examples/webgl_lightshafts.html

<!DOCTYPE html>
<html lang="en">
	<head>
		<title>three.js webgl - Light Shafts</title>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
		<style>
			body {
				font-family: Monospace;
				background-color: #000;
				color: #fff;
				margin: 0px;
				overflow: hidden;
			}
			#info {
				color: #fff;
				position: absolute;
				top: 10px;
				width: 100%;
				text-align: center;
				z-index: 100;
				display:block;
			}
			#info a {
				color: #ffffff;
				font-weight: bold;
			}
		</style>
	</head>

	<body>
		<div id="info">
			<a href="http://threejs.org" target="_blank" rel="noopener">three.js</a> - Light Shafts -
			Model by <a href="https://skfb.ly/6ICER" target="_blank" rel="noopener">Splodeman</a><br />
		</div>

		<script src="../build/three.js"></script>

		<script src="js/controls/OrbitControls.js"></script>
		<script src="js/loaders/GLTFLoader.js"></script>

		<script src="js/WebGL.js"></script>

		<script type="x-shader/x-vertex" id="vertexShader">

		#include <common>

		uniform float speed;
		uniform float time;
		uniform float timeOffset;
		varying vec2 vUv;
		varying float vAlpha;

		void main() {

			vec3 pos = position;

			float l = ( time * speed * 0.01 ) + timeOffset;
			float f = fract( l ); // linear time factor [0,1)
			float a = f * f; // quadratic time factor [0,1)

			// slightly animate the vertices of light shaft if necessary

			// pos.x += cos( l * 20.0 ) * sin( l * 10.0 );

			vAlpha = saturate( 0.7 + min( 1.0, a * 10.0 ) * ( sin( a * 40.0 ) * 0.25 ) );

		  vUv = uv;

			gl_Position = projectionMatrix * modelViewMatrix * vec4( pos, 1.0 );

		}

		</script>

		<script type="x-shader/x-fragment" id="fragmentShader">

		uniform float attenuation;
		uniform vec3 color;
		uniform sampler2D texture;

		varying vec2 vUv;
		varying float vAlpha;

		void main() {

			vec4 textureColor = texture2D( texture, vUv );
			gl_FragColor = vec4( textureColor.rgb * color.rgb, textureColor.a * vAlpha );
			gl_FragColor.a *= pow( gl_FragCoord.z, attenuation );

		}

		</script>

		<script>

			if ( WEBGL.isWebGLAvailable() === false ) {

				document.body.appendChild( WEBGL.getWebGLErrorMessage() );

			}

			var container, controls, clock;
			var camera, scene, renderer, uniforms;

			init();
			animate();

			function init() {

				container = document.createElement( 'div' );
				document.body.appendChild( container );

				camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 0.1, 100 );
				camera.position.set( 3.2, 3, 3.7 );

				controls = new THREE.OrbitControls( camera );
				controls.target.set( 0.5, 1.5, 0 );
				controls.minDistance = 2;
				controls.maxDistance = 20;
				controls.update();

				clock = new THREE.Clock();

				scene = new THREE.Scene();
				scene.background = new THREE.Color( 0xcf8b74 );

				var	light = new THREE.HemisphereLight( 0xffffff, 0x444444 );
				light.position.set( 0, 20, 0 );
				scene.add( light );

				light = new THREE.DirectionalLight( 0xffffff );
				light.position.set( 0, 20, 10 );
				scene.add( light );

			 	// light shafts definition

				var textureLoader = new THREE.TextureLoader();
				var texture = textureLoader.load( 'textures/lightShaft.png' );

				uniforms = {
					// controls how fast the ray attenuates when the camera comes closer
					attenuation: {
						value: 10
					},
					// controls the speed of the animation
					speed: {
						value: 2
					},
					// the color of the ray
					color: {
						value: new THREE.Color( 0xdadc9f )
					},
					// the visual representation of the ray highly depends on the used texture
					texture: {
						value: texture
					},
					// global time value for animation
					time: {
						value: 0
					},
					// individual time offset so rays are animated differently if necessary
					timeOffset: {
						value: 0
					}
				};

				var lightShaftMaterial = new THREE.ShaderMaterial( {
					uniforms: uniforms,
					vertexShader: document.getElementById( 'vertexShader' ).textContent,
					fragmentShader: document.getElementById( 'fragmentShader' ).textContent,
					blending: THREE.AdditiveBlending,
					depthWrite: false,
					transparent: true,
					side: THREE.DoubleSide
				} );

				var lightShaftGeometry = new THREE.PlaneBufferGeometry( 0.5, 5 );

				// model

				var loader = new THREE.GLTFLoader().setPath( 'models/gltf/Tree/' );
				loader.load( 'tree.glb', function ( gltf ) {

					gltf.scene.traverse( function ( child ) {

						if ( child.isMesh )	{

							child.material.transparent = false;
							child.material.alphaTest = 0.5;

						}

					} );

					scene.add( gltf.scene );

					// when the model is loaded, add light shafts

					for ( var i = 0; i < 5; i ++ ) {

						var lightShaft = new THREE.Mesh( lightShaftGeometry, lightShaftMaterial );
						lightShaft.position.x = - 1 + 1.5 * Math.sign( ( i % 2 ) );
						lightShaft.position.y = 2;
						lightShaft.position.z = - 1.5 + ( i * 0.5 );
						lightShaft.rotation.y = Math.PI * 0.2;
						lightShaft.rotation.z = Math.PI * - ( 0.15 + 0.1 * Math.random() );
						scene.add( lightShaft );

					}

				} );

				//

				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				renderer.gammaOutput = true;
				renderer.gammaFactor = 2.2;
				container.appendChild( renderer.domElement );

				window.addEventListener( 'resize', onWindowResize, false );

			}

			function onWindowResize() {

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

				renderer.setSize( window.innerWidth, window.innerHeight );

			}

			//

			function animate() {

				requestAnimationFrame( animate );

				const delta = clock.getDelta();

				uniforms.time.value += delta;

				renderer.render( scene, camera );

			}

		</script>

	</body>
</html>