今天將要介紹的是 CylinderGeometry 幾何體。這也是一種非常簡單的三維幾何體，你甚至不需要指定任何參數就能創建出一個圓柱體。下面給出了常用的幾個屬性：
| 屬性 | 描述 |
|---|---|
| radiusTop | 可選。此屬性定義圓柱體頂部圓半徑。默認值是 20 |
| radiusBottom | 可選。此屬性定義圓柱體底部圓半徑。默認值是 20 |
| height | 可選。此屬性定義圓柱體的高度。默認值是 100 |
| radiusSegments | 可選。此屬性定義圓柱體的上下部的圓截面分成多少段。默認值是 8 |
| heightSegments | 可選。此屬性定義圓柱體豎直方向上分成多少段。默認值是 1 |
| openEnded | 可選。此屬性定義圓柱體的頂部和底部是否爲打開。默認值是 false |
對於上表中提到的相關參數，想必不用多說，你也應該很清楚他們的含義和用法了，下面給出完整示例，代碼如下：
<!DOCTYPE html>
<html>
<head>
<title>示例 05.06 - CylinderGeometry</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 meshMaterial;
var ambientLight;
var spotLight;
//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);
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.radiusTop = 10;
this.radiusBottom = 10;
this.height = 20;
this.radiusSegments = 16;
this.heightSegments = 4;
this.openEnded = true;
this.thetaStart = 0;
this.thetaLength = 2 * Math.PI;
}
/** 定義 dat.GUI 對象，並綁定 guiParams 的幾個屬性 */
var gui = new dat.GUI();
gui.add(guiParams, 'radiusTop', -10, 50, 1).onChange(function(e){updateMesh()});
gui.add(guiParams, 'radiusBottom', -10, 50, 1).onChange(function(e){updateMesh()});
gui.add(guiParams, 'height', 1, 50, 1).onChange(function(e){updateMesh()});
gui.add(guiParams, 'radiusSegments', 2, 20, 1).onChange(function(e){updateMesh()});
gui.add(guiParams, 'heightSegments', 1, 20, 1).onChange(function(e){updateMesh()});
gui.add(guiParams, 'openEnded').onChange(function(e){updateMesh()});
gui.add(guiParams, 'thetaStart', 0, Math.PI, 0.01).onChange(function(e){updateMesh()});
gui.add(guiParams, 'thetaLength', 0, 2 * Math.PI, 0.01).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 instanceof THREE.Line) && mesh != ground) {
//mesh.rotation.x = step;
mesh.rotation.y = step;
//mesh.rotation.z = step;
}
});
}
function updateMesh() {
scene.remove(cylinder);
// 定義 cylinder
var cylinderGeometry = new THREE.CylinderGeometry(guiParams.radiusTop, guiParams.radiusBottom, guiParams.height, guiParams.radiusSegments, guiParams.heightSegments, guiParams.openEnded, guiParams.thetaStart, guiParams.thetaLength);
cylinder = new THREE.SceneUtils.createMultiMaterialObject(cylinderGeometry, meshMaterial);
cylinder.children[1].castShadow = true; // cylinder.children[0] 的材質是 MeshNormalMaterial，不能投射陰影
cylinder.position.set(0, guiParams.height / 2 + 3, 0);
scene.add(cylinder);
}
</script>
</body>
</html>未完待續···