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

# postReference_focusBars Four rows of bar pairs, 8 pairs across the top row and doubling on each row below: the focus chart a depth-of-field reading is taken off. Drawn unlit by `@builtin::shaders.referenceChart`, so a picture of it is measured against the light its properties state. Part of the post-verification reference scenes (`@builtin::scenes.postReference.*`); `@builtin::modules.postMetrics` reads them.

# postReference_skyRamp A sky-blue ramp of light from 0.02 to 0.6 across: a clear sky's gradient. Drawn unlit by `@builtin::shaders.referenceChart`, so a picture of it is measured against the light its properties state. Part of the post-verification reference scenes (`@builtin::scenes.postReference.*`); `@builtin::modules.postMetrics` reads them.

# volumetrics Volumetric (3D-texture) rendering, end to end, in one package. Built entirely on the engine's generic `compute.*` GPU primitives — no Rust changes are needed to author new volumetric content. ## Layout | Asset | Identity | Role | |---|---|---| | `Volume.component` | `@builtin::systems.volumetrics.Volume` | Attach a 3D voxel texture to an entity; raymarches it through the entity's transform AABB. | | `VolumetricSky.component` | `@builtin::systems.volumetrics.VolumetricSky` | Singleton procedural cloud layer with TAA. | | `ParticipatingMedium.component` | `@builtin::systems.volumetrics.ParticipatingMedium` | Mark an entity as fog/smoke/dust that attenuates the light passing through it. | | `mediaTransmittance.module` | `@builtin::systems.volumetrics.mediaTransmittance` | Light-space optical-depth map: the registry, the settings, and the basis the map is built in. | | `mediaShadow.renderFeature` | `@builtin::systems.volumetrics.mediaShadow` | Builds the optical-depth map and attenuates each surface by the density in front of it. | | `volume.module` | `@builtin::systems.volumetrics.volume` | Builders (`noise`/`sphere`/`box`/`wrap`) + the `.zvol` header reader + occupancy + brick paging + the per-entity raymarch dispatch. | | `VolumeSequence.component` | `@builtin::systems.volumetrics.VolumeSequence` | Play an open volume sequence through an entity's transform AABB. | | `volumeSequence.module` | `@builtin::systems.volumetrics.volumeSequence` | A run of `.zvol` frames streamed through a fixed ring of resident volumes. | | `volumeDemos.module` | `@builtin::systems.volumetrics.volumeDemos` | Shared pipeline for the showcase scenes (fill + emissive raymarch + composite). | | `volumetricSky.module` | `@builtin::systems.volumetrics.volumetricSky` | Cloud volume + raymarch + TAA + composite orchestration. | | `shaders/*.shader` | `@builtin::systems.volumetrics.shaders.*` | `volume_raymarch`, `volume_pages`, `volume_pack`, `cloud_noise[_v3/_v5]`, `cloud_raymarch[_v3/_v4/_v5]`, `cloud_taa`. | | `importers/vdb_to_zvol.importer` | (auto-discovered) | `.vdb` → dense `.zvol` via the `openvdb` WASM plugin (procedural fallback when the plugin isn't loaded). | | `presets/cumulus_default.preset` | `@builtin::systems.volumetrics.cumulus_default` | Canonical full `VolumetricSky` weather preset. | | `demo/*.scene` | `@builtin::systems.volumetrics.demo.*` | `sdf_solids`, `smoke_plume`, `nebula`, `godrays`, `zvol_viewer`, `sky`. | ## Path convention — fully-qualified builtin identities Every intra-package reference uses the asset's fully-qualified builtin identity, the same convention every other builtin package follows: ```luau local Volume = require("@builtin::systems.volumetrics.volume") local Sky = require("@builtin::systems.volumetrics.volumetricSky") local V = require("@builtin::systems.volumetrics.volumeDemos") -- shader identities, e.g. asset.resolve("@builtin::systems.volumetrics.shaders.volume_raymarch") ``` Qualified identities are caller-independent: they resolve identically from a module, a scene entrypoint, or a component. Caller-relative (`.sibling`) requires are deliberately avoided here because the component runtime caller identity is `@builtin::components.<Name>`, so a `.sibling` require from a component resolves against the wrong root. (An earlier revision of this package used a `~volumetrics` package-root alias for relocatability; that alias is not resolvable on current main, so the package uses qualified identities throughout.) ## Usage ```luau -- Per-entity volume. The component resolves the name through `Volume.get`, -- so a volume paged into a brick pool renders from the pool under the same -- name: local Volume = require("@builtin::systems.volumetrics.volume") local cloud = Volume.noise({ name = "cloud", size = 64, scale = 4 }) cloud:buildSparse({ brickSize = 8 }) cloud:releaseDense() entity(id).component.add("Volume", { volumeName = "cloud", density = 6.0 }) -- Procedural sky: local sky = entity.spawn("sky") sky.component.add("VolumetricSky", {}) preset.apply("cumulus_default", { entity = sky.id, component = "VolumetricSky" }) -- VDB import: drop a `.vdb` into the VFS; the importer writes a `.zvol` -- alongside it. Load it with the zvol_viewer demo scene. -- Animated run: one `.zvol` per frame, played through a bounded ring. local Seq = require("@builtin::systems.volumetrics.volumeSequence") Seq.open({ name = "plume", frames = framePaths, resident = 3, fps = 24 }) entity(id).component.add("VolumeSequence", { sequenceName = "plume", density = 6.0 }) ``` ## Plugin dependency The VDB importer delegates real OpenVDB parsing to the `openvdb` plugin in the builtin library, `@builtin::plugins.openvdb`. Without the plugin the importer falls back to a deterministic procedural torus so the pipeline stays functional.

# Chrome A polished chrome surface built on the `pbr` shader — fully metallic (`metallic: 1.0`) with a bright near-white base colour (`0.95, 0.95, 0.97`) and very low roughness (`0.05`) for mirror-sharp reflections. Opaque, back-face culled, instanced, with the `_METALLICSPECGLOSSMAP` keyword enabled. ## Inputs - `colors.base_color` (`0.95, 0.95, 0.97, 1.0`) — bright, faintly cool chrome tint. - `floats.metallic` (`1.0`) — fully metallic. - `floats.roughness` (`0.05`) — near-mirror sharpness. - `textures.base_color_texture` (`default:white`): the white base texture the colour multiplies against, so the surface renders `base_color` alone.

# pbr_layered A surface composed from two complete PBR layers: a base, and a top layer laid over it wherever coverage says so. Rust over painted metal, snow over rock, mud over a vehicle, wear over a finish. Pre-blending those into one texture set bakes the coverage in — it can no longer change at runtime, and every entity wearing the material wears it identically. Here both layers keep their own shading inputs and coverage is evaluated per fragment, so the same material can be pristine on one entity and ruined on the next. ## Coverage Coverage is the product of three terms, each neutral by default: | term | property | what it is for | |---|---|---| | mask | `top_mask_texture`, `top_mask_channel`, `top_mask_contrast` | *where* the top layer gathers — creases, edges, upward faces | | material | `top_coverage` | *how far* the look has progressed, for every entity sharing the material | | instance | `top_instance_lane`, `top_instance_component` | how far for *this* entity | `top_coverage` defaults to 0, so a material that sets nothing renders as its base layer alone. `top_mask_contrast` shapes the mask: 1 is a linear ramp, higher values pull the top layer back into the mask's brightest areas, which is what makes rust and snow gather in creases instead of washing evenly over everything. ## Driving it per instance Point the material at an `instanceData` lane, then write that lane per entity: ```lua -- material: top_instance_lane = 0, top_instance_component = 0 local clean, rusted = entity.find("barrel_a"), entity.find("barrel_b") if clean and rusted then renderer.instanceData.set(clean, 0, 0.1) -- nearly clean renderer.instanceData.set(rusted, 0, 0.9) -- heavily rusted end ``` Both entities share one material and one draw path; only the lane differs. ## Texture slot budget WebGPU guarantees 16 sampled textures per fragment stage and the engine's group(0) already holds several. This shader declares **9**, which leaves room for those plus a margin. Two full five-map layers would not fit, so the top layer carries the three maps that make it read as a different material — albedo, roughness/metallic, normal — and takes occlusion and emissive from the base. Layer count is **two**. The cost is fixed and predictable: both layers are always sampled, and coverage selects between their inputs rather than branching. ## Why the inputs blend rather than the results Lighting each layer separately and adding puts more energy back out than arrived, so a half-covered surface would read brighter than either layer alone. Interpolating the shading inputs and lighting once cannot do that.

# Snow Particle A soft, cold-white flake surface for falling-snow particle effects — a near-white base colour (`0.95, 0.97, 1.0`) with a cool blue-grey emissive glow (`0.25, 0.3, 0.4`) so flakes stay faintly visible in shadow. Transparent, double-sided (`cull: none`), and drawn in the transparent queue (`3000`). Built on `@builtin::shaders.snow_material`. ## Inputs - `colors.base_color` — the cold-white flake tint. - `colors.emissive` (`0.25, 0.3, 0.4`) — cool self-illumination that keeps flakes readable in dark scenes. - `floats.roughness` (`0.8`) — matte, non-glossy flakes. - `floats.metallic` (`0.0`) — fully dielectric.

# `referenceChart` surface shader A reference chart drawn on a surface, unlit: each point holds light its properties and its UV state, so a picture of the surface is measured against known input. The post-verification reference scenes (`@builtin::scenes.postReference.*`) are built from its materials (`@builtin::materials.postReference.*`). | `pattern` | Draws | |---|---| | 0 | A grey wedge: one column per whole stop from `evMin` to `evMax`, each middle grey (0.18) at that stop. | | 1 | The 24 ColorChecker Classic patches, 6 x 4, each its published sRGB value read as linear reflectance. | | 2 | A ramp from `low` at u = 0 to `high` at u = 1. | | 3 | A Siemens star of `frequency` spokes, `high` on `low`. | | 4 | A checker `frequency` cells across, `low` and `high`. | | 5 | Focus bars: four rows of bar pairs, `frequency` pairs across the top row, doubling on each row below. | Every pattern's light is multiplied by `color` and `gain`. UV (0, 0) is the surface's top-left, as the front face of `@builtin::meshes.cube` maps it.

# Gold Polished gold — a fully metallic PBR surface with a warm yellow base colour (`1.0, 0.84, 0.0`) and low roughness (`0.25`) for bright, sharp reflections. Built on `@builtin::shaders.pbr`. ## Inputs - `colors.base_color` — the gold tint. - `floats.metallic` (`1.0`) — fully metallic. - `floats.roughness` (`0.25`) — sharpness of the reflection; raise for a brushed look.

# Checkerboard A procedural checkerboard pattern rendered by `@builtin::shaders.checkerboard`, alternating a red base colour (`1.0, 0.2, 0.2`) with a blue emissive colour (`0.2, 0.2, 1.0`). Opaque and non-metallic (`metallic 0.0`) at mid roughness (`0.5`) — useful as a UV / scale test surface. ## Inputs - `colors.base_color` — the red square colour. - `colors.dark_color` — the blue square colour. - `floats.roughness` (`0.5`) — diffuse spread on the lit squares. - `floats.metallic` (`0.0`) — dielectric surface.

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

# Custom Textured A textured opaque surface built on `@builtin::shaders.custom_material`, sampling the `array_texture` builtin over a warm peach base colour (`1.0, 0.8, 0.6`). Non-metallic (`metallic 0.0`) at mid roughness (`0.5`) — a worked example of pairing a custom shader with an array texture. ## Inputs - `textures.base_color_texture` (`@builtin/textures/array_texture`) — the sampled array texture. - `colors.base_color`: the warm peach colour the texture is multiplied by. - `floats.roughness` (`0.5`) — diffuse spread. - `floats.metallic` (`0.0`) — dielectric surface.

# Sky Procedural A fully procedural atmospheric sky with a day/night cycle, built on `@builtin::shaders.procedural_sky`. Renders with no culling and no depth write behind all geometry (queue `1000`), computing gradient, sun, moon and stars analytically from its parameters — no texture required. ## Inputs - `properties.zenith_color` / `horizon_color` / `ground_color` — the atmospheric gradient from overhead (`0.1, 0.3, 0.6`) through the horizon (`0.5, 0.7, 1.0`) to the ground (`0.3, 0.25, 0.2`). - `properties.sun_intensity` (`20`) / `sun_size` (`0.02`) — brightness and disc size of the sun. - `properties.turbidity` (`4`) — atmospheric haze / scattering density. - `properties.stars_intensity` (`1`) / `moon_size` (`0.03`) — night-sky star brightness and moon disc size.

# `fog` post-process shader Depth-keyed distance haze. `pp.add(name, "fog", { density = ..., color = { r, g, b } })` registers it, and `asset.resolve("@builtin::shaders.post.fog", "shader"):getProperties()` reads the knobs below before it is added. The pass reads the scene depth already drawn at a pixel, turns it into a distance in metres with `zero_linear_depth(d, near, far)`, and mixes the frame toward `fogColor` by `1 - exp(-distance * density)` — an exponential falloff, so density sets how many metres of air it takes to reach the fog colour. `near` and `far` are the planes the frame was projected through. They are what a stored depth is turned back into metres by, so they belong to the camera the scene was drawn with rather than to the look: setting them to something the camera does not use moves every surface's distance and with it the whole haze. | Property | Meaning | |---|---| | `density` | Falloff rate. 0 leaves the frame untouched. | | `fogColor` | The colour a fully fogged pixel reaches. | | `near` | The scene camera's near plane, in metres. | | `far` | The scene camera's far plane, in metres. |

# Sky Cubemap A cubemap sky/environment background built on `@builtin::shaders.cubemap_sky`. Renders with no culling and no depth write behind all geometry (queue `1000`), sampling the built-in `Ryfjallet_cubemap` with adjustable rotation and exposure. ## Inputs - `textures.sky_texture` — the cubemap sampled as the sky (`Ryfjallet_cubemap`). - `floats.rotation` (`0.0`) — yaw rotation of the sky around the vertical axis. - `floats.exposure` (`1.0`) — brightness multiplier applied to the sampled colour.

# Default Unlit A flat, unlit surface that renders its base colour directly with no lighting response, built on the `unlit` shader. Uses a white base colour (`1.0, 1.0, 1.0`) over the `default:white` texture with `emissive` (`1.0`) for full brightness — the go-to default for UI, gizmos, and debug geometry that must stay legible regardless of scene lighting. ## Inputs - `colors.base_color` — the flat colour shown directly. - `textures.base_color_texture` (`default:white`) — the white base texture the colour multiplies against. - `floats.emissive` (`1.0`) — full, lighting-independent brightness.

# grass_material.shader Grass, shaded root to tip with per-blade colour variation and a soft half-lambert wrap. The colouring reads `uv.y` as height along a blade — 0 at the root, 1 at the tip — and darkens the roots while warming the tips. Per-blade variation comes from a hash of the fragment's world xz on a 10 cm grid, so every fragment of one blade shares a seed and neighbouring blades drift apart in hue and brightness. The lighting is a diffuse half-lambert wrap kept below saturation, so this shader returns its own final colour instead of a PBR surface. `sway` is how far the vertex stage bends each vertex along its blade, and it is what tells this shader that its mesh is a blade mesh: the bend scales with `uv.y²`, so a vertex at the root holds still while the tip swings hardest. It defaults to 0, at which every vertex arrives where the mesh put it — a material that leaves it there shades a surface without moving it. `@builtin::materials.grass` is that ground surface; `@builtin::materials.grass_blades` sets `sway` to 1 for a blade mesh. ## Properties - `base_color` — the grass green the root→tip gradient is built from. - `sway` (`0`..`4`, default `0`) — how far each vertex bends along its blade.

# Emissive White A bright white light-emitting PBR surface built on the `pbr` shader with the `_EMISSION` keyword enabled. A white base colour (`1.0, 1.0, 1.0`) paired with a strong `emissive` (`20.0`) makes it glow and drive bloom — well suited to light fixtures, emitters, and glowing accents. Non-metallic (`metallic 0.0`) at mid roughness (`0.5`). ## Inputs - `floats.emissive` (`20.0`) — high emission strength that produces the glow. - `keywords: _EMISSION` — enables the emissive path in the PBR shader. - `colors.base_color` — the white surface and emission colour. - `floats.roughness` (`0.5`) — diffuse spread on the lit surface.

# Water An animated water surface with a deep blue base colour (`0.1, 0.3, 0.8`) and low roughness (`0.2`) for glossy, reflective highlights, driven by a scrolling normal map for wave detail. Opaque, back-face culled, instanced, in the opaque queue (`2000`). Built on `@builtin::shaders.water_material`, sampling `@builtin/textures/water_normals`. ## Inputs - `colors.base_color` (`0.1, 0.3, 0.8`) — the water body colour. - `floats.roughness` (`0.2`) — low roughness for sharp specular reflections. - `floats.metallic` (`0.0`) — dielectric surface. - `textures.normal_texture` — the wave normal map (`@builtin/textures/water_normals`).

# postReference_chrome A polished metal: its highlight of a bright light is a sub-pixel specular, the firefly a bloom and a temporal resolve are read on in the post-verification reference scenes.

# Grass blades Swaying grass for a blade mesh, built on `@builtin::shaders.grass_material` with the same green as `@builtin::materials.grass` (`0.22, 0.62, 0.16`) and `sway` at `1.0`. The shader bends each vertex along its blade in proportion to `uv.y²`, so this material belongs on a mesh whose `uv.y` runs 0 at a blade's root to 1 at its tip — a merged field of blades, each a cross of two tapered quads. It inherits the Rust-side render defaults (opaque, back-face culled, queue `2000`) so its pipeline matches the library variant compiled at startup. ## Inputs - `colors.base_color` (`0.22, 0.62, 0.16, 1.0`) — the grass green tint. - `floats.sway` (`1.0`) — the full blade bend. `@builtin::materials.grass` leaves it at the shader's default of `0` for a ground surface.

# Text Default The default surface for Text3D — a white base colour (`1.0, 1.0, 1.0`) drawn with alpha blending and no depth write so glyphs composite cleanly over the scene. Transparent, double-sided (`cull: none`), `depth_write: false`, in the transparent queue (`3000`). Built on the `pbr` shader. ## Inputs - `colors.base_color` (`1.0, 1.0, 1.0`) — the glyph colour. - `render.depth_write` (`false`) — glyphs blend without occluding each other. - `render.cull` (`none`) — text is visible from both sides. - `floats.roughness` (`0.5`) / `floats.metallic` (`0.0`) — dielectric defaults.

# procedural_sky The editable atmospheric sky: a day/night gradient with a sun disc and glow, a procedural star field, and a moon opposite the sun, authored entirely from material properties — no texture backs it. Day, night and the dawn/dusk blend all derive from the directional light's elevation, so the sky follows whatever drives the scene's sun; there is no time-of-day uniform. The gradient's zenith, horizon and ground colours, the sun's size and intensity, the stars, the moon, turbidity and exposure come from `properties.yaml`. Output is radiance scaled by `exposure` — the scene's own tone-mapping does the range compression, the same contract as every sky-domain shader. The `ProceduralSky` component owns the runtime material over this shader (`__procedural_sky`) and pushes its fields here; `sky.get()` reports the resulting configuration.

# error_marker The surface of the ERROR sign: the magenta and dark purple world-space checker the engine's error pipeline draws, as an unlit surface shader. The `error_marker` material draws the sign with it.

# Grid Background A procedural background/reference-grid surface built on `@builtin::shaders.grid_bg`. It draws grid lines over a black base colour (`0.0, 0.0, 0.0`) with full roughness (`1.0`) and no metallic response, rendered opaque with culling disabled (`cull: none`) and instancing enabled so it can back many objects at once. ## Inputs - `colors.base_color` (`0.0, 0.0, 0.0, 1.0`) — black backdrop behind the grid lines. - `floats.roughness` (`1.0`) — fully diffuse, no highlights. - `render.cull` (`none`) — visible from both faces. - `render.instancing` (`true`) — supports instanced draws.

# Standard Default The baseline PBR surface — a neutral white base colour (`1.0, 1.0, 1.0`), half roughness (`0.5`), non-metallic (`0.0`), wired with the full standard texture set (base colour, normal, roughness-metallic, emissive, occlusion) and the `_NORMALMAP` / `_OCCLUSIONMAP` keywords enabled. Opaque, back-face culled, instanced, in the opaque queue (`2000`). Built on `@builtin::shaders.pbr`. This is the starting point most materials copy and retint. ## Inputs - `colors.base_color` (`1.0, 1.0, 1.0`) — the albedo tint over the base colour texture. - `floats.roughness` (`0.5`) / `floats.metallic` (`0.0`) — dielectric, mid-gloss default. - `floats.normal_strength` (`1.0`) / `floats.ao_strength` (`1.0`) — normal-map and occlusion intensity. - `textures.normal_texture` / `textures.roughness_metallic_texture` / `textures.occlusion_texture` — the PBR map slots, seeded with neutral defaults.

# eye.shader An eye: an iris refracting behind a clear cornea. The iris sample is displaced by refracting the view ray at the cornea and walking it `iris_depth` inward, so the iris slides as the viewing angle changes. The cornea itself is the engine's clearcoat lobe, which keeps one continuous specular highlight across the iris and the sclera. `iris_radius`, `pupil_radius` and `limbus_softness` shape the disc; `iris_texture` is sampled in the refracted frame, `sclera_texture` in the surface's own UVs.

# postReference_grey18 A lit 18% grey (middle grey) surface, rough and dielectric: what a light of known intensity is read off in the post-verification reference scenes.

# loading_backdrop (screen shader) A calm, slowly drifting full-screen backdrop for the world loading screen. A deep near-black field carries two large, soft glows that move along slow independent orbits, finished with a gentle vignette and a faint animated grain that keeps the gradient from banding. Animation is driven entirely by `engine.time`, so it advances on its own during boot with no per-frame uniform updates. It is quiet by design, so it sits behind the world's cover image, title, and progress bar. Drawn through the `backgroundShader` UI style after registration with `ui.registerBackgroundShader`.

# Parallax Cube (Flat) A brick surface built on `@builtin::shaders.pbr_parallax_occlusion` with `parallax_depth_scale = 0`, so the ray-march is bypassed and the shared brick textures render as plain textured PBR (rough `0.7`, non-metallic, white base colour). Opaque, back-face culled, queue `2000`. Pair it with `parallax_cube` to A/B the parallax effect from a fixed viewpoint. ## Inputs - `floats.parallax_depth_scale` (`0.0`) — disables the occlusion ray-march, flattening the surface. - `floats.roughness` (`0.7`) — matte brick finish. - `floats.normal_scale` (`1.0`) — strength of the normal map. - `textures.height_texture` — the brick height map (unused while depth scale is `0`).

# postReference_siemensStar A Siemens star of 36 spokes, 0.9 on 0.02: the spokes narrow below a pixel toward the centre, where a temporal resolve aliases. Drawn unlit by `@builtin::shaders.referenceChart`, so a picture of it is measured against the light its properties state. Part of the post-verification reference scenes (`@builtin::scenes.postReference.*`); `@builtin::modules.postMetrics` reads them.

# Skybox An unlit cubemap skybox rendered from the inside of the mesh, built on `@builtin::shaders.cubemap_unlit`. Uses front-face culling and no depth write so it draws behind all scene geometry (queue `1000`), sampling the built-in `Ryfjallet_cubemap` environment. ## Inputs - `textures.base_color_texture` — the cubemap sampled as the background (`Ryfjallet_cubemap`). - `floats.reflect_mode` (`0.0`) — samples the cube directly as a background rather than as a reflection. - `colors.base_color` (`1.0, 1.0, 1.0`) — tint applied to the sampled cubemap.

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

# fluidSurface A GPU particle simulation, rendered as a continuous liquid. Water made of particles has a problem: the particles are spheres, and a pile of spheres looks like a pile of spheres. Turning them into a mesh every frame is expensive and the mesh is thrown away immediately. This package skips the mesh — it renders the particles into screen-space fields and shades those, so the particle data never leaves the GPU and the cost scales with screen pixels rather than with the surface's geometric complexity. ## What it does ```lua local fluidSurface = require("@builtin::systems.fluidSurface.modules.fluidSurface") local rts = fluidSurface.attach("lake", { particles = { buffer = sim, stride = 16, posOffset = 0, count = 400000, velOffset = 4 }, radius = 0.35, }) ``` `particles` describes the record layout of the buffer the caller's simulation writes: how wide a record is, where the position sits in it, and how many are live. Pass the handle a compute shader's `createBuffer` answered. Everything after that happens per frame until `detach`. `update` moves the live knobs — the particle count as a sim grows, the sun direction as the day turns, any composite property: ```lua fluidSurface.update("lake", { count = active, sunDir = { 0.3, 0.8, 0.2 } }) ``` ## The chain 1. **Splat** (engine raster). Every particle draws as a velocity-stretched billboard: nearest-surface depth, hardware z-tested; additive thickness and thickness-weighted colour; and, when the records carry a foam weight, an additive foam sprite layer. 2. **Narrow-range filter** (`fluid_narrow_x` → `fluid_narrow_y`, ping-ponged `iterations` times). Neighbour depths are clamped into a band around the centre before averaging, so particles fuse into a surface while silhouettes stay crisp. The body is the `fluid_narrow_filter` shader module, included by both axes. 3. **Resolve** (one of `fluid_resolve`, `fluid_resolve_col`, `fluid_resolve_foam`, `fluid_resolve_col_foam`). Packs smoothed depth, blurred thickness and the foam fraction into `data`, and the mean liquid colour along each ray into `liq`. Which one runs is decided by whether the records carry a colour and a foam weight, because that changes which textures the pass binds. 4. **Composite** (`fluid_surface_composite`, a post-process shader). Refracts the already-rendered scene through the surface normals, absorbs along the view ray by Beer–Lambert, marches the reflected ray against scene depth so the water mirrors what is above it, adds sun specular, and lays foam on the thin edges. Depth-tested against the scene, so fluid behind geometry stays hidden. Every stage runs at `resolutionScale` of the screen (half by default). ## Sharing The passes are compiled once and shared by every surface. What a surface owns is its render targets, its own filter-parameter buffer, and its own composite — which is why two lakes at different particle radii filter at different widths without interfering.

# postReference_greyWedge The grey wedge: one column per whole stop from -10 to +10, each middle grey (0.18) at that exposure. Drawn unlit by `@builtin::shaders.referenceChart`, so a picture of it is measured against the light its properties state. Part of the post-verification reference scenes (`@builtin::scenes.postReference.*`); `@builtin::modules.postMetrics` reads them.

# Checkerboard White A static white/grey checkerboard rendered by `@builtin::shaders.checkerboard`, alternating a white base colour (`1.0, 1.0, 1.0`) with a dark grey check colour (`0.3, 0.3, 0.3`). Animation is disabled (`animation_speed 0.0`), giving a fixed, neutral grid — ideal as a level-design blockout or scale-reference floor. Opaque, non-metallic (`metallic 0.0`) at mid roughness (`0.5`). ## Inputs - `colors.base_color` — the white square colour. - `colors.check_color` — the dark grey square colour. - `floats.animation_speed` (`0.0`) — held at zero for a static pattern. - `floats.roughness` (`0.5`) — diffuse spread on the squares.

# postReference_white A flat unlit white of 0.8 light: the thin geometry of the temporal reference scene (wires, a fence, a fan's blades) drawn against the dark, so every pixel it touches stands out from its neighbours. Drawn by `@builtin::shaders.referenceChart`. Part of the post-verification reference scenes (`@builtin::scenes.postReference.*`); `@builtin::modules.postMetrics` reads them.

# parallax_cube Brick wall material using `@builtin::shaders.pbr_parallax_occlusion` with the parallax march enabled (`parallax_depth_scale = 0.08`, 48 ray-march layers). Pair with `parallax_cube_flat` for a same-textures, no-POM A/B comparison. ## Shader `@builtin::shaders.pbr_parallax_occlusion` — see that shader's README for the full parameter list. ## Textures All from `@builtin::textures.parallax_bricks` (height/normal derived from three.js's MIT-licensed `brick_bump` + `brick_diffuse`): - `base_color_texture` → `bricks_albedo` - `normal_texture` → `bricks_normal` - `roughness_metallic_texture` → `bricks_roughness` - `occlusion_texture` → `bricks_ao` - `height_texture` → `bricks_height` ## Usage ```luau Material.Apply(entityId, "parallax_cube") -- Override at runtime: Material.SetProperty("parallax_cube", "parallax_depth_scale", 0.12) ``` Pair it with `parallax_cube_flat` (same textures, `parallax_depth_scale = 0`) to compare the ray-marched surface against a flat-mapped baseline. ## Notes - `Material.SetProperty` mutations are global — every entity using `parallax_cube` sees the change. If you need per-entity variation, derive a new material name and override the property there. - Use under any standard camera (forward path). The deferred path is not yet POM-aware; materials applied to a deferred camera will render as plain textured PBR.

# `colorGrade` post-process shader Brightness, saturation and contrast as multipliers around an identity of 1.0. `pp.add(name, "colorGrade", { brightness = 1.1, saturation = 0.8 })` registers it, and `asset.resolve("@builtin::shaders.post.colorGrade", "shader"):getProperties()` reads the knobs below before it is added. The three run in that order on the sampled frame: brightness scales the colour, saturation mixes it against its own Rec. 709 luminance, and contrast pushes it away from mid grey. Each is a multiplier, so 1.0 leaves the frame as it was and all three at 1.0 pass it through unchanged. `color_correction` grades the same three quantities as ADDITIVE offsets around 0.0 and adds a tint colour, so a look authored for one does not transfer to the other by copying its numbers. | Property | Meaning | |---|---| | `brightness` | Multiplies the colour. | | `saturation` | 0 is luminance alone, 1 is the frame's own colour. | | `contrast` | Scales distance from mid grey. |

# Neon A glowing cyan neon surface built on `@builtin::shaders.pbr` with emission enabled. It pairs a bright cyan-blue base colour (`0.2, 0.8, 1.0`) with a matching emissive colour driven hard by `emissive: 5.0`, so it reads as a self-lit light source. Low roughness (`0.2`), non-metallic, opaque, instanced, with the `_EMISSION` keyword enabled. ## Inputs - `colors.emissive` (`0.2, 0.8, 1.0, 1.0`) — cyan glow colour. - `floats.emissive_intensity` (`5.0`) — strong emissive intensity (feeds bloom). - `colors.base_color` (`0.2, 0.8, 1.0, 1.0`) — matching cyan base tint. - `floats.roughness` (`0.2`) — glossy surface under direct light.

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

# subsurface A metallic-roughness surface that also transports light beneath itself, for skin, foliage, wax, marble and thin fabric. Set `subsurface_color` to the tint of the light that scatters through; leaving it black makes this a plain metallic-rough surface. `subsurface_radius` sets how far light spreads beneath — larger values wrap the shading further past the terminator, and reach further in whichever channels the colour is strongest in. `thickness` (and `thickness_texture`) control how readily a backlit surface glows. Thin geometry transmits; thick geometry stays solid. Both effects are evaluated in the engine's light loop, so they are shadowed and attenuated like every other lobe.

# postReference_checker A checker of 64 cells across, 0.8 on 0.03: the high-frequency background a fast object crosses. Drawn unlit by `@builtin::shaders.referenceChart`, so a picture of it is measured against the light its properties state. Part of the post-verification reference scenes (`@builtin::scenes.postReference.*`); `@builtin::modules.postMetrics` reads them.

# postReference_colorChecker The 24 patches of the ColorChecker Classic, each its published sRGB value read as linear reflectance. Drawn unlit by `@builtin::shaders.referenceChart`, so a picture of it is measured against the light its properties state. Part of the post-verification reference scenes (`@builtin::scenes.postReference.*`); `@builtin::modules.postMetrics` reads them.

# Error Test Intentionally broken material used to exercise the renderer's error-handling and fallback paths. It targets `@builtin::shaders.error_shader` and carries a bright magenta base colour (`1.0, 0.0, 1.0`) — the classic "missing/failed" flag colour — with mid roughness (`0.5`), opaque render type, and back-face culling. ## Inputs - `colors.base_color` (`1.0, 0.0, 1.0, 1.0`) — magenta error flag tint. - `floats.roughness` (`0.5`) — neutral surface roughness. - `render.type` (`opaque`) / `render.queue` (`2000`) — drawn in the standard opaque pass.

# Animated Color An opaque, back-culled surface whose colour animates over time, driven by `@builtin::shaders.animate_shader`. Starts from a white base colour (`1.0, 1.0, 1.0`) with an `emissive` of `1.0` so the shifting colour reads brightly, at mid roughness (`0.5`) and fully non-metallic (`metallic 0.0`). ## Inputs - `colors.base_color` — the starting colour the animation modulates. - `floats.emissive` (`1.0`) — self-illumination strength of the animated colour. - `floats.roughness` (`0.5`) — matte diffuse spread. - `floats.metallic` (`0.0`) — dielectric, non-metallic surface.

# billboard Camera-facing billboard shader for textured quads — labels, sprites, and 3D text. All four corners of the quad sit at the same anchor, so the vertex's world position is the anchor under any entity or parent transform. Each corner carries its in-plane offset in the vertex colour; the vertex stage offsets the corner in world space facing whichever camera renders the pass, so the quad is visible and correctly framed from the main viewport, an offscreen capture, and a render-texture camera alike. Because the offset is applied in world space before projection, the quad keeps real extent and stays drawn when the anchor leaves the frustum. The horizontal axis stays world-level, so it tracks a pitching camera without rolling. The world size lives in the per-corner offset (resizing rebuilds the vertex colours), so there are no size material properties, and the mesh declares its own render bounds so frustum culling keeps it. The fragment mirrors `unlit`: `base_color * base_color_texture` with masked-transparency cutoff.

# foliage.shader Vegetation that sways with the scene's wind. The motion comes from the engine's frame-global wind (`rendering.setWind`), so every material reading it agrees on direction, speed and gust phase — a gust crosses a whole field instead of each plant animating on its own clock. `compliance` scales how far this material yields — 1 for a grass blade, 0.1 for a trunk. The mesh's red vertex channel is how freely each vertex moves: 1 at a blade's tip, 0 at its root, so a blade pivots from its base. A mesh with no authored vertex colours reads white and sways as a whole. The gust phase is a function of world position, so a gust travels across a field rather than every instance of the same mesh swaying in unison. With no wind set the sway is zero and the surface renders as a plain lit material.

# `lut` post-process shader Colour grading through a lookup table. `pp.add(name, "lut", { texture = ... })` registers it; `@builtin::modules.lut` builds, imports and installs the tables it reads. `lut_texture` is a LUT **strip**: an N-entry colour cube laid out as one row of N square tiles, so the image measures `N*N` wide by `N` tall. Tile `b` holds the plane of constant blue index, red runs across a tile and green runs down it. N comes from the texture's own height, so this one shader serves a 16-, 32- or 64-entry cube. The eight lattice entries around a colour are fetched with `textureLoad` at exact texel coordinates and interpolated in the shader. That makes the result independent of the texture's filter and wrap mode, and each blue plane is read from its own tile. A texture whose shape is not a strip — including the 1×1 fallback bound when the effect has no table — returns the frame untouched, so adding the effect before its table exists changes nothing. | Property | Meaning | |---|---| | `amount` | 0 = the ungraded frame, 1 = the table's answer. | | `lut_texture` | The strip. |

# Error Text A 3D "ERROR" text model used as the visible fallback when an asset fails to load — spawned in place of missing geometry so a broken reference is obvious in-scene instead of silently invisible. Decomposed from `ERRORText.fbx` into this bundle (mesh + material + texture + entity template). ## Composition - Root `error_text` → `Sketchfab_model` → the `ERRORText.fbx` node hierarchy. - Carries the extruded "ERROR" letter mesh, its material, and texture as private subassets. ## Usage Spawned automatically by the engine as the placeholder for an unresolved asset; can also be spawned directly to test the fallback path.

# Plastic White A clean white plastic — a non-metallic PBR surface with a pure white base colour (`1.0, 1.0, 1.0`) and mid roughness (`0.5`) for a soft dielectric sheen. Built on `@builtin::shaders.pbr`. Opaque, back-face culled, queue `2000`. ## Inputs - `colors.base_color` (`1.0, 1.0, 1.0`) — the white plastic tint. - `floats.roughness` (`0.5`) — soft, semi-glossy highlight. - `floats.metallic` (`0.0`) — dielectric (non-metal) response. - `floats.emissive` (`0.0`) — no self-illumination.

# postReference_darkRamp A ramp of light from 0 at the left edge to 0.1 at the right: the dark gradient an undithered 8-bit display path bands on. Drawn unlit by `@builtin::shaders.referenceChart`, so a picture of it is measured against the light its properties state. Part of the post-verification reference scenes (`@builtin::scenes.postReference.*`); `@builtin::modules.postMetrics` reads them.

# pbr The engine's standard physically-based material — the full glTF metallic-roughness workflow lit by the shared `@builtin::shaderModules.pbr_shading` model. This is the default surface shader a model uses when its material doesn't specify another, and it is also registered under the legacy alias **`standard`** (the name many materials reference). It is a `surface()` shader: it fills a `PbrSurface` and the engine generates every pipeline entry point and lights it. Every parameter defaults to a neutral value, so a material that sets nothing renders as a clean dielectric; the advanced lobes only cost anything when a material opts into them. ## Properties | Property | Type | Default | Meaning | |---|---|---|---| | `base_color` | color | `[1,1,1,1]` | Albedo tint, multiplied by `base_color_texture` and vertex colour. | | `emissive` | color | `[0,0,0,1]` | Emissive tint, multiplied by `emissive_texture` and `emissive_intensity`. | | `emissive_intensity` | float | `1.0` | HDR multiplier on the emissive output. | | `roughness` | range | `0.5` | Perceptual roughness, multiplied by the green channel of `roughness_metallic_texture`. | | `metallic` | range | `0.0` | Metalness, multiplied by the blue channel of `roughness_metallic_texture`. | | `reflectance` | range | `0.5` | Dielectric reflectance knob (neutral 0.5 → 4% F0). | | `ior` | float | `1.5` | Index of refraction → dielectric F0 and the refraction direction. | | `normal_scale` | float | `1.0` | Strength of the tangent-space `normal_texture`. | | `occlusion_strength` | range | `1.0` | Blend of the `occlusion_texture` (R) into the ambient term. | | `clearcoat` | range | `0.0` | Strength of a second dielectric clearcoat specular lobe. | | `clearcoat_roughness` | range | `0.0` | Roughness of the clearcoat lobe. | | `anisotropy` | float | `0.0` | Anisotropic highlight stretch along the tangent ([-1,1]). | | `sheen_color` | color | `[0,0,0,1]` | Tint of the sheen lobe — the retroreflective rim of velvet, satin and brushed fabric. Black leaves the base untouched. | | `sheen_roughness` | range | `0.3` | Width of the sheen lobe. | | `iridescence` | range | `0.0` | Blend toward the thin-film response, the hue that shifts with view angle. | | `iridescence_thickness` | float | `400.0` | Film thickness in nanometres — which wavelengths cancel and which reinforce. | | `iridescence_ior` | float | `1.3` | Index of refraction of the film. | | `subsurface_color` | color | `[0,0,0,1]` | Tint of the light that entered the surface, scattered beneath it and left again. Black leaves the base untouched. | | `subsurface_radius` | float | `0.5` | How far the diffuse falloff wraps past the terminator, taken per channel against `subsurface_color`. | | `fibre_color` | color | `[0,0,0,1]` | Tint of the second of the two highlights a hair or fur strand gives. Black leaves the base untouched. | | `fibre_specular` | range | `0.35` | Strength of the first strand highlight, in the light's own colour. | | `fibre_shift` | float | `0.06` | How far apart the two strand highlights sit along the fibre. | | `fibre_roughness` | range | `0.1` | Width of the first strand highlight. | | `transmission` | range | `0.0` | Specular transmission — refracts the environment through the surface. | | `thickness` | float | `0.0` | Volume thickness for Beer–Lambert transmission absorption. | | `attenuation_color` | color | `[1,1,1,1]` | Transmission absorption tint. | | `attenuation_distance` | float | large | Beer–Lambert absorption distance. | | `uv_scale` | float2 | `[1,1]` | UV tiling applied before every texture sample. | | `uv_offset` | float2 | `[0,0]` | UV offset applied before every texture sample. | | `alpha_cutoff` | range | `0.0` | Mask threshold — fragments with `alpha <` this are discarded (0 = no cutoff). | | `double_sided` | bool | `false` | Flip the shading normal on back faces. | | `receives_fog` | bool | `true` | Whether the screen-space fog passes (height fog, aerial perspective) reach this surface. `false` leaves an opaque deferred draw at the colour it shaded to, however deep in the medium it stands — see below. | ### Emissive authoring The glow output is `emissive × emissive_intensity` (× the `emissive_texture`). The glow **colour** is `emissive`, a vec; the **intensity** over it is `emissive_intensity`, a scalar. So `{ emissive = {0.1, 0.9, 1, 1}, emissive_intensity = 5 }` is a cyan glow at 5×, and it is these two names that `getProperties()` lists and `setProperty` writes. A spelling another engine's convention uses for the same role — `emissive_color`, `emission`, `emissive_tint` — is resolved onto `emissive` when the material is authored, so content carried in from glTF, Unity or Godot reaches the property under the name this shader declares. Where two such spellings meet on one of the two names, the shape of each value says which of them it is: a vec is the colour and a number is the intensity, so `{ emissive_color = {0.2, 0.8, 1, 1}, emissive = 5 }` is the same cyan glow at 5x. Two values of one shape are one property's, and the one written under the name the shader declares applies while the other is named in a warning. A bare positive scalar `emissive` with no colour beside it is the "turn emission on" shorthand and means a white glow at that intensity, so `emissive = 20` on a white material lights up. ### The lobes over the base layer Beyond metallic-roughness, the shading model carries six layers this material declares. Each is gated on its own neutral value, so a material that sets none of them shades as a plain dielectric and each one costs only where it is asked for. | Layer | Turned on by | What it looks like | |---|---|---| | Clearcoat | `clearcoat > 0` | A second dielectric specular lobe on top — car paint, lacquer, a varnished surface. | | Anisotropy | `anisotropy ~= 0` | The highlight stretches along the tangent — brushed metal, a vinyl record. | | Sheen | `sheen_color` above black | A retroreflective rim that brightens toward grazing angles — velvet, satin, dusty cloth. | | Iridescence | `iridescence > 0` | The specular hue shifts with view angle — an oil slick, a soap film, anodised metal, a beetle shell. Thickness picks the colours. | | Subsurface | `subsurface_color` above black | Light wraps past the terminator and glows through thin geometry lit from behind — skin, wax, marble, a leaf. `thickness` gates how much reaches the far side. | | Fibre | `fibre_color` above black | The two offset highlights a strand gives instead of the one a surface gives — hair, fur. Taken around the world tangent as the fibre axis. | All six are evaluated inside the engine's own light loop, once for every light that reaches the surface, so each one is shadowed, attenuated and cone-masked with the base layer it sits over. An oil-slicked wet surface is `iridescence = 1`, an `iridescence_thickness` around 300-500 nm and a low `roughness` over a dark `base_color`. Skin is a warm `subsurface_color` with a `subsurface_radius` near 0.5. Velvet is a `sheen_color` at the fabric's own hue over a dark base. ### Standing outside the fog `receives_fog = 0` declares that the screen-space fog passes — `heightFog` and `aerialPerspective` in `@builtin::systems.atmosphere` — leave this surface at the colour it shaded to. The declaration travels to those passes as a per-pixel surface flag written into the alpha of the G-buffer normal (`@builtin::shaderModules.surface_flags`). Only the deferred G-buffer fragment entry writes that channel, so the declaration reaches the fog from an **opaque** draw on the **deferred** path. A draw the renderer sends through the forward fragment entry — every draw on the forward path, and the transparent phase on either path — writes no G-buffer channel to carry it, and its pixels take the fog like any other. ## Textures (glTF metallic-roughness set) | Slot | Default | Channels | |---|---|---| | `base_color_texture` | white | RGBA albedo (sRGB). | | `roughness_metallic_texture` | white | G = roughness, B = metallic (glTF packing). | | `emissive_texture` | white | RGB emissive (sRGB). | | `normal_texture` | flat-normal | Tangent-space normal map. | | `occlusion_texture` | white | R = ambient occlusion. | Because the engine holds the full `PbrSurface`, the capture tool's debug passes (albedo / roughness / metallic / AO / emissive / world-normal / shadow / depth / motion) all read real material data.

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

# Decal Default The default material a `DecalProjector` stamps when none is assigned. A flat cyan tint (`0.05, 0.95, 1.0`) on `@builtin::shaders.pbr`. Assign a material with a `base_color_texture` to project a texture; the projector samples the material's base colour at the box-local XY of every surface inside its projection box.

# hair.shader A hair or fur strand. Its specular is a pair of offset bands rather than one spot: a fibre reflects into a cone around its own axis, so the highlights are taken around the world tangent — which on strand geometry runs root to tip. `fibre_color` tints the second, broader band and is what switches both on; `fibre_shift` sets how far apart they sit and `fibre_roughness` how narrow the first one is. Colour comes from `base_color` times the per-vertex colour, so a groom carries its own root-to-tip gradient under one material. `transmission_color` and `transmission` are the light that carries through a strand — the glow along a backlit edge. Both faces of a ribbon stand for the same round fibre, so back faces are lit like front ones.

# `bloom` post-process shader The light a bright surface spills into the pixels around it. A half-resolution `bright` pass extracts what stands above `threshold`, a pyramid of `downsample` passes carries it down to 1/64 of the view, and a chain of `upsample` passes carries it back up, blending each octave into the one above it. `composite` adds the result to the scene. `tools.use("pp", "add", "glow", "bloom")` registers it — the shader declares `space: light`, so the effect takes the scene layer: the rendered picture before the UI is drawn, over the scene's own light in a float target, which is where a bloom belongs. ## Passes | Pass | Scale | What it does | |---|---|---| | `bright` | 0.5 | Extracts what stands above `threshold` from a 2x2 block of the scene, soft-kneed by `softKnee`. | | `down1`…`down5` | 0.25 … 0.015625 | Each halves the previous octave's resolution with a 13-tap filter; `down1` also Karis-averages its five taps to keep a single bright texel from dominating. | | `up4`…`up0` | 0.03125 … 0.5 | Each carries the smaller octave up with a 3x3 tent and blends it into the next one by `scatter`. | | `composite` | (view size) | Adds the bloomed image to the scene, scaled by `intensity`. | ## Properties | Property | Default | Range | Meaning | |---|---|---|---| | `threshold` | 1.0 | 0–16 | The brightness the `bright` pass extracts above. | | `softKnee` | 0.5 | 0–1 | How wide the roll-in is around `threshold`, so a surface crossing it brightens rather than pops. | | `intensity` | 0.6 | 0–4 | How much of the bloomed image the `composite` pass adds back to the scene. | | `scatter` | 0.7 | 0–1 | How much of each octave an `upsample` pass blends into the one above it, and so how far the halo carries. | | `levels` | 6 | 1–8 | How many octaves of the pyramid draw. | | `clampMax` | 16 | 0–64 | The per-texel cap the `bright` pass applies before extracting, so one blazing pixel cannot blow out its octave. | `levels` and the 8-texel floor an octave's short side must clear are both read per pass, not baked into the pass list: an octave past either one returns the larger image it was handed unchanged, so a slider drag on `levels` changes what the twelve passes DO and never how many there are. Eleven scratch targets in the scene format, the largest at half the view — about 11 MB at 1080p.

# Sky Equirectangular An equirectangular panorama sky/environment background built on `@builtin::shaders.equirect_sky`. Renders with no culling and no depth write behind all geometry (queue `1000`), with adjustable rotation and exposure. Assign an equirectangular image to `sky_texture` (via `material.setTexture` or a Skybox) to display a panorama. ## Inputs - `textures.sky_texture` — the equirectangular panorama image to sample. Falls back to black, so a sky with nothing assigned reads as night rather than as an error. Assign a `.texture` by guid, identity, name, or path: ```luau renderer.material.setTexture("@builtin::materials.sky_equirect", "sky_texture", "my_panorama.texture") ``` An image dropped into `/zero/source` imports into a sibling `<stem>.texture` container and the loose file is removed, so reference the container (or its identity) rather than the original image path. - `floats.rotation` (`0.0`) — yaw rotation of the panorama around the vertical axis. - `floats.exposure` (`1.0`) — brightness multiplier applied to the sampled colour.

# PBR Parallax Occlusion Surface shader that extends the engine's Cook-Torrance PBR pipeline with Parallax Occlusion Mapping. Per fragment it ray-marches a height texture in tangent space, discards pixels whose intersection escapes the [0,1] UV tile, softly fades a horizon margin so the discard isn't a hard step, and runs a second short ray-march toward the directional light for self-shadowing. The rest of the fragment shader is the standard PBR you get from `@builtin::shaders.standard` — directional + point lights + cascade shadow map + procedural-sky IBL approximation — so a material using this shader still receives full scene lighting. ## Domain `surface` — bind to a `.material`. ## Files - `shader.wgsl` — vertex + fragment shader. Naga-validated. - `README.md` — this file. ## Texture slots Standard PBR slots plus a sixth `height_texture`: | `@group(1)` binding | Slot name | Notes | |---|---|---| | 1/2 | `base_color_texture` | albedo | | 3/4 | `normal_texture` | tangent-space normals | | 5/6 | `roughness_metallic_texture` | G = roughness, B = metallic (glTF) | | 7/8 | `emissive_texture` | optional emissive | | 9/10 | `occlusion_texture` | optional AO | | 11/12 | `height_texture` | R = depth into surface (0 = at face, 1 = deep) | The engine reflects @group(1) bindings via naga and builds the bind-group layout per shader, so adding the sixth slot needs no Rust changes. ## Parameters The standard `StandardMaterial` uniform fields apply unchanged; the two fields that drive POM are: - `parallax_depth_scale: f32` — max UV offset, in UV-space units. Useful range ~0.05–0.15. **POM is gated on this being > 0** — set it to 0 and the shader degrades to plain textured PBR. It is also the width of the band the tile clip trims inward from the border of the [0,1] tile, since the march never offsets the UV further. - `max_parallax_layer_count: f32` — ray-march iteration cap. 16 reads as stair-stepped at oblique angles; 48–64 is the smooth-quality band; 128 is the cost ceiling. ## Notes - Heightmap convention: **black = at surface, white = deep**. If you bring in a heightmap authored the other way (white = high), invert it in your import step or you'll get inside-out parallax. - The vertex shader is the engine-standard one; the parallax effect is entirely in the fragment shader and uses no extra vertex attributes. - The march runs in the forward `fragment` entry point, so a material using this shader under a deferred camera renders as plain textured PBR. - For curved meshes, tangent-space POM produces mild distortion at high curvature. For roughly-planar surfaces (walls, floors, signs) it looks correct.

# ps1 A full PS1-style retro shader and a worked example of a **self-shading `fragment()` shader** — one that returns the final pixel itself instead of describing a PBR surface. It emulates the three signature traits of original PlayStation hardware, each mapped onto a generic engine capability: 1. **Vertex snapping** (`vertex_clip`) — the integer-grid vertex wobble, snapping NDC xy to a low-res grid set by `snap_resolution` (low = chunkier). 2. **Per-vertex (Gouraud) lighting** (`vertex_clip` writes `ClipVertex.color`) — the PS1 lit at vertices and the rasterizer interpolated the colour; there was no per-pixel lighting. The shader computes Lambert sun + ambient from the world normal at each vertex and writes it into the vertex colour, which the engine forwards into the interpolated `vertex_color` the fragment reads. Flat, gradient-banded shading — never a per-pixel highlight. 3. **Affine texture mapping** (`FragmentData.affine_uv`) — the PS1 had no perspective-correct UV interpolation, so textures "swim" / warp across triangles. We sample with the engine's non-perspective-correct `affine_uv` channel instead of `uv`, reproducing the warp exactly. On top of those: the texture is quantized to a `tex_resolution`×`tex_resolution` texel grid (the PS1 256×256 texture page) and the final colour is run through a 4×4 Bayer ordered dither + colour-level quantization (the PS1 banded look). No shadow-map sampling — the PS1 had none. ## Properties | Property | Type | Default | Meaning | |---|---|---|---| | `base_color` | color | `[1,1,1,1]` | Tint multiplied into the texture. | | `snap_resolution` | float | `160` | Vertex-snap grid resolution (lower = chunkier wobble). | | `tex_resolution` | float | `256` | Texture sampled at `tex_resolution`×`tex_resolution` texels (PS1 256×256 page). | | `dither_amount` | float | `0.06` | Strength of the Bayer dither applied before quantization. | | `color_levels` | float | `16` | Number of quantization levels per channel (lower = more banding). | | `base_color_texture` | texture (white) | — | Albedo texture, sampled affinely in `fragment()`. | ## Framework capabilities this exercises - **`ClipVertex` is a post-transform vertex-shading hook**: it carries world-space geometry (`world_normal`, `world_position`) and the sun/ambient light context, and writing its `color` field performs per-vertex (Gouraud) shading — the engine forwards it to the interpolated `vertex_color`. Leave `color` untouched and the mesh's per-vertex colour passes through. - **`FragmentData.affine_uv`** is the primary UV interpolated *without* perspective correction — always available alongside the perspective-correct `uv`. Sample with it for the PS1 swim; sample with `uv` for normal mapping.

# error_marker The material of the ERROR sign a Model or SkinnedModel shows in place of a mesh that failed to resolve, to become GPU-resident, or to pose. It draws the `error_marker` shader's magenta checker.

# Brushed Metal A brushed metallic surface built on the `pbr` shader — fully metallic (`metallic: 1.0`) with a neutral grey base colour (`0.6, 0.6, 0.6`) and moderate roughness (`0.3`) that softens reflections into the muted sheen of brushed steel or aluminium. Opaque, back-face culled, instanced, with the `_METALLICSPECGLOSSMAP` keyword enabled. ## Inputs - `colors.base_color` (`0.6, 0.6, 0.6, 1.0`) — neutral metal grey. - `floats.metallic` (`1.0`) — fully metallic. - `floats.roughness` (`0.3`) — softened, brushed reflections. - `textures.base_color_texture` (`default:white`): the white base texture the colour multiplies against, so the surface renders `base_color` alone.

# postReference_emitter A flat emitter answering with 16 times the display's white: the source a bloom reading is taken around. Drawn unlit by `@builtin::shaders.referenceChart`, so a picture of it is measured against the light its properties state. Part of the post-verification reference scenes (`@builtin::scenes.postReference.*`); `@builtin::modules.postMetrics` reads them.

# Sky Solid A flat solid-colour background built on `@builtin::shaders.solid_sky`. Renders with no culling and no depth write behind all geometry (queue `1000`), filling the sky with a single dark-grey colour (`0.2, 0.2, 0.2`) at unit exposure. ## Inputs - `colors.solid_color` (`0.2, 0.2, 0.2`) — the flat fill colour of the background. - `floats.exposure` (`1.0`) — brightness multiplier applied to the fill colour.

# Grass A soft green ground surface built on `@builtin::shaders.grass_material`, with a natural green base colour (`0.22, 0.62, 0.16`), high roughness (`0.75`) for a diffuse, non-shiny look, and no metallic or emissive contribution. It inherits the Rust-side render defaults (opaque, back-face culled, queue `2000`) so its pipeline matches the library variant compiled at startup. It leaves the shader's `sway` at its default of `0`, so it shades whatever geometry it is applied to and leaves every vertex where the mesh puts it; `@builtin::materials.grass_blades` is the same green on a blade mesh that bends. ## Inputs - `colors.base_color` (`0.22, 0.62, 0.16, 1.0`) — the grass green tint. - `floats.roughness` (`0.75`) — matte, diffuse surface. - `floats.metallic` (`0.0`) / `floats.emissive` (`0.0`) — non-metallic, non-glowing.

# debugBillboard Camera-facing billboard shader for the debug overlay's icon sprites. Each instance renders a procedural glyph (camera, light, audio, reflection probe, player) selected by glyph id — drawn analytically in the fragment shader, so icons stay crisp at any zoom with no texture atlas. Consumed by the debugViz icon system.

# Cubemap Env A chrome-ball environment surface that samples a cubemap for mirror-like reflections, built on `@builtin::shaders.cubemap_unlit`. `reflect_mode` (`1.0`) selects the reflection path, and the `Ryfjallet_cubemap` builtin texture supplies the environment. Opaque, with a white base colour (`1.0, 1.0, 1.0`) so the cubemap colours pass through untinted. ## Inputs - `textures.base_color_texture` (`@builtin/textures/Ryfjallet_cubemap`) — the environment cubemap that is reflected. - `floats.reflect_mode` (`1.0`) — selects the reflection sampling mode. - `colors.base_color` — white tint that leaves the reflected colours unchanged.

# Solid Line A flat, opaque line surface with a bright green base colour (`0.0, 1.0, 0.5`) for drawing gizmos, paths, and debug geometry. Opaque, back-face culled, instanced, and rendered in the opaque queue (`2000`). Built on `@builtin::shaders.line_material`. ## Inputs - `colors.base_color` (`0.0, 1.0, 0.5`) — the line colour. - `floats.roughness` (`0.5`) — surface roughness. - `floats.emissive` (`0.0`) — no self-illumination. - `render.instancing` (`true`) — many lines draw in a single instanced batch.

# Unlit The minimal **unlit** surface shader: it emits `base_color * base_color_texture + emissive` with **no lighting**. Use it for UI-in-world, flat-shaded props, emissive signage, debug geometry — anything that should display its own colour regardless of scene lights. It is the deliberate counterpart to [`pbr`](../pbr.shader/README.md): where PBR carries the full StandardMaterial parameter set (roughness, metallic, normal, clearcoat, transmission, …), `unlit` declares **only** what an unlit surface uses. Authored as a self-shading `fragment()` shader, so it owns the final pixel and works in both the forward and deferred paths via the engine-generated entry points. ## Properties | Property | Type | Default | Meaning | |---|---|---|---| | `base_color` | color | `1,1,1,1` | Flat colour, multiplied by `base_color_texture`. | | `emissive` | color | `0,0,0,1` | Added on top (multiplied by `emissive_texture`). | | `alpha_cutoff` | range | `0` | `>0` enables masked transparency (discard below the cutoff). | | `uv_scale` | float2 | `1,1` | UV tiling, applied as `uv * uv_scale + uv_offset`. | | `uv_offset` | float2 | `0,0` | UV translation. | | `base_color_texture` | texture | white | Albedo texture. | | `emissive_texture` | texture | white | Emissive mask/texture. | Entity tint (the per-instance `Model`/`SkinnedModel` tint) is applied by the engine after `fragment()` returns, so this shader does not handle it.

# Glass Clear glass — a smooth, transparent PBR surface with a faint blue tint (`0.9, 0.95, 1.0`) and low alpha (`0.3`). Rendered in the transparent queue with backface culling off (`cull: none`) so both faces of thin geometry show. Built on `@builtin::shaders.pbr`. ## Inputs - `colors.base_color` — tint and opacity (the alpha channel drives how much shows through). - `floats.roughness` (`0.0`) — perfectly smooth; raise for frosted glass.

# sheen_film.shader A metallic-roughness surface carrying two lobes the standard material does not: a sheen lobe for fabric, and thin-film iridescence. `sheen` scales the lobe, `sheen_color` tints it and `sheen_roughness` sets its width — a low roughness gives satin's tight rim, a high one velvet's broad glow. `iridescence` blends toward the thin-film response, `iridescence_thickness` (in nanometres) sets which wavelengths interfere and so which hues appear, and `iridescence_ior` sets how strongly the film refracts. Both are off at their defaults, and both are evaluated by the engine's light loop, so they are shadowed and lit like any other surface.

# loading_bar (screen shader) The world loading-screen progress-bar fill. A horizontal ember→deep orange gradient with a soft highlight that sweeps across it and a faint vertical gloss, so the bar reads as actively working rather than a flat block. Animated entirely by `engine.time`. Drawn as the `backgroundShader` fill of the progress element, whose width is the load fraction.

# pbrReflective `pbr`, plus a reflection the surface traces for itself against the scene already drawn. Every property means exactly what it means on `pbr`; `screen_reflection` scales how much of the traced reflection reaches the pixel. Reach for this on a surface a reflection PASS cannot serve: anything in the transparent queue — glass, a canopy, a wet sheet, a puddle. A pass traces the surface the depth buffer holds, so it has no pixel to trace for a sheet of glass and no normal to trace with. This fragment has both. ## Why it is a separate shader Whether a shader reads the scene-colour binding is decided from its compiled module, and the surface framework injects `zero::pbr` into every surface shader in the engine. A trace reachable from there would make every material in every scene a scene-colour reader, and the renderer would take the scene-colour copy and route through the sampleable intermediate for every world, reflective or not. Held in this shader, that cost lands on the scenes that asked for it. An opaque surface does not need this: the reflections render feature traces those in one pass, under its own settings, which is cheaper than a march per fragment.

# Default The neutral fallback surface — a plain white, non-metallic PBR material with mid roughness (`0.5`), sampling the built-in white texture. This is what an object renders as when no material is assigned. Built on `@builtin::shaders.pbr`. ## Inputs - `colors.base_color` — the flat tint (white by default). - `floats.roughness` (`0.5`) / `floats.metallic` (`0.0`) — a neutral matte dielectric. - `textures.base_color_texture` — the built-in `default:white` texture.

# Triplanar Checker A checkerboard surface projected triplanarly, so the pattern stays uniform across arbitrary geometry with no UVs and no stretching. Neutral white base colour (`1.0, 1.0, 1.0`), half roughness (`0.5`), non-metallic, with a projection sharpness of `4.0` controlling how tightly the three axis projections blend at edges. Opaque, back-face culled, instanced, in the opaque queue (`2000`). Built on `@builtin::shaders.triplanar`, sampling `@builtin/textures/array_texture`. ## Inputs - `floats.triplanar_sharpness` (`4.0`) — blend tightness between the X/Y/Z projections. - `colors.base_color` (`1.0, 1.0, 1.0`) — tint over the projected texture. - `textures.base_color_texture` — the projected checker source (`@builtin/textures/array_texture`). - `floats.roughness` (`0.5`) / `floats.metallic` (`0.0`) — dielectric, mid-gloss default.

# SkinnedModel Component that drives skinned model playback and animation graph integration. Like `Model`, it carries the `material` field (`AssetRef<material>`) — material lives on the model that renders it, not as a standalone component. Set it at add time or assign `entity(id).component.get("SkinnedModel").material = "..."` later; `:setMaterialProperty` / `:getMaterialProperty` / `:getMaterialPropertyNames` operate on the assigned material (registry-wide). ## Blend model `skinning` chooses how the pass combines a vertex's joint influences. - `"linear"` (default) averages the joint matrices themselves. The average of two rotations is not a rotation, so a strongly twisted joint loses volume toward its axis — at a 180° twist a limb collapses onto the axis entirely. - `"dualQuaternion"` averages the joints' rigid motions as unit dual quaternions and renormalises, so the blend is a rotation at every weight and the cross-section is carried through the twist. Non-uniform joint scale rides along as a separately blended stretch. It costs a quaternion extraction per influence, so it is worth setting on characters whose wrists, shoulders or spine twist far, and leaving off elsewhere. ```lua entity.find("hero").component.get("SkinnedModel").skinning = "dualQuaternion" ``` A rig at rest renders identically under either model. ## Render self-check A few frames after its mesh attaches, a SkinnedModel checks that the mesh names something the engine can draw (on the GPU, or held off the device until this display puts it back) and that the pose it is drawn in has not collapsed it: the posed vertices the skinning pass wrote are measured against the mesh's own bind-pose extent, so a 1 cm part of a prop is judged by its own size. A mesh that fails is swapped for the builtin ERROR marker, drawn un-skinned with the error material, and the reason is logged. Setting `model` again takes the marker down and checks the new mesh. `renderCheck()` answers the verdict: `{ state = "pending" | "passed" | "failed" | "skipped", reason }`. ```lua local v = entity.find("prop_part").component.get("SkinnedModel"):renderCheck() if v.state == "failed" then print(v.reason) end ```

# deprecatedParticles (deprecated) > **Deprecated.** This belongs to the earlier particle substrate. It stays loadable by identity and guid for content that already uses it; nothing new should use it, and search does not offer it. Particles are procgen sim nodes (`sim.spawn`, `sim.particles`, `sim.shader`) played through an effect: use `@builtin::assetTypes.effect`. The package holds the GPU particle engine module (`engine`), the `deprecatedParticles` module over it, the `DeprecatedParticleEmitter` and `DeprecatedSimpleParticleEmitter` components, the shaders, compute shaders and materials they draw with, and a demo scene. The package's `.metadata` carries the deprecation marker, so every asset inside is deprecated.

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

# Cel Shaded A stylised, toon-shaded opaque surface built on `@builtin::shaders.extended_material`, with a warm red-orange base colour (`0.9, 0.3, 0.2`). The sun's light is cut into flat bands that multiply the base colour, so every band renders the hue of `base_color` and only its brightness steps; ambient light lifts the side facing away from the sun in the same hue. High roughness (`0.8`) keeps the surface matte: its specular term stays below the first band, so each lit band is one flat colour. ## Inputs - `colors.base_color`: the surface colour every band renders in, multiplied by `base_color_texture`. - `floats.roughness` (`0.8`): the size and strength of the specular highlight, which is banded with the rest of the sun's light; 0 is a small bright highlight. At four bands, a roughness of 0.5 or more keeps the highlight below the first band, so none shows. - `floats.quantize_steps` (`4`): the number of bands the sun's light is cut into; 0 shades smoothly. - `textures.base_color_texture`: an optional surface texture, drawn multiplied by `base_color`. Unset, it is white, and the surface renders `base_color` alone.

# assetType (asset type) The `assetType` is the **type of types** — the meta-type that every `<typename>.assetType/` folder is an instance of, including itself. A `<typename>.assetType/` folder declares a new asset type called `<typename>`: its on-disk shape, its identity rule, and the structural contract instances of the type must satisfy. This type is self-hosting. `assetType.assetType/` conforms to its own schema — a `type.yaml` plus a `README.md` — so the type system is defined in terms of itself rather than a hidden engine special-case (the same way a C compiler is written in C). Every asset in the engine, including each `.assetType` definition, now resolves to a registered assetType: a `.material` resolves to `material.assetType`, and `material.assetType` resolves to `assetType.assetType`, which resolves to itself. ## Why it exists Assets used to be mapped to their type *implicitly*, by matching the folder suffix against a name-keyed registry. That match carried no stored link: nothing on a `Foo.material` recorded *which* `material.assetType` it was written against, so two worlds shipping a same-named type could silently disagree. Making `assetType` a real, resolvable asset closes that gap — the link from an asset to its type is now an explicit reference pinned in the asset's `.refs` sidecar (`via: "asset_type"`), exactly like every other dependency. ## Where it lives - Source: `/zero/source/.../<typename>.assetType/` - Identity: `<typename>` (the `.assetType` suffix strips from the identity; the folder retains the suffix on disk). - Folder shape: - `type.yaml` — the structural spec the validator reads. **Required.** - `README.md` — type-level documentation. **Required.** - `about.yaml` — three short plain-language texts saying what the type is for (see "Say what your type is for" below). Every built-in type ships one. - `behavior.luau` — optional behavior/scaffolding module. - `template/` — optional canonical placeholder body the templater copies into a new asset of the type. - `<name>.module/` — optional shared code the type ships to **every instance** of it, conventionally `shared.module/` (see below). ## Shared code its instances reach (`asset.containing` + `.modules`) A type ships code every instance of it uses by declaring the modules in its own `behavior.luau`, as a map of tracked `require`s: ```luau -- inside <typename>.assetType/behavior.luau M.modules = { shared = require(".shared") } -- the sibling shared.module/ ``` An instance reaches it with one location-independent line: ```luau -- inside any foo.<typename>/init.luau local api = asset.containing(__FILE__).modules.shared ``` `__FILE__` is the chunk's own VFS path; `asset.containing` resolves the calling asset, and `.modules.<name>` follows the instance's pinned `typeRef` (the type's **guid**, recorded in the instance's `.refs` as `via = "asset_type"`) to the module its type declares. Because resolution follows that link rather than a category name, the same line in an instance of a different type resolves to that type's module, and identically-named modules in two types never collide. `asset.typeRef(target)` reads that guid for any target; `asset.resolve(asset.typeRef(target))` gives the full `AssetRef<assetType>`. See `assetTypes/README.md` § "Shared code: type-owned modules" for the full mechanism. ## How to create one Authoring a new asset type is just creating a `<typename>.assetType/` folder under `/zero/source/`. The engine registers `<typename>` as a category **the moment the folder is written** — no engine restart, no Rust change, and it works for built-in (`@builtin/assetTypes/`) and user-defined types identically. Once `<typename>` is registered, `<name>.<typename>/` folders are recognised as assets of that type and resolve their `asset_type` link back to this definition. Creating a `<name>.<typename>/` folder *before* its `<typename>.assetType/` exists fails fast: the suffix has no registered type, so the folder can't be a valid asset. Author the type first. ## Say what your type is for (`about.yaml`) Every type carries a small `about.yaml` beside its `type.yaml`, and the README you write for the type documents how to author an asset of it. Both are required, and both are meant to be written as you make the type, while you know what it is for. `about.yaml` answers three questions in plain words, one key each: ```yaml intent: "Sets the typeface of the text in your game: UI, labels, signs and 3D lettering." function: "A font, from a TTF, OTF or WOFF file, made available to all of Zero's text, including 3D text." usage: "You choose it by name for your UI or your text, and the text appears in that typeface." ``` - **`intent`** is what the type is for in someone's game. Name the whole range of things it covers, in the words a game maker would use for them. - **`function`** is how it works today: what an asset of the type is made of and what the engine does with it. - **`usage`** is what a person or an agent does with one: how they pick it, place it, call it, or hand it to something else. A few habits keep it useful. Write about the type as a whole, so the text holds for every asset of it, and leave out any one asset's name. Say what the type does right now. Stay with words a game maker would say, and mention a file name or a call only where a game maker would know it. The limits are in bytes: `intent` 800, `function` 1500, `usage` 1200. Each is generous, and a few sentences usually say it. Why bother: agents working in a world read these three texts to learn what your type is for, so they reach for it when it fits and use it the way you meant. People searching find the type by what they want to make, and the three texts let them tell at a glance whether it is the one they need. `asset.create("assetType", name)` scaffolds the file with all three keys, and a README whose first paragraph is a `[[describe]]` note. Each value starts with `[[describe]]` followed by a note on what to write; replace the whole value with your own words. A value or a README line that still starts with `[[describe]]` counts as not written yet, which the push's check of each asset it carries against its type reports, naming the file. A type you leave as it was is not asked, so older types stand. Many types at once, or one you would rather not write by hand: `services describe` lists the types that lack these texts and what filling them costs, and `{ mode = "all" }` writes them into the same files, where you edit them like anything else you wrote. Where the texts show up: `asset.inspect("<typename>", "assetType")` returns them as `detail.about`, `assetTypeRef:getAbout()` returns them as a table with the keys `intent`, `function` and `usage`, the type's `types/<typename>` guide page ends with an "About this type" section holding them, and the Inspector's Type section lists them at the top. The guide page is this README plus that section, so a README that explains the type well and an `about.yaml` that says what it is for read well together. ## Ask your assets to say what they are A type can ask each of its assets to carry a description: a file, written by the author or generated, that says what that asset is and what it is for. The people and agents who find an asset read it to decide whether it fits, and the author knows what it is for at the moment of making it. **1. Declare the file with a `described` check.** This is the whole requirement: ```yaml files: required: - path: "README.md" # any file name works kind: "file" content: - { check: "described", message: "Say what this widget is for and where it goes." } ``` With that in place: - An asset whose file is missing, empty, or still has a line starting with `[[describe]]` does not meet the type's requirements. `asset.validate` names it, `zm status` and `world.publishBlockers()` list it, and a push that carries it is refused with `message`. - `services describe` finds it (`mode = "find"` lists it and the price) and can write the description for it (`mode = "all"`). It writes only this file. For a YAML file that holds several texts, name the keys and their limits in bytes, the way this type does for `about.yaml`: ```yaml content: - check: "described" keys: - { key: "intent", max_bytes: 800 } - { key: "usage", max_bytes: 1200 } message: "Write intent and usage." ``` `headings` names sections a Markdown file must have. `assetTypes/README.md` has the full check. **2. Optionally, steer what gets generated with a `describe:` block:** ```yaml describe: guidance: "Say what the widget shows, what input it reacts to, and where it fits in a UI." examples: - "<identity of an asset of this type whose description reads well>" ``` `guidance` says what a description of your type covers, and `examples` names assets whose descriptions show the shape you want. Without the block, generation still works from the general describing guide and the check's `message`. An example is an asset of your type in the library whose description is a true, written one, never a scaffold's placeholder, and never the asset being described. When the library has none, leave `examples` empty rather than name one that is not. A type whose assets the model cannot perceive (a sound it cannot hear, a motion it cannot see) says so in `guidance`: the description comes only from what the asset's own files state, such as its name and the `.metadata` where a generation service records the prompt that made it, and when they state nothing the model answers `cannot` with that reason. `services describe` then fails that one asset with the reason and leaves its file as it was. **3. Start the file unwritten in your template.** Put a heading and one line that starts with `[[describe]]` and a short note on what to write, in `template/<file>`, so a new asset starts unwritten rather than with text that only looks written. Do not put example content in it: every new asset carries the template verbatim, and the same text on many assets makes them impossible to tell apart in search. Types whose assets say what they are through their own content (a mesh, a texture, a sound) leave this out: declare nothing and nothing is asked. ## The `behavior.luau` contract `behavior.luau` is the type's code. It returns ONE table, and the keys below are the ones the framework reads off it for EVERY type — the surface you get by declaring them. Anything else on the table is your own: reachable by name through `require("@builtin::assetTypes.assetType.shared.ref").loadTypeModule("<typename>")` for a system that knows your type (`computeShader` publishes `dispatchKey` that way), and never called by the framework. ```luau local M = {} M.ref = { ... } -- methods on every AssetRef of this type M.modules = { ... } -- shared code the instances reach M.global = {} -- reserved key; ship the empty table function M.onCreate(name, opts) ... end return M ``` ### The tables | Key | Shape | What the engine does with it | |-----|-------|------------------------------| | `M.ref` | `{ [name] = function(self, ...) }` | Every function becomes a method on every `AssetRef` of this type: `ref:name(...)`, with `self` the ref. This is how a type gives its instances an API. Two names in here are contracted — see below. | | `M.modules` | `{ [name] = require(".sibling") }` | Shared code the type's instances reach through `asset.containing(__FILE__).modules.<name>`, resolved by the instance's pinned `typeRef` guid. See the section above. | | `M.refShapes` | `{ [method] = "TypeName" }` | Declares the result type of a `M.ref` method so the LSP can check what a call site does with it. See the `M.refShapes` section below. | | `M.events` | an events schema | The events an ASSET of this type fires, declared the way a component declares its own. Readers subscribe through `ref.events.<name>:connect(...)`; firing authority stays with the type. Keyed by the asset's guid, so every resolver of the same asset shares the signals and a re-resolved ref re-attaches to subscriptions already there. | | `M.namePattern` | a Lua pattern string | The name shape `asset.create` enforces for instances of this type, replacing the default `^[A-Za-z][A-Za-z0-9_]*$`. | | `M.global` | `{}` | Reserved. Ship the empty table. | ### The lifecycle hooks Each is optional; a type that omits one costs nothing. The engine calls them: | Hook | Signature | When it fires | |------|-----------|---------------| | `M.onCreate` | `(name, opts) -> { [filename] = contents }` | On `asset.create("<type>", name, opts)`. Returns the files that scaffold the new instance, as a map of relative path to contents; the framework writes them. The `opts` type annotation is the schema `asset.create` validates the caller's arguments against, so annotate it. | | `M.onReplace` | `(dest, files) -> { [filename] = contents }` | On an `asset.create` that writes over an asset already at `dest`, after `onCreate`. Receives the files `onCreate` produced and returns the files to write, so a type that re-derives its content (a rig re-imported from its source file) can carry what an author added to the asset it replaces. Optional. | | `M.onRegister` | `(self)` | Once per instance, the first time it registers: on `engine.onWorldLoaded` for instances already in the world, immediately on a live `asset.create`, and when an instance arrives after that sweep (installed, pulled, or synced from a peer). Guarded by the instance's path, so a double trigger never double-registers. An instance that leaves the runtime releases the guard, so one arriving at the same path again registers. This is what makes "write an asset into the world and it takes effect live" work for content that registers into a runtime registry. The `@builtin` library is excluded from the sweep. | | `M.onChange` | `(ref, change)` | On every VFS write to a file INSIDE one of this type's instances. `change` is `{ path, asset, type, kind, origin }`: `kind` is `"edited"` or `"seeded"`, `origin` is `"local"` or `"remote"` (an importer runs on the originator only). **Filter on `change.path`**: the hook fires for any file under the folder, so act on the one you care about. It runs as its own task and may wait on what it reads: a `vfs.read` of bytes only the blob store holds (a binary file on the web build) fetches them. The writes to one asset reach the hook in the order they were made, each once the hook before it has finished. A re-entrancy guard suppresses writes back into the same asset routed inline from the hook, and a write the hook makes is routed on a later frame like any other, so the hook must be convergent on its own: diff the meaningful state and short-circuit while your own regeneration is in flight. | | `M.onDelete` | `(ref)` | When an instance of this type leaves the runtime: it is deleted, or the engine swaps away from the world binding that held it. Its files are gone from `/zero/source` by then. A removal routed while the instance's `onChange` is waiting reaches `onDelete` once that hook, and every write queued behind it, has finished. On a swap the instance still exists in the world it belongs to, and a VFS write the hook makes reaches the world now bound. | | `M.validate` | `(assetRef) -> { { code, message, severity? } }` | On `asset.validate`, after the structural `type.yaml` check, for the type's own SEMANTIC validation. `severity` defaults to `"error"`; error-severity problems flip `ok` to false, warnings do not. A hook that raises or returns a non-table is itself reported as a `validate.hook_failed` error. `world.push` runs this per user asset, so declaring it enforces your type's rules at publish time with no further wiring. | ### The two contracted `M.ref` names Most `M.ref` methods are your type's own surface: name them what you like, return what you like. Two are read by the engine and mean the same thing for every type, so their shape is fixed: - **`instantiate(self, target?, opts?) -> (root, idMap)`** — makes an instance part of the scene. Defining it is the whole opt-in: `ref:canInstantiate()` is true exactly when it exists. Its **return is a contract** — see the next section. - **`inspect(self) -> detail`** — the type-specific half of `asset.inspect`. See its section below. ### Names a type cannot shadow Some keys resolve on every `AssetRef` before per-type dispatch, so an `M.ref` entry of the same name is never reached: `canInstantiate`, `getSource` / `getBytes` / `getText`, `exists`, `deps`, `meta`, `runtime`, `events`, `modules`, `typeRef`, and the residency flags `has_backing_asset`, `has_runtime_changes`, `cpu_resident`, `gpu_resident`. These are the behaviours every asset must expose identically, which is why they win. ### Reloading A `behavior.luau` edit ripples to existing refs with no restart: dispatch reads `mod.ref` fresh each time and `require`'s cache is re-run in place. A type whose folder appears at runtime is picked up on the next dispatch — negative results are not cached either. ## The names your type's assets hold (`references:`) An asset that names another asset by a string depends on it: the named asset travels with it into a pack or a pull, and a name nothing answers to is an unresolved dependency `worldValidation` reports and the push gate refuses. The engine reads `require(...)` and the asset lookups on its own; a name your type's format or API carries anywhere else is one you declare, in `type.yaml`: ```yaml references: # A top-level key of this type's own files that holds a name (or a table of them). keys: - { key: "shader", type: "shader" } # A call's argument, counting from 1, wherever the call is written. args: - { call: "g:node", position: 2, type: "procNode" } # A field of the options table a call takes. fields: - { call: "fx.beam", field: "material", type: "material" } ``` `type` is the category the name resolves in, one of `asset.categories()`. An argument declared once per category, at the same `call` and `position`, takes the name from whichever category answers. A key or a field holds one category: declared again with another `type`, it takes the later one. The block is declared as the type registers, when the library or the world holding it is laid into the VFS, so every reference table reads it whatever script has or has not run. `asset.declareReferenceKey`, `asset.declareReferenceArg` and `asset.declareReferenceField` declare the same things from a script, for a surface that is no type's. ## What search does with your type (`indexing:`) A type declares what search embeds for its instances. **This is not optional and there is no useful default**: ZeroMind runs your declaration and adds nothing of its own, so anything you do not point at is absent from the index — silently, and for every instance of the type forever. Twenty types once shipped with no `indexing:` block and every instance of them was unfindable. A type whose instances are never searchable (a run record, a log) says so with `indexing: none`; every other type declares a recipe. A type without an `about.yaml` beside its `type.yaml` refuses every push that carries it, whether or not the push edited the type. Texts in it that are not written yet follow the rule every `described` file follows: they refuse the push that edits, stages or commits the type. Two words carry the whole thing, and they are the same two the search tool exposes: - **`identity`** — what an instance IS. For anything you can look at, that is the picture (`content:` + `modality: image`, matched directly by a text query). For everything else it is the authored text that says what it is. - **`capability`** — what it DOES and how it is made. Code, settings, the model-written summary of them. A type with no behaviour has no `capability` entry. A type with nothing to look at has no image. Leaving a slot empty is a statement; filling it with whatever happens to be lying around is not. The one you have to decide when authoring a type is: *for an instance of this, what is the thing a person would recognise it by, and what is the thing it does?* A texture answers "the image" and "its compression settings". A module answers "its README" and "its code". Write those two answers into `indexing:` and the rest follows. Three specifics worth knowing before you write one: - **`derive` is instructed by this type's own `README.md`.** A model reads an instance's source and writes a description; what it embeds is the description, not the source. It follows your README to know what it is looking at, so a type whose README says what its instances are gets good derivations for free. There is no prompt to name. - **`derive` loses detail.** It keeps the main technique and drops secondary ones. If the source is code you want searchable by its own vocabulary, declare the same files a second time as `capability` with `extractor: verbatim`. Two entries, same role, different failure modes. - **Never `source: { field: name }`.** A filename is one or two words with no usable embedding, and a corpus indexed that way answers "language runtime" with `say_runtime_2.soundClip`. `facets:` is the second stage: a `file:` embedded whole (`.metadata`, so keys nobody declared still get indexed) plus computed keys that state a value for every instance including `false` — the raw file can imply "not rigged" and can never say it. The full schema, every extractor and the facet sources are in [`assetTypes/README.md`](../README.md); the scaffolded block with inline guidance is in [`template/type.yaml`](template/type.yaml). ## A container whose contents work together (`system: true`) A type that is a container can say its contents are one working whole by declaring `system: true` at the top level of its `type.yaml`. `package` declares it: the components, modules, scenes and tools a package ships are parts of one system. The declaration is plain data, read from the decoded `type.yaml` (`require("@builtin::assetTypes.assetType.shared.declaration").of("package").system`), and a type that leaves it out is an ordinary type. ## What your type looks like (`preview:`) A type declares how its instances are pictured, and the engine makes the picture when something needs it: staging an instance whose `preview.png` is missing or pictures content it no longer holds queues a render, a view that shows the instance asks for one, and `ref:preview()` renders one on demand. An edit renders nothing on its own. Each `preview.png` records the content it pictured, which is how a stale one is told from a current one. The preview studio owns the light, the backdrop, the framing and the camera, and nothing in the world reaches it, so an instance pictures the same in every world. Declare one of four recipes: | `kind` | The picture is | Your type provides | |---|---|---| | `instantiate` | the asset stood in the studio through its own `instantiate` | `ref.instantiate` | | `image` | a file the instance holds, fitted to the frame, nothing rendered | `source.files`, the candidate files in order | | `surface` | the asset painted on a builtin mesh | `mesh`, and `ref.previewMaterial(self) -> { material }` | | `custom` | whatever `ref.preview(self, opts)` returns | `ref.preview` | ```yaml preview: kind: surface mesh: sphere ``` A scene-instantiable type that declares nothing still answers `ref:preview()` through its `instantiate`, but persists no picture: the declaration is what makes the engine keep one. List `preview.png` among the type's files so an instance may hold it. The picture is findable only when `indexing.content` names it. The two are separate statements, and neither is derived from the other: ```yaml indexing: content: - role: identity modality: image source: { file: "preview.png" } ``` `@builtin::assetTypes.assetType.shared.previewRecipe` reads the declaration; the scaffolded block with inline guidance is in [`template/type.yaml`](template/type.yaml). ## Typing a result from the instance (`M.refShapes`) Every method on `M.ref` is checked against the type its `--!return` names, and every asset of the type gets the same one. That is right for most methods and wrong for the ones whose result is shaped by the ASSET: a method answering one entry per child folder, per row of a config, per binding an input map declares. The widest true annotation for those is `{ [string]: Thing }`, and an indexer accepts every key — so a caller's typo reads as valid and nothing reports. `M.refShapes` lets the type state the result per instance. Each entry is `function(self) -> (typeExpression, source?)`: a Luau type expression for THIS asset, and the module whose type vocabulary the expression uses. Read the asset; never run it — stating a type must not take effect. ```lua -- inputMap.assetType/behavior.luau — the shipped example. -- `activate()` hands back one handle per control the map declares. M.refShapes = { activate = function(self): (string, string) local names = {} for _, control in ipairs(M.ref.controls(self)) do table.insert(names, control.name .. ": Handle") end if #names == 0 then return "", "" end return "{ " .. table.concat(names, ", ") .. " }", "@builtin::modules.zinput.scheme" end, } ``` With it, `map.jump:onPressed(fn)` resolves and `map.noexisting` is reported with the map's real controls. Without it, both pass silently. ### What the call site has to say A per-instance type is matched by the asset's IDENTITY, so it applies only where the reference the method is called on says WHICH asset. Two spellings do: ```lua -- a component field, whose declared default names the asset public = { map = Field.assetRef("inputMap", "@builtin::inputMaps.default", Sync) } local controls = public.map:activate() -- typed for THAT map -- an annotation, naming category and identity local m: AssetRef<"inputMap", "@builtin::inputMaps.default"> ``` `asset.resolve("<identity>", "<category>")` carries the CATEGORY, so the methods the category defines are checked on the result — but not which asset it found, so a per-instance result keeps the category's declared return. A reference that names no asset (`asset.resolve(someVariable)`, a value passed in as a parameter) carries neither, and calls on it are unchecked. That is the same rule everywhere: the checker states what the code states, and a name computed at runtime states nothing. ### The result is a value, not a binding The type belongs to the expression, so it travels the way any inferred type travels. Indexing the call's result is checked; stashing it in a module local and indexing it from another function is not, because the local's declared type is what carries across — and `any` (or no annotation) carries nothing: ```lua -- checked: `d.greting` is reported function awake() local d = public.dialogue:lines() d.greeting:say() end -- NOT checked: `lines` is a module local typed `any` local lines: any = nil function awake() lines = public.dialogue:lines() end function start() lines.greting:say() end ``` Bind what you need at the call site and the names stay checked in both places — the asset-derived type at the boundary, ordinary scoping after it: ```lua local lineGreeting = nil function awake() local d = public.dialogue:lines() lineGreeting = d.greeting -- `d.greting` is reported here end function start() lineGreeting:say() end ``` ### When nothing is reported and you expected something From a call site, a type that is correct and a type that was never published look the same: no diagnostic either way. `require("@builtin::assetTypes.assetType.shared.refShapes").published()` answers which it is. It returns two maps — the category surfaces, and the per-asset results keyed by identity and then by method: ```lua local shapes = require("@builtin::assetTypes.assetType.shared.refShapes").published() shapes.categories.dialogue --> "{ lines: () -> any, lineNames: () -> { string } }" shapes.returns.Shopkeeper.lines --> "{ browsing: Line, farewell: Line, greeting: Line, wares: Line }" ``` An identity absent from `returns` was never published for, which is a different thing from published-and-correct — and the reason to look here rather than at the call site. The answers are recomputed when an instance is written, so a control added to a map reaches the checker with no restart. Only types that declare `refShapes` are read per instance, and at most 64 assets of one type are — past that the type keeps its declared return and the engine log names what was dropped. ## The instantiate hook (`M.ref.instantiate`) — a contracted return A type opts into becoming part of the scene by defining `instantiate` on its `ref` table. That is the whole opt-in: `ref:canInstantiate()` is true exactly when the hook exists, so consumers offer a scene path — an `Asset.source` field, a viewport drop, a tool argument — by CAPABILITY rather than by a list of type names. Unlike `inspect`, this hook's **return is a contract**. A caller writes one piece of code against every instantiable type, so what comes back cannot vary by type: ```lua -- behavior.luau local Instantiable = require("@builtin::assetTypes.assetType.shared.instantiable") local M = {} M.ref = { instantiate = function(self, target, opts) local root = Instantiable.root(self, target, opts) -- IN: the base opts -- ... compose whatever this type is, under `root`, NOW ... return Instantiable.result(self, root, idMap) -- OUT: the contract end, } return M ``` **IN.** `target` is an owning entity ref: the instance lands under (or, for a hierarchy type, onto) that owner. With no target the type spawns a fresh root. `position`, `rotation`, `scale`, `name` and `temporary` mean the same for every type — `Instantiable.root` applies them to a root you mint, `Instantiable.place` to one you adopt, so you never re-read the spec. Honour more opts of your own if your type needs them, and document them in the hook's `--!arg` docs. **OUT.** Return `(root, idMap)` through `Instantiable.result`: - **`root`** — the composed root, as an `EntityRef`. Composition is **synchronous**: everything your type builds is live when you return, so the caller can parent to it and read its components in the same statement. Do not defer the work to a component's `awake` and return an empty shell — a root that is not live is refused. - **`idMap`** — the `originalId -> runtimeId` map naming what you spawned, or nil for a type with no addressable children (`result` normalises it to `{}`). **A caller never receives nil.** A component that re-composes your asset on every load keeps this map and passes it back in, which is how a cross-entity reference into the composition survives a reload. `AssetRef` runs every `instantiate` through `result` on the way out whether or not your type called it, so returning something else fails at your own call rather than handing a caller a nil root. Calling it yourself is still how you say what you return, and running it twice changes nothing. `@builtin::assetTypes.assetType.shared.instantiable`'s README is the full reference for both halves. ## The inspect hook (`M.ref.inspect`) `asset.inspect(ref)` resolves `ref`, builds a common envelope shared by every asset (`identity`, `name`, `guid`, `source`, `typeName`, `typeDefinitionPath`, `scope`, `origin`, `description`, `tags`), then calls the resolved type's own inspect hook — `M.ref.inspect(self)` on `behavior.luau` — for the type-specific `detail`. The hook returns *only* `detail`; the framework fills in everything else: ```lua -- behavior.luau local M = {} M.ref = { inspect = function(self) -- self.path is the asset's own folder. Parse the asset's OWN -- files — source text, a native payload header, its `.metadata` -- — never runtime state (a live component instance, a GPU -- upload, a compiled schema): inspect must work on an asset that -- hasn't been compiled, uploaded, or registered yet. return { -- type-specific fields, whatever this type wants to surface } end, } return M ``` A type that omits `M.ref.inspect` yields the generic record: the envelope alone, `detail = nil`. That's a valid, working state — not an error — but it means agents calling `asset.inspect` / `tools.use("assets","describe", ...)` on an instance of the type see only identity and scope, none of what makes an instance of it meaningful. Declaring the hook is what makes a type's instances inspectable for what they actually are. A hook that raises leaves `detail = nil` and sets `record.warning` to the error text — `asset.inspect` itself never raises for a resolved ref. ## Discovery - `asset.list("assetType")` — every registered asset type. - `asset.inspect("<typename>")` — the type's identity, source path, and this README, plus its `about.yaml` texts as `detail.about`. - `asset.resolve("<typename>", "assetType")` — the `<typename>.assetType` asset itself (used by the validator to find the type's `type.yaml`). ## Related - `assetTypes/README.md` — the full `type.yaml` schema and validator rules. - `@builtin::assetTypes.assetType.shared.instantiable` — the instantiation contract's shared implementation, both halves. - Every other `*.assetType/` here — the concrete types built on this meta-type. ## The Inspector a type ships Every type names the file its Inspector sections come from with `inspector: { type: "inspector.luau" }` in its type.yaml. `asset.create("assetType", name)` scaffolds the block and an `inspector.luau` whose Contents section lists an asset's files, built from `ctx.parts`. `asset.validate` on a type that names none reports `assetType.inspector_required` (an error for a `@builtin` type the engine's library authors; a warning for a world's own, and for one the library carries by reference, which the world that published it answers for), and one whose file does not load `assetType.inspector_invalid`. ## In the Inspector Type: what the type.yaml declares (suffix, container, primary files, the settings and inspector blocks), whether the type ships a behavior, how many instances it has, and **Open** for its files. Schema: the settings every instance carries, as read-only typed controls at their defaults (a type whose schema is per instance says where it is declared). Instances: a link to each of the first 20 assets of the type, and how many there are when there are more.

# cascades render feature Draws the `cascades` capture view: which directional-shadow cascade each pixel samples. A geometry pass over `@geometry.opaque` replaces every surface's own material with the cascade shader, which asks `zshadow_select_cascade` — the same function the lit path calls — for the cascade covering that fragment and emits one flat band colour for it. Because the colour comes from the selection itself, a split that moves on screen is a split that moved in the renderer. Bands: red cascade 0 (nearest), green 1, blue 2, yellow 3, grey past the last split. Where the shadow term fades out over the tail of the range (`fadeFraction`), the band mixes toward that grey over exactly that tail, so the gradient on screen is the fade; with `fadeFraction = 0` the boundary is hard. Magenta everywhere means no cascade data reached the frame: the shadow pass is off, or the scene has no directional light casting into it. Brightness carries the surface normal so the scene stays readable; the hue is the cascade and nothing else changes it. The pass carries the view's debug channel, so it does not draw for a camera that is not a capture of `pass = "cascades"`. It tests `lessEqual` against the depth the opaque pass already wrote and writes none of its own. The feature is created on demand by `@builtin::systems.renderDiagnostics.renderDiagnostics`.

# countingView module Builds a camera view that counts, per pixel, how many fragments satisfy a depth predicate, and colours the count. `overdraw` and `zfighting` are both instances of it; a diagnostic of your own is one more. ```luau local CountingView = require("@builtin::systems.renderDiagnostics.countingView") return CountingView.new({ view = "myView", -- the name `capture pass=myView` selects geometry = "@geometry.all", -- which drawables are counted depthCompare = "always", -- which of their fragments count levels = 16, -- counts that fit before the sum saturates mapShader = asset.resolve("~.shaders.myViewMap", "shader"), }) ``` The return value is a `.renderFeature` module — `render` enqueues the view's passes, `teardown` releases them — so a feature's whole `init.luau` is this one call. Register the name separately with `renderer.captureView.register` so `capture pass=<name>` resolves to it. ## The two knobs that decide the question `depthCompare` runs against the scene depth the frame already resolved: - `"always"` counts every fragment the rasterizer produced, hidden ones included — the shading work a pixel costs. - `"lessEqual"` counts only fragments reaching the winning depth — one per pixel, unless surfaces are close enough that the depth buffer cannot tell them apart. `geometry` narrows what is counted: `"@geometry.all"`, `"@geometry.opaque"` or `"@geometry.transparent"`. ## Reading the count `levels` is how many counts fit before the accumulated sum saturates at 1.0, so a view's open-ended "this many or more" band belongs at or below that number. `mapShader` is a `@domain: post-process` `.shader` asset declaring `fn zero_count_color(n: i32) -> vec3<f32>` — the view's reading of the decoded count, `0` where nothing was counted — over the shared decode body: ```wgsl // @domain: post-process fn zero_count_color(n: i32) -> vec3<f32> { ... } #include "~.shaders.countMap" ``` Flat, nameable bands read better from a still than a continuous ramp: the question is which band a region falls in, not how bright it is.

# overdraw render feature Draws the `overdraw` capture view: how many fragments each pixel cost. A geometry pass over `@geometry.all` blends a whole unit additively into a private float target with the depth test switched off, so each pixel accumulates one unit per fragment that rasterized over it — the fragments a depth test would reject included, because they cost the same shading. A full-screen pass then reads the count and writes one flat band colour per layer count. Bands: black 0, blue 1, cyan 2, green 3, yellow 4, orange 5-6, red 7-9, white 10+. Both passes carry the view's debug channel, so neither draws for a camera that is not a capture of `pass = "overdraw"`. The feature is created on demand by `@builtin::systems.renderDiagnostics.renderDiagnostics`.

# renderDiagnostics module Publishes the `overdraw` and `zfighting` capture views, so `capture pass=<name>` resolves to them. Requiring the module registers both. ```luau local diagnostics = require("@builtin::systems.renderDiagnostics.renderDiagnostics") diagnostics.register() -- idempotent; already done by the require diagnostics.unregister() -- withdraw both views and drop their features ``` Registration is cheap and permanent: each view's passes are gated to the debug channel the registration hands out, so they are skipped for every camera that is not a capture selecting that view. The feature that draws a view is created the first time it is selected, through the registration's `ensure`. `renderer.captureView.list()` enumerates every registered view, and the package readme has what each colour band means.

# countMap The decode a counting camera view reads its result through: it recovers a per-pixel count from the fraction a counting geometry pass accumulated, and calls the view's own reading of that count. A counting view blends `1 / levels` additively for every fragment that satisfies its depth predicate, so its target holds `count / levels`. This body reads that fraction back out of the scene colour, multiplies by the `levels` the pass used — carried in `engine.params.x` — and rounds to the whole count. ## Using it The including shader declares the view's reading of a count and includes this body: ```wgsl // @domain: post-process fn zero_count_color(n: i32) -> vec3<f32> { if (n <= 0) { return vec3<f32>(0.0, 0.0, 0.0); } return vec3<f32>(1.0, 1.0, 1.0); } #include "~.shaders.countMap" ``` `n` is 0 where nothing was counted, and saturates at `levels` — so a view's open-ended "this many or more" band belongs at or below that number. Flat, nameable bands read better from a still than a continuous ramp: the question is which band a region falls in, not how bright it is.

# zfighting render feature Draws the `zfighting` capture view: where two opaque surfaces sit too close together for the depth buffer to keep them apart. A full-screen fill blacks out the lit scene, a geometry pass over `@geometry.opaque` re-runs the depth test the scene already resolved (`lessEqual`, writing no depth of its own) and blends a quarter-unit additively into the scene target, and a full-screen pass turns the resulting count into a verdict colour. The count accumulates into the scene target rather than a private one because only that target carries the scene's depth buffer, and the depth test is the whole measurement. The counting pass carries a depth bias, which is what makes the measurement match what the eye sees. Unbiased, the test is exact to the last step the buffer holds, so it counts a second surface only where the two land on the identical value — a contour through the fight rather than the fight. The bias widens the test to a band 16 steps deep, plus four times the fragment's depth gradient, so every surface close enough for the winner to change hands is counted. Stating the band in depth-buffer steps keeps it honest at range: the steps grow with distance and so does the fight. Verdict: near-black no opaque surface, dark grey one surface (healthy), red two surfaces the buffer cannot separate, white three or more. All three passes carry the view's debug channel, so none draws for a camera that is not a capture of `pass = "zfighting"`. The feature is created on demand by `@builtin::systems.renderDiagnostics.renderDiagnostics`.

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

# Material (asset type) A material is a named, configured instance of a `.shader`. The shader defines the surface look (lighting model, available property fields, texture slots); the material picks values for those fields and a shader to bind to. Renderable entities reference materials, not shaders, so the same geometry can wear different materials and the same material can be reused across many entities. Entities sharing one material can still differ in a value: every drawn object carries four `vec4` lanes of its own that a surface shader reads as `input.shader_data[lane]` and `renderer.instanceData.set` writes. Use that for a dissolve at its own progress per subject, a hit flash at its own age, a fill level per instance — a material per entity is for when the LOOK differs, not when a number does. > New to how a material relates to its shader, its textures, and the live GPU > material behind it? Read `core/resource-model` first. It also covers the > difference between an authored `.material` asset (this type) and a runtime GPU > material made with `renderer.material.create`. ## When to use one - You want a named surface configuration an entity wears by referencing it from its `Model` component (`material = "@.../<Name>"`). - You want runtime property tweaks (`asset.resolve(ref):setProperty(...)`) to affect every entity using the material at once. - You want to publish a curated look (`Gold`, `RedGlow`, `BrickWall`) other authors can reuse without re-typing shader bindings. If you need a brand-new lighting model or a custom visual effect, you need a `.shader` first; the material wraps it. ## Where it lives - Source: `/zero/source/.../<Name>.material/` - Identity: `<Name>` (the `.material` suffix strips). - Folder shape: - `mat.yaml` — canonical material spec (shader + property values). **Required.** - `preview.png` — the material's rendered shader-ball still, its persisted visual description. **Required.** Rendered when the material is staged (`zm add`) with its preview missing or stale, and by `generatePreviews`; it syncs, publishes, feeds image-based search, and gives browsers a thumbnail. - `README.md` / `.metadata` — optional prose + tags, indexed when an author writes real ones. - `textures/` — optional folder for embedded textures. Validator allows the folder; its interior is unrestricted. - `shaders/` — optional folder for a co-located custom shader. Same rule. ## How to create one ```luau asset.create("material", "<Name>") -- Creates: /zero/source/<Name>.material/ -- mat.yaml (shader binding + property scaffold) -- preview.png (rendered when the material is staged with `zm add`; the -- picture lands as a change the next `zm add` stages) -- `folder` places it in a subfolder of /source instead of the root: asset.create("material", "<Name>", { folder = "materials" }) ``` Pass the shader and initial values through `asset.create`, then tune with `setProperty` and keep what you tuned with `saveDefinition`: ```luau local mat = asset.create("material", "<Name>", { shader = "@builtin::shaders.pbr" }) mat:setProperty("base_color", { 0.8, 0.6, 0.1, 1 }) mat:setProperty("roughness", 0.3) mat:saveDefinition() -- writes the tuned values into mat.yaml ``` This mints the `.material` asset and returns a handle you tune with `setProperty`. A set is a runtime change: it reaches the GPU material and every entity wearing it, and `saveDefinition` is the call that writes it into `mat.yaml`, so a property driven every frame costs no file write and leaves the authored file as its author wrote it. A purely runtime `asset.create` lives only for the session. For an ephemeral, runtime-only GPU material that is not an asset at all, use `renderer.material.create` instead (see `core/resource-model`). ## How it operates 1. **Property reflection.** The bound shader's uniform struct fields become the material's configurable properties — no manual property declarations needed. `naga` introspects the shader at load. 2. **Property values.** `mat.yaml` groups values by type, each block keyed by the shader's field names: `properties:` holds scalars and colors/vectors, `ints:` holds integer-typed fields, `bools:` holds boolean-typed fields, and `textures:` holds texture slots. Omitted fields take the shader's default. A scalar is a bare number (`roughness: 0.5`); a color or vector is an array (`base_color: [1, 1, 1, 1]`). `shader:` is the shader's identity string. This is the shape every material the engine writes uses. A `saveDefinition` writes the changed values into the file where they already stand and leaves the rest of it — its comments, the order of its keys and blocks, the spelling of its literals — untouched. The older `floats:` / `colors:` blocks (with `{ r, g, b, a }` map colors) still load for materials hand-authored that way. 3. **Render state.** `render:` holds how the mesh is drawn rather than what the shader reads: `blend` (the equation the fragment composites with, also spelled `type`), `cull`, `depth_write`, `depth_compare` and `topology`. The `.shader` type README's "The render block" section lists every value each key takes, and `asset.create`'s `render` argument takes the same keys and values. 4. **Application.** An entity wears a material by referencing it from its `Model` component (`material = "@.../<Name>"`). Materials affect every entity that references them; runtime `asset.resolve(ref):setProperty(...)` changes propagate to all of them immediately, and last until the next mode change unless `saveDefinition` writes them into `mat.yaml`. 5. **Texture binding.** Texture slots accept `color:r,g,b,a` for solid colors, `default:white` / `default:black` / `default:normal` for the engine's own fallback texels, `@builtin::textures.<name>` for builtins, `path/to/image.png` for file textures, or a render-target handle for camera renders. The GPU texture cache reads the `color:` and `default:` forms from the string itself, so a slot written in one names no asset and carries nothing with the material when it travels; every other form names a texture asset the slot depends on. A texture in `base_color_texture` is multiplied by `base_color`: every built-in surface shader declaring both draws the texture's colour times `base_color`, channel by channel. Under the default white `base_color` the texture shows as itself, and a coloured `base_color` tints it. The two read a colour differently: `base_color` is linear, and the slot reads its texels as sRGB-encoded, a `color:` value's included, the way it reads an image. A colour stated in both places is therefore multiplied by a darker copy of itself: `color:0.62,0.14,0.05,1` in the slot decodes to `0.34, 0.017, 0.0039`, so beside `base_color` `0.62, 0.14, 0.05` the surface draws `0.21, 0.0024, 0.0002`, far darker than either. State a solid colour once, as `base_color`, and leave the slot at its default white. 6. **Hot reload.** Editing `mat.yaml` repacks the GPU uniform buffer on the next frame; visible immediately. 7. **Inspector.** `type.yaml` names `inspector: { type: "inspector.luau" }`, and `inspector.luau` declares the material's sections beside the generic ones: `shader` (the bound shader, swappable), `properties` (each shader field as its typed control) and `textures` (each texture slot as an asset chip). They read the material through `mat:getShaderRef()` (the bound shader's ref, `~` expanded) and `mat:getTextures()` (slot name → `{ ref, name }`: the bound texture's guid and the id the material names it by). An edit there is an authoring write: `mat:writeProperty(name, value)` and `mat:writeTexture(slot, texture)` write the value into `mat.yaml` (and drop the session's own value for it, so the material reads what the file holds), and `setShader` rewrites the file; inside an undo operation each file write is recorded, so undo puts `mat.yaml` back. `setProperty` / `setTexture` stay runtime writes that last until the next mode change. ## Discovery - `asset.list("material")` — every registered material. - `asset.inspect("<name>")` — shader binding, property values, source path, this type README. - `ls /zero/source/<Name>.material` lists the files the folder holds. - `asset.resolve("<name>"):getProperties()` — the property fields exposed by the bound shader, each at the value it currently holds: what `mat.yaml` authored until something writes to the material, and the written value from then on, whichever call wrote it. That is the value the surface is drawn with. Read them back rather than guessing names; which fields exist comes from the shader. - `asset.resolve("<name>"):getDefinition()` — the authored `mat.yaml` bytes, the value the material rests at. - `asset.resolve("<name>"):getShader()` — the shader the material binds. ## Authoring conventions - Use lowercase, descriptive names (`brushed_steel`, `red_glow`, `tarmac_wet`). Avoid shader-name suffixes in the material name — the binding lives in `mat.yaml::shader`. - Drive every property the shader exposes; defaults are a fallback, not a contract for which fields exist. - Embed textures alongside the material (`textures/` subfolder) when they're used only by this material; reference shared textures from `@builtin::textures.*` or a library. ## Common pitfalls - **Property names must match the shader's uniform struct exactly** (case-sensitive). Misnamed properties silently get the shader's default. - **`base_color_texture` multiplies `base_color`.** A `color:` texture holding the same value as `base_color` multiplies the colour by its own sRGB-decoded value, so the surface renders far darker than the value written. Write a solid colour as `base_color` alone. - **Broken shaders break the material.** A material whose shader has a parse error renders as the magenta checkerboard. Inspect the shader first if the material looks wrong. - **`setProperty` targets the material, not the entity.** Changes affect every entity that references the material. - **`setProperty` is a runtime change.** It reaches the GPU, not the file: call `saveDefinition` to write the current values into `mat.yaml`. For a per-entity override that no other entity sees, give the entity its own copy with `Model:applySessionMaterial(renderer.material.create(...))`. - **Renaming the folder changes the identity.** Update every `Model` component and `asset.create` callsite that references it. ## Related types - `.shader` — defines what properties exist; required before a material can bind to it. - `.preset` — captures a component configuration; conceptually similar to a material, but for components instead of shaders.

# SubsurfaceScattering Marks an entity's meshes as carrying light beneath the surface. The terminator softens and warms instead of ending on a line, and light spreads through a thin edge instead of stopping at it. ```lua entity(headId).component.add("SubsurfaceScattering", { color = { 1.0, 0.3, 0.16 }, radius = 0.02, }) ``` Every field is live — editing one in the inspector moves the shading on the next frame, and the values persist with the scene. Removing the component stops the entity scattering, and the pass is released with the last marked entity. | field | effect | |---|---| | `color` | What light becomes beneath the surface. Its channels also set how far each one travels, so a tint weighted to red spreads red furthest. | | `radius` | How far light travels beneath the surface before leaving, in world units over [0, 1]. Skin at human scale sits near 0.02. | | `strength` | How much of the spread is mixed back into the frame, in [0, 1]. 0 leaves the shading exactly as it was lit. | A radius below zero is reported as a warning and the last good setting stays live, so a typo in the inspector does not stop the component. Code that marks meshes at runtime can drive the same settings through `@builtin::systems.subsurfaceScattering.subsurface`.

# sssDiffusion The render pass behind the `SubsurfaceScattering` component and the `subsurface` module. The transport it draws is a spread of exitant light across a surface, so it runs on the frame that was just drawn. Each marked mesh is drawn into a mask carrying its tint and radius — one draw per group of meshes sharing both. Two passes then spread the lit colour along that mask, once across and once down; two lines rather than a disc is what makes the reach cost twice the taps instead of their square. A final pass mixes the result back by `strength`. Weights are a Gaussian in units of each channel's own reach, and the reach is the tint: a channel the surface passes freely is the one that travels furthest, which is what carries red past the terminator while green and blue stop at it. Taps are confined to the mask and to a depth tolerance, so light spreads across one surface and stops at its silhouette rather than dragging the background into it. The radius is world-space, converted to a pixel span from each pixel's own depth, so a surface keeps the same softness as the camera moves toward it. Depth and camera come from the render target being drawn, so the pass is correct in offscreen captures and RTT cameras at their own resolutions.

# sssMask Fills a marked mesh's silhouette with the scattering it was authored with: the tint in RGB, and in alpha the world-space distance light travels beneath the surface before it leaves, over [0, 1]. Alpha above zero is what marks a pixel as scattering at all, so a target cleared to zero reads as "no subsurface here". A geometry pass draws through a material pipeline built for the frame's own colour format, which is why the mask is 8-bit rather than float. One group holds one radius, so that quantisation lands on the authored value rather than varying across a surface. One material carries one group's values and `sssDiffusion.renderFeature` issues one draw per group, so meshes scattering differently keep their own numbers. | property | meaning | |---|---| | `scatter_color` | The tint, and per channel how far that channel travels. | | `scatter_radius` | The distance light travels beneath the surface, in world units. |

# sss_across Blurs subsurface diffusion across the image — one half of the separable pair. The body is `sss_diffuse`; this shader supplies the axis. ## Includes - `sss_diffuse` ## Bindings | name | kind | |------|------| | `sss_src` | `texture2d` | | `sss_mask` | `texture2d` | | `scene_depth` | `texture_depth` | | `frame_cam` | `buffer` | | `sss_params` | `buffer` | | `sss_out` | `storage2d (rgba16f)` |

# sss_composite Composites the diffused subsurface term back over the lit scene. ## Bindings | name | kind | |------|------| | `scene_color` | `texture2d` | | `sss_diffused` | `texture2d` | | `sss_mask` | `texture2d` | | `sss_params` | `buffer` | | `composite_out` | `storage2d (rgba16f)` |

# sss_diffuse One separable subsurface-diffusion blur. The including shader defines `AXIS` — the direction this pass blurs along — so the same body serves the horizontal and the vertical halves of the separable pair. ```wgsl const AXIS: vec2<f32> = vec2<f32>(1.0, 0.0); #include "@builtin::systems.subsurfaceScattering.sss_diffuse" ```

# sss_down Blurs subsurface diffusion down the image — one half of the separable pair. The body is `sss_diffuse`; this shader supplies the axis. ## Includes - `sss_diffuse` ## Bindings | name | kind | |------|------| | `sss_src` | `texture2d` | | `sss_mask` | `texture2d` | | `scene_depth` | `texture_depth` | | `frame_cam` | `buffer` | | `sss_params` | `buffer` | | `sss_out` | `storage2d (rgba16f)` |

# subsurface Light that enters a surface at one point and leaves at another — the transport that softens and warms the terminator on skin. ```lua local subsurface = require("@builtin::systems.subsurfaceScattering.subsurface") subsurface.mark(headId, { color = { 1, 0.3, 0.16 }, radius = 0.02 }) subsurface.unmark(headId) --> true when it had been marked subsurface.marked(headId) --> { color, radius }, or nil subsurface.list() --> every entity scattering, sorted subsurface.groups() --> the marked set gathered by what it scatters subsurface.setStrength(0.7) --> how much of the spread reaches the frame subsurface.active() --> is the pass running subsurface.clear() --> unmark everything, release the pass ``` `mark` on an entity that is already marked replaces what it scatters. A radius below zero is an error rather than a silent clamp, and an entity that does not exist is an error rather than a mark that never draws. The pass is created with the first mark and released with the last. `groups` is what the render feature draws from: meshes sharing a tint and a radius are one draw, so per-entity scattering costs one pass per distinct setting rather than one per mesh. It also drops entities that have since been despawned, so a removed character does not keep its group alive. For scattering a scene should simply have, author the `SubsurfaceScattering` component instead — same settings, persists with the scene, edits live in the inspector. The full description of the knobs and how the passes work is in the package readme: `guides { path = "systems/subsurfaceScattering" }`.

# ScreenSpaceReflections Reflections off the scene's own drawn frame, as a one-feature component. A scene lists its features together, each with its settings, on `RenderFeatures` (`{ feature = "@builtin::systems.reflections.ssr", settings = { ... } }`); this component carries the same knobs as fields for one feature. ```lua local id = entity.spawn("reflections").id entity(id).component.add("ScreenSpaceReflections", { intensity = 1.0, maxDistance = 40, quality = "high", }) ``` Polished floors start reflecting what stands on them, wet ground reflects what is above it, and metal picks up its surroundings — all from geometry the camera can already see, with nothing authored per surface. Roughness decides who gets them. A screen-space ray traces one direction, which is a mirror; `roughnessCutoff` is where that stops being a fair stand-in for a surface's real lobe, and past it the pass leaves the surface alone. Every field is live: edit one in the inspector and the reflections follow. Setting `intensity` to 0 turns them off without losing the rest of the settings. How much a reflection shows through is the surface's own Fresnel term, so metal takes almost all of it and a dielectric floor takes a few percent head-on and more at a grazing angle — the same way a wet road reads dry underfoot and mirror-like down the street. For code that adjusts reflections at runtime, reach for `@builtin::systems.reflections.ssr` — same options, no component. The full description of what each knob does and how the passes work is in the package readme: `guides { path = "systems/reflections" }`.

# Polished floor A polished stone floor with three coloured pillars standing on it, under an afternoon sky, with screen-space reflections listed on the scene's `RenderFeatures` entity — so the floor reflects the pillars, and a player walking across it, rather than the sky alone. Load it with `scene.load("@builtin::systems.reflections.demo.polished_floor")`. Players arrive facing the pillars from floor height, which is the grazing angle a polished dielectric reflects at most strongly. ## What it shows - **The feature on one entity.** `render_features` carries a `RenderFeatures` list with `@builtin::systems.reflections.ssr` at `intensity = 1`, `maxDistance = 60`, `quality = "high"`. Delete the entity and the floor mirrors the sky alone; put it back and the pillars stand in the floor. - **Only what the camera sees.** A pillar's reflection comes from the frame the camera drew, so turning away from a pillar takes its reflection with it, and the reflection fades toward the screen edge rather than cutting off. - **The environment underneath.** Where a ray finds nothing the floor keeps the sky reflection the environment gives it, at the same mip and Fresnel weight, so the seam between the two is a change of content and not of brightness. - **Roughness decides who reflects.** The floor sits at roughness 0.06, the pillars at 0.55 — above the feature's `roughnessCutoff` — so the floor is the one surface tracing reflections in the scene. ## Contents - `floor` — a 60 m slab of `PolishedStone`, a near-black dielectric at roughness 0.06, with a collider. - `pillar_1..3` — 1.6 × 5 × 1.6 m boxes in `PillarRed`, `PillarGreen`, `PillarBlue`, sunk into the slab. - `sun`, `ambient`, `sky` — a side-lit afternoon under a `ProceduralSky`. - `render_features` — the `RenderFeatures` entity this scene exists for. - `PlayerSetups` / `Spawns` — the humanoid player on an orbital-follow camera, spawning in front of the pillars. The scene's player intent is `"spawns"`. ## Entry point - `entrypoint.luau` — nothing to set up: the reflections run from the `RenderFeatures` entity the moment the scene loads.

# ssr Screen-space reflections — polished floors reflect what stands on them, from the frame the engine has already drawn. ```lua local ssr = require("@builtin::systems.reflections.ssr") ssr.set({ intensity = 1, maxDistance = 40, quality = "high" }) ssr.get() --> the settings in force ssr.active() --> are the reflection passes running ssr.clear() --> off, settings kept for the next set() ``` `set` takes any subset — omitted fields keep their current value, so adjusting one knob does not mean restating the rest. An `intensity` of 0 turns reflections off and releases the passes rather than running them at zero strength. `roughnessCutoff` is the field that decides who gets reflections at all. A screen-space ray traces one direction, which describes a mirror; past the cutoff a real surface scatters over a lobe too wide for one ray to stand in for, and the pass leaves those surfaces alone. `maxDistance` and `quality` trade against each other. Quality sets how many steps the march spends, so a long distance at a low quality samples coarsely — reflections thin out at range rather than disappearing, because refinement adapts to the step size on its own. For reflections a scene should simply have, author the `ScreenSpaceReflections` component instead — it carries the same settings, persists with the scene, and edits live in the inspector. This module is for code that changes reflections at runtime: a quality slider, a cutscene, weather turning pavement wet. The full description of what each knob does and how the passes work is in the package readme: `guides { path = "systems/reflections" }`.

# ssr The render feature behind `ScreenSpaceReflections` and `@builtin::systems.reflections.ssr`. One compute pass runs at the `afterDepthPrepass` seam, once the visibility raster has laid the frame's depth and before anything shades: | order | pass | output | |---|---|---| | 60 | `ssr_trace` | reflected colour plus a confidence weight, per pixel, into `@scene.reflection` | That channel is what a material's environment term reads the same frame, at its own pixel: the traced reflection stands in for the probes and the sky to the degree the trace trusts it, and the material's own Fresnel, roughness and tint weigh it into the pixel the way they weigh any environment. Nothing here touches the lit picture. The trace marches against this frame's depth, which the visibility raster has just written, so the reflection stands where the camera is now. What it reads about the surfaces — the reflecting surface's normal and roughness, the hit's normal and its colour — comes from the previous frame: the G-buffer as that frame left it (`readsPrevious`), and `@scene.colorHistory`, the light it ended with, each reprojected through the previous view-projection `@frame.camera` carries in its rows `[5..9)`. A point the previous frame did not show reflects its environment alone. ## The march `ssr_trace` reflects the view ray about the surface normal and walks it through the depth buffer. Steps are uniform in **screen** space, not world space. A ray heading toward the horizon covers enormous world distance across a few pixels, so stepping in world units there means either missing every thin occluder near the camera or spending the whole budget on distance nothing can be seen at. The world parameter is recovered from the screen parameter through `1/w`, which is what interpolates linearly under perspective. At each step the ray's world position is compared against the world position reconstructed from the depth sample under it. Comparing in world space is what lets `thickness` mean a distance in world units rather than a depth-buffer epsilon whose meaning changes with range. The march looks only for the **crossing** — where the ray first passes behind the depth buffer. Thickness is tested after bisecting that crossing, not during the march: one march step covers roughly as much depth as a surface is thick, so a ray tested during the march can jump from in front of a surface to well behind it without ever landing inside it. Bisection runs for whichever is larger, the quality tier's budget or however many halvings bring one march step under `thickness`. A coarse march that stopped bisecting early would leave the crossing bracketed more loosely than a surface is thick, and every hit would then fail the thickness test — long-range reflections would vanish outright instead of thinning. A hit is rejected when the surface it landed on faces along the ray, because what is on screen there is that surface's far side. ## What the channel holds `ssr_out` is `@scene.reflection`: linear radiance in `.rgb`, and in `.a` the confidence — the edge fade, the range fade, how squarely the ray carried on into the scene, and `intensity`, multiplied — so `intensity` is how much of the trace reaches the picture and a miss is a zero the material reads as "the environment alone". The channel is cleared at the top of every scene render this feature does not run for, so such a frame reflects the environment alone too. The trace reads the light the previous frame ended with, so it runs on the lit channel alone (`debugChannel = 0`); a camera drawing a diagnostic pass is drawn lit first, unpresented, so the trace runs for where that camera stands, and the diagnostic reads the channel traced for it. The cutoff exists because a single ray describes a mirror: past it the lobe a rough surface gathers over is wider than one ray can stand in for, and the material keeps the prefiltered environment it already has.

# ssr_common The screen-space reflection passes' shared ground: the view-space reconstruction from depth, and the ray-to-screen projection the march steps along. Included with `#include "@builtin::systems.reflections.ssr_common"`.

# ssr_trace Marches a reflection ray through the depth buffer and reports where it hit. ## Includes - `ssr_common` ## Bindings | name | kind | |------|------| | `scene_color` | `texture2d` | | `scene_depth` | `texture_depth` | | `scene_normal` | `texture2d` | | `scene_material` | `texture2d` (`sample: uint`) | | `frame_cam` | `buffer` | | `ssr_params` | `buffer` | | `ssr_out` | `storage2d (rgba16f)` |

# ParticipatingMedium Marks its entity as a volume of fog, smoke, dust or steam — something light has to travel through. What is behind the volume comes out dimmer than what is beside it, and overlapping volumes stack. ```luau local id = entity.spawn("fog_bank").id entity(id).component.add("ParticipatingMedium", { sizeX = 30, sizeY = 8, sizeZ = 30, density = 0.15, }) ``` ## Fields | Field | Meaning | |---|---| | `shape` | `"box"` (default) or `"sphere"` | | `density` | Extinction per world unit. `0` releases the medium. | | `sizeX` / `sizeY` / `sizeZ` | Half-extents, for a box | | `radius` | Radius, for a sphere | `density` is the physical knob: a ray crossing `d` world units of a medium of density `k` leaves with `exp(-k * d)` of the light it entered with. A 20-unit bank at `0.15` therefore passes about 5% of the light straight through it. The entity's position places the volume; move the entity and the shadow moves with it. ## Notes - The light-space map is sized to the bounding sphere of everything registered. A small bank sharing a scene with a very large one lands on few texels — set `extent` and `centre` through `mediaTransmittance.set` to bias the map toward the region you care about. - Attenuation applies to surfaces. The sky keeps its own colour. - The attenuated light is the sun's: `sunDirection` sets which way the map's rays travel. See `mediaTransmittance` for the scene-wide settings and the direct API.