---
title: "3D model files (.glb, .obj): API"
package: "@phaser-ae/model-files-3d"
tier: Free
version: 3.0.0-1
released: 2026-10-19
updated: 2026-10-20
description: "Loads model files made by an artist, glTF binary and Wavefront OBJ, as meshes the 3D world can spawn, with node and skinned animation."
url: https://phaser.io/packs/model-files-3d/api
site: Phaser - https://phaser.io
---

# 3D model files (.glb, .obj): API

`@phaser-ae/model-files-3d` — Load authored model files (.glb, .obj) as meshes, with node and skinned animation; for models built from data, use model-3d.

## The pack

### `modelFiles3d`

```ts
function modelFiles3d(): Pack<{ modelFiles: ModelFiles3dApi }>
```

The `model-files-3d` pack: `.glb` files as meshes. Needs a 3D world to draw them and the kernel loader to
fetch them. Headless (no image decoding) a model still loads and spawns — it simply wears no texture.

## Functions

### `composeWorlds`

```ts
function composeWorlds( parents: Int32Array | number[], locals: Float32Array, worlds: Float32Array, ): void
```

Compose world matrices for every node from local matrices. `parents[i]` is
the parent node index or -1 for roots — parents may appear ANYWHERE in the
array (glTF imposes no parent-before-child order), so nodes are resolved
iteratively until every one has a resolved parent. locals and worlds are
16-floats-per-node arrays; worlds must not alias locals.

### `decomposeTRS`

```ts
function decomposeTRS(m: Float32Array): { t: [number, number, number]; e: [number, number, number]; // [yaw, pitch, roll] s: [number, number, number]; }
```

Decompose an affine TRS matrix (glTF forbids skew) into translation, scale
and Euler angles in the ENGINE's rotation order: the mesh shader applies
roll (Z), then pitch (X), then yaw (Y) — R = Ry(yaw)·Rx(pitch)·Rz(roll) —
so writing these onto a mesh's yaw/pitch/roll reproduces the matrix's
orientation exactly. Same convention (gimbal branch included) as
physics3d's quatToEuler: at pitch = ±90° roll is folded into yaw. Scale is
per-column length; a negative determinant folds into the sign of s.z.

### `jointPalette`

```ts
function jointPalette(skin: GlbSkinOut, worlds: Float32Array, out: Float32Array): void
```

palette[j] = worlds[skin.joints[j]] × inverseBind[j] — 16 floats per joint
into `out`. Allocation-free hot path, called per frame per skinned model.

### `mat4MulTo`

```ts
function mat4MulTo(a: Float32Array, b: Float32Array, out: Float32Array): void
```

out = a × b, allocation-free (out must not alias a or b). Column-major.

### `parseGlb`

```ts
function parseGlb(buffer: ArrayBuffer): GlbData
```

Parses a GLB (glTF 2.0 Binary) file into renderer-ready data. Pure: no DOM,
no GPU, no fetch. Static primitives come out world-baked; animated or
skinned content stays unbaked, with the rig on `rig`. Throws on a malformed file, on one that is Draco- or
meshopt-compressed (this reader decodes neither), on one that requires another extension it does not implement,
and on sparse accessors or data outside the GLB's own BIN chunk.

### `parseMtl`

```ts
function parseMtl(text: string): Record<string, ObjMaterial>
```

Parse a .mtl file into materials by name.

### `parseObj`

```ts
function parseObj(text: string): ObjData
```

Parse a .obj file into per-material triangle soups.

### `quatSlerp`

```ts
function quatSlerp( ax: number, ay: number, az: number, aw: number, bx: number, by: number, bz: number, bw: number, t: number, ): [number, number, number, number]
```

Shortest-path spherical lerp between quats a and b (components, not
objects — the hot path never allocates inputs). When the quats are
near-parallel the sin() denominator degenerates, so we fall back to
normalized lerp, which is indistinguishable there.

### `sampleChannel`

```ts
function sampleChannel(ch: GlbChannel, tt: number, out: Float32Array): void
```

Sample one animation channel at time `tt` (caller pre-wraps for looping)
into `out` (3 floats for translation/scale, 4 for rotation). Binary-searches
the keyframe span; STEP holds the left key, LINEAR lerps (slerp for
rotation), CUBICSPLINE reads the middle element of each in/value/out triplet
and lerps linearly between keys. Clamps outside the keyframe range.

### `skinInto`

```ts
function skinInto( rest: Float32Array, joints: Uint16Array, weights: Float32Array, palette: Float32Array, out: Float32Array, ): void
```

CPU-skin a stride-8 vertex soup: each position by the weighted palette matrices, each normal by their
rotation only. This is what puts a skinned pose on screen without a second render pipeline; a vertex-shader
skin is the same maths moved onto the GPU, and is the optimisation this leaves on the table.

### `trsToMat4`

```ts
function trsToMat4( t: readonly number[], r: readonly number[], s: readonly number[], out?: Float32Array, ): Float32Array
```

Bake translation + quaternion + scale into a column-major mat4 (T·R·S —
scale first, then rotate, then translate; same convention as math3d).

## Classes

### `AnimMixer`

```ts
class AnimMixer
```

The pure clip mixer: tracks the active clip plus an optional crossfade from
the previous one. Every update(dt) advances time, samples each animated
channel, blends poses during a fade (lerp t/s, slerp r), bakes local
matrices and composes world matrices. Nodes no clip ever animates keep
their rest matrices, computed once. All per-frame work is allocation-free.

- `readonly anims: readonly string[]` — Clip names, in rig order — play() accepts a name or this index.
- `readonly locals: Float32Array` — Local (16/node) and world (16/node) matrices, rebuilt by update().
- `readonly worlds: Float32Array` — The composed world matrices, 16 floats per node, rebuilt by update().
- `time: number` — Seconds into the current clip.
- `playing: boolean` — True while a clip is active (one-shots flip to false when they finish).
- `done: boolean` — One-shot finished — sticky until the next play().
- `constructor(rig: GlbRig)`
- `play(clip: string | number, opts: { loop?: boolean; fade?: number } = {}): void` — Start a clip by name or index. Crossfades from the current clip over `fade` seconds (0 = hard cut). Unknown names are ignored.
- `seek(t: number): void` — Jump the current clip to `t` seconds, wrapped into its duration when it loops. `time` is only a MIRROR of the playing clip's own clock, rebuilt by every update — assigning it looks like it works and is overwritten on the next frame. This is the real seek, and it is what phasing a crowd off each other needs.
- `update(dt: number): void` — Advance by dt seconds and rebuild locals + worlds. Honours `playing`: set it false to FREEZE the pose (walk → idle), true to resume.

## Types

### `GlbAnimOut`

```ts
interface GlbAnimOut
```

One animation: a named set of channels and its total length.

- `name: string` — The animation name — 'anim0', 'anim1'… when the file gives none.
- `duration: number` — The animation length, in seconds — the latest end time across the channels.
- `channels: GlbChannel[]` — The channels this animation drives.

### `GlbChannel`

```ts
interface GlbChannel
```

One animation channel: keyframes that drive one property of one node.

- `node: number` — The target node index into rig.nodes.
- `path: 'translation' | 'rotation' | 'scale'` — Which node property the channel drives.
- `interpolation: 'LINEAR' | 'STEP' | 'CUBICSPLINE'` — The glTF sampler interpolation mode.
- `times: Float32Array` — The key times, in seconds, ascending.
- `values: Float32Array` — Packed values: 3 floats per key (t/s) or 4 (rotation). For CUBICSPLINE the raw inTangent/value/outTangent triplets are packed as authored (3× the element count per key) — the runtime samples the middle element.

### `GlbData`

```ts
interface GlbData
```

The full result of `parseGlb` — everything the renderer needs from one GLB file.

- `primitives: GlbPrimitiveOut[]` — The expanded mesh primitives, one per glTF primitive.
- `materials: GlbMaterial[]` — The materials the primitives index into.
- `images: GlbImage[]` — The embedded texture images the materials index into.
- `bounds: { min: [number, number, number]; max: [number, number, number] }` — The world-space bounding box over all primitives.
- `rig: GlbRig | null` — Node hierarchy + animations + skins — null when the file has neither animations nor skins (everything baked, nothing to drive).

### `GlbImage`

```ts
interface GlbImage
```

One embedded texture image — the raw encoded bytes, not decoded pixels.

- `mimeType: string` — The image format: 'image/png' or 'image/jpeg'.
- `bytes: Uint8Array` — The encoded image bytes — a view into the file's BIN chunk, not a copy.

### `GlbMaterial`

```ts
interface GlbMaterial
```

One material record — the metallic-roughness factors and texture indices the renderer consumes.

- `name: string` — The material name from the file — 'material0', 'material1'… when the file gives none.
- `color: [number, number, number, number]` — baseColorFactor rgba (default [1,1,1,1]).
- `metallic: number` — metallicFactor (default 1 per spec).
- `rough: number` — roughnessFactor (default 1).
- `colorImage?: number` — images[] index for baseColorTexture, if any.
- `mrImage?: number` — metallicRoughness texture image index (glTF: g = rough, b = metallic — MULTIPLIES the factors). DamagedHelmet-class models keep all their material variation here.
- `normalImage?: number` — images[] index for normalTexture, if any.
- `normalScale?: number` — normalTexture.scale (default 1), only when normalImage present.
- `emissive?: [number, number, number]` — emissiveFactor if non-zero.

### `GlbNodeOut`

```ts
interface GlbNodeOut
```

One node of the retained hierarchy, with its local TRS transform.

- `name: string` — The node name from the file — 'node0', 'node1'… when the file gives none.
- `parent: number` — Parent node index, -1 for roots.
- `t: [number, number, number]` — Local TRS (matrix nodes are decomposed — glTF forbids skew so the decomposition is exact).
- `r: [number, number, number, number]` — The local rotation, as a quaternion x, y, z, w.
- `s: [number, number, number]` — The local scale, per axis.

### `GlbPrimitiveOut`

```ts
interface GlbPrimitiveOut
```

One mesh primitive, expanded to a renderer-ready triangle soup.

- `verts: Float32Array` — NON-INDEXED triangle soup, stride 8: pos(3) normal(3) uv(2). When `baked`, the owning node's WORLD transform is applied to positions and (inverse-transpose-rotated, renormalised) normals; otherwise verts are as authored — node-local, or skin-space for skinned primitives.
- `material: number | null` — materials[] index or null.
- `node: number` — Owning node index into rig.nodes (always set, even when rig is null).
- `skin: number | null` — skins[] index, or null when the primitive is not skinned.
- `baked: boolean` — true = verts carry the world transform (the static fast path).
- `joints?: Uint16Array` — 4 joint indices per vertex (into skins[skin].joints), expanded non-indexed like verts. Only present when skinned.
- `weights?: Float32Array` — 4 weights per vertex, normalized to sum 1 (degenerate all-zero quads become [1,0,0,0]). Only present when skinned.

### `GlbRig`

```ts
interface GlbRig
```

The retained animation data: node hierarchy, animations and skins, for the runtime to sample.

- `nodes: GlbNodeOut[]` — The full node hierarchy, in glTF node order.
- `anims: GlbAnimOut[]` — The animations, each with its sampled channels.
- `skins: GlbSkinOut[]` — The skins the skinned primitives index into.

### `GlbSkinOut`

```ts
interface GlbSkinOut
```

One skin: the joint nodes and their inverse bind matrices.

- `joints: number[]` — The joint list, as indices into rig.nodes.
- `inverseBind: Float32Array` — The inverse bind matrices — 16 floats per joint, column-major.

### `Model`

```ts
interface Model
```

A loaded model: its parts, and the size it was before being fitted to the unit box.

- `readonly key: string` — The key it was loaded under.
- `readonly parts: ReadonlyArray<ModelPart>` — One part per material.
- `readonly size: { x: number; y: number; z: number }` — The model's size in its own file's units, before unit-fitting — multiply by it to restore real scale.
- `readonly triangles: number` — Triangles across every part.
- `readonly rig: GlbRig | null` — The node hierarchy, animations and skins, or null when the file has none.
- `readonly fit: { scale: number; cx: number; cy: number; cz: number }` — The unit-fit that was baked into the vertices, so an animated pose can be put through the same one.

### `ModelFiles3dApi`

```ts
interface ModelFiles3dApi
```

`game.modelFiles`.

- `load(key: string, url: string): Promise<Model>` — Load a .glb or .obj and register its meshes — the extension decides. Resolves to the model; loading the same key twice returns the first.
- `add(key: string, buffer: ArrayBuffer): Model` — Turn an already-fetched .glb buffer into a model — for a file that arrived some other way.
- `addObj(key: string, objText: string, mtlText?: string): Model` — Turn already-fetched OBJ text (and optionally its MTL) into a model.
- `get(key: string): Model | undefined` — A loaded model by key, or undefined.
- `readonly keys: ReadonlyArray<string>` — Every loaded key.
- `spawn(key: string, spec?: ModelSpawnSpec): ModelHandle` — Spawn a loaded model. Throws if the key is not loaded.

### `ModelHandle`

```ts
interface ModelHandle
```

A spawned model. Its parts are ordinary roster objects that all share one origin (the file's transforms
are baked into the vertices), so setting a pose here sets the same pose on each — which is why a model
needs no parenting to move as one thing. A NODE-ANIMATED part is the one exception: its node's own moving
transform rides on the handle's pose (the model's yaw turns a door's offset, not just the door), and the
handle keeps it composed whenever x, y, z, yaw, pitch, roll or size is set.

- `readonly parts: ReadonlyArray<Handle>` — The roster objects, one per part.
- `x: number` — World x.
- `y: number` — World y.
- `z: number` — World z.
- `yaw: number` — Yaw, radians.
- `pitch: number` — Pitch, radians.
- `roll: number` — Roll, radians.
- `size: number` — Size in world units.
- `readonly alive: boolean` — Whether every part is still alive.
- `visible: boolean` — Show or hide the whole model.
- `kill(): void` — Remove every part.
- `readonly clips: ReadonlyArray<string>` — The animation names this model carries, in file order.
- `play(clip: string | number, opts?: { loop?: boolean; speed?: number; fade?: number; at?: number }): void` — Play a clip by name or index; a `fade` crossfades from whatever is playing, and `at` starts it that many seconds in. `at` is how a CROWD stops marching in lockstep. Spawn eight of the same model, play the same clip on each at a different `at`, and they read as eight people rather than one person copied — it is the cheapest thing that buys that, and without it the only alternative is eight models.
- `stop(): void` — Stop animating and freeze the pose where it is (the model does not return to its rest pose).
- `readonly playing: string | null` — The clip playing now, or null.
- `time: number` — Seconds into the current clip. Settable, so a clip can be scrubbed or re-phased while it runs.
- `speed: number` — Playback speed. Default 1.

### `ModelPart`

```ts
interface ModelPart
```

One drawable piece of a loaded model: a mesh, and the material it wears.

- `readonly mesh: number` — The mesh id instances carry.
- `readonly frame: number` — Atlas frame for the base-colour texture, or 0 for none.
- `readonly color: string` — The material's base colour, css.
- `readonly alpha: number` — Below 1 the part draws in the transparent pass.
- `readonly material: number` — The registered material this part wears — its metallic, roughness, emissive and maps.
- `readonly node: number` — The rig node this part belongs to, or −1 when it was merged into the static soup.
- `readonly skin: number | null` — The skin index this part is bound to, or null when it is not skinned.
- `readonly rest?: Float32Array` — A skinned part's rest vertices, kept so it can be re-skinned every frame.
- `readonly verts: Float32Array` — This part's INTERLEAVED vertices as they were registered — position, normal and uv a vertex. Kept so a loaded model can be handed to something that needs the geometry rather than the mesh id: `vector3d.wireframe(part.verts)` turns any model into outline edges without a second loader.
- `readonly joints?: Uint16Array` — Four joint indices a vertex.
- `readonly weights?: Float32Array` — Their weights.

### `ModelSpawnSpec`

```ts
interface ModelSpawnSpec
```

What `modelFiles.spawn` takes.

- `x?: number` — World position. Default 0.
- `y?: number` — Height; y is UP. Default 0.
- `z?: number` — Depth. Default 0.
- `size?: number` — Size in world units — the model is fitted to a unit box, so this is its largest dimension. Default 1.
- `yaw?: number` — Yaw about y, radians.
- `pitch?: number` — Pitch about x, radians.
- `roll?: number` — Roll about z, radians.
- `tint?: string` — Multiply this over every part's own material colour. Default white.
- `id?: string` — Object id prefix. Default the model key.
- `layer?: LayerName` — Layer. Default the world's first.
- `tags?: string[]` — Tags put on every part.

### `ObjData`

```ts
interface ObjData
```

A parsed .obj file: triangle groups, the mtllib reference and the bounds.

- `groups: ObjGroup[]` — The per-material triangle groups, in file order.
- `mtllib: string | null` — The mtllib filename as written (may not match reality), or null.
- `bounds: { min: [number, number, number]; max: [number, number, number] }` — The axis-aligned bounds of every vertex, as min and max [x, y, z].

### `ObjGroup`

```ts
interface ObjGroup
```

One per-material triangle group in a parsed .obj file.

- `material: string | null` — usemtl name, or null before any usemtl.
- `verts: Float32Array` — Triangulated soup, stride 8: pos(3) normal(3) uv(2), CCW as authored.

### `ObjMaterial`

```ts
interface ObjMaterial
```

One material record parsed from a .mtl file, as parseMtl returns it.

- `name: string` — The newmtl name — the key usemtl lines refer to.
- `color: [number, number, number]` — Kd diffuse 0..1 (default [0.7, 0.7, 0.7]).
- `map?: string` — map_Kd path EXACTLY as written (may be broken/absolute — the loader layer decides what to do with it).
- `ns?: number` — Ns shininess if present.
- `opacity?: number` — d / (1 - Tr) opacity if present (default 1).
- `emissive?: [number, number, number]` — Ke emissive if present.

---

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