Threejs FundamentalsSAFE

An agent skill published by cloudai-x.

The instruction file, verbatim from the audited commit — this is the text the model reads, and the surface the audit's instruction layer examines. Quoted here so you can judge it without cloning anything.

---
name: threejs-fundamentals
description: "Three.js scene setup: scenes and fog, cameras, the renderer and tone mapping, the animation loop, object hierarchies, transforms, core math and cleanup, on WebGL or with WebGPU and TSL. Use when creating a scene from scratch, configuring a camera or renderer, handling resize, or arranging objects."
---

# Three.js Fundamentals

Targets three.js r186. Examples use WebGLRenderer; the WebGPU and TSL section uses WebGPURenderer.

## Quick Start

```javascript
import * as THREE from "three";

const renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setPixelRatio(window.devicePixelRatio);
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

const scene = new THREE.Scene();
scene.background = new THREE.Color(0x111318);

const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
camera.position.set(0, 1.5, 5);

const cube = new THREE.Mesh(
  new THREE.BoxGeometry(1, 1, 1),
  new THREE.MeshStandardMaterial({ color: 0x3a86ff }),
);
scene.add(cube);
const light = new THREE.DirectionalLight(0xffffff, 2);
light.position.set(3, 4, 5); // shines from its position toward the origin
scene.add(light);
scene.add(new THREE.AmbientLight(0xffffff, 0.4));

const timer = new THREE.Timer();
timer.connect(document); // freezes the delta while the tab is hidden

function animate() {
  timer.update(); // advance the timer first thing each frame
  cube.rotation.y += timer.getDelta(); // seconds since the previous frame
  renderer.render(scene, camera);
}
renderer.setAnimationLoop(animate);

window.addEventListener("resize", () => {
  camera.aspect = window.innerWidth / window.innerHeight;
  camera.updateProjectionMatrix();
  renderer.setSize(window.innerWidth, window.innerHeight);
});
```

Without a bundler, the browser loads three.js as ES modules through an import map; this is the map for the WebGLRenderer examples above:

```html
<script type="importmap">
{
  "imports": {
    "three": "https://cdn.jsdelivr.net/npm/[email protected]/build/three.module.js",
    "three/addons/": "https://cdn.jsdelivr.net/npm/[email protected]/examples/jsm/"
  }
}
</script>
```

For WebGPURenderer work, map all four keys — `three.tsl.js` imports `three/webgpu`, so the map fails without that entry:

```html
<script type="importmap">
{
  "imports": {
    "three": "https://cdn.jsdelivr.net/npm/[email protected]/build/three.webgpu.js",
    "three/webgpu": "https://cdn.jsdelivr.net/npm/[email protected]/build/three.webgpu.js",
    "three/tsl": "https://cdn.jsdelivr.net/npm/[email protected]/build/three.tsl.js",
    "three/addons/": "https://cdn.jsdelivr.net/npm/[email protected]/examples/jsm/"
  }
}
</script>
```

## Scene

```javascript
const scene = new THREE.Scene();

scene.background = new THREE.Color(0x111318); // solid color
scene.fog = new THREE.Fog(0x111318, 1, 100); // linear fog: near, far
scene.fog = new THREE.FogExp2(0x111318, 0.02); // exponential fog: density (pick one)
```

- `scene.background` also accepts a `CubeTexture`, or a `Texture` whose `mapping` is `THREE.EquirectangularReflectionMapping`; a plain unmapped texture is drawn as a flat screen-filling quad, not a skybox.
- `scene.environment` lights `MeshStandardMaterial` and `MeshPhysicalMaterial` on both renderers, and `MeshLambertMaterial` and `MeshPhongMaterial` on WebGLRenderer only. `scene.environmentIntensity` scales it — `material.envMapIntensity` scales only `material.envMap`. See threejs-loaders for HDR environments.

## Cameras

### PerspectiveCamera

```javascript
// PerspectiveCamera(fov in degrees, aspect, near, far)
const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
camera.position.set(0, 5, 10);
camera.lookAt(0, 0, 0); // rotates the camera to face the target

camera.fov = 60;
camera.updateProjectionMatrix(); // required after changing fov, aspect, near or far
```

### OrthographicCamera

```javascript
// OrthographicCamera(left, right, top, bottom, near, far); frustum size in world units
const aspect = window.innerWidth / window.innerHeight;
const frustumHeight = 10;
const camera = new THREE.OrthographicCamera(
  (-frustumHeight * aspect) / 2,
  (frustumHeight * aspect) / 2,
  frustumHeight / 2,
  -frustumHeight / 2,
  0.1,
  1000,
);
// on resize: recompute left and right from the new aspect, then call camera.updateProjectionMatrix()
```

### ArrayCamera

```javascript
// Renders the scene once per sub-camera, each into its own viewport.
// Viewport units under WebGLRenderer are drawing-buffer pixels (CSS size × pixel ratio);
// WebGPURenderer multiplies CSS pixels by the pixel ratio itself.
const width = window.innerWidth;
const height = window.innerHeight;
const dpr = renderer.getPixelRatio();
const cameras = [];
for (let i = 0; i < 4; i++) {
  const subCamera = new THREE.PerspectiveCamera(75, width / height, 0.1, 100);
  subCamera.viewport = new THREE.Vector4(
    ((i % 2) * width * dpr) / 2,
    (Math.floor(i / 2) * height * dpr) / 2,
    (width * dpr) / 2,
    (height * dpr) / 2,
  );
  subCamera.position.set(-2 + (i % 2) * 4, 1.5, 6);
  subCamera.lookAt(0, 0, 0);
  subCamera.updateMatrixWorld(); // sub-cameras are not scene-graph children; update them when they move
  cameras.push(subCamera);
}
const arrayCamera = new THREE.ArrayCamera(cameras);
arrayCamera.position.set(0, 1.5, 6); // WebGLRenderer culls every viewport with this camera's frustum (fov 50, aspect 1 by default); WebGPURenderer uses each sub-camera's frustum
renderer.render(scene, arrayCamera);
```

### CubeCamera

```javascript
const cubeRenderTarget = new THREE.WebGLCubeRenderTarget(256);
const cubeCamera = new THREE.CubeCamera(0.1, 1000, cubeRenderTarget);
scene.add(cubeCamera);

const chrome = new THREE.Mesh(
  new THREE.SphereGeometry(1, 32, 16),
  new THREE.MeshStandardMaterial({ color: 0xffffff, metalness: 1, roughness: 0 }),
);
chrome.material.envMap = cubeRenderTarget.texture;
scene.add(chrome);

// 

SAFEgrade B · trust 89/100 Nothing in the source contradicts what it says it does. Grade A is reserved for packages that have also passed the behavioural sandbox.

What the source does

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none-observed

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Shell

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Dependencies

pinned

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Findings (0)

No findings outside the package's declared scope.

Gates applied: no_behavioural_pass.

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