examples/webgl_materials_texture_partialupdate.html

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	<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">
		<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 noreferrer">three.js</a> - partial texture update <br/>
			replace parts of an existing texture with all data of another texture
		</div>

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

		<script type="module">

			import * as THREE from 'three';

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

			let last = 0;
			const position = new THREE.Vector2();
			const color = new THREE.Color();

			init();

			async 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();

				const loader = new THREE.TextureLoader();
				diffuseMap = await loader.loadAsync( 'textures/floors/FloorsCheckerboard_S_Diffuse.jpg' );
				diffuseMap.colorSpace = THREE.SRGBColorSpace;
				diffuseMap.minFilter = THREE.LinearFilter;
				diffuseMap.generateMipmaps = false;

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

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

				//

				const width = 32;
				const height = 32;

				const data = new Uint8Array( width * height * 4 );
				dataTexture = new THREE.DataTexture( data, width, height );

				//

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

				//

				window.addEventListener( 'resize', onWindowResize );

			}

			function onWindowResize() {

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

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

			}

			function animate() {

				const elapsedTime = clock.getElapsedTime();

				if ( elapsedTime - last > 0.1 ) {

					last = elapsedTime;

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

					// generate new color data

					updateDataTexture( dataTexture );

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

					renderer.copyTextureToTexture( dataTexture, diffuseMap, null, position );

				}

				renderer.render( scene, camera );

			}

			function updateDataTexture( texture ) {

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

				// generate a random color and update texture data

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

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

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

					const stride = i * 4;

					data[ stride ] = r;
					data[ stride + 1 ] = g;
					data[ stride + 2 ] = b;
					data[ stride + 3 ] = 1;

				}

			}

		</script>

	</body>
</html>