examples/webgl_postprocessing_transition.html

<!DOCTYPE html>
<html lang="en">
	<head>
		<title>three.js webgl - scenes transition</title>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
		<link type="text/css" rel="stylesheet" href="main.css">
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	<body>

		<div id="info">
			<a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> webgl scene transitions<br/>
			by <a href="https://twitter.com/fernandojsg">fernandojsg</a> - <a href="https://github.com/kile/three.js-demos">github</a>
		</div>

		<script type="importmap">
			{
				"imports": {
					"three": "../build/three.module.js",
					"three/addons/": "./jsm/"
				}
			}
		</script>

		<script type="module">

			import * as THREE from 'three';

			import Stats from 'three/addons/libs/stats.module.js';
			import { GUI } from 'three/addons/libs/lil-gui.module.min.js';
			import TWEEN from 'three/addons/libs/tween.module.js';
			import { EffectComposer } from 'three/addons/postprocessing/EffectComposer.js';
			import { RenderTransitionPass } from 'three/addons/postprocessing/RenderTransitionPass.js';
			import { OutputPass } from 'three/addons/postprocessing/OutputPass.js';

			let stats;
			let renderer, composer, renderTransitionPass;

			const textures = [];
			const clock = new THREE.Clock();

			const params = {
				sceneAnimate: true,
				transitionAnimate: true,
				transition: 0,
				useTexture: true,
				texture: 5,
				cycle: true,
				threshold: 0.1,
			};

			const fxSceneA = new FXScene( new THREE.BoxGeometry( 2, 2, 2 ), new THREE.Vector3( 0, - 0.4, 0 ), 0xffffff );
			const fxSceneB = new FXScene( new THREE.IcosahedronGeometry( 1, 1 ), new THREE.Vector3( 0, 0.2, 0.1 ), 0x000000 );

			init();

			function init() {

				initGUI();
				initTextures();

				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				renderer.setAnimationLoop( animate );
				document.body.appendChild( renderer.domElement );

				composer = new EffectComposer( renderer );

				stats = new Stats();
				document.body.appendChild( stats.dom );

				renderTransitionPass = new RenderTransitionPass( fxSceneA.scene, fxSceneA.camera, fxSceneB.scene, fxSceneB.camera );
				renderTransitionPass.setTexture( textures[ 0 ] );
				composer.addPass( renderTransitionPass );

				const outputPass = new OutputPass();
				composer.addPass( outputPass );

			}

			window.addEventListener( 'resize', onWindowResize );

			function onWindowResize() {

				fxSceneA.resize();
				fxSceneB.resize();
				renderer.setSize( window.innerWidth, window.innerHeight );
				composer.setSize( window.innerWidth, window.innerHeight );

			}

			new TWEEN.Tween( params )
				.to( { transition: 1 }, 1500 )
				.onUpdate( function () {

					renderTransitionPass.setTransition( params.transition );

					// Change the current alpha texture after each transition
					if ( params.cycle ) {

						if ( params.transition == 0 || params.transition == 1 ) {

							params.texture = ( params.texture + 1 ) % textures.length;
							renderTransitionPass.setTexture( textures[ params.texture ] );

						}

					}

				} )
				.repeat( Infinity )
				.delay( 2000 )
				.yoyo( true )
				.start();

			function animate() {

				// Transition animation
				if ( params.transitionAnimate ) TWEEN.update();

				const delta = clock.getDelta();
				fxSceneA.update( delta );
				fxSceneB.update( delta );

				render();
				stats.update();

			}

			function initTextures() {

				const loader = new THREE.TextureLoader();

				for ( let i = 0; i < 6; i ++ ) {

					textures[ i ] = loader.load( 'textures/transition/transition' + ( i + 1 ) + '.png' );

				}

			}

			function initGUI() {

				const gui = new GUI();

				gui.add( params, 'sceneAnimate' ).name( 'Animate scene' );
				gui.add( params, 'transitionAnimate' ).name( 'Animate transition' );
				gui.add( params, 'transition', 0, 1, 0.01 ).onChange( function ( value ) {

					renderTransitionPass.setTransition( value );

				} ).listen();

				gui.add( params, 'useTexture' ).onChange( function ( value ) {

					renderTransitionPass.useTexture( value );

				} );

				gui.add( params, 'texture', { Perlin: 0, Squares: 1, Cells: 2, Distort: 3, Gradient: 4, Radial: 5 } ).onChange( function ( value ) {

					renderTransitionPass.setTexture( textures[ value ] );

				} ).listen();

				gui.add( params, 'cycle' );

				gui.add( params, 'threshold', 0, 1, 0.01 ).onChange( function ( value ) {

					renderTransitionPass.setTextureThreshold( value );

				} );

			}


			function render() {

				// Prevent render both scenes when it's not necessary
				if ( params.transition === 0 ) {

					renderer.render( fxSceneB.scene, fxSceneB.camera );

				} else if ( params.transition === 1 ) {

					renderer.render( fxSceneA.scene, fxSceneA.camera );

				} else {

					// When 0 < transition < 1 render transition between two scenes
					composer.render();

				}

			}

			function FXScene( geometry, rotationSpeed, backgroundColor ) {

				const camera = new THREE.PerspectiveCamera( 50, window.innerWidth / window.innerHeight, 0.1, 100 );
				camera.position.z = 20;

				// Setup scene
				const scene = new THREE.Scene();
				scene.background = new THREE.Color( backgroundColor );
				scene.add( new THREE.AmbientLight( 0xaaaaaa, 3 ) );

				const light = new THREE.DirectionalLight( 0xffffff, 3 );
				light.position.set( 0, 1, 4 );
				scene.add( light );

				this.rotationSpeed = rotationSpeed;

				const color = geometry.type === 'BoxGeometry' ? 0x0000ff : 0xff0000;
				const material = new THREE.MeshPhongMaterial( { color: color, flatShading: true } );
				const mesh = generateInstancedMesh( geometry, material, 500 );
				scene.add( mesh );

				this.scene = scene;
				this.camera = camera;
				this.mesh = mesh;

				this.update = function ( delta ) {

					if ( params.sceneAnimate ) {

						mesh.rotation.x += this.rotationSpeed.x * delta;
						mesh.rotation.y += this.rotationSpeed.y * delta;
						mesh.rotation.z += this.rotationSpeed.z * delta;

					}

				};

				this.resize = function () {

					camera.aspect = window.innerWidth / window.innerHeight;
					camera.updateProjectionMatrix();

				};

			}

			function generateInstancedMesh( geometry, material, count ) {

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

				const dummy = new THREE.Object3D();
				const color = new THREE.Color();

				for ( let i = 0; i < count; i ++ ) {

					dummy.position.x = Math.random() * 100 - 50;
					dummy.position.y = Math.random() * 60 - 30;
					dummy.position.z = Math.random() * 80 - 40;

					dummy.rotation.x = Math.random() * 2 * Math.PI;
					dummy.rotation.y = Math.random() * 2 * Math.PI;
					dummy.rotation.z = Math.random() * 2 * Math.PI;

					dummy.scale.x = Math.random() * 2 + 1;

					if ( geometry.type === 'BoxGeometry' ) {

						dummy.scale.y = Math.random() * 2 + 1;
						dummy.scale.z = Math.random() * 2 + 1;

					} else {

						dummy.scale.y = dummy.scale.x;
						dummy.scale.z = dummy.scale.x;

					}

					dummy.updateMatrix();

					mesh.setMatrixAt( i, dummy.matrix );
					mesh.setColorAt( i, color.setScalar( 0.1 + 0.9 * Math.random() ) );

				}

				return mesh;

			}
		</script>
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