threejs（Three.js 3D 开发）

Three.js Production Patterns

Resource Cleanup

• Call .dispose() on geometries, materials, and textures before removing objects — Three.js never garbage collects GPU resources automatically
• When removing a mesh: mesh.geometry.dispose(); mesh.material.dispose(); scene.remove(mesh) — missing any step causes memory leaks
• Textures loaded via TextureLoader stay in GPU memory forever unless explicitly disposed — track and clean up on scene transitions

Render Loop

• Always use renderer.setAnimationLoop(animate) instead of manual requestAnimationFrame — it handles VR, pauses when tab is hidden, and provides proper timing
• For animations, use clock.getDelta() for frame-independent movement — raw frame counting breaks on different refresh rates

Responsive Canvas

• On window resize, update both camera aspect AND renderer size: camera.aspect = width/height; camera.updateProjectionMatrix(); renderer.setSize(width, height)
• Missing updateProjectionMatrix() after aspect change causes stretched/squished rendering
• Use renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2)) — values above 2 kill performance with minimal visual benefit

Imports and Setup

• OrbitControls and other addons: import { OrbitControls } from 'three/addons/controls/OrbitControls.js' — the path varies by bundler, check your setup
• Always set controls.enableDamping = true with OrbitControls and call controls.update() in render loop — without this, damping silently fails

Lighting

• MeshBasicMaterial ignores all lights — use MeshStandardMaterial or MeshPhongMaterial for lit scenes
• Add ambient light (new THREE.AmbientLight(0xffffff, 0.5)) as baseline — scenes with only directional lights have pitch-black shadows
• HDR environment maps via PMREMGenerator give far better reflections than point lights on metallic materials

Loading Assets

• GLTFLoader is the standard for 3D models — use Draco compression for large meshes (add DRACOLoader)
• Texture loading is async — models may render black until textures load; use LoadingManager for loading screens
• CORS blocks textures from other domains — host assets on same origin or configure proper CORS headers

Camera Issues

• Default near/far planes (0.1 to 1000) cause z-fighting on large scenes — adjust to smallest range that fits your scene
• Camera inside an object renders nothing — check position after loading external models (they may have unexpected transforms)
• PerspectiveCamera FOV is vertical, not horizontal — 75 degrees is a common default

Performance

• Merge static geometries with BufferGeometryUtils.mergeBufferGeometries() — each mesh is a draw call, fewer meshes = faster
• Use InstancedMesh for many identical objects — hundreds of draw calls become one
• Set object.frustumCulled = true (default) but verify large objects aren't disappearing at edges — bounding sphere may be wrong
• Call renderer.info to debug draw calls, triangles, and textures in memory

Animation

• AnimationMixer requires mixer.update(delta) every frame with actual delta time — passing 0 or skipping frames breaks animations
• Skinned meshes (characters) need SkeletonHelper during development to debug bone issues