threejs

Three.js — WebGL 3D Scenes Skill

When to use

• Real 3D: product spins, interactive hero scenes, shaders/material effects, 3D data viz
• You need full control beyond “background effects”
• You can budget time for asset pipeline + performance tuning

Core mental model

• Create:
• Scene (root graph)
• Camera (Perspective/Orthographic)
• Renderer (WebGLRenderer)
• Mesh = Geometry + Material
• Lights (if using non-unlit materials)
• Render loop:
• requestAnimationFrame(animate)
• Update time-based animations, controls, mixers, then renderer.render(scene, camera)

Key APIs/patterns

• Setup:
• const renderer = new THREE.WebGLRenderer({ canvas, antialias, alpha })
• renderer.setSize(width, height, false)
• renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2))
• Camera:
• camera.aspect = width / height; camera.updateProjectionMatrix()
• Scene graph:
• scene.add(object) / object.position/rotation/scale
• Loading assets:
• GLTFLoader (models), TextureLoader (images), DRACOLoader (compressed glTF)
• Controls (common):
• OrbitControls (debug/product), PointerLockControls (FPS), custom pointer handlers
• Cleanup (important in SPAs):
• geometry.dispose(), material.dispose(), texture.dispose(), renderer.dispose()
• Remove event listeners; cancel RAF.

Common pitfalls

• Not handling resize → stretched/cropped rendering
• Too high devicePixelRatio → mobile GPU meltdown
• Leaking WebGL resources (not disposing) → crashes after route changes
• Loading huge textures/models → slow start; use compressed textures, Draco/KTX2, smaller maps
• Using too many lights/shadows → expensive; fake lighting with baked textures when possible

Quick recipes

1) Minimal spinning cube

import * as THREE from "three";

const canvas = document.querySelector("#c");
const renderer = new THREE.WebGLRenderer({ canvas, antialias: true, alpha: true });

const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(45, 1, 0.1, 100);
camera.position.set(0, 0, 4);

const geom = new THREE.BoxGeometry(1, 1, 1);
const mat = new THREE.MeshStandardMaterial({ color: 0x7c3aed });
const mesh = new THREE.Mesh(geom, mat);
scene.add(mesh);

scene.add(new THREE.AmbientLight(0xffffff, 0.8));
const dir = new THREE.DirectionalLight(0xffffff, 0.8);
dir.position.set(2, 2, 2);
scene.add(dir);

function resize() {
  const w = canvas.clientWidth;
  const h = canvas.clientHeight;
  renderer.setSize(w, h, false);
  renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2));
  camera.aspect = w / h;
  camera.updateProjectionMatrix();
}
window.addEventListener("resize", resize);
resize();

function animate(t) {
  mesh.rotation.y = t * 0.0006;
  renderer.render(scene, camera);
  requestAnimationFrame(animate);
}
requestAnimationFrame(animate);

2) Respect reduced motion

• If prefers-reduced-motion: reduce, render a still frame (no RAF) or slow updates.

What to ask the user

• Is this decorative (hero) or functional 3D (product viewer)?
• Target devices: mobile? older iPhones?
• Asset format availability (glTF, HDRI, textures) and file size constraints
• Accessibility/reduced motion requirements