SKILL.md

three.js Scene Setup

Create the foundation of a three.js app: module loading, the scene/camera/renderer trio, the render loop, responsive resizing, and camera controls. Patterns target r186. Read the installed three version before changing an existing project because examples and addons move across releases.

When to use

Use when bootstrapping a three.js scene, fixing a blank/black canvas, making the canvas responsive, setting up the animation loop, or adding OrbitControls.
Use when package.json depends on three and code does import * as THREE from 'three'.

When not to use: loading .gltf/.glb models or skinned animation → threejs-gltf-loading. Materials, lights, shadows, environment maps → threejs-materials-lighting. 2D rendering → pixijs-rendering.

Core workflow

Load three.js as an ES module with an import map. Since r137 the bare specifier 'three' must be resolved by an import map (in HTML) or a bundler; map 'three/addons/' too. Addons (controls, loaders) live under three/addons/....
Create the trio. A Scene (root of the graph), a PerspectiveCamera(fov, aspect, near, far) moved back from the origin, and a WebGLRenderer whose domElement is in the DOM. Set size and pixelRatio.
Add a mesh. new Mesh(geometry, material) and scene.add(mesh). With a lit material you also need a light (see threejs-materials-lighting).
Drive a render loop with renderer.setAnimationLoop(fn). It's the modern, WebXR-/WebGPU-safe replacement for hand-rolled requestAnimationFrame. Use a Timer for delta time (Clock is deprecated since r183).
Handle resize so the camera aspect and renderer match the canvas; update camera.aspect, call updateProjectionMatrix(), and renderer.setSize(...).
Add OrbitControls for orbit/pan/zoom while developing. Confirm something actually renders (a lit cube, the controls responding) before assuming success.

Patterns

1. HTML import map + module entry (no bundler)

<canvas id="c"></canvas>
<script type="importmap">
{
  "imports": {
    "three": "https://cdn.jsdelivr.net/npm/three@0.186.1/build/three.module.js",
    "three/addons/": "https://cdn.jsdelivr.net/npm/three@0.186.1/examples/jsm/"
  }
}
</script>
<script type="module" src="./main.js"></script>

With a bundler (Vite/webpack), skip the import map and just npm i three; the same import statements resolve.

2. Scene + camera + renderer

// main.js
import * as THREE from 'three';

const canvas = document.querySelector('#c');
const renderer = new THREE.WebGLRenderer({ canvas, antialias: true });
renderer.setPixelRatio(Math.min(window.devicePixelRatio, 1.5)); // starting budget; profile on target hardware
renderer.setSize(window.innerWidth, window.innerHeight);

const scene = new THREE.Scene();
scene.background = new THREE.Color(0x101018);

const camera = new THREE.PerspectiveCamera(
  60,                                   // vertical field of view (degrees)
  window.innerWidth / window.innerHeight, // aspect
  0.1,                                  // near
  100                                   // far
);
camera.position.set(3, 2, 5);
camera.lookAt(0, 0, 0);

const cube = new THREE.Mesh(
  new THREE.BoxGeometry(1, 1, 1),
  new THREE.MeshNormalMaterial()        // unlit; shows orientation without a light
);
scene.add(cube);

3. The render loop (setAnimationLoop + Timer)

const timer = new THREE.Timer();        // replaces the deprecated THREE.Clock (r183+)
timer.connect(document);                // optional: no huge delta after a hidden tab

renderer.setAnimationLoop(() => {
  timer.update();                      // use performance.now(), like visibility reset
  const dt = Math.min(Math.max(timer.getDelta(), 0), 0.1); // seconds; bound stalls and negative deltas
  cube.rotation.x += dt;                // frame-rate independent
  cube.rotation.y += dt * 0.7;
  renderer.render(scene, camera);
});
// renderer.setAnimationLoop(null); // stop the loop
// timer.dispose();                 // remove visibility listener when tearing down

In r186, visibility reset samples performance.now(). A supplied animation-frame timestamp can precede that reset and produce a negative delta. Using update() keeps the clock source consistent; the lower clamp also protects a fixed-step accumulator. Feed the bounded dt into simulation, not raw getDelta(). The 0.1-second upper bound deliberately drops excess time after a stall; tune it to the game's catch-up policy rather than using it for real-world deadlines.

4. Responsive resize

function onResize() {
  const w = window.innerWidth, h = window.innerHeight;
  camera.aspect = w / h;
  camera.updateProjectionMatrix();      // required after changing aspect
  renderer.setSize(w, h);
}
window.addEventListener('resize', onResize);

5. OrbitControls (orbit / pan / zoom)

import { OrbitControls } from 'three/addons/controls/OrbitControls.js';

const controls = new OrbitControls(camera, renderer.domElement);
controls.enableDamping = true;          // inertial feel
controls.target.set(0, 0, 0);

renderer.setAnimationLoop(() => {
  controls.update();                    // needed every frame when damping is on
  renderer.render(scene, camera);
});

6. Opting into WebGPURenderer (only when you need it)

WebGLRenderer stays the default choice for compatibility. Switch to WebGPURenderer when the project needs TSL node materials or compute shaders; it falls back to a WebGL 2 backend where WebGPU is unavailable.

// Official WebGPU examples map both "three" and "three/webgpu" to
// build/three.webgpu.js, plus "three/tsl" to build/three.tsl.js.
import * as THREE from 'three/webgpu';

const renderer = new THREE.WebGPURenderer({ antialias: true });
renderer.setPixelRatio(Math.min(window.devicePixelRatio, 1.5)); // starting budget; profile on target hardware
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
await renderer.init();                  // required before direct render()/compute()

renderer.setAnimationLoop(() => renderer.render(scene, camera));

Scenes, cameras, built-in Mesh*Materials, and most addons carry over; custom GLSL (ShaderMaterial, onBeforeCompile) does not.

7. Resolution is a performance budget

A ratio of 2 draws four times as many pixels as 1 at the same CSS size. A cap of 2 does nothing on a 2× display. Start games around 1.25–1.5, expose a resolution setting, and profile the target device; these are tuning defaults, not an FPS guarantee. Lower resolution helps fill-rate bottlenecks, not CPU-bound simulation.

For adaptive resolution, measure several seconds of frame time after assets and shader warm-up. Ignore hidden-tab intervals and loading stalls. If sustained GPU/fill-rate pressure exceeds the budget, lower the ratio in 0.25 steps to a chosen floor (for example 1), never above the device ratio or user setting. Use a cooldown and a separate recovery threshold before raising it again to avoid oscillation. Reapply the chosen ratio on display/DPR changes and resize render targets or postprocessing buffers consistently with the renderer.

Pitfalls

Failed to resolve module specifier "three" → missing import map (or bundler config). Map both "three" and "three/addons/"; addon paths must end with /.
Black canvas, no errors → camera is at the origin (inside/behind the object), or you used a lit material (MeshStandardMaterial) with no light. Move the camera back; use MeshNormalMaterial/MeshBasicMaterial to verify geometry first.
Nothing animates → you never called renderer.render inside the loop, or you call setAnimationLoop but render outside it.
Stretched / squashed view on resize → you resized the renderer but didn't update camera.aspect + updateProjectionMatrix().
Blurry or slow on HiDPI → balance sharpness against fill rate with a resolution setting. Start around 1.25–1.5; a cap of 2 still renders 4× the pixels of 1×.
Simulation freezes after restoring a tab → r186 can mix a frame timestamp with visibility-reset time. Use timer.update() and clamp simulation delta to [0, 0.1] as above so a negative delta cannot drain the fixed-step accumulator.
OrbitControls feel dead → with enableDamping = true you must call controls.update() every frame.
Old tutorials use <script src="three.min.js"> or examples/js/... → examples/js was removed in r148 and build/three.min.js in r161; use type="module" + import maps.
.render() called before the backend is initialized (WebGPURenderer) → call await renderer.init() before any direct render()/compute(), or render only from setAnimationLoop, which initializes first.
Material "ShaderMaterial" is not compatible, or an onBeforeCompile patch is ignored (WebGPURenderer) → it renders node materials only; port the effect to TSL, or stay on WebGLRenderer.

References

Primary sources: r186 Timer implementation and r186 responsive rendering manual.
For coordinate conventions, the scene-graph (Group, parent/child transforms, Object3D add/remove), OrthographicCamera for 2.5D, and disposing of geometries/materials/textures to avoid leaks, read references/scene-graph.md.

Related skills

threejs-materials-lighting — give surfaces a lit look (lights, shadows, PBR).
threejs-gltf-loading — load 3D models and play their animations.
pixijs-rendering — 2D rendering in the browser.
fps-shooter — a 3D genre template that composes three.js skills.