three.js之自定义一个正方体（网格）
本节主要通过自定义顶点和平面的方式，创造一个立方体。真正的开始走近three.js。
效果图
坐标系
坐标系支持右手定则。图中红色是x轴，绿色是y轴，蓝色是z轴
源码
引入的插件js【本人的csdn也有下载资源，如果打不开git可以在csdn下载】：
- three.js
- dat.gui.js
- Stats.js
- TrackballControls.js
- SceneUtils.js
- util.js
<!DOCTYPE html>
<html><head><meta charset="utf-8"><title></title><link type="text/css" rel="stylesheet" href="../css/index.css" /><script src="../libs/three.js"></script><script src="../libs/Stats.js"></script><script src="../libs/dat.gui.js"></script><script src="../libs/TrackballControls.js"></script><script src="../js/util/three_util.js"></script><script src="../js/util/SceneUtils.js"></script></head><body><div id="webgl-output"></div><script src="../js/3.js"></script></body>
</html>3.js
var stats = initStats();
var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 100);
var renderer = new THREE.WebGLRenderer();
renderer.setClearColor(new THREE.Color(0x000000));
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.shadowMap.enabled = true;var planeGeometry = new THREE.PlaneGeometry(60, 40, 1, 1);
var planeMaterial = new THREE.MeshLambertMaterial({color: 0xffffff
});
var plane = new THREE.Mesh(planeGeometry, planeMaterial);
plane.receiveShadow = true;
plane.rotation.x = -0.5 * Math.PI;
plane.position.x = 0;
plane.position.y = 0;
plane.position.z = 0;
scene.add(plane);camera.position.x = -30;
camera.position.y = 40;
camera.position.z = 30;
camera.lookAt(scene.position);// 设置8个顶点
var vertices = [new THREE.Vector3(1,1,1),new THREE.Vector3(1,5,1),new THREE.Vector3(1,1,5),new THREE.Vector3(1,5,5),new THREE.Vector3(5,1,1),new THREE.Vector3(5,5,1),new THREE.Vector3(5,1,5),new THREE.Vector3(5,5,5)
]// 构建立方体所需要的十二个三角形平面
var faces = [new THREE.Face3(0,2,1),new THREE.Face3(2,3,1),new THREE.Face3(7,3,2),new THREE.Face3(7,2,6),new THREE.Face3(5,7,6),new THREE.Face3(4,5,6),new THREE.Face3(1,5,0),new THREE.Face3(0,5,4),new THREE.Face3(5,1,3),new THREE.Face3(5,3,7),new THREE.Face3(2,0,4),new THREE.Face3(2,4,6)
]var geom = new THREE.Geometry()
geom.vertices = vertices
geom.faces = faces
geom.computeFaceNormals()
// 设置两种材质，这样方便同时看颜色和骨架
var materials = [new THREE.MeshBasicMaterial({color: 0x000000, wireframe: true}),new THREE.MeshLambertMaterial({opacity: 0.6, color: 0x44ff44, transparent: true})
];
// materials这样做的原因是，除了显示绿色透明的立方体外，我还想显示一个线框。因为使用线框可以很容易地找出顶点和面的位置。
// SceneUtils是SceneUtils里的方法
var mesh = THREE.SceneUtils.createMultiMaterialObject(geom, materials);
mesh.castShadow = true;
mesh.children.forEach(function (e) {e.castShadow = true
});scene.add(mesh);var ambientLight = new THREE.AmbientLight(0x3c3c3c);
scene.add(ambientLight);var spotLight = new THREE.SpotLight(0xffffff, 1.2, 150, 120);
spotLight.position.set(-40, 60, -10);
spotLight.castShadow = true;
scene.add(spotLight);document.getElementById("webgl-output").appendChild(renderer.domElement);
var trackballControls = initTrackballControls(camera, renderer);
var clock = new THREE.Clock();
render();function render() {trackballControls.update(clock.getDelta());stats.update();requestAnimationFrame(render);renderer.render(scene, camera);
}
注意点：
- 通过vertices方法设置顶点，通过faces设置平面。
- three里平面是由三角形构成的，所以我们要用三角形去拼装成一个个平面，比如我们要构建一个正方体，那么就需要定义8个顶点和12个三角形，
- 三角形的顶点顺序是有规则的，当三个点是顺时针排列的时候，平面是面向相机的（面向相机的平面带颜色），反之则相反。（当然也可以伸出右手，让手指顺着顶点排列的顺序弯曲，这时候大拇指指向的方向就是平面的正面即有颜色的一侧。类似我们高中物理的电磁感应的右手定则一样。）
- 示例中引用了SceneUtils.js里的createMultiMaterialObject方法，主要是为了构建一个同时支持两种材质的平面。
网格的方法
- mesh.rotation.x = Math.PI * 0.4 或 mesh.rotation.set(Math.PI * 0.4, 0, 0) 或 mesh.rotation = new THREE.Vector3(Math.PI * 0.4, 0, 0)
- mesh.position.x = 4 或 mesh.position.set(4, 0, 0) 或 mesh.position = new THREE.Vector3(Math.PI * 0.4, 0, 0)
- mesh.scaleX = 4 或 mesh.scale = 4 或 mesh.scale.set(4, 0, 0)
- mesh.translateX = 4或 mesh.translate.set(4, 0, 0)
- mesh.visible = true 或 false
