examples/webgl_buffergeometry_indexed.html

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		<title>three.js webgl - buffergeometry - indexed</title>
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		<div id="info"><a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> webgl - buffergeometry - indexed</div>

		<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';
			import { GUI } from 'three/addons/libs/lil-gui.module.min.js';

			let camera, scene, renderer, stats;

			let mesh;

			init();

			function init() {

				//

				camera = new THREE.PerspectiveCamera( 27, window.innerWidth / window.innerHeight, 1, 3500 );
				camera.position.z = 64;

				scene = new THREE.Scene();
				scene.background = new THREE.Color( 0x050505 );

				//

				const light = new THREE.HemisphereLight();
				light.intensity = 3;
				scene.add( light );

				//

				const geometry = new THREE.BufferGeometry();

				const indices = [];

				const vertices = [];
				const normals = [];
				const colors = [];

				const size = 20;
				const segments = 10;

				const halfSize = size / 2;
				const segmentSize = size / segments;

				const _color = new THREE.Color();

				// generate vertices, normals and color data for a simple grid geometry

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

					const y = ( i * segmentSize ) - halfSize;

					for ( let j = 0; j <= segments; j ++ ) {

						const x = ( j * segmentSize ) - halfSize;

						vertices.push( x, - y, 0 );
						normals.push( 0, 0, 1 );

						const r = ( x / size ) + 0.5;
						const g = ( y / size ) + 0.5;

						_color.setRGB( r, g, 1, THREE.SRGBColorSpace );

						colors.push( _color.r, _color.g, _color.b );

					}

				}

				// generate indices (data for element array buffer)

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

					for ( let j = 0; j < segments; j ++ ) {

						const a = i * ( segments + 1 ) + ( j + 1 );
						const b = i * ( segments + 1 ) + j;
						const c = ( i + 1 ) * ( segments + 1 ) + j;
						const d = ( i + 1 ) * ( segments + 1 ) + ( j + 1 );

						// generate two faces (triangles) per iteration

						indices.push( a, b, d ); // face one
						indices.push( b, c, d ); // face two

					}

				}

				//

				geometry.setIndex( indices );
				geometry.setAttribute( 'position', new THREE.Float32BufferAttribute( vertices, 3 ) );
				geometry.setAttribute( 'normal', new THREE.Float32BufferAttribute( normals, 3 ) );
				geometry.setAttribute( 'color', new THREE.Float32BufferAttribute( colors, 3 ) );

				const material = new THREE.MeshPhongMaterial( {
					side: THREE.DoubleSide,
					vertexColors: true
				} );

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

				//

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

				//

				stats = new Stats();
				document.body.appendChild( stats.dom );

				//

				const gui = new GUI();
				gui.add( material, 'wireframe' );

				//

				window.addEventListener( 'resize', onWindowResize );

			}

			function onWindowResize() {

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

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

			}

			//

			function animate() {

				const time = Date.now() * 0.001;

				mesh.rotation.x = time * 0.25;
				mesh.rotation.y = time * 0.5;

				renderer.render( scene, camera );

				stats.update();

			}

		</script>

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