Grouping Objects in Three.js

In Three.js, you can group objects together using THREE.Group. A THREE.Group is a special type of Object3D that acts as a container for other objects. When you add objects to a group, their transformations (position, rotation, scale) become relative to the group's transformation. This allows you to move, rotate, or scale multiple objects as a single unit.

How to Use THREE.Group

1. Create a THREE.Group instance:

const group = new THREE.Group();

2. Add objects to the group:

You can add any Object3D (like Mesh, Light, Camera, or even other Groups) to a group using its add() method.

const boxGeometry = new THREE.BoxGeometry(0.5, 0.5, 0.5);
const boxMaterial = new THREE.MeshBasicMaterial({ color: 0xff0000 });
const box = new THREE.Mesh(boxGeometry, boxMaterial);
box.position.set(-0.75, 0, 0); // Position relative to the group

const sphereGeometry = new THREE.SphereGeometry(0.4, 32, 32);
const sphereMaterial = new THREE.MeshBasicMaterial({ color: 0x0000ff });
const sphere = new THREE.Mesh(sphereGeometry, sphereMaterial);
sphere.position.set(0.75, 0, 0); // Position relative to the group

group.add(box);
group.add(sphere);

3. Add the group to the scene:

Once objects are added to the group, you add the group itself to your scene.

scene.add(group);

4. Transform the group:

Now, any transformations applied to the group will affect all its children.

group.position.set(0, 0, 0); // Moves the entire group
group.rotation.y = Math.PI / 4; // Rotates the entire group
group.scale.set(1.5, 1.5, 1.5); // Scales the entire group

Key Benefits of Grouping:

• Hierarchical Transformations: Simplifies managing complex scenes by allowing you to transform multiple objects as a single entity.
• Organization: Helps organize your scene graph, making it easier to manage and understand relationships between objects.
• Performance (Indirectly): While not a direct performance boost for rendering, it can simplify updates and calculations if you're moving many objects together.

Example: Grouping Objects

This example demonstrates how to create a group of objects and apply transformations to the entire group.