three.js Materials & Lighting

Make three.js surfaces look right: pick the correct material, light the scene,
enable shadows, and add image-based lighting. Patterns target r165+, verified
against r184 (lighting is physically based by default since r155).

When to use

• Use when a mesh renders black or flat, when choosing a material, adding lights,
  enabling shadows, or setting up environment-map reflections (IBL).
• Use when code constructs MeshStandardMaterial, DirectionalLight, etc., or sets
  renderer.shadowMap.enabled or scene.environment.

When not to use: the renderer/camera/loop → threejs-scene-setup. Loading
models (whose PBR materials this complements) → threejs-gltf-loading. Custom
GLSL/ShaderMaterial is its own topic; for the portable concept see
shader-programming.

Core workflow

1. Pick a material by need. MeshStandardMaterial (PBR: roughness,
   metalness, reacts to lights/IBL) for realism; MeshPhysicalMaterial for
   clearcoat/transmission; MeshBasicMaterial (unlit, ignores lights) for UI/flat;
   MeshNormalMaterial/MeshDepthMaterial for debugging.
2. Add light, or nothing shows. Lit materials need a light source and/or
   scene.environment. Combine a soft fill (AmbientLight/HemisphereLight) with a
   key DirectionalLight.
3. Mind light intensity. Since r155, lighting is physically based; modern
   intensities are higher than old tutorials (a key DirectionalLight ≈ 1–3).
4. Enable shadows in three places. renderer.shadowMap.enabled = true, the
   light's castShadow = true, and each mesh's castShadow/receiveShadow. Then
   fit the light's shadow camera to the scene.
5. Use an environment map for grounded reflections. Assign an equirectangular or
   PMREM-processed texture to scene.environment; PBR materials pick it up
   automatically.
6. Verify under real lighting — confirm the surface responds to the key light
   (highlights move), shadows land where expected, and reflections look plausible.

Patterns

1. PBR material under a 3-light rig

import * as THREE from 'three';

const material = new THREE.MeshStandardMaterial({
  color: 0xcc4444,
  roughness: 0.5,     // 0 = mirror, 1 = fully matte
  metalness: 0.0,     // 0 = dielectric (plastic/wood), 1 = metal
});
const mesh = new THREE.Mesh(new THREE.SphereGeometry(1, 32, 16), material);
scene.add(mesh);

// Soft sky/ground fill + a directional key light.
scene.add(new THREE.HemisphereLight(0xbbddff, 0x443322, 1.0)); // sky, ground, intensity
const key = new THREE.DirectionalLight(0xffffff, 2.5);
key.position.set(5, 10, 7);
scene.add(key);

2. Unlit material (no light needed)

// MeshBasicMaterial ignores lights — for flat color, UI, or sprites/labels.
const flat = new THREE.MeshBasicMaterial({ color: 0x44aa88 });
// A textured color map should be tagged sRGB so colors aren't washed out:
const tex = new THREE.TextureLoader().load('assets/logo.png');
tex.colorSpace = THREE.SRGBColorSpace;
const logo = new THREE.MeshBasicMaterial({ map: tex, transparent: true });

3. Shadows (the three required switches + camera fit)

renderer.shadowMap.enabled = true;
renderer.shadowMap.type = THREE.PCFSoftShadowMap;     // softer edges

const sun = new THREE.DirectionalLight(0xffffff, 3);
sun.position.set(8, 12, 6);
sun.castShadow = true;
sun.shadow.mapSize.set(2048, 2048);                   // default 512; raise for crisp
// DirectionalLight uses an OrthographicCamera — fit it tightly to the scene:
const cam = sun.shadow.camera;
cam.near = 1; cam.far = 40;
cam.left = -15; cam.right = 15; cam.top = 15; cam.bottom = -15;
scene.add(sun);

mesh.castShadow = true;
ground.receiveShadow = true;                          // a plane to catch the shadow

4. PBR textures on a material

const loader = new THREE.TextureLoader();
const colorMap = loader.load('assets/brick_color.jpg');
colorMap.colorSpace = THREE.SRGBColorSpace;           // color maps are sRGB
const normalMap = loader.load('assets/brick_normal.jpg'); // data maps stay linear
const roughMap  = loader.load('assets/brick_rough.jpg');

const brick = new THREE.MeshStandardMaterial({
  map: colorMap,
  normalMap,
  roughnessMap: roughMap,
  metalness: 0,
});

5. Image-based lighting from an HDR environment

import { RGBELoader } from 'three/addons/loaders/RGBELoader.js';

new RGBELoader().load('assets/studio.hdr', (hdr) => {
  hdr.mapping = THREE.EquirectangularReflectionMapping;
  scene.environment = hdr;     // lights + reflects all PBR materials
  scene.background = hdr;       // optional: show it as the backdrop
});
// Optional cinematic tone curve:
renderer.toneMapping = THREE.ACESFilmicToneMapping;
renderer.toneMappingExposure = 1.0;

Pitfalls

• Mesh is pure black → a lit material with no light and no scene.environment.
  Add a light or an environment map; to confirm geometry, temporarily swap to
  MeshBasicMaterial/MeshNormalMaterial.
• Scene too dark even with lights → old tutorial intensities. r155+ is physically
  based; raise intensities (key light ≈ 2–3) or add an environment map.
• Shadows don't appear → you missed one of the three switches
  (renderer.shadowMap.enabled, light.castShadow, mesh castShadow/
  receiveShadow).
• Shadows are cut off or blocky → the DirectionalLight's orthographic
  shadow.camera frustum is too big/small or doesn't cover the scene; tighten
  left/right/top/bottom/near/far and raise shadow.mapSize. Visualise it with
  new THREE.CameraHelper(light.shadow.camera).
• Shadow acne / peter-panning → adjust light.shadow.bias (small negative) and
  light.shadow.normalBias.
• Colors look washed out / too bright → color (albedo) textures need
  texture.colorSpace = THREE.SRGBColorSpace; normal/roughness/metalness maps must
  stay linear (leave them as NoColorSpace).
• PointLight shadows tank performance → a point light renders the scene 6 times
  (cube map). Prefer one shadow-casting DirectionalLight; use cheaper fakes
  elsewhere.

References

• For the material cheat-sheet (which Mesh*Material for which look), light types
  and their parameters/units, transparency vs alphaTest ordering, and the
  PMREMGenerator/RoomEnvironment route to IBL without an HDR file, read
  references/materials-lights-table.md.

Related skills

• threejs-scene-setup — renderer, camera, and loop (set shadowMap, tone mapping).
• threejs-gltf-loading — models arrive with PBR materials this skill tunes.
• shader-programming — custom shader effects (engine-agnostic concept).