Threejs Scene Setup Agent Skill

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 r165+ and are verified against r184.

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 r147 the bare

specifier 'three' and 'three/addons/' must be mapped (in HTML or by a

bundler). 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

Clock for delta time.

• 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/[email protected]/build/three.module.js",
    "three/addons/": "https://cdn.jsdelivr.net/npm/[email protected]/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, 2)); // cap for perf
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 + Clock)

const clock = new THREE.Clock();

renderer.setAnimationLoop(() => {
  const dt = clock.getDelta();          // seconds since last frame
  cube.rotation.x += dt;                // frame-rate independent
  cube.rotation.y += dt * 0.7;
  renderer.render(scene, camera);
});
// renderer.setAnimationLoop(null); // stop the loop

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);
});

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 jagged on HiDPI → set renderer.setPixelRatio(...); cap it (≈2) so

4K/retina screens don't tank performance.

• OrbitControls feel dead → with enableDamping = true you must call

controls.update() every frame.

• Old tutorials use <script src="three.min.js"> → since r147 three.js ships

ES modules only; use type="module" + import maps.

References

• 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.