這一篇將要介紹的內容是如何爲物體的每一個面單獨指定材質。也許一些老資格的 three.js men 會想到 MeshFaceMaterial 材質。但在新版 three.js 中已經不存在這種材質了，因爲原則上來講，舊版中的 MeshFaceMaterial 材質其實就是一個材質數組。舉個例子，假如我們在場景中加入一個立方體，這個立方體上有六個面，你可以通過定義一個長度爲六的材質數組來爲每一個面單獨指定一種材質（比如不同的顏色）即可。代碼實現也很簡單，如下代碼片段所示：
var matArray = [];
matArray.push(new THREE.MeshBasicMaterial({color: 0x009e60}));
matArray.push(new THREE.MeshBasicMaterial({color: 0x0051ba}));
matArray.push(new THREE.MeshBasicMaterial({color: 0xffd500}));
matArray.push(new THREE.MeshBasicMaterial({color: 0xff5800}));
matArray.push(new THREE.MeshBasicMaterial({color: 0xc41e3a}));
matArray.push(new THREE.MeshBasicMaterial({color: 0xffffff}));
var cube = new THREE.Mesh(new THREE.BoxGeometry(3, 3, 3), matArray);接下來，讓我們在此基礎上來研究一下，看看如何生成出一個類似魔方的圖形出來，如下圖所示：
大概的思路是，魔方由一些小方塊組成，規律是：沿 x 軸方向 3 個，沿 y 軸方向 3 個，沿 z 軸方向 3 個，核心代碼如下：
var cubeGeometry = new THREE.BoxGeometry(2.9, 2.9, 2.9);
var group = new THREE.Mesh();
for (var x = 0; x < 3; x++) {
for (var y = 0; y < 3; y++) {
for (var z = 0; z < 3; z++) {
var subcube = new THREE.Mesh(cubeGeometry, matArray);
subcube.position.set(x * 3 - 3, y * 3 + 3, z * 3 - 3);
group.add(subcube);
}
}
}
scene.add(group);<!DOCTYPE html>
<html>
<head>
<title>示例 04.05 - FaceMaterial</title>
<script src="../build/three.js"></script>
<script src="../build/js/controls/OrbitControls.js"></script>
<script src="../build/js/libs/stats.min.js"></script>
<script src="../build/js/libs/dat.gui.min.js"></script>
<script src="../jquery/jquery-3.2.1.min.js"></script>
<style>
body {
/* 設置 margin 爲 0，並且 overflow 爲 hidden，來完成頁面樣式 */
margin: 0;
overflow: hidden;
}
/* 統計對象的樣式 */
#Stats-output {
position: absolute;
left: 0px;
top: 0px;
}
</style>
</head>
<body>
<!-- 用於 WebGL 輸出的 Div -->
<div id="webgl-output"></div>
<!-- 用於統計 FPS 輸出的 Div -->
<div id="stats-output"></div>
<!-- 運行 Three.js 示例的 Javascript 代碼 -->
<script type="text/javascript">
var scene;
var camera;
var render;
var webglRender;
var canvasRender;
var controls;
var stats;
var guiParams;
var ground;
var cube;
var group;
var meshMaterial;
var ambientLight;
$(function() {
stats = initStats();
scene = new THREE.Scene();
webglRender = new THREE.WebGLRenderer( {antialias: true, alpha: true} ); // antialias 抗鋸齒
webglRender.setSize(window.innerWidth, window.innerHeight);
webglRender.setClearColor(0x000000, 1.0);
//webglRender.shadowMap.enabled = true; // 允許陰影投射
render = webglRender;
camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 30, 1000); // 2147483647
camera.position.set(-50, 40, 50);
var target = new THREE.Vector3(0, 0 , 0);
controls = new THREE.OrbitControls(camera, render.domElement);
controls.target = target;
camera.lookAt(target);
$('#webgl-output')[0].appendChild(render.domElement);
window.addEventListener('resize', onWindowResize, false);
ambientLight = new THREE.AmbientLight(0x000000);
scene.add(ambientLight);
// 加入一個平面
var groundGeometry = new THREE.PlaneGeometry(100, 100, 4, 4);
var groundMaterial = new THREE.MeshBasicMaterial({color: 0x777777});
ground = new THREE.Mesh(groundGeometry, groundMaterial);
ground.rotation.set(-0.5 * Math.PI, 0, 0); // 沿着 X軸旋轉-90°
scene.add(ground);
// 定義 cube
var cubeGeometry = new THREE.BoxGeometry(2.9, 2.9, 2.9);
// 材質
meshMaterial = [];
meshMaterial.push(new THREE.MeshBasicMaterial({color: 0x009e60, flatShading: true}));
meshMaterial.push(new THREE.MeshBasicMaterial({color: 0x0051ba, flatShading: true}));
meshMaterial.push(new THREE.MeshBasicMaterial({color: 0xffd500, flatShading: true}));
meshMaterial.push(new THREE.MeshBasicMaterial({color: 0xff5800, flatShading: true}));
meshMaterial.push(new THREE.MeshBasicMaterial({color: 0xc41e3a, flatShading: true}));
meshMaterial.push(new THREE.MeshBasicMaterial({color: 0xffffff, flatShading: true}));
// 加入單個立方體
cube = new THREE.Mesh(cubeGeometry, meshMaterial);
cube.position.set(0, 3, 15);
scene.add(cube);
// 加入一個魔方
group = new THREE.Mesh();
for (var x = 0; x < 3; x++) {
for (var y = 0; y < 3; y++) {
for (var z = 0; z < 3; z++) {
var subcube = new THREE.Mesh(cubeGeometry, meshMaterial);
subcube.position.set(x * 3 - 3, y * 3 + 3, z * 3 - 3);
group.add(subcube);
}
}
}
scene.add(group);
/** 用來保存那些需要修改的變量 */
guiParams = new function() {
this.rotationSpeed = 0.02;
}
/** 定義 dat.GUI 對象，並綁定 guiParams 的幾個屬性 */
var gui = new dat.GUI();
gui.add(guiParams, 'rotationSpeed', 0.01, 1.0);
renderScene();
});
/** 渲染場景 */
function renderScene() {
stats.update();
rotateMesh(); // 旋轉物體
requestAnimationFrame(renderScene);
render.render(scene, camera);
}
/** 初始化 stats 統計對象 */
function initStats() {
stats = new Stats();
stats.setMode(0); // 0 爲監測 FPS；1 爲監測渲染時間
$('#stats-output').append(stats.domElement);
return stats;
}
/** 當瀏覽器窗口大小變化時觸發 */
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
render.setSize(window.innerWidth, window.innerHeight);
}
/** 旋轉物體 */
function rotateMesh() {
scene.traverse(function(mesh) {
if (mesh instanceof THREE.Mesh && (mesh === group || mesh === cube)) {
//mesh.rotation.x += guiParams.rotationSpeed;
mesh.rotation.y += guiParams.rotationSpeed;
//mesh.rotation.z += guiParams.rotationSpeed;
}
});
}
</script>
</body>
</html>未完待續···