examples/webgl_framebuffer_texture.html

<!DOCTYPE html>
<html lang="en">
	<head>
		<title>three.js webgl - framebuffer - texture</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 {
				background:#777;
				padding:0;
				margin:0;
				overflow:hidden;
			}

			#info {
				position: absolute;
				top: 0px;
				width: 100%;
				color: #ffffff;
				padding: 5px;
				font-family:Monospace;
				font-size:13px;
				text-align:center;
			}

			a {
				color: #ffffff;
			}

			#overlay {
				position: fixed;
				display: flex;
				flex-direction: column;
				justify-content: center;
				align-items: center;
				height: 100%;
				width: 100%;
				top: 0;
				z-index: 999;
			}

			#overlay > div {
				height: 128px;
				width: 128px;
				border: 1px solid white;
			}
		</style>

		<script src="../build/three.js"></script>
		<script src="js/controls/OrbitControls.js"></script>
		<script src="js/WebGL.js"></script>

	</head>
	<body>

		<div id="info">
			<a href="https://threejs.org" target="_blank" rel="noopener noreferrer">three.js</a> framebuffer to texture <br/>
			The area of the white square is copied from the framebuffer to a texture (shown in the top-left corner).
		</div>

		<div id="overlay">
			<div>
			</div>
		</div>

		<script>

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

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

			}

			var camera, scene, renderer;
			var mesh, sprite, texture;

			var cameraOrtho, sceneOrtho;

			var dpr = window.devicePixelRatio;

			var textureSize = 128 * dpr;
			var vector = new THREE.Vector2();

			init();
			animate();

			function init() {

				//

				var width = window.innerWidth;
				var height = window.innerHeight;

				camera = new THREE.PerspectiveCamera( 70, width / height, 1, 1000 );
				camera.position.z = 20;

				cameraOrtho = new THREE.OrthographicCamera( - width / 2, width / 2, height / 2, - height / 2, 1, 10 );
				cameraOrtho.position.z = 10;

				scene = new THREE.Scene();
				scene.background = new THREE.Color( 0x20252f );
				sceneOrtho = new THREE.Scene();

				//

				var geometry = new THREE.TorusKnotBufferGeometry( 3, 1, 256, 32 );
				var material = new THREE.MeshStandardMaterial( { color: 0x6083c2 } );

				mesh = new THREE.Mesh( geometry, material );
				scene.add( mesh );

				//
				var ambientLight = new THREE.AmbientLight( 0xcccccc, 0.4 );
				scene.add( ambientLight );

				var pointLight = new THREE.PointLight( 0xffffff, 0.8 );
				camera.add( pointLight );
				scene.add( camera );

				//

				var data = new Uint8Array( textureSize * textureSize * 3 );

				texture = new THREE.DataTexture( data, textureSize, textureSize, THREE.RGBFormat );
				texture.minFilter = THREE.NearestFilter;
				texture.magFilter = THREE.NearestFilter;
				texture.needsUpdate = true;

				//

				var spriteMaterial = new THREE.SpriteMaterial( { map: texture } );
				sprite = new THREE.Sprite( spriteMaterial );
				sprite.scale.set( textureSize, textureSize, 1 );
				sceneOrtho.add( sprite );

				updateSpritePosition();

				//

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

				//

				var overlay = document.getElementById( 'overlay' );
				var controls = new THREE.OrbitControls( camera, overlay );
				controls.enablePan = false;

				//

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

			}

			function onWindowResize() {

				var width = window.innerWidth;
				var height = window.innerHeight;

				camera.aspect = width / height;
				camera.updateProjectionMatrix();

				cameraOrtho.left = - width / 2;
				cameraOrtho.right = width / 2;
				cameraOrtho.top = height / 2;
				cameraOrtho.bottom = - height / 2;
				cameraOrtho.updateProjectionMatrix();

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

				updateSpritePosition();

			}

			function updateSpritePosition() {

				var halfWidth = window.innerWidth / 2;
				var halfHeight = window.innerHeight / 2;

				var halfImageWidth = textureSize / 2;
				var halfImageHeight = textureSize / 2;

				sprite.position.set( - halfWidth + halfImageWidth, halfHeight - halfImageHeight, 1 );

			}

			function animate() {

				requestAnimationFrame( animate );

				mesh.rotation.x += 0.005;
				mesh.rotation.y += 0.01;

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

				// calculate start position for copying data

				vector.x = ( window.innerWidth * dpr / 2 ) - ( textureSize / 2 );
				vector.y = ( window.innerHeight * dpr / 2 ) - ( textureSize / 2 );

				renderer.copyFramebufferToTexture( vector, texture );

				renderer.clearDepth();
				renderer.render( sceneOrtho, cameraOrtho );

			}

		</script>

	</body>
</html>