Scene Switching in Three.js

In Three.js, switching between scenes involves managing multiple THREE.Scene objects and rendering one at a time based on user interaction or application logic. Below is a step-by-step guide on how to implement scene switching.

1. Creating Multiple Scenes

You need to define multiple scene objects, each representing a different 3D environment.

const scene1 = new THREE.Scene();
const scene2 = new THREE.Scene();

You can populate each scene with unique objects, lighting, and settings.

2. Common Camera and Renderer

The camera and renderer can be shared across scenes, as their primary function is to display the content of whichever scene is currently active.

const renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
camera.position.set(0, 0, 5);

3. Switching Between Scenes

To switch between scenes, track the current scene in a variable and update it when needed:

let currentScene = scene1;

function switchScene() {
    currentScene = (currentScene === scene1) ? scene2 : scene1;
}

You can call the switchScene() function to toggle between scenes.

4. Rendering the Active Scene

In the animation loop, render only the active scene (stored in currentScene).

function animate() {
    requestAnimationFrame(animate);
    renderer.render(currentScene, camera);
}

animate();

5. Triggering Scene Switch

Scene switching can be triggered by events such as keypresses or button clicks. For example, switching on a keypress:

document.addEventListener('keydown', (event) => {
    if (event.key === 's') {  // Switch scenes on 'S' key press
        switchScene();
    }
});

This setup enables easy switching between scenes based on user interaction or programmatic triggers.

Conclusion

Switching scenes in Three.js is as simple as updating the active scene reference and rendering it. With this setup, you can create complex applications with multiple 3D environments or levels, switching between them dynamically.