Threejs Fundamentals

When to Use

• You need to scaffold the core structure of a Three.js application (scene, camera, renderer, animation loop).
• The task involves scenes, cameras, renderers, transforms, resize handling, or object hierarchy basics.
• You need guidance on Three.js coordinate systems, math utilities (Vector3, Matrix4, Quaternion, Euler, Color), or common patterns like cleanup and loading managers.
• You want foundational Three.js guidance before working on specialized topics like shaders, post-processing, or advanced geometry manipulation.

Prerequisites

• A JavaScript/TypeScript project with three installed (npm install three).
• Three.js r152+ for outputColorSpace; r183+ for Timer and experimental WebGPU renderer.
• A browser with WebGL support (or WebGPU for the experimental renderer path).

Procedure

1. Create the Core Scene Structure

Set up scene, camera, renderer, a sample mesh, lighting, and the animation loop.

import * as THREE from "three";

// Create scene, camera, renderer
const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(
  75,
  window.innerWidth / window.innerHeight,
  0.1,
  1000,
);
const renderer = new THREE.WebGLRenderer({ antialias: true });

renderer.setSize(window.innerWidth, window.innerHeight);
renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2));
document.body.appendChild(renderer.domElement);

// Add a mesh
const geometry = new THREE.BoxGeometry(1, 1, 1);
const material = new THREE.MeshStandardMaterial({ color: 0x00ff00 });
const cube = new THREE.Mesh(geometry, material);
scene.add(cube);

// Add light
scene.add(new THREE.AmbientLight(0xffffff, 0.5));
const dirLight = new THREE.DirectionalLight(0xffffff, 1);
dirLight.position.set(5, 5, 5);
scene.add(dirLight);

camera.position.z = 5;

// Animation loop — prefer setAnimationLoop over manual requestAnimationFrame
renderer.setAnimationLoop(() => {
  cube.rotation.x += 0.01;
  cube.rotation.y += 0.01;
  renderer.render(scene, camera);
});

// Handle resize
window.addEventListener("resize", () => {
  camera.aspect = window.innerWidth / window.innerHeight;
  camera.updateProjectionMatrix();
  renderer.setSize(window.innerWidth, window.innerHeight);
});

2. Configure the Scene

The Scene is the container for all 3D objects, lights, and cameras.

const scene = new THREE.Scene();
scene.background = new THREE.Color(0x000000); // Solid color
scene.background = texture;                   // Skybox texture
scene.background = cubeTexture;               // Cubemap
scene.environment = envMap;                   // Environment map for PBR
scene.fog = new THREE.Fog(0xffffff, 1, 100);  // Linear fog
scene.fog = new THREE.FogExp2(0xffffff, 0.02); // Exponential fog

3. Choose and Configure a Camera

PerspectiveCamera — most common, simulates human eye.

// PerspectiveCamera(fov, aspect, near, far)
const camera = new THREE.PerspectiveCamera(
  75,                                      // Field of view (degrees)
  window.innerWidth / window.innerHeight,  // Aspect ratio
  0.1,                                     // Near clipping plane
  1000,                                    // Far clipping plane
);

camera.position.set(0, 5, 10);
camera.lookAt(0, 0, 0);
camera.updateProjectionMatrix(); // Call after changing fov, aspect, near, far

OrthographicCamera — no perspective distortion, good for 2D/isometric.

// OrthographicCamera(left, right, top, bottom, near, far)
const aspect = window.innerWidth / window.innerHeight;
const frustumSize = 10;
const camera = new THREE.OrthographicCamera(
  (frustumSize * aspect) / -2,
  (frustumSize * aspect) / 2,
  frustumSize / 2,
  frustumSize / -2,
  0.1,
  1000,
);

ArrayCamera — multiple viewports with sub-cameras.

const cameras = [];
for (let i = 0; i < 4; i++) {
  const subcamera = new THREE.PerspectiveCamera(40, 1, 0.1, 100);
  subcamera.viewport = new THREE.Vector4(
    Math.floor(i % 2) * 0.5,
    Math.floor(i / 2) * 0.5,
    0.5,
    0.5,
  );
  cameras.push(subcamera);
}
const arrayCamera = new THREE.ArrayCamera(cameras);

CubeCamera — renders environment maps for reflections.

const cubeRenderTarget = new THREE.WebGLCubeRenderTarget(256);
const cubeCamera = new THREE.CubeCamera(0.1, 1000, cubeRenderTarget);
scene.add(cubeCamera);

// Use for reflections
material.envMap = cubeRenderTarget.texture;

// Update each frame (expensive!)
cubeCamera.position.copy(reflectiveMesh.position);
cubeCamera.update(renderer, scene);

4. Configure the WebGLRenderer

const renderer = new THREE.WebGLRenderer({
  canvas: document.querySelector("#canvas"), // Optional existing canvas
  antialias: true,        // Smooth edges
  alpha: true,            // Transparent background
  powerPreference: "high-performance", // GPU hint
  preserveDrawingBuffer: true, // For screenshots
});

renderer.setSize(width, height);
renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2));

// Tone mapping
renderer.toneMapping = THREE.ACESFilmicToneMapping;
renderer.toneMappingExposure = 1.0;

// Color space (Three.js r152+)
renderer.outputColorSpace = THREE.SRGBColorSpace;

// Shadows
renderer.shadowMap.enabled = true;
renderer.shadowMap.type = THREE.PCFSoftShadowMap;

// Clear color
renderer.setClearColor(0x000000, 1);

// Render
renderer.render(scene, camera);

5. Work with Object3D, Group, and Mesh

Object3D is the base class for all 3D objects. Mesh, Group, Light, and Camera all extend Object3D.

const obj = new THREE.Object3D();

// Transform
obj.position.set(x, y, z);
obj.rotation.set(x, y, z);           // Euler angles (radians)
obj.quaternion.set(x, y, z, w);      // Quaternion rotation
obj.scale.set(x, y, z);

// Local vs World transforms
obj.getWorldPosition(targetVector);
obj.getWorldQuaternion(targetQuaternion);
obj.getWorldDirection(targetVector);

// Hierarchy
obj.add(child);
obj.remove(child);
obj.parent;
obj.children;

// Visibility
obj.visible = false;

// Layers (for selective rendering/raycasting)
obj.layers.set(1);
obj.layers.enable(2);
obj.layers.disable(0);

// Traverse hierarchy
obj.traverse((child) => {
  if (child.isMesh) child.material.color.set(0xff0000);
});

// Matrix updates
obj.matrixAutoUpdate = true;     // Default: auto-update matrices
obj.updateMatrix();              // Manual matrix update
obj.updateMatrixWorld(true);     // Update world matrix recursively

Group — empty container for organizing objects.

const group = new THREE.Group();
group.add(mesh1);
group.add(mesh2);
scene.add(group);

// Transform entire group
group.position.x = 5;
group.rotation.y = Math.PI / 4;

Mesh — combines geometry and material.

const mesh = new THREE.Mesh(geometry, material);

// Multiple materials (one per geometry group)
const mesh = new THREE.Mesh(geometry, [material1, material2]);

// Useful properties
mesh.geometry;
mesh.material;
mesh.castShadow = true;
mesh.receiveShadow = true;

// Frustum culling
mesh.frustumCulled = true; // Default: skip if outside camera view

// Render order
mesh.renderOrder = 10; // Higher = rendered later

6. Understand the Coordinate System

Three.js uses a right-handed coordinate system:

• +X points right
• +Y points up
• +Z points toward viewer (out of screen)

// Axes helper
const axesHelper = new THREE.AxesHelper(5);
scene.add(axesHelper); // Red=X, Green=Y, Blue=Z

7. Use Math Utilities

Vector3

const v = new THREE.Vector3(x, y, z);
v.set(x, y, z);
v.copy(otherVector);
v.clone();

// Operations (modify in place)
v.add(v2);
v.sub(v2);
v.multiply(v2);
v.multiplyScalar(2);
v.divideScalar(2);
v.normalize();
v.negate();
v.clamp(min, max);
v.lerp(target, alpha);

// Calculations (return new value)
v.length();
v.lengthSq(); // Faster than length()
v.distanceTo(v2);
v.dot(v2);
v.cross(v2); // Modifies v
v.angleTo(v2);

// Transform
v.applyMatrix4(matrix);
v.applyQuaternion(q);
v.project(camera);    // World to NDC
v.unproject(camera);  // NDC to world

Matrix4

const m = new THREE.Matrix4();
m.identity();
m.copy(other);
m.clone();

// Build transforms
m.makeTranslation(x, y, z);
m.makeRotationX(theta);
m.makeRotationY(theta);
m.makeRotationZ(theta);
m.makeRotationFromQuaternion(q);
m.makeScale(x, y, z);

// Compose/decompose
m.compose(position, quaternion, scale);
m.decompose(position, quaternion, scale);

// Operations
m.multiply(m2);    // m = m * m2
m.premultiply(m2); // m = m2 * m
m.invert();
m.transpose();

// Camera matrices
m.makePerspective(left, right, top, bottom, near, far);
m.makeOrthographic(left, right, top, bottom, near, far);
m.lookAt(eye, target, up);

Quaternion

const q = new THREE.Quaternion();
q.setFromEuler(euler);
q.setFromAxisAngle(axis, angle);
q.setFromRotationMatrix(matrix);

q.multiply(q2);
q.slerp(target, t); // Spherical interpolation
q.normalize();
q.invert();

Euler

const euler = new THREE.Euler(x, y, z, "XYZ"); // Order matters!
euler.setFromQuaternion(q);
euler.setFromRotationMatrix(m);

// Rotation orders: 'XYZ', 'YXZ', 'ZXY', 'XZY', 'YZX', 'ZYX'

Color

const color = new THREE.Color(0xff0000);
const color = new THREE.Color("red");
const color = new THREE.Color("rgb(255, 0, 0)");
const color = new THREE.Color("#ff0000");

color.setHex(0x00ff00);
color.setRGB(r, g, b); // 0-1 range
color.setHSL(h, s, l); // 0-1 range

color.lerp(otherColor, alpha);
color.multiply(otherColor);
color.multiplyScalar(2);

MathUtils

THREE.MathUtils.clamp(value, min, max);
THREE.MathUtils.lerp(start, end, alpha);
THREE.MathUtils.mapLinear(value, inMin, inMax, outMin, outMax);
THREE.MathUtils.degToRad(degrees);
THREE.MathUtils.radToDeg(radians);
THREE.MathUtils.randFloat(min, max);
THREE.MathUtils.randInt(min, max);
THREE.MathUtils.smoothstep(x, min, max);
THREE.MathUtils.smootherstep(x, min, max);

8. Implement Proper Cleanup

Always dispose geometries, materials, textures, and the renderer when tearing down a scene to avoid GPU memory leaks.

function dispose() {
  // Dispose geometries
  mesh.geometry.dispose();

  // Dispose materials
  if (Array.isArray(mesh.material)) {
    mesh.material.forEach((m) => m.dispose());
  } else {
    mesh.material.dispose();
  }

  // Dispose textures
  texture.dispose();

  // Remove from scene
  scene.remove(mesh);

  // Dispose renderer
  renderer.dispose();
}

9. Use Timer or Clock for Frame-Rate-Independent Animation

Timer (recommended in r183) — pauses when tab is hidden, cleaner API:

const timer = new THREE.Timer();

renderer.setAnimationLoop(() => {
  timer.update();
  const delta = timer.getDelta();
  const elapsed = timer.getElapsed();

  mesh.rotation.y += delta * 0.5;
  renderer.render(scene, camera);
});

Clock (legacy, still works):

const clock = new THREE.Clock();

function animate() {
  const delta = clock.getDelta();        // Time since last frame (seconds)
  const elapsed = clock.getElapsedTime(); // Total time (seconds)

  mesh.rotation.y += delta * 0.5; // Consistent speed regardless of framerate

  requestAnimationFrame(animate);
  renderer.render(scene, camera);
}

10. Handle Responsive Canvas

function onWindowResize() {
  const width = window.innerWidth;
  const height = window.innerHeight;

  camera.aspect = width / height;
  camera.updateProjectionMatrix();

  renderer.setSize(width, height);
  renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2));
}
window.addEventListener("resize", onWindowResize);

11. Track Asset Loading with LoadingManager

const manager = new THREE.LoadingManager();

manager.onStart = (url, loaded, total) => console.log("Started loading");
manager.onLoad = () => console.log("All loaded");
manager.onProgress = (url, loaded, total) => console.log(`${loaded}/${total}`);
manager.onError = (url) => console.error(`Error loading ${url}`);

const textureLoader = new THREE.TextureLoader(manager);
const gltfLoader = new GLTFLoader(manager);

12. Apply Performance Optimizations

1. Limit draw calls: Merge geometries, use instancing, atlas textures.
2. Frustum culling: Enabled by default; ensure bounding boxes are correct.
3. LOD (Level of Detail): Use THREE.LOD for distance-based mesh switching.
4. Object pooling: Reuse objects instead of creating/destroying.
5. Avoid getWorldPosition in loops: Cache results.

// Merge static geometries
import { mergeGeometries } from "three/examples/jsm/utils/BufferGeometryUtils.js";
const merged = mergeGeometries([geo1, geo2, geo3]);

// LOD
const lod = new THREE.LOD();
lod.addLevel(highDetailMesh, 0);
lod.addLevel(medDetailMesh, 50);
lod.addLevel(lowDetailMesh, 100);
scene.add(lod);

13. (Optional) Use the WebGPU Renderer (r183+)

Three.js includes an experimental WebGPU renderer as an alternative to WebGL:

import { WebGPURenderer } from "three/addons/renderers/webgpu/WebGPURenderer.js";

const renderer = new WebGPURenderer({ antialias: true });
await renderer.init();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

WebGPU uses TSL (Three.js Shading Language) instead of GLSL. The WebGL renderer remains the default and is fully supported.

Pitfalls

• Forgetting updateProjectionMatrix(): After changing fov, aspect, near, or far on a camera, you must call camera.updateProjectionMatrix() or the change will not take effect.
• Not capping pixel ratio: Always use renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2)) — uncapped DPR on high-DPI devices causes severe performance degradation.
• Memory leaks from missing disposal: Failing to call .dispose() on geometries, materials, textures, and the renderer causes GPU memory leaks. This is critical in SPA route changes or scene rebuilds.
• Euler rotation order: Euler rotation order matters. Changing the default "XYZ" order can produce different results. Prefer quaternions for complex rotational interpolation.
• cross() modifies in place: Vector3.cross(v2) modifies the calling vector, not v2. Use v.clone().cross(v2) if you need to preserve the original.
• CubeCamera is expensive: Calling cubeCamera.update(renderer, scene) every frame is costly. Only update when the environment changes or throttle updates.
• WebGPU is experimental: The WebGPU renderer uses TSL, not GLSL. Existing GLSL shaders will not work. The WebGL renderer remains the default.
• preserveDrawingBuffer: true has a performance cost — only enable it when you need screenshots via canvas.toDataURL().
• matrixAutoUpdate: If you set obj.matrixAutoUpdate = false for performance, you must manually call obj.updateMatrix() and obj.updateMatrixWorld(true) or transforms will not apply.

Verification

1. Confirm Three.js is installed and check version:

   npm list three
   

   Expected output shows three@x.x.x installed. Verify x.x.x meets your feature requirements (r152+ for outputColorSpace, r183+ for Timer/WebGPU).

2. Verify the scene renders: Open the page in a browser. You should see a green cube rotating on both X and Y axes against a black background.

3. Check for console errors: Open DevTools Console — no errors or warnings should appear. Common warnings to watch for:

   • THREE.WebGLRenderer: ... is not a property of renderer — indicates a typo or deprecated API.
   • Material/light mismatch causing a black mesh — MeshStandardMaterial requires lights; MeshBasicMaterial does not.

4. Verify resize handling: Resize the browser window. The canvas should fill the viewport and the cube should not distort (aspect ratio is corrected).

5. Verify cleanup (if implemented): After calling your dispose() function, check that:

   • The canvas is removed or blank.
   • No WebGL: CONTEXT_LOST errors appear.
   • GPU memory is released (check via browser DevTools Memory tab or performance.memory in Chromium).

Related Skills

• threejs-geometry — Geometry creation and manipulation
• threejs-materials — Material types and properties
• threejs-lighting — Light types and shadows