threejs-loaders

What this skill does

# Three.js Loaders

## When to Use
- You need to load models, textures, HDR assets, or other external resources in Three.js.
- The task involves `GLTFLoader`, `TextureLoader`, loading progress, or async asset orchestration.
- You are managing scene assets rather than authoring geometry or shaders directly.

## Quick Start

```javascript
import * as THREE from "three";
import { GLTFLoader } from "three/addons/loaders/GLTFLoader.js";

// Load GLTF model
const loader = new GLTFLoader();
loader.load("model.glb", (gltf) => {
  scene.add(gltf.scene);
});

// Load texture
const textureLoader = new THREE.TextureLoader();
const texture = textureLoader.load("texture.jpg");
```

## LoadingManager

Coordinate multiple loaders and track progress.

```javascript
const manager = new THREE.LoadingManager();

// Callbacks
manager.onStart = (url, loaded, total) => {
  console.log(`Started loading: ${url}`);
};

manager.onLoad = () => {
  console.log("All assets loaded!");
  startGame();
};

manager.onProgress = (url, loaded, total) => {
  const progress = (loaded / total) * 100;
  console.log(`Loading: ${progress.toFixed(1)}%`);
  updateProgressBar(progress);
};

manager.onError = (url) => {
  console.error(`Error loading: ${url}`);
};

// Use manager with loaders
const textureLoader = new THREE.TextureLoader(manager);
const gltfLoader = new GLTFLoader(manager);

// Load assets
textureLoader.load("texture1.jpg");
textureLoader.load("texture2.jpg");
gltfLoader.load("model.glb");
// onLoad fires when ALL are complete
```

## Texture Loading

### TextureLoader

```javascript
const loader = new THREE.TextureLoader();

// Callback style
loader.load(
  "texture.jpg",
  (texture) => {
    // onLoad
    material.map = texture;
    material.needsUpdate = true;
  },
  undefined, // onProgress - not supported for image loading
  (error) => {
    // onError
    console.error("Error loading texture", error);
  },
);

// Synchronous (returns texture, loads async)
const texture = loader.load("texture.jpg");
material.map = texture;
```

### Texture Configuration

```javascript
const texture = loader.load("texture.jpg", (tex) => {
  // Color space (important for color accuracy)
  tex.colorSpace = THREE.SRGBColorSpace; // For color/albedo maps
  // tex.colorSpace = THREE.LinearSRGBColorSpace;  // For data maps (normal, roughness)

  // Wrapping
  tex.wrapS = THREE.RepeatWrapping;
  tex.wrapT = THREE.RepeatWrapping;
  // ClampToEdgeWrapping, RepeatWrapping, MirroredRepeatWrapping

  // Repeat/offset
  tex.repeat.set(2, 2);
  tex.offset.set(0.5, 0.5);
  tex.rotation = Math.PI / 4;
  tex.center.set(0.5, 0.5);

  // Filtering
  tex.minFilter = THREE.LinearMipmapLinearFilter; // Default
  tex.magFilter = THREE.LinearFilter; // Default
  // NearestFilter - pixelated
  // LinearFilter - smooth
  // LinearMipmapLinearFilter - smooth with mipmaps

  // Anisotropic filtering (sharper at angles)
  tex.anisotropy = renderer.capabilities.getMaxAnisotropy();

  // Flip Y (usually true for standard textures)
  tex.flipY = true;

  tex.needsUpdate = true;
});
```

### CubeTextureLoader

For environment maps and skyboxes.

```javascript
const loader = new THREE.CubeTextureLoader();

// Load 6 faces
const cubeTexture = loader.load([
  "px.jpg",
  "nx.jpg", // positive/negative X
  "py.jpg",
  "ny.jpg", // positive/negative Y
  "pz.jpg",
  "nz.jpg", // positive/negative Z
]);

// Use as background
scene.background = cubeTexture;

// Use as environment map
scene.environment = cubeTexture;
material.envMap = cubeTexture;
```

### HDR/EXR Loading

```javascript
import { RGBELoader } from "three/addons/loaders/RGBELoader.js";
import { EXRLoader } from "three/addons/loaders/EXRLoader.js";

// HDR
const rgbeLoader = new RGBELoader();
rgbeLoader.load("environment.hdr", (texture) => {
  texture.mapping = THREE.EquirectangularReflectionMapping;
  scene.environment = texture;
  scene.background = texture;
});

// EXR
const exrLoader = new EXRLoader();
exrLoader.load("environment.exr", (texture) => {
  texture.mapping = THREE.EquirectangularReflectionMapping;
  scene.environment = texture;
});
```

### PMREMGenerator

Generate prefiltered environment maps for PBR.

```javascript
import { RGBELoader } from "three/addons/loaders/RGBELoader.js";

const pmremGenerator = new THREE.PMREMGenerator(renderer);
pmremGenerator.compileEquirectangularShader();

new RGBELoader().load("environment.hdr", (texture) => {
  const envMap = pmremGenerator.fromEquirectangular(texture).texture;

  scene.environment = envMap;
  scene.background = envMap;

  texture.dispose();
  pmremGenerator.dispose();
});
```

## GLTF/GLB Loading

The most common 3D format for web.

```javascript
import { GLTFLoader } from "three/addons/loaders/GLTFLoader.js";

const loader = new GLTFLoader();

loader.load("model.glb", (gltf) => {
  // The loaded scene
  const model = gltf.scene;
  scene.add(model);

  // Animations
  const animations = gltf.animations;
  if (animations.length > 0) {
    const mixer = new THREE.AnimationMixer(model);
    animations.forEach((clip) => {
      mixer.clipAction(clip).play();
    });
  }

  // Cameras (if any)
  const cameras = gltf.cameras;

  // Asset info
  console.log(gltf.asset); // Version, generator, etc.

  // User data from Blender/etc
  console.log(gltf.userData);
});
```

### GLTF with Draco Compression

```javascript
import { GLTFLoader } from "three/addons/loaders/GLTFLoader.js";
import { DRACOLoader } from "three/addons/loaders/DRACOLoader.js";

const dracoLoader = new DRACOLoader();
dracoLoader.setDecoderPath(
  "https://www.gstatic.com/draco/versioned/decoders/1.5.6/",
);
dracoLoader.preload();

const gltfLoader = new GLTFLoader();
gltfLoader.setDRACOLoader(dracoLoader);

gltfLoader.load("compressed-model.glb", (gltf) => {
  scene.add(gltf.scene);
});
```

### GLTF with KTX2 Textures

```javascript
import { GLTFLoader } from "three/addons/loaders/GLTFLoader.js";
import { KTX2Loader } from "three/addons/loaders/KTX2Loader.js";

const ktx2Loader = new KTX2Loader();
ktx2Loader.setTranscoderPath(
  "https://cdn.jsdelivr.net/npm/[email protected]/examples/jsm/libs/basis/",
);
ktx2Loader.detectSupport(renderer);

const gltfLoader = new GLTFLoader();
gltfLoader.setKTX2Loader(ktx2Loader);

gltfLoader.load("model-with-ktx2.glb", (gltf) => {
  scene.add(gltf.scene);
});
```

### GLTF with Meshopt Compression (r183)

```javascript
import { GLTFLoader } from "three/addons/loaders/GLTFLoader.js";
import { MeshoptDecoder } from "three/addons/libs/meshopt_decoder.module.js";

const gltfLoader = new GLTFLoader();
gltfLoader.setMeshoptDecoder(MeshoptDecoder);

gltfLoader.load("compressed-model.glb", (gltf) => {
  scene.add(gltf.scene);
});
```

**KHR_meshopt_compression** is an alternative to Draco that often provides better compression for animated meshes and preserves mesh topology.

### Process GLTF Content

```javascript
loader.load("model.glb", (gltf) => {
  const model = gltf.scene;

  // Enable shadows
  model.traverse((child) => {
    if (child.isMesh) {
      child.castShadow = true;
      child.receiveShadow = true;
    }
  });

  // Find specific mesh
  const head = model.getObjectByName("Head");

  // Adjust materials
  model.traverse((child) => {
    if (child.isMesh && child.material) {
      child.material.envMapIntensity = 0.5;
    }
  });

  // Center and scale
  const box = new THREE.Box3().setFromObject(model);
  const center = box.getCenter(new THREE.Vector3());
  const size = box.getSize(new THREE.Vector3());

  model.position.sub(center);
  const maxDim = Math.max(size.x, size.y, size.z);
  model.scale.setScalar(1 / maxDim);

  scene.add(model);
});
```

## Other Model Formats

### OBJ + MTL

```javascript
import { OBJLoader } from "three/addons/loaders/OBJLoader.js";
import { MTLLoader } from "three/addons/loaders/MTLLoader.js";

const mtlLoader = new MTLLoader();
mtlLoader.load("model.mtl", (materials) => {
  materials.preload();

  const objLoader = new OBJLoader();
  objLoader.setMaterials(materials);