examples/webgl_read_float_buffer.html

<!DOCTYPE html>
<html lang="en">
	<head>
		<title>three.js webgl - read float pixels</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">
	</head>
	<body>

		<div id="container"></div>
		<div id="info">
			<a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> read float pixels webgl example<br/>
			<span id="values"></span>
		</div>

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

			varying vec2 vUv;
			uniform sampler2D tDiffuse;

			void main() {

				gl_FragColor = texture2D( tDiffuse, vUv );

			}

		</script>

		<script id="fragment_shader_pass_1" type="x-shader/x-fragment">

			varying vec2 vUv;
			uniform float time;

			void main() {

				float r = vUv.x;
				if( vUv.y < 0.5 ) r = 0.0;
				float g = vUv.y;
				if( vUv.x < 0.5 ) g = 0.0;

				gl_FragColor = vec4( r, g, time, 1.0 );

			}

		</script>

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

			varying vec2 vUv;

			void main() {

				vUv = uv;
				gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );

			}

		</script>

		<!-- Import maps polyfill -->
		<!-- Remove this when import maps will be widely supported -->
		<script async src="https://unpkg.com/es-module-shims@1.3.6/dist/es-module-shims.js"></script>

		<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';

			let container, stats;

			let cameraRTT, sceneRTT, sceneScreen, renderer, zmesh1, zmesh2;

			let mouseX = 0, mouseY = 0;

			const windowHalfX = window.innerWidth / 2;
			const windowHalfY = window.innerHeight / 2;

			let rtTexture, material, quad;

			let delta = 0.01;
			let valueNode;

			init();
			animate();

			function init() {

				container = document.getElementById( 'container' );

				cameraRTT = new THREE.OrthographicCamera( window.innerWidth / - 2, window.innerWidth / 2, window.innerHeight / 2, window.innerHeight / - 2, - 10000, 10000 );
				cameraRTT.position.z = 100;

				//

				sceneRTT = new THREE.Scene();
				sceneScreen = new THREE.Scene();

				let light = new THREE.DirectionalLight( 0xffffff );
				light.position.set( 0, 0, 1 ).normalize();
				sceneRTT.add( light );

				light = new THREE.DirectionalLight( 0xffaaaa, 1.5 );
				light.position.set( 0, 0, - 1 ).normalize();
				sceneRTT.add( light );

				rtTexture = new THREE.WebGLRenderTarget( window.innerWidth, window.innerHeight, { minFilter: THREE.LinearFilter, magFilter: THREE.NearestFilter, format: THREE.RGBAFormat, type: THREE.FloatType } );

				material = new THREE.ShaderMaterial( {

					uniforms: { 'time': { value: 0.0 } },
					vertexShader: document.getElementById( 'vertexShader' ).textContent,
					fragmentShader: document.getElementById( 'fragment_shader_pass_1' ).textContent

				} );

				const materialScreen = new THREE.ShaderMaterial( {

					uniforms: { 'tDiffuse': { value: rtTexture.texture } },
					vertexShader: document.getElementById( 'vertexShader' ).textContent,
					fragmentShader: document.getElementById( 'fragment_shader_screen' ).textContent,

					depthWrite: false

				} );

				const plane = new THREE.PlaneGeometry( window.innerWidth, window.innerHeight );

				quad = new THREE.Mesh( plane, material );
				quad.position.z = - 100;
				sceneRTT.add( quad );

				const geometry = new THREE.TorusGeometry( 100, 25, 15, 30 );

				const mat1 = new THREE.MeshPhongMaterial( { color: 0x555555, specular: 0xffaa00, shininess: 5 } );
				const mat2 = new THREE.MeshPhongMaterial( { color: 0x550000, specular: 0xff2200, shininess: 5 } );

				zmesh1 = new THREE.Mesh( geometry, mat1 );
				zmesh1.position.set( 0, 0, 100 );
				zmesh1.scale.set( 1.5, 1.5, 1.5 );
				sceneRTT.add( zmesh1 );

				zmesh2 = new THREE.Mesh( geometry, mat2 );
				zmesh2.position.set( 0, 150, 100 );
				zmesh2.scale.set( 0.75, 0.75, 0.75 );
				sceneRTT.add( zmesh2 );

				quad = new THREE.Mesh( plane, materialScreen );
				quad.position.z = - 100;
				sceneScreen.add( quad );

				renderer = new THREE.WebGLRenderer();
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				renderer.autoClear = false;

				container.appendChild( renderer.domElement );

				stats = new Stats();
				container.appendChild( stats.dom );

				valueNode = document.getElementById( 'values' );

				document.addEventListener( 'mousemove', onDocumentMouseMove );

			}

			function onDocumentMouseMove( event ) {

				mouseX = ( event.clientX - windowHalfX );
				mouseY = ( event.clientY - windowHalfY );

			}

			//

			function animate() {

				requestAnimationFrame( animate );

				render();
				stats.update();

			}

			function render() {

				const time = Date.now() * 0.0015;

				if ( zmesh1 && zmesh2 ) {

					zmesh1.rotation.y = - time;
					zmesh2.rotation.y = - time + Math.PI / 2;

				}

				if ( material.uniforms[ 'time' ].value > 1 || material.uniforms[ 'time' ].value < 0 ) {

					delta *= - 1;

				}

				material.uniforms[ 'time' ].value += delta;

				renderer.clear();

				// Render first scene into texture

				renderer.setRenderTarget( rtTexture );
				renderer.clear();
				renderer.render( sceneRTT, cameraRTT );

				// Render full screen quad with generated texture

				renderer.setRenderTarget( null );
				renderer.render( sceneScreen, cameraRTT );

				const read = new Float32Array( 4 );
				renderer.readRenderTargetPixels( rtTexture, windowHalfX + mouseX, windowHalfY - mouseY, 1, 1, read );

				valueNode.innerHTML = 'r:' + read[ 0 ] + '<br/>g:' + read[ 1 ] + '<br/>b:' + read[ 2 ];

			}

		</script>
	</body>
</html>