's input, a live run or the scene; the body reads values back from the device to the CPU; the next state is not a record of Columns the state's own shape; or a `step` value the body reads takes a new value in more than six steps (a body that adds `step.time` to a column, say). - `play:report().steps[<step id>]` holds `steps`, `replays`, `recorded`, `interpreted` (steps cooked node by node), `plannedDispatches` (what one list queues), `dispatches` (queued in all), `allocations` and `uploads` (buffers made and uploads done by steps), `ops` (nodes cooked in steps, by op), `staticNodes`, `variants`, `mode` (`replay` or `cook`), `reason` and `keyValues` (the `step` values of the last step). - `stepplan.setPlanning(false)` makes the solvers begun after cook every step node by node, which is how a planned body is held to the numbers a cooked one gives. A state column the next state names as a Field, a number or a vector is evaluated into a column of the state's own length and type. ### Constructs A construct is a node the evaluator itself knows: `construct.member`, `construct.item`, `construct.member_set`, `construct.column`, `construct.column_set`, `construct.column_remove` and `construct.engine` and `construct.select` are cooked; `construct.pick`, `construct.compare` and `construct.where` are written out in the plan (a compare of two constants is their answer, a `compare` otherwise calls the `math.lt`, `le`, `gt`, `ge`, `eq` or `ne` node of its operator, and a `where` over a condition the plan does not know is a `construct.select` node). `construct.select` chooses `a` where `cond` holds and `b` where it does not: numbers, vectors and Fields element by element (`math.where`), and a Geometry, a record or a text by a condition that is one value, which a condition over the elements of a column is not (it is refused naming `g.pick`). A Column or a Geometry a construct reads from a record or a list is a clone of it. `construct.expr` is the arithmetic of a graph as one node. The plan writes each operator (`+ - * /`, `math.*`, `vector.*`, `g.compare`) as a `cpu.call` of a function of `fieldc.operators` and the `construct.item` that reads its result, and after the flat graph is written out it gathers every connected set of them, with the `x`, `y`, `z` and `w` reads of their results and the `g.where` choices between them that a condition per element makes, into one `construct.expr` whose `tape` lists the steps (`{ fn, args }`, `{ fn = "where", choice = true, args }` or `{ lane, args }`, each operand a `leaf`, an earlier `step` or a `const`) and whose `leaves` are the values the steps read. A condition is per element when it stands on an element field or on a column of the elements of a class; the cook makes both alternatives of such a choice and chooses between them element by element, so the plan decides nothing for it. A `construct.select` whose condition is one value the cook answers, or whose alternatives are whole values, stays a node. Each call step runs through `callrun.invoke`, the call `cpu.call` makes, and the node answers the last step. `flat.folds[id]` lists the flat id of the call or choice each step stands for, and `describeFailure` reads a failing step at that call. A node the plan, a watch or an output names, and a member written for another alternative of a choice than its reader, stays a `cpu.call` and a `construct.item`; a member a decision names is the root of an expression of its own. An expression holds members a cook derives a number through (a replay of a recorded list works those out again for other values of the graph's inputs) or members it does not, never both. `docs/specs/procgen-system.md` section 13.1 has the rules. The expressions whose tapes state the same steps hold one frozen tape table, filed by a text that states the tape exactly (a number by its bits, a vector by its three components, a string with its length), and each node holds its own `{ kind = "const", value }` reference to it (`expand.setTapesShared`). `construct.member` reads `count` and `keys` of a plain list or record (the number of members, the sorted names of a record or the places of a list; a value that is nothing has none), `count`, `type` and `lanes` of a Field (the length of the longest column its chain reads, its element type, its components; a Field that reads no column has no length, and the read refuses naming `geometry.point.count`, `column.count` and `g.field.index({ domain })`), and `count`, `type` and `lanes` of a Column. `construct.member` also reads `x`, `y`, `z` and `w` of a vector (a Field of that component for a Field, a Column of that component for a Column of Vec2, Vec3, Vec4 or Quat), the classes of a Geometry, its `material` and its `names` (the attribute names each class holds). On a class of a Geometry a read of a `detail` column answers the value the detail holds. `count` of a Column or of a class of a Geometry is the live count when the elements are an appended or compacted output (a Column of one word, which a kernel with a `domain_count` binding reads the live count through, and a kernel without one runs over the capacity); `capacity` of either is the number of elements the run is allocated for. A record a graph holds under a name a class goes by (`point`, `vertex`, ...) is read and written as a record: `x.point.name` is the member of the member. `construct.column`, `construct.column_set` and `construct.column_remove` take `edge` beside `point`, `vertex`, `primitive` and `detail`: an edge is a unique point pair of the primitives, so the class counts them and a column written on it is one value per edge. `count_set` takes the four stored classes. `construct.column_set` writes a Column, a Field evaluated over the class it is written into, a vector or a number, a record or a text (one value for every element, a constant Record or String column) or a list of records or texts (one to an element, held in a Record or String column on the CPU); a record whose fields are numbers is a record, and a list of numbers is a vector. A column that is the structure of a geometry (`point.id`, `vertex.pt`, `primitive.vstart`, `vcount`, `curve` and `closed`) holds whole numbers: a number, a Field or a Column written to it is stored as an Int, and so is a value written to a column that already holds Int. A detail value is held as itself, a record among them, and `construct.column_remove` removes it. The inputs of every construct take nothing as a value: an optional input a call left out reaches them as nothing. `construct.scene { what }` answers where the graph stands in the scene it is cooked in (`entity`, `placement`, `inverse`, `rotation`); it is read as `g.clock.placement` and the other names, and as `g.transform`. ### What the plan answers A construct that answers while the plan is made cooks the nodes it reads (a wait in `report.waits`, a readback named as one) and records the answer, which is what the play compares to decide whether the plan still stands. - `check { cond } message`: a condition that is false refuses the play with the message. - `has { geometry, class, name }` is the Bool of whether the class holds the column; `names { geometry, class }` is the list of attribute names the class holds. A `for` over the names has one copy per name. - `fold` with `stop`: after each pass but the last the stop is answered, and the fold ends at the first pass whose stop holds. `"changed"` holds when the pass left its state as it found it (numbers by value, a Column or a Geometry by what its runs hold: a device run read for the comparison is a readback wait). A stop function's scope reads `fold_before` and `fold_after` and its result is the Bool. The report's fold scope states `copies`, `stop` (`"changed"` or `"function"`) and `stopped`; each answer is a wait named "the stop of fold '<id>' after pass <n>". - A node asset called with plain inputs (an input with options, or of type Bool or String) is the graph its source builds for those values (`builder.forInputs`); a play built for other plain inputs plans again. Constructs cooked as nodes: - `count_set { geometry, class, count }`: the geometry with the class's element count set. A number sets it; a live count Column (an appended output's) becomes the live count over the capacity it carries; arithmetic over a live count (`kept.indices_count * 6`, a Field over live counts) is evaluated on the device as one word, and the class is as large as that arithmetic reaches when every count it reads is full (`substrate.atCapacity`). - `material_set { geometry, material }`: the geometry carrying the material (a Material value, an asset reference or a name; nothing for none). - `step_between { step, index }`: how far from 0 to 1 the step has come through the span of graph time the present covers; `step_sample { step, value }` is the value, which a step body samples at the step's time. The step record carries `dt`, `time`, `graphTime`, `index`, `first`, `start` (the time the step began at) and `progress`. An `element` ref is the Field the graph's `g.element` stands for: `id` and `P` are fields the field compiler fuses into the chain they sit in; a column of the evaluation domain is `fieldc.element(field, class)`. ### Cooking Every play cooks into one store of the world, filed by content key (the op, its version, the seed, the params and the keys of the inputs): a node of any graph that cooks the same op over the same inputs is cooked once. A value that holds an asset reference is keyed by what the asset's files hold, so editing a module a node calls cooks the node again. The nodes a play pulls from and every step are the play's own. An output node answers a Handle (a table with a `release` function). `cpu.call` owns its list of results: a Handle in it is released when the cook is superseded and when the play ends. A present evaluates the pulls whose keys can have moved and leaves the others standing with the Handles they hold. A pull stands when the plans made since it was evaluated reached none of the nodes its key stands on (`moveKeys` files them), it was evaluated at this clock, with these inputs, at this registry revision and before the play last moved on the device, no module or asset a cook read was edited, and its cone holds no solver, no graph used as a node, no live read and no CPU registration. A pull whose cone reads the scene stands while the digest of the scene state the plan reads (`play:liveDigest()`) is the one it was evaluated at. A play that takes over the node cache of the play it replaces takes the Handles with it. The device shape of a plan (`eval.timeOnDevice` with `keptWith`: which nodes keep the play's time from reaching it through live values alone) is the sum of the share each node of its flat graph holds. A plan made against its base states it from the base's: the nodes the plan wrote anew are taken again and every other node keeps its share (`eval.deviceShapePatches()` counts these, `eval.deviceShapeWalks()` the walks of every node). The causes are listed in node id order. ### What procgen keeps (`proc.memory`) Every play, whoever started it, and each module-level cache that holds procgen state (the kept bodies, the answers kept plans hold, the frames timelines keep, the world store the plays share) is a keeper. `proc.memory.report()` answers `{ total, luau, budget, tiers, plays, keepers, byPart, commits, dropped, pending }`: the bytes each keeper holds, a play by part (`graph`, `plan.flat`, `plan.inlined`, `plan.origins`, `plan.reuse`, `plan.cones`, `plan`, `nodeCache.values`, `nodeCache.pulled`, `nodeCache.entries`, `nodeCache.solvers`, `play.coneMemo`, `play.stats`, `play`) with the tier of the state, and the bytes the Luau heap holds (`luau`). A part states its bytes from counts kept where its state is filed and let go of: a plan's flat node count and rows, a node cache's entries, solvers and the entries whose values were let go of (`eval.cacheCounts(cache)`, kept by `fileEntry`, `dropEntry` and the store's writes), the kept bodies' flat nodes (`expand.bodyCounts().kept`). The bytes one unit costs are `proc.memory.PER`, fitted to the heap that letting each part go gave back. The tier of a part is what letting it go costs: 1 a table made again when read (the table of origins the flat graph and the profile file by flat id, the cook times, the answers kept plans hold, the frames timelines keep), 2 a node cache value or kept body cooked or planned again where an edit reaches it, 3 the play's edit state (the plan's reuse record and cones and the answers kept for the pulls: the next plan is made without its base), 4 the cache as a whole, 5 (`proc.memory.STANDS`) what a present stands on, which no budget lets go of. With a budget (`proc.memory.setBudget(bytes)`; none by default) the ledger reads its total at the commit points: after `Play.replan` has made its plan the play's, after a present settles, and on a pressure signal (`proc.memory.signal`). Over the budget it lets go of tier 1, then 2, 3 and 4, the module-level keepers first and then the plays used longest ago first, until the total is at 80% of the budget. A tier can be switched off (`proc.memory.setTier(tier, false)`). A play whose present or plan is running is left whole, and when one runs besides the play that commits, the check waits for the next commit point. `report().dropped` lists the commit points that let go of state: the budget, the total before and after, the bytes by tier and the keepers and plays that gave them. What each tier lets go of, and why a play answers what it answered: tier 1 is made from the plan when read (`expand.originsOf`, `profile.originsOf`). Tier 2 is `eval.letGoValues`: an entry that no pull answers and nothing stands on in the world is left a trimmed one (no key, no values), as `trimToBound` leaves one, and the values it held are released unless another entry, the world store, a value a handle stands on or a registration the device rewrites reaches them (`registration.reads` lists what a rewrite reads and lands in), and a value that holds a live run is left to its registration; the next cook that reaches the node derives its key from its inputs and makes the values again. A kept body let go of is planned again where a call needs it, as with `expand.setBodiesEnabled(false)`, whether or not a play holds a reuse record: a plan answers the same plan, keys and reads from kept bodies and from bodies planned afresh. Tier 3 is `expand.dropReuse` and `expand.dropCones` and a play without its answers (`play.coneMemo`): the next plan has no base, which is a plan made as a first one, and its dirty set names the ledger (`withoutBase`); the cones are keyed whole and the plan's watches are read by cooking them, as with `expand.setWatchesCarried(false)`; the device shape is stated from every node (`eval.deviceShapeWalks`). Tier 4 is tier 2 for every entry, the pulls' too, while the handles the play shows stand.

# fieldc A Field is a per-element expression. `fieldc` holds what a Field is made of and how it runs: a chain of templates over a position leaf, an element number, column reads and numbers is written as one WGSL function and runs as ONE dispatch of `kernels/map`, wherever it is consumed. Nothing dispatches per operator. ## Where a Field is evaluated ```luau local column = fieldc.evaluate(field, domain, opts) ``` The one entry point a consumer of a Field calls (a kernel's input, an attribute write, an output): `device.kernel` for a Field bound to a column input, `attribute.write` for a Field value, and every other node that needs a Column. - `field`: a Field, a Column, a `BufferRef` (a device column handed through `cpu.call`), a number or a vector record. A Column an op hands a chain as an operand is a leaf of the chain, read where it is held. - `domain`: a number of elements, or a Geometry (its `opts.class` elements, points by default), whose attributes the leaves reading the evaluation domain bind. - `opts`: `{ class, count, type, clock, where, label }`. `type = "Int"` writes i32 words (a Field tagged Int does so by default). `clock` is `{ time, frame, fps, duration }`: animated values are first sampled there. `where` names the caller in a refusal. - Answers a Column of the domain's count. Raises, naming what refused, when the chain cannot be written as a function: a chain whose last field is a `Field.fn` (a Luau function of the element) states no expression, and the refusal says so. A constant Field (`proc.Field.constant`) is the same value at every element, as a number is. - The first evaluation of a chain whose kernel is new waits, in a thread that can yield, for the device to build it (`compute_abi.awaitProgram`). A kernel the device refuses raises there, naming the caller and the compiler's message, so no evaluation answers a column no dispatch wrote. A thread that cannot yield does not wait. A chain holding an animated value or a live run answers a live column. `fieldc.liveRuns` finds it and `fieldc.tick(runs, clock)` rewrites it each frame: the animated values are sampled at the clock and written into the numbers the dispatch reads, and the dispatch runs again into the same run. An animated input therefore changes the result every frame without a cook. ## Fields the nodes make | Construct | Module | Answers | |---|---|---| | `fieldc.field(v)` | `fieldc` | any socket value as a Field: Field, Column, BufferRef, number, vector, animated value | | `operators.apply(name, ...)` | `fieldc.operators` | `math.*`: the plain result over numbers and vectors, a Field over a run or a Field | | `fieldc.element(name, class?, width?)` | `fieldc` | what `g.element` stands for: `"id"`, `"P"`, or a column of the domain (`g.element.point.N` is `element("N", "point")`) | | `leaves.elementId()` | `fieldc.leaves` | the element number, an Int Field (`g.element.id`) | | `fieldc.position` | `fieldc` | the position leaf `p` (`g.element.P`, and an unwired `field.position()`): the domain's `point.P` where the chain is evaluated over a Geometry, the point `fieldc.withPosition` names inside a substitution; `fieldc.evaluate` refuses a chain that reads it over a number of elements with no geometry | | `leaves.context(class, name, width?)` | `fieldc.leaves` | an attribute of the evaluation domain | | `leaves.rand(seed, scope, id)` | `fieldc.leaves` | the unit draw, equal to `hash.unitFloat` to the bit | | `leaves.call(fn, args)` | `fieldc.leaves` | a function of a prelude shader module of `kernels/` | | `leaves.gather(column, index)` | `fieldc.leaves` | a run read at computed elements | | `leaves.substitute(field, position)` | `fieldc.leaves` | the chain read at another point (`fieldc.withPosition`) | | `leaves.index(domain)` | `fieldc.leaves` | an Int column of 0 to n - 1 | An animated value that becomes a Field (`fieldc.field`) is the live field holding its value at a time: inside a node's cook, the time of the clock the cook runs at (the evaluator runs each cook through `fieldc.pcallSampling`), so a curve handed to a node asset and read by a field op follows `opts.clock` of `proc.eval`; outside any cook, time 0. It stays a live field: a present for a later time rewrites the run it lands in (`fieldc.tick`), and the node is not cooked again for the time. `fieldc.op(field, wgsl, stride, args)` binds a Column or a `BufferRef` among `args` as the run it is, the way `fieldc.field` does, so a field op given a column reads it where it lives on the device and nothing is read back. `leaves.call` (the `field.call` node) calls a function of a module of `kernels/` that compiles inside a field chain's kernel. The first call into a module compiles a `kernels/map` variant that includes it and waits for the device's verdict; a module written for one kernel (`walk_core`, `walk_advance`, `hash_walk`, the `bvh_*` and `intersect_core` modules, each naming what its includer binds or declares) does not compile there, and a call of its functions is refused naming the function, the module and the compiler's message. A Field made by these answers `f.x`, `f.y`, `f.z`, `f.w` as the Field of that component. Components are Fields, so the Field of a vector is built from them with `operators.vec2`, `operators.vec3` or `operators.vec4`; Luau's `vector.create` takes numbers. ## How the leaves reach the kernel A chain's leaves are columns. `kernels/map` states every leaf's shape in its `cols` table and reads up to as many leaves as one dispatch has storage buffers for (`compute_abi.directLimit`: 8 per stage on every target, less the table, the numbers and the output, so 5 for `map`) straight from the buffer of the leaf's own run, at no cost beyond the binding. A chain of up to 5 leaf columns is the one dispatch of `map` and nothing else. Leaves past those are copied into the table, one copy dispatch each. `fieldc.bindSpec(spec, { direct })` makes the table; `direct` is the list of leaf slots read from their own runs (`compute_abi.directPlan(columns, limit)`), and the variant is made with the same list: `program:variant({ specialize = ..., direct = { cols = direct } })`. Without `direct` every leaf is copied into the table. `fieldc.operators` folds numbers: every operand a number or vector gives a number or vector. A narrower operand widens to the widest (a number applies to every component, a shorter vector reads 0 where it has none). Division and remainder by 0, the square root and the logarithm of a value at or below 0 answer 0. ## The walk step contract (for `kernels/walk`) A walk kernel takes its per-walker function as a Field spec, the way `kernels/map` takes `TEMPLATE`. ```luau local spec = fieldc.walkSpec(step, { width = 2, count = walkers, done = stop }) -- a state of 8 floats: lanes 0 to 3 in `step`, lanes 4 to 7 in `high` local wide = fieldc.walkSpec(low, { width = 8, count = walkers, high = high }) local bound = fieldc.bindSpec(spec) -- specialize = spec.specialize; bind cols = bound.cols:buffer(), u = bound.u ``` - `width`: floats per state, 1 to 8. `step` is the next state's lanes 0 to 3, a Field of `min(width, 4)` components; above 4, `opts.high` is the Field of the `width - 4` components of lanes 4 to 7. - The state is read through `fieldc.walkState(count, first?)`: `count` (1 to 4) lanes from lane `first` (default 0), all inside lanes 0 to 3 or all inside lanes 4 to 7. A state of 8 floats is read as two leaves, `walkState(4, 0)` and `walkState(4, 4)`. The nodes `field.walk_state({ count, first })` and `field.walk_index()` are these leaves in a graph. - `step` and `high` are written over the state leaves, `fieldc.walkIndex()` (the step number k, from 0), `leaves.elementId()` (the walker's number), Column reads (one value per walker, or a gather at a computed index) and numbers. - `opts.done`: an optional Field<Float> over the same leaves; the walker stops before step k when it is not 0. - `spec.specialize` is a table of the specialization values the walk kernel takes, ready to hand to `device.kernel` / `program:variant` as its `specialize` value: `WALK_STEP` (`zero_walk_chain_step(s, s_hi, k, id)`), `WALK_STEP_HI` (`zero_walk_chain_step_hi(s, s_hi, k, id)`, or `s_hi` when `width` is 4 or less), `WALK_DONE` (`zero_walk_chain_done(s, s_hi, k, id)`, or `false` when there is no `done`) and `WALK_PRELUDE`, the module-scope WGSL that defines those functions, preceded by the preludes the chain calls. Lanes 0 to `width - 1` of `s` (lanes 0 to 3) and `s_hi` (lanes 4 to 7) are the state. - The functions read its leaves through a `cols` columns binding (`cols_f32(slot, i, 0u)`, `cols_vec3(slot, i)`, `cols_i32` for Int runs) and its numbers through `u_get(k)`: the kernel declares those two bindings exactly as `kernels/map` does. `fieldc.bindSpec(spec)` answers the table (`cols`) and the numbers buffer (`u`) to bind; `release()` lets both go. - A read past a run's end reads its last element. ## Other entry points `fieldc.mapSpec(chain, count, domain, { position })` writes a chain as one function for `kernels/map` and `fieldc.runMap(spec)` runs it. `fieldc.compile` / `fieldc.column` write the same chain as a kernel of its own, for the consumers that bind buffers directly.

# proc.fields Value wrappers for the procedural-generation type system: `Field<T>`, `PointCloud` and `Population`. Part of `@builtin::systems.procgen.proc`. Typed values backed by plain strided Luau arrays. - **`Field<T>`** — a lazy per-element value. `Field.constant(t, values)`, `Field.fn(t, stride, f)`, `Field.buffer(t, stride, buf)`; `:sample(id)` → the `stride` components, `:materialize(count)` → a flat `count*stride` array. - **`PointCloud`** — the value a `.procNode` input declared `PointCloud` receives (`proc.substrate.toPointCloud`); every other input, and every op, takes points as a `Geometry` (`proc.geometry.new`). `PointCloud.new(positions)` (flat stride-3 array); `:count()`, `:position(id)`, `:setAttribute(name, field)` / `:getAttribute(name)` / `:attributeNames()`. - **`Field.transform(offset, orient, scale)`** — a per-element transform whose three parts are fields of their own, so each compiles to the device; `:transformParts()` hands them back. Every value carries a `__proc_type` tag that `proc.types.typeOf` reads (`"Field<Vec3>"`, `"PointCloud"`, `"Population"`).

# proc.fusion The dispatches of a recorded compute list that compute one element each, made into one dispatch per chain. A per-element kernel declares in its `bindings.yaml` that it is one (`fusion:`): the function `element(i)` that is its value at `i`, the guard that leaves a thread out, and the binding it writes. A dispatch whose output nothing else needs is absorbed into the dispatch that reads it, which calls its `element` function in place of the read, so a chain is one generated kernel; a dispatch no answer depends on is dropped. `plan`, `build`, `fuse` and `apply` make and apply the fused list, `stages` and `applyStages` schedule a list's per-element dispatches into stage kernels by dependency level, `setEnabled` turns fusion on or off, and `counts` and `stageCounts` report what was fused. Part of `@builtin::systems.procgen.proc`; required as `@builtin::systems.procgen.proc.fusion`.

# proc.geometry CPU geometry container (positions/indices/normals/uvs) + bounds, normal recompute, and renderer.mesh.create args. Part of `@builtin::systems.procgen.proc`.

# proc.graph The graph data model and its definition entry: the nodes a graph holds, the normalized `InputRef` edges between them, its inputs and outputs, and its JSON (de)serialization. Required as `@builtin::systems.procgen.proc.graph`; the top-level `proc` module re-exports its entries as `proc.define`, `proc.graph(id)` (`new`), `proc.fromJSON` and `proc.op`. `define(function(g) ... end)` builds a graph in the call form, whose authoring surface is `proc.builder`: nodes called by asset identity (`g.points.disc({ ... })`), inputs typed by their defaults (`g:input`), sockets that take Luau's operators, members, columns and `for`, and the declarations a graph states about itself: `g:describe` (what it makes), `g:output` (what it gives), `g:family`, `g:timeline`, `g:still` and `g:cost`. The result is a graph with `surface = "call"` that records each node by the guid of the asset it calls. `refusedInput(graph, name, value)` names why a value is not one an input holds. `fromJSON(doc)` reads a graph document back and `graph:toJSON()` writes it. Part of `@builtin::systems.procgen.proc`.

# proc.hash Deterministic, portable scoped hashing for the procgen evaluator. `scoped(seed, graphId, compositePath, nodeId, channel, elementId) -> number` folds its arguments with 32-bit FNV-1a (via an exact 16-bit-split `mul32`) and a final avalanche, producing a bit-identical `u32` on native, WASM, and Android. `unitFloat(...)` maps the same scope to a value in `[0, 1)` for deterministic random draws. No `math.random` / `os.time` / float transcendentals — determinism is the contract. The per-element scope (`elementId`) keeps a given element's draw stable as unrelated element counts grow.

# proc.noise Deterministic, portable value/gradient noise. Part of `@builtin::systems.procgen.proc`. Built on the integer-lattice hash in `proc.hash` (`latticeCell2/3` / `unitCell2/3` — the corner hashes of one cell, each bit-identical to the matching `hashInts` call): every lattice corner's random value/gradient is integer-derived, and the only continuous math is the quintic fade + linear interpolation. No float transcendentals and no `math.random`, so the result is bit-identical on native, WASM, and Android — which is what makes a procedural texture reproducible everywhere. Exposes `value2`/`value3`, `gradient2`/`gradient3`, and `fbm`.

# proc.ops Op-family loader: registers every procedural op against the registry. Part of `@builtin::systems.procgen.proc`.

# proc.parity The machinery behind the procgen rewrite's parity harness (`procgenParity`), its sheet tests (`procgenSheet`) and the `procgen.coverage` tool. - `parity.json`: `entries` holds one entry per current op. Each names its new composition (`new`, node ids as `nodebox.name`, or `nodebox.*` for any node of a nodebox), its class (`exact`, `meaning` with an `invariant`, `gone` for a named decision with a `note`, `unmapped` where the sheet names no counterpart), and `tolerance` the comparison reads. An entry that states `decided` (the text of the ruling that accepts the difference between the op and its node) keeps running: the value differences its comparison finds are reported as accepted, under the verdict `decided`, and are held to nothing, while a node that raises and the cost findings stay findings (`accepting`, `decidedLines`). `budgets` states, per op, the read-backs its node may make (`{ "<op>": { "readbacks": n } }`); an op without one may make as many as the current op does. `types` maps a socket's type to the fixture a case builds for it. `tolerance` holds the global bounds (`attribute`, `bounds`, `picture`, `costRatio`, `costFloorMs`). `suites` names, per parity suite, the nodeboxes whose entries it compares (`suites()`); `onNodes` names, per on-nodes suite, the existing suites it runs with their ops answered by their nodes, and `onNodesLeft` the suites no on-nodes suite runs. `cases` holds a case per op that needs more than the defaults and names only content the library ships. A parity suite states the cases whose inputs are its test fixtures in the `cases.json` of its folder (`{ "cases": { "<op>": case } }`), since the library ships its test content nowhere; `cases()` is both together, one case per op, and an engine whose library leaves the suite out finds no case for those ops. - A case states `params`, `fixtures` (a fixture by input socket), `node` (the new node a multi-node entry compares against), `nodeBy` (`{ param, nodes = { value = node } }`: for an entry whose op one node per value of a param answers, the node an existing suite's call reaches for each value, which `standIns` runs; a value it names no node for is refused), `rename` (`inputs`, `params`, `outputs`: the new node's names where they differ, `false` leaves a name out), `compare` (`bounds`: a Geometry is held to its bounds alone, for an output whose element layout differs by design; `ramp`: two ramps are held to the values they read at the same positions), `sink` (`asset` or `handles`: the op writes to the world, each side under its own name and what it wrote is compared and removed), `world` (entities spawned for the run; `scene` takes the run's root scene, `settle` waits until the op runs on them), `tolerance` (bounds that replace the global ones for this case, `{ attribute = 0.05 }`: for an op whose values come from the device's sampler, whose fixed-point weights and decode answer within a fraction of a percent of the exact blend a node computes), `ignore` (outputs left out), `unreachable` (the sentence that says why the harness has no fixture for the case; the entry then counts as a harness error) and, for an op that is a solver over a timeline, `suite` and `describe` (the group of an existing suite that holds its comparison; `deferred` leaves that group to the suite's own run and states the entry pending, for a group that costs the suite's whole time a second time inside this one). - A fixture is a name (`mesh`, `points`, `curve`, `positionField`, or a type named in `types`), a current op run on its own fixtures (`{ op, params, inputs, output }`; the new side builds it through the node that replaces the op when the entry for that op names exactly one, so a ramp, a group, a prefab, a raster or an Sdf a node reads is one that library made; `shared: true` makes both sides take what the current op makes, for inputs the entry under test is held to and the op that made them is not), a node run on its own fixtures (`{ node, params, inputs, output }`, a new node by id), a list (`{ list }`), a record (`{ record }`) or a literal (`{ value }`). A case's `newInputs` are fixtures only the new side takes, for an input the current op states as a param (a texture the node reads where the op names the asset). - `sheet.json`: the composition sheet's expectations: the eight ops, the 23 kernel families with their tallies (a kernel asset `<kernel>_<pass>` belongs to the family `<kernel>`), the layers, the L2 ids as the core package names them, `universalUses` (the L2 nodes every row may call), one row per node family (the kernel families, L2 nodes and ops a node of the row may name; `authorKernel` for rows whose nodes run a kernel the author names; which nodes may stand on one kernel family alone), and the reported numbers. `scan()` finds the new parts in the library: the nodes of every built-in nodebox wherever its package keeps it, the kernel families with their pass assets, and the modules that sit beside nodes. `analyze(src, ...)` reads a node's source: the nodes it calls (`g.<name>(...)`), the ops it names (`op.<name>`), the kernel families it names, a structural hash per call, and WGSL text in its strings. `rowViolations(scan, node)`, `dispatchViolations(scan, node)` and `directCallers(scan)` state what a node breaks of the sheet. `valuesHold(result)` reads a comparison's values alone, which is what lets an existing suite run on the nodes of an op whose cost is over. `assess(scan, entry)` states where an entry stands (`decided`, `unmapped`, `pending`, `ready`); `compare(scan, entry)` runs a ready entry's current op beside its node; `checkCase(entry)` runs the current op on the entry's case. `redirect(map, fn)` runs `fn` with `registry.get` answering a new node for each op id in `map`; `runSuite(name, redirect)` runs an existing suite's cases through the test framework's own runner, and `runSuiteOnNodes(scan, name, ops)` runs it as it stands and with its ops answered by their new nodes. `report(opts)` is the coverage report. A comparison states cost as separate numbers (`result.cost`): `oldMs` (the current op's CPU time), `planMs` (the evaluation outside the nodes' own cooks: expanding the call form, lowering refs and constructs, scheduling, with the plan's share of the waiting taken out), `cookMs` (the CPU time the nodes' cooks spend, with their share of the waiting taken out), `waitMs` (the time in `task.wait`, a read-back's frames, shared between the cooks and the plan by the read-backs each made), `dispatches` (device dispatches queued), `readbacks` (read-backs the substrate counted) and `frames` (frames that passed during the evaluation). A Field in an output is read over the Geometry its side was given, a Column by its values, and a Bool answers 1 or 0. The cost ratio of `tolerance` is applied to `cookMs` against `oldMs`; the read-back count is asserted against the op's budget on its own, so a read-back removed from a node shows as `frames` falling to zero. Times are the median of three runs; counts are the last run's. A comparison states its values and its cost apart. `result.valueFindings` are the differences in what the node answers and `result.costFindings` the cost and read-back findings (`result.findings` holds both). `verdict(assessed, result)` reads them as `value` (`equal`, `differ`, `missing` for an attribute, layer or column the new output lacks, `raised` for a node that failed on the case's inputs, `harness` for a case whose inputs could not be made, `skipped`, `decided`) and `cost` (`within`, `over`, `none`); `summary(scan)` counts every entry under exactly one of `pass`, `costOver`, `differ`, `missing`, `raised`, `harness`, `skipped` and `decided` and reports the same per family (the nodebox of the entry's first new node) with the median and worst cost ratio. What is compared where the two libraries carry a value differently: a Geometry by its live counts (a domain allocated at a capacity compares its live front), a Raster layer by layer at the grid's cell centres, a Texture by size, channel count and texels (bytes scaled to 0 to 1 and held to half a byte step), a count the new library holds on the device as a one-word column by its value, a Population against the instanced points by instance count, and a list of numbers against a list of records of numbers as one layout finding that says whether the numbers agree.

# proc.placement Where a graph stands in the world, as a 4x4 matrix held as 16 numbers column after column: the layout `entity:worldMatrix()` and `camera.viewData().viewProj` answer in. A graph is evaluated in its own space, whose origin is the entity it stands on. A Generator draws what it makes under its entity, so the graph's origin stands where the entity does, and an effect built at the origin works wherever it is played. A node that pulls from the scene (`scene.fetch`, `terrain.ground`, `sim.scene_colliders`) reads that origin from the scene the evaluation hands it, `ctx:scene().origin()`, and takes what it reads from the world into the graph's space. A graph evaluated standing on no entity has the world's origin for its own (`proc.placement.IDENTITY`). `mul`, `inverse`, `point`, `scale`, `rotation`, `turn` and `conjugate` are the matrix and quaternion steps such a node takes.

# proc.preview Type-dispatched visualization of any proc value. `visualize(value, name?, opts?)` materializes the value into temporary scene entities and answers `{ entities, framing?, stats, cleanup }`: a Geometry draws as a mesh, a population of points carrying a Mesh as one merged Geometry, bare points as a marker cube at every point, a `Field<T>` as a heatmap on a quad, a Material as a lit sphere wearing it, a Texture on a unit quad, and a Prefab or Bundle as the persisted bundle instantiated. `cleanup()` despawns everything it spawned. `shows(value)` and `isDrawn(value)` say whether it has a picture for a value. `markedPoints(value)` answers bare points the device holds as a population of marker boxes, which the translation layer draws as one instanced draw a play moves on the device. The `procgen` toolbox's `preview` tool drives capture on top of it. Part of `@builtin::systems.procgen.proc`; reached as `proc.preview`.

# proc.records Record kinds: the values a graph moves that become assets when saved (a material, a mesh, a texture, a user's own). `proc.record({ name, asset, applies?, fields?, live?, release?, save?, load? })` defines a kind; a `.procRecord` asset's `init.luau` returns one. A record carries its kind's guid as `kind`; the node that writes it states the kind on the geometry's detail attribute `records` (`{ [guid] = reference }`), and output, export and import find the definition there. `save` and `load` default to the asset type's own `graph.write` and `graph.read`. A kind whose `live` value holds something (a scratch asset) states `release`, which output calls once nothing stands on the value. Part of `@builtin::systems.procgen.proc`.

# proc.registry The operation registry: register/lookup/schema/search/help for procedural ops. Part of `@builtin::systems.procgen.proc`.

# proc_field_noise (compute shader) 2D value-noise field: `dst[i] = value2(seed, coords[i] * freq)`. One GPU thread per element. Re-implements `proc.noise.value2` — the integer FNV-1a lattice hash (`proc.hash.hashInts`) is bit-exact-portable, so the `u32` hash here matches the Luau `bit32` hash exactly; the quintic-faded bilinear interpolation runs in `f32` (vs the CPU's `f64`), bounded to `f32` rounding. It reads `coords` (one `vec2<f32>` per element) and writes `dst` (one `f32` per element); `seed` (int, default 0) and `freq` (float, default 1.0) are its params. The `gpu.noise` op (`proc.gpu.eval("noise", { input = coords, count = n, seed = 7, freq = 0.1 })`) dispatches it and returns `dst` as a GPU-backed `Field`.

# proc_field_scale (compute shader) Element-wise scale of an `f32` field: `dst[i] = src[i] * scale`. One GPU thread per element. Reads a storage buffer (`src`), writes a storage buffer (`dst`), and multiplies by the `scale` params uniform. The `gpu.scale` op (`proc.gpu.eval("scale", { input = f, count = n, scale = 2 })`) dispatches it and returns `dst` as a GPU-backed `Field`.

# proc_raster_apply_accumulator Folds one tile's fixed-point accumulator into a layer, clearing the accumulator for the next batch. `proc.raster`'s `Raster:resolveAccumulator(layerName, scratchName, work?)` runs this after `proc_raster_edge_add` has folded in what a neighbour pushed across the seam, then refreshes `layerName`'s apron so the next step reads a consistent neighbourhood. It reads `params` (lane 0 holds the tile's stored-cell stride), adds each cell of `delta`, an `atomic<i32>` accumulator in units of 1/65536, into the same cell of `field`, and sets that cell of `delta` to 0. One thread per stored cell, apron included, in 8x8 workgroups.

# proc_raster_apron Refreshes one tile's apron ring of one layer from the neighbour tile that owns those cells, one dispatch per (destination tile, neighbour direction). `proc.raster`'s `Raster:exchangeAprons(name, work?)` drives it, over every neighbour pair a work set touches. Any iterative raster kernel op whose per-cell result depends on a previous step's neighbourhood needs its written layer's apron refreshed this way between steps, or a later step reads a neighbour's stale interior instead of what that neighbour actually computed. `params` describes the block in stored-cell coordinates: lane 0 holds (stride, block width, block height, 0) and lane 1 holds (destination x0, z0, source x0, z0). It reads the block from the neighbour's `src` and writes it into this tile's `dst`, one thread per cell of the block in 8x8 workgroups. The same shader moves an edge band and a corner square.

# proc_raster_copy Copies one raster tile into another, cell for cell, apron included. `proc.raster` runs it for its channel set's checkpoints, restores and clears, and for `Raster:copy()`. A checkpoint is a copy of every live channel tile taken as the state after a stack index, so an edit to an op after that index restores the copy instead of re-running the ops up to it. A clear is the same copy with a zeroed tile as the source. `Raster:copy()` duplicates every layer's tiles so a mutating op leaves the original untouched. `dst`'s length decides how many cells are copied, so the two tiles must be the same shape. It reads `src` and writes `dst`, one thread per cell, apron included, 64 to a workgroup.

# proc_raster_edge_add Adds a neighbour tile's apron-ring fixed-point accumulator into this tile's interior, one dispatch per (destination tile, neighbour direction). `proc.raster`'s `Raster:resolveAccumulator(layerName, scratchName, work?)` drives it, before folding the accumulator into `layerName` and refreshing `layerName`'s apron. Droplet and thermal erosion both accumulate this way — any tiled kernel op whose per-cell result can spill across a tile seam needs the same fold. `params` describes the block the way `proc_raster_apron` takes it: lane 0 holds (stride, block width, block height, 0) and lane 1 holds (destination x0, z0, source x0, z0), the source block in the neighbour's apron ring and the destination in this tile's interior. It reads the neighbour's accumulator `src` as plain integers and adds each non-zero cell into this tile's `dst` with an atomic integer add, one thread per cell of the block in 8x8 workgroups.

# proc.substrate The substrate a graph carries: a geometry, its four domains (point, vertex, primitive, detail) and the named columns over them. A point is a position and an identity; a vertex is one primitive's use of one point; a primitive is a run of vertices (a face, a curve or a volume); detail is the geometry itself, one element. An attribute is a named, typed column over one domain. A numeric column is a `substrate.createBuffer` handle, the engine's one buffer primitive, so the handle a column holds is the one a kernel runs over and a compute shader binds; a column of a type a buffer cannot express (text, a reference, a record) is carried as values and placed on the device interned. `Geometry`, `Column` and `Domain` are the value types; `fromArrays`, `fromPositions`, `fromCurves` and `fromPointCloud` build a geometry. `man proc.substrate` lists every function with its arguments. Part of `@builtin::systems.procgen.proc`; reached as `proc.substrate`.

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

# 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.

# yaml.module YAML decode + encode for authored engine content. Pure Luau, no engine dependencies — a general parsing library, not data-system plumbing. ```luau local Yaml = require("@builtin::modules.yaml") local doc = Yaml.decode(vfs.read(path)) vfs.write(path, Yaml.encode(doc)) ``` ## Supported subset - Block mappings (`key: value`) and block sequences (`- item`), nested to any depth. - Compact sequence-of-mapping entries (`- path: x` / ` kind: y`). - Flow collections — `{ a: 1, b: 2 }` and `[1, 2, 3]` — single line. - Plain scalars with type inference: `~` / `null` → nil, `true` / `false` → boolean, numeric literals → number, everything else → string. - Single- and double-quoted strings (`''` escapes a literal quote inside a single-quoted string; `\n` `\t` `\r` `\\` `\"` inside a double-quoted one). A quote opens a quoted scalar where a scalar begins — after `key:`, after a `- ` entry marker, or inside a flow collection — so a plain scalar carries an apostrophe as data (`note: the world's rules`). Quoted keys are read in flow mappings. - `#` comments — honored outside quotes, so a `#` inside a quoted string is kept as data. - Literal (`|`) and folded (`>`) block scalars, with a chomping indicator (`-` strips the final newline, `+` keeps every trailing blank line, none keeps one newline) and an indentation indicator (`1`-`9`: the content's indent past the parent's), in either order (`|-`, `>+`, `|2`, `>1-`). A block scalar's content is literal text: quotes (balanced or not), `#`, `key: value` and `---` inside it are data. - An optional leading `---` document marker. ## Loud-error contract Constructs outside the subset above raise instead of misparsing: anchors/aliases (`&`, `*`), tags (`!`), directives (`%`), multi-document streams (a second `---`), a block-scalar header it cannot read (`|x`, `|-+`, `|0`), tab indentation, and inconsistent indentation (both block structure and block-scalar bodies). Every error carries the offending line number (`yaml: line N: ...`), so a bad config points straight at the line to fix. Tab indentation is rejected everywhere — including block-scalar body lines whose leading whitespace contains a tab. A tab after the first non-space character of a line is content and passes through. ## API - `Yaml.decode(text: string): any` — decode a YAML document into a Luau value (table, scalar, or nil for an empty document). Raises on malformed input or an unsupported construct. - `Yaml.decodeWithComments(text: string): (any, boolean)` — decode as `decode` does, and report whether the text carries a comment by the decoder's own rule: a `#` at a line's start or after whitespace, outside a quoted scalar and outside a block scalar. Re-encoding the value drops such comments, so an editor that writes a document back reads this first. - `Yaml.encode(value: table): string` — encode a Luau table as YAML (block style, two-space indent, alphabetically sorted keys). Raises on values YAML can't represent (functions, userdata, non-string mapping keys). A top-level empty table encodes to an empty document, which decodes back to `nil` (the YAML empty-document ambiguity).

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

# 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.