今天是最後一篇介紹 three.js 中常用的基礎幾何體。本篇將要介紹的是 PolyhedronGeometry 幾何體。翻譯成中文就叫多面體。多面體是一種只有平面和直邊的幾何體。多數情況下我們不會使用這種幾何體，因爲 three.js 庫爲我們提供了幾種特定的多面體，如：TetrahedronGeometry 四面體、OctahedronGeometry 八面體、DodecahedronGeometry 十二面體、IcosahedronGeometry 二十面體。
我們先來看看 PolyhedronGeometry 多面體的幾個常用屬性：
| 屬性 | 描述 |
|---|---|
| vertices | 必須。此屬性定義構成多面體的頂點 |
| faces | 必須。此屬性定義由 vertices 中的點構成的面 |
| radius | 可選。此屬性定義多面體的大小。默認值是 1 |
| detail | 可選。此屬性定義給多面體添加哪種額外細節。取值範圍是大於等於 0。當設爲 0 時，多面體的每一個面都不會有任何細節；爲 1 時，每一個面多將再次分成 4 個小三角形表示；爲 2 時，再次分隔的每一個面又會繼續分成 4 個小三角形，以此類推 |
<!DOCTYPE html>
<html>
<head>
<title>示例 05.09 - PolyhedronGeometry</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 box;
//var sphere;
//var cylinder;
//var plane;
//var torus;
//var torusKnot;
var polyhedron;
var meshMaterial;
var ambientLight;
var spotLight;
var axesHelper;
//var cameraHelper;
$(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(0xeeeeee, 1.0);
webglRender.shadowMap.enabled = true; // 允許陰影投射
render = webglRender;
camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.01, 1000); // 2147483647
camera.position.set(-45.5, 68.2, 90.9);
var target = new THREE.Vector3(10, 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);
// 加入一個座標軸：X（橙色）、Y（綠色）、Z（藍色）
axesHelper = new THREE.AxesHelper(60);
scene.add(axesHelper);
ambientLight = new THREE.AmbientLight(0x0c0c0c);
scene.add(ambientLight);
spotLight = new THREE.SpotLight(0xffffff);
spotLight.position.set(0, 60, 30);
spotLight.shadow.mapSize.width = 5120; // 必須是 2的冪，默認值爲 512
spotLight.shadow.mapSize.height = 5120; // 必須是 2的冪，默認值爲 512
spotLight.castShadow = true;
scene.add(spotLight);
//cameraHelper = new THREE.CameraHelper(spotLight.shadow.camera);
//scene.add(cameraHelper);
// 加入一個地面
var groundGeometry = new THREE.PlaneGeometry(100, 100, 4, 4);
var groundMaterial = new THREE.MeshLambertMaterial({color: 0x777777}); // MeshBasicMaterial 材質不能接收陰影
ground = new THREE.Mesh(groundGeometry, groundMaterial);
ground.rotation.set(-0.5 * Math.PI, 0, 0); // 沿着 X軸旋轉-90°
ground.receiveShadow = true;
scene.add(ground);
// 材質
meshMaterial = [
new THREE.MeshNormalMaterial({side: THREE.DoubleSide}),
new THREE.MeshBasicMaterial({wireframe: true})
];
/** 用來保存那些需要修改的變量 */
guiParams = new function() {
this.rotationSpeed = 0.02;
this.radius = 12;
this.detail = 0;
this.type = 'Tetrahedron';
}
/** 定義 dat.GUI 對象，並綁定 guiParams 的幾個屬性 */
var gui = new dat.GUI();
gui.add(guiParams, 'radius', 1, 30, 1).onChange(function(e){updateMesh()});
gui.add(guiParams, 'detail', 0, 5, 1).onChange(function(e){updateMesh()});
gui.add(guiParams, 'type', ['Tetrahedron', 'Octahedron', 'Icosahedron', 'Dodecahedron', 'Polyhedron']).onChange(function(e){updateMesh()});
updateMesh();
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 */
var step = 0;
function rotateMesh() {
step += guiParams.rotationSpeed;
scene.traverse(function(mesh) {
if (mesh instanceof THREE.Mesh && mesh != ground && mesh != axesHelper) {
//mesh.rotation.x = step;
mesh.rotation.y = step;
//mesh.rotation.z = step;
}
});
}
function updateMesh() {
scene.remove(polyhedron);
// 定義 polyhedron
var polyhedronGeometry;
switch(guiParams.type) {
case 'Tetrahedron': // 四面體
polyhedronGeometry = new THREE.TetrahedronGeometry(guiParams.radius, guiParams.detail);
break;
case 'Octahedron': // 八面體
polyhedronGeometry = new THREE.OctahedronGeometry(guiParams.radius, guiParams.detail);
break;
case 'Dodecahedron': // 十二面體
polyhedronGeometry = new THREE.DodecahedronGeometry(guiParams.radius, guiParams.detail);
break;
case 'Icosahedron': // 二十面體
polyhedronGeometry = new THREE.IcosahedronGeometry(guiParams.radius, guiParams.detail);
break;
case 'Polyhedron': // 自定義多面體
var verticesOfCube = [
1, 0, 1,
1, 0, -1,
-1, 0, -1,
-1, 0, 1,
0, 1, 0
];
var indicesOfFaces = [
0, 1, 2,
2, 3, 0,
0, 1, 4,
1, 2, 4,
2, 3, 4,
3, 0, 4
];
polyhedronGeometry = new THREE.PolyhedronGeometry(verticesOfCube, indicesOfFaces, guiParams.radius, guiParams.detail);
break;
};
polyhedron = new THREE.SceneUtils.createMultiMaterialObject(polyhedronGeometry, meshMaterial);
polyhedron.children[1].castShadow = true; // polyhedron.children[0] 的材質是 MeshNormalMaterial，不能投射陰影
polyhedron.position.set(0, guiParams.radius * 2 + 3, 0);
scene.add(polyhedron);
}
</script>
</body>
</html>未完待續···