examples/webgl_materials_texture_partialupdate.html

<!DOCTYPE html>
<html lang="en">
	<head>
		<title>three.js webgl - texture - partial update</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;
			}
		</style>

		<script src="../build/three.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> - partial texture update <br/>
			replace parts of an existing texture with all data of another texture
		</div>

		<script>

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

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

			}

			var camera, scene, renderer, clock, dataTexture, diffuseMap;

			init();

			function init() {

				camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 0.01, 10 );
				camera.position.z = 2;

				scene = new THREE.Scene();

				clock = new THREE.Clock();

				var loader = new THREE.TextureLoader();
				diffuseMap = loader.load( 'textures/floors/FloorsCheckerboard_S_Diffuse.jpg', animate );
				diffuseMap.minFilter = THREE.LinearFilter;
				diffuseMap.generateMipmaps = false;

				var geometry = new THREE.PlaneBufferGeometry( 2, 2 );
				var material = new THREE.MeshBasicMaterial( { map: diffuseMap } );

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

				//

				var width = 32;
				var height = 32;

				var data = new Uint8Array( width * height * 3 );
				dataTexture = new THREE.DataTexture( data, width, height, THREE.RGBFormat );

				//

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

				//

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

			}

			function onWindowResize() {

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

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

			}

			var last = 0;
			var position = new THREE.Vector2();

			function animate() {

				requestAnimationFrame( animate );

				var elapsedTime = clock.getElapsedTime();

				if ( elapsedTime - last > 0.1 ) {

					last = elapsedTime;

					position.x = ( 32 * THREE.Math.randInt( 1, 16 ) ) - 32;
					position.y = ( 32 * THREE.Math.randInt( 1, 16 ) ) - 32;

					// generate new color data

					updateDataTexture( dataTexture );

					// perform copy from src to dest texture to a random position

					renderer.copyTextureToTexture( position, dataTexture, diffuseMap );

				}

				renderer.render( scene, camera );

			}

			var color = new THREE.Color();

			function updateDataTexture( texture ) {

				var size = texture.image.width * texture.image.height;
				var data = texture.image.data;

				// generate a random color and update texture data

				color.setHex( Math.random() * 0xffffff );

				var r = Math.floor( color.r * 255 );
				var g = Math.floor( color.g * 255 );
				var b = Math.floor( color.b * 255 );

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

					var stride = i * 3;

					data[ stride ] = r;
					data[ stride + 1 ] = g;
					data[ stride + 2 ] = b;

				}

			}

		</script>

	</body>
</html>