《一起来学three.js构建WebGL应用》第一课

是时候开始我们致力于WebGL的新系列文章。这是我们的第一节课，我们主要做些的基本功能：创建一个场景，相机，渲染器，控制器（OrbitControls）。我们也将创建简单的定向光，加上一些对象（不同的几何形状）的阴影。为了使事情更快，我们决定采取一个最流行的WebGL框架——three.js。为什么使用three.js？事实上，它是开源的JavaScript框架，它也是增长最迅速的和讨论很热烈的引擎。在这里，已经准备了很多会用到的东西，从基本的点和向量，到做准备工作的场景、着色器，甚至立体效果。

Live Demo

HTML

我们可以省略这一步，但是，通常，我们在每一节课都会做。这是我们这节课的HTML结构：



    
        
        
        WebGL With Three.js - Lesson 1 | Script Tutorials
        
         //本地样式表
    
    
        
        
        
        
         // 我们待会要写的内容

在这段代码中，我们引入了所有今天要用到的库。

Javascript

我希望你已经见过我们的demo和想象组成它的基本元素，我们将一步一步解释每个部分的创建。

主体

我们的场景看起来像这样：

var lesson1 = {
    scene: null,
    camera: null,
    renderer: null,
    container: null,
    controls: null,
    clock: null,
    stats: null,

    init: function() { // 初始化

    }
};

// 使场景动画化
function animate() {
    requestAnimationFrame(animate);
    render();
    update();
}

// 更新控制器状态
function update() {
    lesson1.controls.update(lesson1.clock.getDelta());
    lesson1.stats.update();
}

// 渲染场景
function render() {
    if (lesson1.renderer) {
        lesson1.renderer.render(lesson1.scene, lesson1.camera);
    }
}

// 在页面加载时初始化 lesson 对象
function initializeLesson() {
    lesson1.init();
    animate();
}

if (window.addEventListener)
    window.addEventListener('load', initializeLesson, false);
else if (window.attachEvent)
    window.attachEvent('onload', initializeLesson);
else window.onload = initializeLesson;

这是用 three.js 建应用的常用结构。几乎所有的东西都将在init方法里创建。

场景创建、相机和渲染

它们是我们场景的主要元素，接下来的代码将创建一个空场景，包含一个前景相机和可用的阴影映射渲染：

// 创建主要场景
this.scene = new THREE.Scene();

var SCREEN_WIDTH = window.innerWidth,
    SCREEN_HEIGHT = window.innerHeight;

// 准备相机
var VIEW_ANGLE = 45, ASPECT = SCREEN_WIDTH / SCREEN_HEIGHT, NEAR = 1, FAR = 10000;
this.camera = new THREE.PerspectiveCamera( VIEW_ANGLE, ASPECT, NEAR, FAR);
this.scene.add(this.camera);
this.camera.position.set(-1000, 1000, 0);
this.camera.lookAt(new THREE.Vector3(0,0,0));

// 准备渲染
this.renderer = new THREE.WebGLRenderer({antialias:true, alpha: false});
this.renderer.setSize(SCREEN_WIDTH, SCREEN_HEIGHT);
this.renderer.setClearColor(0xffffff);

this.renderer.shadowMapEnabled = true;
this.renderer.shadowMapSoft = true;

// 准备容器
this.container = document.createElement('div');
document.body.appendChild(this.container);
this.container.appendChild(this.renderer.domElement);

// 事件
THREEx.WindowResize(this.renderer, this.camera);

我们将相机把相机放在45度角，设为全屏幕大小，WebGLRenderer设为白色，再把我们的场景添加到HTML文档中，而且在浏览器窗口大小变化时，用THREEx.WindowResize 来控制渲染和相机的变化。

OrbitControls 和 Stats

为了能够在某种程度上控制相机的 —— three.js 给我们提供了现成的控件。其中之一是 OrbitControls，它能在场景中绕其轴线旋转。一个小插件stats.min.js将有助于我们看到场景的统计（FPS）。

// 准备控制器 (OrbitControls)
this.controls = new THREE.OrbitControls(this.camera, this.renderer.domElement);
this.controls.target = new THREE.Vector3(0, 0, 0);

// 准备计时器
this.clock = new THREE.Clock();

// 准备统计
this.stats = new Stats();
this.stats.domElement.style.position = 'absolute';
this.stats.domElement.style.bottom = '0px';
this.stats.domElement.style.zIndex = 10;
this.container.appendChild( this.stats.domElement );

因此，我们准备好了四个元素。

光和场地的创作

光是一个场景中的重要元素，在我们的第一个教程，我们将创建最简单的定向光线，因为我们要添加基本的阴影：

// 添加定向光线
var dLight = new THREE.DirectionalLight(0xffffff);
dLight.position.set(1, 1000, 1);
dLight.castShadow = true;
dLight.shadowCameraVisible = true;
dLight.shadowDarkness = 0.2;
dLight.shadowMapWidth = dLight.shadowMapHeight = 1000;
this.scene.add(dLight);

// 添加粒子光线
particleLight = new THREE.Mesh( new THREE.SphereGeometry(10, 10, 10), new THREE.MeshBasicMaterial({ color: 0x44ff44 }));
particleLight.position = dLight.position;
this.scene.add(particleLight);

// 添加简单的场地
var groundGeometry = new THREE.PlaneGeometry(1000, 1000, 1, 1);
ground = new THREE.Mesh(groundGeometry, new THREE.MeshLambertMaterial({
    color: this.getRandColor()
}));
ground.position.y = 0;
ground.rotation.x = - Math.PI / 2;
ground.receiveShadow = true;
this.scene.add(ground);

当我们创建灯光时，用了两个参数 castShadow 和 shadowCameraVisible。这将使我们能够直观地看到光在哪里，理解构造的过程（和边界）的阴影。
你也可能会注意到，在添加光后，我们增加了一个球形物体——为你准备的，以便直观地知道我们的定向光源在什么位置。我们用一个平面作为地面去接收阴影——我们设置的receiveShadow参数为true。

颜色

我们将在场景中添加额外的对象。我用一个方法来生成不同颜色的部件。这个方法将从颜色列表中随机返回一个预定义的颜色。

var colors = [
    0xFF62B0,
    0x9A03FE,
    0x62D0FF,
    0x48FB0D,
    0xDFA800,
    0xC27E3A,
    0x990099,
    0x9669FE,
    0x23819C,
    0x01F33E,
    0xB6BA18,
    0xFF800D,
    0xB96F6F,
    0x4A9586
];

getRandColor: function() {
    return colors[Math.floor(Math.random() * colors.length)];
}

CircleGeometry 、 CubeGeometry、CylinderGeometry 和 ExtrudeGeometry

几何对象是用必要的数据（点、顶点、面等）来描述三维模型。我们将创建平面的圆、立方体和圆柱体。Extrude Geometry是用来制作从路径凸出的形状。我们要做个凸出的三角形：

// 添加圆形
var circle = new THREE.Mesh(new THREE.CircleGeometry(70, 50), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
circle.rotation.x = - Math.PI / 2;
circle.rotation.y = - Math.PI / 3;
circle.rotation.z = Math.PI / 3;
circle.position.x = -300;
circle.position.y = 150;
circle.position.z = -300;
circle.castShadow = circle.receiveShadow = true;
this.scene.add(circle);

// 添加方块
var cube = new THREE.Mesh(new THREE.CubeGeometry(100, 100, 100), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
cube.rotation.x = cube.rotation.z = Math.PI * 0.1;
cube.position.x = -300;
cube.position.y = 150;
cube.position.z = -100;
cube.castShadow = cube.receiveShadow = true;
this.scene.add(cube);

// 添加圆柱
var cube = new THREE.Mesh(new THREE.CylinderGeometry(60, 80, 90, 32), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
cube.rotation.x = cube.rotation.z = Math.PI * 0.1;
cube.position.x = -300;
cube.position.y = 150;
cube.position.z = 100;
cube.castShadow = cube.receiveShadow = true;
this.scene.add(cube);

// 添加不规则的物体
var extrudeSettings = {
    amount: 10,
    steps: 10,
    bevelSegments: 10,
    bevelSize: 10,
    bevelThickness: 10
};
var triangleShape = new THREE.Shape();
triangleShape.moveTo(  0, -50 );
triangleShape.lineTo(  -50, 50 );
triangleShape.lineTo( 50, 50 );
triangleShape.lineTo(  0, -50 );

var extrude = new THREE.Mesh(new THREE.ExtrudeGeometry(triangleShape, extrudeSettings), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
extrude.rotation.y = Math.PI / 2;
extrude.position.x = -300;
extrude.position.y = 150;
extrude.position.z = 300;
extrude.castShadow = extrude.receiveShadow = true;
this.scene.add(extrude);

几何体建好后，我们可以创建一个在这个几何的基础上的网格。

IcosahedronGeometry 、 OctahedronGeometry 、 RingGeometry 和 ShapeGeometry

接下来我们将创建四个元素：二十面体、八面体、环，和用shapegeometry对象自定义的路径（形状）：

// 二十面体
var icosahedron = new THREE.Mesh(new THREE.IcosahedronGeometry(70), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
icosahedron.position.x = -100;
icosahedron.position.y = 150;
icosahedron.position.z = -300;
icosahedron.castShadow = icosahedron.receiveShadow = true;
this.scene.add(icosahedron);

// 八面体
var octahedron = new THREE.Mesh(new THREE.OctahedronGeometry(70), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
octahedron.position.x = -100;
octahedron.position.y = 150;
octahedron.position.z = -100;
octahedron.castShadow = octahedron.receiveShadow = true;
this.scene.add(octahedron);

// 环
var ring = new THREE.Mesh(new THREE.RingGeometry(30, 70, 32), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
ring.rotation.y = -Math.PI / 2;
ring.position.x = -100;
ring.position.y = 150;
ring.position.z = 100;
ring.castShadow = ring.receiveShadow = true;
this.scene.add(ring);

// 几何结构
var shapeG = new THREE.Mesh(new THREE.ShapeGeometry(triangleShape), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
shapeG.rotation.y = -Math.PI / 2;
shapeG.position.x = -100;
shapeG.position.y = 150;
shapeG.position.z = 300;
shapeG.castShadow = shapeG.receiveShadow = true;
this.scene.add(shapeG);

SphereGeometry 、 TetrahedronGeometry 、 TorusGeometry、 TorusKnotGeometry 和 TubeGeometry

最后，我们创建一个球体、四面体、圆环、圆环管：

// 球体
var sphere = new THREE.Mesh(new THREE.SphereGeometry(70, 32, 32), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
sphere.rotation.y = -Math.PI / 2;
sphere.position.x = 100;
sphere.position.y = 150;
sphere.position.z = -300;
sphere.castShadow = sphere.receiveShadow = true;
this.scene.add(sphere);

// 四面体
var tetrahedron = new THREE.Mesh(new THREE.TetrahedronGeometry(70), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
tetrahedron.position.x = 100;
tetrahedron.position.y = 150;
tetrahedron.position.z = -100;
tetrahedron.castShadow = tetrahedron.receiveShadow = true;
this.scene.add(tetrahedron);

// 圆环
var torus = new THREE.Mesh(new THREE.TorusGeometry(70, 20, 16, 100), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
torus.rotation.y = -Math.PI / 2;
torus.position.x = 100;
torus.position.y = 150;
torus.position.z = 100;
torus.castShadow = torus.receiveShadow = true;
this.scene.add(torus);

// 圆环管
var torusK = new THREE.Mesh(new THREE.TorusKnotGeometry(70, 20, 16, 100), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
torusK.rotation.y = -Math.PI / 2;
torusK.position.x = 100;
torusK.position.y = 150;
torusK.position.z = 300;
torusK.castShadow = torusK.receiveShadow = true;
this.scene.add(torusK);

// 不规则的圆环结管
var points = [];
for (var i = 0; i < 10; i++) {
    var randomX = -100 + Math.round(Math.random() * 200);
    var randomY = -100 + Math.round(Math.random() * 200);
    var randomZ = -100 + Math.round(Math.random() * 200);

    points.push(new THREE.Vector3(randomX, randomY, randomZ));
}
var tube = new THREE.Mesh(new THREE.TubeGeometry(new THREE.SplineCurve3(points), 64, 20), new THREE.MeshLambertMaterial({ color: this.getRandColor() }));
tube.rotation.y = -Math.PI / 2;
tube.position.x = 0;
tube.position.y = 500;
tube.position.z = 0;
tube.castShadow = tube.receiveShadow = true;
this.scene.add(tube);

注意构造管过程，TubeGeometry 允许我们通过一组点建立一个圆柱形物体。

光的平滑运动

为了顺利地将光，我们只需要在update方法里添加以下代码：

var timer = Date.now() * 0.000025;
particleLight.position.x = Math.sin(timer * 5) * 300;
particleLight.position.z = Math.cos(timer * 5) * 300;

未完待续~

原文 WebGL With Three.js – Lesson 1
由 SegmentFault 编译