threejs-lighting

name	threejs-lighting
allowed-tools	Read, Glob
description	Three.js lighting - light types, shadows, environment lighting. Use when adding lights, configuring shadows, setting up IBL, or optimizing lighting performance.

Three.js Lighting

Iron Law

Every scene using MeshStandardMaterial or MeshPhysicalMaterial requires at least one light — these materials render as pure black without illumination.

Quick Start

import * as THREE from "three";

// Basic lighting setup
const ambientLight = new THREE.AmbientLight(0xffffff, 0.5);
scene.add(ambientLight);

const directionalLight = new THREE.DirectionalLight(0xffffff, 1);
directionalLight.position.set(5, 5, 5);
scene.add(directionalLight);

Light Types Overview

Light	Description	Shadow Support	Cost
AmbientLight	Uniform everywhere	No	Very Low
HemisphereLight	Sky/ground gradient	No	Very Low
DirectionalLight	Parallel rays (sun)	Yes	Low
PointLight	Omnidirectional (bulb)	Yes	Medium
SpotLight	Cone-shaped	Yes	Medium
RectAreaLight	Area light (window)	No*	High

*RectAreaLight shadows require custom solutions

AmbientLight

Illuminates all objects equally. No direction, no shadows.

// AmbientLight(color, intensity)
const ambient = new THREE.AmbientLight(0xffffff, 0.5);
scene.add(ambient);

// Modify at runtime
ambient.color.set(0xffffcc);
ambient.intensity = 0.3;

HemisphereLight

Gradient from sky to ground color. Good for outdoor scenes.

// HemisphereLight(skyColor, groundColor, intensity)
const hemi = new THREE.HemisphereLight(0x87ceeb, 0x8b4513, 0.6);
hemi.position.set(0, 50, 0);
scene.add(hemi);

// Properties
hemi.color; // Sky color
hemi.groundColor; // Ground color
hemi.intensity;

DirectionalLight

Parallel light rays. Simulates distant light source (sun).

// DirectionalLight(color, intensity)
const dirLight = new THREE.DirectionalLight(0xffffff, 1);
dirLight.position.set(5, 10, 5);

// Light points at target (default: 0, 0, 0)
dirLight.target.position.set(0, 0, 0);
scene.add(dirLight.target);

scene.add(dirLight);

DirectionalLight Shadows

dirLight.castShadow = true;

// Shadow map size (higher = sharper, more expensive)
dirLight.shadow.mapSize.width = 2048;
dirLight.shadow.mapSize.height = 2048;

// Shadow camera (orthographic)
dirLight.shadow.camera.near = 0.5;
dirLight.shadow.camera.far = 50;
dirLight.shadow.camera.left = -10;
dirLight.shadow.camera.right = 10;
dirLight.shadow.camera.top = 10;
dirLight.shadow.camera.bottom = -10;

// Shadow softness
dirLight.shadow.radius = 4; // Blur radius (PCFSoftShadowMap only)

// Shadow bias (fixes shadow acne)
dirLight.shadow.bias = -0.0001;
dirLight.shadow.normalBias = 0.02;

// Helper to visualize shadow camera
const helper = new THREE.CameraHelper(dirLight.shadow.camera);
scene.add(helper);

PointLight

Emits light in all directions from a point. Like a light bulb.

// PointLight(color, intensity, distance, decay)
const pointLight = new THREE.PointLight(0xffffff, 1, 100, 2);
pointLight.position.set(0, 5, 0);
scene.add(pointLight);

// Properties
pointLight.distance; // Maximum range (0 = infinite)
pointLight.decay; // Light falloff (physically correct = 2)

PointLight Shadows

pointLight.castShadow = true;
pointLight.shadow.mapSize.width = 1024;
pointLight.shadow.mapSize.height = 1024;

// Shadow camera (perspective - 6 directions for cube map)
pointLight.shadow.camera.near = 0.5;
pointLight.shadow.camera.far = 50;

pointLight.shadow.bias = -0.005;

SpotLight

Cone-shaped light. Like a flashlight or stage light.

// SpotLight(color, intensity, distance, angle, penumbra, decay)
const spotLight = new THREE.SpotLight(0xffffff, 1, 100, Math.PI / 6, 0.5, 2);
spotLight.position.set(0, 10, 0);

// Target (light points at this)
spotLight.target.position.set(0, 0, 0);
scene.add(spotLight.target);

scene.add(spotLight);

// Properties
spotLight.angle; // Cone angle (radians, max Math.PI/2)
spotLight.penumbra; // Soft edge (0-1)
spotLight.distance; // Range
spotLight.decay; // Falloff

SpotLight Shadows

spotLight.castShadow = true;
spotLight.shadow.mapSize.width = 1024;
spotLight.shadow.mapSize.height = 1024;

// Shadow camera (perspective)
spotLight.shadow.camera.near = 0.5;
spotLight.shadow.camera.far = 50;
spotLight.shadow.camera.fov = 30;

spotLight.shadow.bias = -0.0001;

// Focus (affects shadow projection)
spotLight.shadow.focus = 1;

RectAreaLight

Rectangular area light. Great for soft, realistic lighting.

import { RectAreaLightHelper } from "three/examples/jsm/helpers/RectAreaLightHelper.js";
import { RectAreaLightUniformsLib } from "three/examples/jsm/lights/RectAreaLightUniformsLib.js";

// Must initialize uniforms first
RectAreaLightUniformsLib.init();

// RectAreaLight(color, intensity, width, height)
const rectLight = new THREE.RectAreaLight(0xffffff, 5, 4, 2);
rectLight.position.set(0, 5, 0);
rectLight.lookAt(0, 0, 0);
scene.add(rectLight);

// Helper
const helper = new RectAreaLightHelper(rectLight);
rectLight.add(helper);

// Note: Only works with MeshStandardMaterial and MeshPhysicalMaterial
// Does not cast shadows natively

Shadow Setup

Enable Shadows

// 1. Enable on renderer
renderer.shadowMap.enabled = true;
renderer.shadowMap.type = THREE.PCFSoftShadowMap;

// Shadow map types:
// THREE.BasicShadowMap - fastest, low quality
// THREE.PCFShadowMap - default, filtered
// THREE.PCFSoftShadowMap - softer edges
// THREE.VSMShadowMap - variance shadow map

// 2. Enable on light
light.castShadow = true;

// 3. Enable on objects
mesh.castShadow = true;
mesh.receiveShadow = true;

// Ground plane
floor.receiveShadow = true;
floor.castShadow = false; // Usually false for floors

Optimizing Shadows

// Tight shadow camera frustum
const d = 10;
dirLight.shadow.camera.left = -d;
dirLight.shadow.camera.right = d;
dirLight.shadow.camera.top = d;
dirLight.shadow.camera.bottom = -d;
dirLight.shadow.camera.near = 0.5;
dirLight.shadow.camera.far = 30;

// Fix shadow acne
dirLight.shadow.bias = -0.0001; // Depth bias
dirLight.shadow.normalBias = 0.02; // Bias along normal

// Shadow map size (balance quality vs performance)
// 512 - low quality
// 1024 - medium quality
// 2048 - high quality
// 4096 - very high quality (expensive)

Contact Shadows (Fake, Fast)

import { ContactShadows } from "three/examples/jsm/objects/ContactShadows.js";

const contactShadows = new ContactShadows({
  resolution: 512,
  blur: 2,
  opacity: 0.5,
  scale: 10,
  position: [0, 0, 0],
});
scene.add(contactShadows);

Light Helpers

import { RectAreaLightHelper } from "three/examples/jsm/helpers/RectAreaLightHelper.js";

// DirectionalLight helper
const dirHelper = new THREE.DirectionalLightHelper(dirLight, 5);
scene.add(dirHelper);

// PointLight helper
const pointHelper = new THREE.PointLightHelper(pointLight, 1);
scene.add(pointHelper);

// SpotLight helper
const spotHelper = new THREE.SpotLightHelper(spotLight);
scene.add(spotHelper);

// Hemisphere helper
const hemiHelper = new THREE.HemisphereLightHelper(hemiLight, 5);
scene.add(hemiHelper);

// RectAreaLight helper
const rectHelper = new RectAreaLightHelper(rectLight);
rectLight.add(rectHelper);

// Update helpers when light changes
dirHelper.update();
spotHelper.update();

Environment Lighting (IBL)

Image-Based Lighting using HDR environment maps.

import { RGBELoader } from "three/examples/jsm/loaders/RGBELoader.js";

const rgbeLoader = new RGBELoader();
rgbeLoader.load("environment.hdr", (texture) => {
  texture.mapping = THREE.EquirectangularReflectionMapping;

  // Set as scene environment (affects all PBR materials)
  scene.environment = texture;

  // Optional: also use as background
  scene.background = texture;
  scene.backgroundBlurriness = 0; // 0-1, blur the background
  scene.backgroundIntensity = 1;
});

// PMREMGenerator for better reflections
const pmremGenerator = new THREE.PMREMGenerator(renderer);
pmremGenerator.compileEquirectangularShader();

rgbeLoader.load("environment.hdr", (texture) => {
  const envMap = pmremGenerator.fromEquirectangular(texture).texture;
  scene.environment = envMap;
  texture.dispose();
  pmremGenerator.dispose();
});

Cube Texture Environment

const cubeLoader = new THREE.CubeTextureLoader();
const envMap = cubeLoader.load([
  "px.jpg",
  "nx.jpg",
  "py.jpg",
  "ny.jpg",
  "pz.jpg",
  "nz.jpg",
]);

scene.environment = envMap;
scene.background = envMap;

Light Probes (Advanced)

Capture lighting from a point in space for ambient lighting.

import { LightProbeGenerator } from "three/examples/jsm/lights/LightProbeGenerator.js";

// Generate from cube texture
const lightProbe = new THREE.LightProbe();
scene.add(lightProbe);

lightProbe.copy(LightProbeGenerator.fromCubeTexture(cubeTexture));

// Or from render target
const cubeCamera = new THREE.CubeCamera(
  0.1,
  100,
  new THREE.WebGLCubeRenderTarget(256),
);
cubeCamera.update(renderer, scene);
lightProbe.copy(
  LightProbeGenerator.fromCubeRenderTarget(renderer, cubeCamera.renderTarget),
);

Common Lighting Setups

Three-Point Lighting

// Key light (main light)
const keyLight = new THREE.DirectionalLight(0xffffff, 1);
keyLight.position.set(5, 5, 5);
scene.add(keyLight);

// Fill light (softer, opposite side)
const fillLight = new THREE.DirectionalLight(0xffffff, 0.5);
fillLight.position.set(-5, 3, 5);
scene.add(fillLight);

// Back light (rim lighting)
const backLight = new THREE.DirectionalLight(0xffffff, 0.3);
backLight.position.set(0, 5, -5);
scene.add(backLight);

// Ambient fill
const ambient = new THREE.AmbientLight(0x404040, 0.3);
scene.add(ambient);

Outdoor Daylight

// Sun
const sun = new THREE.DirectionalLight(0xffffcc, 1.5);
sun.position.set(50, 100, 50);
sun.castShadow = true;
scene.add(sun);

// Sky ambient
const hemi = new THREE.HemisphereLight(0x87ceeb, 0x8b4513, 0.6);
scene.add(hemi);

Indoor Studio

// Multiple area lights
RectAreaLightUniformsLib.init();

const light1 = new THREE.RectAreaLight(0xffffff, 5, 2, 2);
light1.position.set(3, 3, 3);
light1.lookAt(0, 0, 0);
scene.add(light1);

const light2 = new THREE.RectAreaLight(0xffffff, 3, 2, 2);
light2.position.set(-3, 3, 3);
light2.lookAt(0, 0, 0);
scene.add(light2);

// Ambient fill
const ambient = new THREE.AmbientLight(0x404040, 0.2);
scene.add(ambient);

Light Animation

const clock = new THREE.Clock();

function animate() {
  const time = clock.getElapsedTime();

  // Orbit light around scene
  light.position.x = Math.cos(time) * 5;
  light.position.z = Math.sin(time) * 5;

  // Pulsing intensity
  light.intensity = 1 + Math.sin(time * 2) * 0.5;

  // Color cycling
  light.color.setHSL((time * 0.1) % 1, 1, 0.5);

  // Update helpers if using
  lightHelper.update();
}

Performance Tips

1. Limit light count: Each light adds shader complexity
2. Use baked lighting: For static scenes, bake to textures
3. Smaller shadow maps: 512-1024 often sufficient
4. Tight shadow frustums: Only cover needed area
5. Disable unused shadows: Not all lights need shadows
6. Use light layers: Exclude objects from certain lights

// Light layers
light.layers.set(1); // Light only affects layer 1
mesh.layers.enable(1); // Mesh is on layer 1
otherMesh.layers.disable(1); // Other mesh not affected

// Selective shadows
mesh.castShadow = true;
mesh.receiveShadow = true;
decorMesh.castShadow = false; // Small objects often don't need to cast

See Also

• threejs-materials - Material light response
• threejs-textures - Lightmaps and environment maps
• threejs-postprocessing - Bloom and other light effects