Threejs Fundamentals

Three.js Fundamentals

Use this skill for the rendering foundation of a general Three.js web experience. For a playable game's system, lifecycle, or release work, use web-game-development; for a narrowly scoped rendering concern, route to the matching threejs-* skill.

When to use this skill

• Set up or repair a scene, camera, renderer, canvas ownership, or animation loop
• Choose perspective versus orthographic projection or correct world/local transforms
• Make rendering responsive, color-managed, and safe on high-DPI displays
• Diagnose blank scenes, clipped content, wrong camera framing, or leaking GPU resources

Instructions

Step 1: Establish the project contract

1. Read the installed three version and existing renderer/canvas ownership before changing imports or initialization.
2. Keep one owner for the render loop and resize listener. Framework wrappers such as React Three Fiber own those lifecycle concerns; do not add a competing raw loop.
3. Confirm the render backend before using backend-specific APIs. This skill defaults to WebGLRenderer; verify WebGPU patterns against the installed Three.js revision.

Step 2: Build the smallest visible scene

Use an explicit scene, camera, renderer, one lit mesh, and a render loop before layering in loaders, shaders, or post-processing.

import * as THREE from "three";

const width = window.innerWidth;
const height = window.innerHeight;

const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(50, width / height, 0.1, 100);
camera.position.set(0, 1, 4);

const renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setSize(width, height);
renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2));
renderer.outputColorSpace = THREE.SRGBColorSpace;

const mesh = new THREE.Mesh(
  new THREE.BoxGeometry(),
  new THREE.MeshStandardMaterial({ color: 0x4f8cff }),
);
scene.add(new THREE.HemisphereLight(0xffffff, 0x334455, 2));
scene.add(mesh);

function render() {
  renderer.render(scene, camera);
  requestAnimationFrame(render);
}
render();

Use a Group to give a feature one transform root. Change position, quaternion, or scale intentionally; local coordinates compose through parents, while world-space queries require updateWorldMatrix when the scene has not rendered yet.

Step 3: Handle resize and disposal explicitly

function resize(width, height) {
  camera.aspect = width / height;
  camera.updateProjectionMatrix();
  renderer.setSize(width, height, false);
}

function disposeObject(root) {
  root.traverse((object) => {
    object.geometry?.dispose();
    const materials = Array.isArray(object.material)
      ? object.material
      : [object.material];
    for (const material of materials) material?.dispose();
  });
}

Dispose textures and render targets owned by the feature as well. Do not dispose shared resources until every consumer is gone.

Step 4: Verify observable rendering behavior

• Confirm a visible mesh and stable camera framing at the intended canvas size.
• Resize through narrow, wide, and high-DPI cases; the drawing buffer must not stretch.
• Check the browser console for WebGL warnings and inspect renderer.info only as a diagnostic, not as a test oracle.
• Run the repository's build, typecheck, and relevant visual/browser test when present.

Decision guide

Examples

Perspective product view

Use a PerspectiveCamera for a physically familiar object view. Set a deliberately small near plane only when needed; an unnecessarily tiny near value wastes depth precision and causes z-fighting.

Isometric-like board view

Use an OrthographicCamera when scale must remain constant across depth. Recalculate left/right/top/bottom from aspect ratio on resize, then call updateProjectionMatrix().

Best practices

1. Keep one requestAnimationFrame owner per canvas.
2. Clamp pixel ratio; unbounded device pixel ratio is a silent GPU-cost multiplier.
3. Use MeshStandardMaterial plus intentional lighting for normal PBR work instead of compensating for an unlit scene with arbitrary color values.
4. Keep camera clipping planes as tight as the scene permits.
5. Pair every feature-owned GPU allocation with a teardown path.

References

• Three.js Fundamentals source coverage
• Three.js documentation
• Three.js manual: creating a scene