# Threejs Skills

> Create 3D scenes, interactive experiences, and visual effects using Three.js. Use when user requests 3D graphics, WebGL experiences, 3D visualizations, animations, or interactive 3D elements.

- Skill: `ranbot-ai/threejs-skills` (Agent Skill)
- Install (CLI): `npx skillmds add ranbot-ai/threejs-skills`
- Raw SKILL.md: https://api.skillmd.com/api/skills/ranbot-ai/threejs-skills/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: ranbot-ai (https://skillmd.com/u/ranbot-ai)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/ranbot-ai/threejs-skills

---



# Three.js Skills

Systematically create high-quality 3D scenes and interactive experiences using Three.js best practices.

## When to Use

- Requests 3D visualizations or graphics ("create a 3D model", "show in 3D")
- Wants interactive 3D experiences ("rotating cube", "explorable scene")
- Needs WebGL or canvas-based rendering
- Asks for animations, particles, or visual effects
- Mentions Three.js, WebGL, or 3D rendering
- Wants to visualize data in 3D space

## Core Setup Pattern

### 1. Essential Three.js Imports

Always use the correct CDN version (r128):

```javascript
import * as THREE from "https://cdnjs.cloudflare.com/ajax/libs/three.js/r128/three.min.js";
```

**CRITICAL**: Do NOT use example imports like `THREE.OrbitControls` - they won't work on the CDN.

### 2. Scene Initialization

Every Three.js artifact needs these core components:

```javascript
// Scene - contains all 3D objects
const scene = new THREE.Scene();

// Camera - defines viewing perspective
const camera = new THREE.PerspectiveCamera(
  75, // Field of view
  window.innerWidth / window.innerHeight, // Aspect ratio
  0.1, // Near clipping plane
  1000, // Far clipping plane
);
camera.position.z = 5;

// Renderer - draws the scene
const renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
```

### 3. Animation Loop

Use requestAnimationFrame for smooth rendering:

```javascript
function animate() {
  requestAnimationFrame(animate);

  // Update object transformations here
  mesh.rotation.x += 0.01;
  mesh.rotation.y += 0.01;

  renderer.render(scene, camera);
}
animate();
```

## Systematic Development Process

### 1. Define the Scene

Start by identifying:

- **What objects** need to be rendered
- **Camera position** and field of view
- **Lighting setup** required
- **Interaction model** (static, rotating, user-controlled)

### 2. Build Geometry

Choose appropriate geometry types:

**Basic Shapes:**

- `BoxGeometry` - cubes, rectangular prisms
- `SphereGeometry` - spheres, planets
- `CylinderGeometry` - cylinders, tubes
- `PlaneGeometry` - flat surfaces, ground planes
- `TorusGeometry` - donuts, rings

**IMPORTANT**: Do NOT use `CapsuleGeometry` (introduced in r142, not available in r128)

**Alternatives for capsules:**

- Combine `CylinderGeometry` + 2 `SphereGeometry`
- Use `SphereGeometry` with adjusted parameters
- Create custom geometry with vertices

### 3. Apply Materials

Choose materials based on visual needs:

**Common Materials:**

- `MeshBasicMaterial` - unlit, flat colors (no lighting needed)
- `MeshStandardMaterial` - physically-based, realistic (needs lighting)
- `MeshPhongMaterial` - shiny surfaces with specular highlights
- `MeshLambertMaterial` - matte surfaces, diffuse reflection

```javascript
const material = new THREE.MeshStandardMaterial({
  color: 0x00ff00,
  metalness: 0.5,
  roughness: 0.5,
});
```

### 4. Add Lighting

**If using lit materials** (Standard, Phong, Lambert), add lights:

```javascript
// Ambient light - general illumination
const ambientLight = new THREE.AmbientLight(0xffffff, 0.5);
scene.add(ambientLight);

// Directional light - like sunlight
const directionalLight = new THREE.DirectionalLight(0xffffff, 0.8);
directionalLight.position.set(5, 5, 5);
scene.add(directionalLight);
```

**Skip lighting** if using `MeshBasicMaterial` - it's unlit by design.

### 5. Handle Responsiveness

Always add window resize handling:

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

## Common Patterns

### Rotating Object

```javascript
function animate() {
  requestAnimationFrame(animate);
  mesh.rotation.x += 0.01;
  mesh.rotation.y += 0.01;
  renderer.render(scene, camera);
}
```

### Custom Camera Controls (OrbitControls Alternative)

Since `THREE.OrbitControls` isn't available on CDN, implement custom controls:

```javascript
let isDragging = false;
let previousMousePosition = { x: 0, y: 0 };

renderer.domElement.addEventListener("mousedown", () => {
  isDragging = true;
});

renderer.domElement.addEventListener("mouseup", () => {
  isDragging = false;
});

renderer.domElement.addEventListener("mousemove", (event) => {
  if (isDragging) {
    const deltaX = event.clientX - previousMousePosition.x;
    const deltaY = event.clientY - previousMousePosition.y;

    // Rotate camera around scene
    const rotationSpeed = 0.005;
    camera.position.x += deltaX * rotationSpeed;
    camera.position.y -= deltaY * rotationSpeed;
    camera.lookAt(scene.position);
  }

  previousMousePosition = { x: event.clientX, y: event.clientY };
});

// Zoom with mouse wheel
renderer.domElement.addEventListener("wheel", (event) => {
  event.preventDefault();
  camera.position.z += event.deltaY * 0.01;
  camera.position.z = Math.max(2, Math.min(20, cam