每日见闻之Three.js 官方demo 学习Buffergeometry

js 复制代码

<!DOCTYPE html>
<html lang="en">
	<head>
		<title>three.js webgl - buffergeometry</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> webgl - buffergeometry</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';

			let container, stats;

			let camera, scene, renderer;

			let mesh;

			init();
			animate();

			function init() {

				container = document.getElementById( 'container' );

				//

				camera = new THREE.PerspectiveCamera( 27, window.innerWidth / window.innerHeight, 1, 3500 );
				camera.position.z = 2750;

				scene = new THREE.Scene();
				scene.background = new THREE.Color( 0x050505 );
				scene.fog = new THREE.Fog( 0x050505, 2000, 3500 );

				//

				scene.add( new THREE.AmbientLight( 0xcccccc ) );

				const light1 = new THREE.DirectionalLight( 0xffffff, 1.5 );
				light1.position.set( 1, 1, 1 );
				scene.add( light1 );

				const light2 = new THREE.DirectionalLight( 0xffffff, 4.5 );
				light2.position.set( 0, - 1, 0 );
				scene.add( light2 );

				//

				const triangles = 160000;

				const geometry = new THREE.BufferGeometry();

				const positions = [];
				const normals = [];
				const colors = [];

				const color = new THREE.Color();

				const n = 800, n2 = n / 2;	// triangles spread in the cube
				const d = 12, d2 = d / 2;	// individual triangle size

				const pA = new THREE.Vector3();
				const pB = new THREE.Vector3();
				const pC = new THREE.Vector3();

				const cb = new THREE.Vector3();
				const ab = new THREE.Vector3();

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

					// positions

					const x = Math.random() * n - n2;
					const y = Math.random() * n - n2;
					const z = Math.random() * n - n2;

					const ax = x + Math.random() * d - d2;
					const ay = y + Math.random() * d - d2;
					const az = z + Math.random() * d - d2;

					const bx = x + Math.random() * d - d2;
					const by = y + Math.random() * d - d2;
					const bz = z + Math.random() * d - d2;

					const cx = x + Math.random() * d - d2;
					const cy = y + Math.random() * d - d2;
					const cz = z + Math.random() * d - d2;

					positions.push( ax, ay, az );
					positions.push( bx, by, bz );
					positions.push( cx, cy, cz );

					// flat face normals

					pA.set( ax, ay, az );
					pB.set( bx, by, bz );
					pC.set( cx, cy, cz );

					cb.subVectors( pC, pB );
					ab.subVectors( pA, pB );
					cb.cross( ab );

					cb.normalize();

					const nx = cb.x;
					const ny = cb.y;
					const nz = cb.z;

					normals.push( nx, ny, nz );
					normals.push( nx, ny, nz );
					normals.push( nx, ny, nz );

					// colors

					const vx = ( x / n ) + 0.5;
					const vy = ( y / n ) + 0.5;
					const vz = ( z / n ) + 0.5;

					color.setRGB( vx, vy, vz );

					const alpha = Math.random();

					colors.push( color.r, color.g, color.b, alpha );
					colors.push( color.r, color.g, color.b, alpha );
					colors.push( color.r, color.g, color.b, alpha );

				}

				function disposeArray() {

					this.array = null;

				}

				geometry.setAttribute( 'position', new THREE.Float32BufferAttribute( positions, 3 ).onUpload( disposeArray ) );
				geometry.setAttribute( 'normal', new THREE.Float32BufferAttribute( normals, 3 ).onUpload( disposeArray ) );
				geometry.setAttribute( 'color', new THREE.Float32BufferAttribute( colors, 4 ).onUpload( disposeArray ) );

				geometry.computeBoundingSphere();

				const material = new THREE.MeshPhongMaterial( {
					color: 0xd5d5d5, specular: 0xffffff, shininess: 250,
					side: THREE.DoubleSide, vertexColors: true, transparent: 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 );
				container.appendChild( renderer.domElement );

				//

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

				//

				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>

	</body>
</html>

Buffergeometry 主要就是下面这个三个参数

const positions = []; 顶点坐标每三个点是一个坐标每三个坐标是一个三角形也就是一个顶点

js 复制代码

//计算每一个三角形的三个顶点的坐标
const x = Math.random() * n - n2;
const y = Math.random() * n - n2;
const z = Math.random() * n - n2;
const ax = x + Math.random() * d - d2;
const ay = y + Math.random() * d - d2;
const az = z + Math.random() * d - d2;

const bx = x + Math.random() * d - d2;
const by = y + Math.random() * d - d2;
const bz = z + Math.random() * d - d2;

const cx = x + Math.random() * d - d2;
const cy = y + Math.random() * d - d2;
const cz = z + Math.random() * d - d2;

positions.push( ax, ay, az );
positions.push( bx, by, bz );
positions.push( cx, cy, cz );

const normals = []; 法向量每个坐标点需要对应一个法向量这个法向量是用来表示跟上面的三角形垂直的方向。

js 复制代码

//计算法向量的代码
cb.subVectors( pC, pB );
ab.subVectors( pA, pB );
cb.cross( ab );

const colors = [];每一个坐标点对应一个颜色，三角形中的颜色通过渐变计算得出

js 复制代码

//计算三角形每个顶点对应的颜色 三角形 三个角 所以push 3次
const vx = ( x / n ) + 0.5;
const vy = ( y / n ) + 0.5;
const vz = ( z / n ) + 0.5;

color.setRGB( vx, vy, vz );

const alpha = Math.random();

colors.push( color.r, color.g, color.b, alpha );
colors.push( color.r, color.g, color.b, alpha );
colors.push( color.r, color.g, color.b, alpha );

stats 统计性能的工具