這是一個官方的小例子就是分析學習下。
https://threejs.org/examples/#webgl_geometry_extrude_shapes

開頭的引入js沒什麼好說

<script src="../build/three.js"></script>

//這是滑鼠控制的工具
<script src="js/controls/TrackballControls.js"></script>

接著分析程式碼

var camera, scene, renderer, controls;

init();
animate();

開頭簡單例子就幫忙總結了一下three.js 大舞臺搭建

1. camera   攝像機 
2. scene     場景（畫板）
3. renderer  渲染器 （畫筆）
4. controls   這裡就是場景畫面的控制器
5. init() 初始化上面的幾個元素
6. animate()  動畫，場景變換 

下面開始看看init()到底都做了些什麼

function init() {
                 //初始化畫筆
	             renderer = new THREE.WebGLRenderer();

                //設定裝置畫素比。通常用於避免HiDPI裝置上繪圖模糊
                //不懂的PixelRatio的同學可以看下這篇部落格
                //https://www.cnblogs.com/timejs/p/5409533.html
				renderer.setPixelRatio( window.devicePixelRatio );
                
                //將輸出canvas的大小調整為(width, height)並考慮裝置畫素比
				renderer.setSize( window.innerWidth, window.innerHeight );
				document.body.appendChild( renderer.domElement );


                //初始化場景
				scene = new THREE.Scene();
				scene.background = new THREE.Color( 0x222222 );

                //初始化攝像機
				camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 1, 1000 );
				camera.position.set( 0, 0, 500 );

                //控制器
				controls = new THREE.TrackballControls( camera, renderer.domElement );
				controls.minDistance = 200;
				controls.maxDistance = 500;

                //設定環境光 （此燈全域性均勻地照亮場景中的所有物件）
				scene.add( new THREE.AmbientLight( 0x222222 ) );

                //點光源
				var light = new THREE.PointLight( 0xffffff );
				light.position.copy( camera.position );
				scene.add( light );

				//使用Catmull-Rom演算法從一系列點建立平滑的三維樣條曲線 。
				var closedSpline = new THREE.CatmullRomCurve3( [
					new THREE.Vector3( - 60, - 100, 60 ),
					new THREE.Vector3( - 60, 20, 60 ),
					new THREE.Vector3( - 60, 120, 60 ),
					new THREE.Vector3( 60, 20, - 60 ),
					new THREE.Vector3( 60, - 100, - 60 )
				] );

                //曲線的型別
				closedSpline.curveType = 'catmullrom';
                //是否閉合
				closedSpline.closed = true;

				var extrudeSettings = {
					steps: 100,
					bevelEnabled: false,//允許斜面
					extrudePath: closedSpline //THREE.CurvePath。應該擠出形狀的3D樣條路徑
				};


				var pts = [], count = 3;
                
				for ( var i = 0; i < count; i ++ ) {

					var l = 20;

					var a = 2 * i / count * Math.PI;

					pts.push( new THREE.Vector2( Math.cos( a ) * l, Math.sin( a ) * l ) );

				}
                
                //三邊形
				var shape = new THREE.Shape( pts );
                
                //從路徑形狀建立拉伸的圖形
				var geometry = new THREE.ExtrudeBufferGeometry( shape, extrudeSettings );
                
                //非光澤表面 
				var material = new THREE.MeshLambertMaterial( { color: 0xb00000, wireframe: false } );

				var mesh = new THREE.Mesh( geometry, material );

				scene.add( mesh );


				var randomPoints = [];

				for ( var i = 0; i < 10; i ++ ) {

					randomPoints.push( new THREE.Vector3( ( i - 4.5 ) * 50, THREE.Math.randFloat( - 50, 50 ), THREE.Math.randFloat( - 50, 50 ) ) );

				}

				var randomSpline = new THREE.CatmullRomCurve3( randomPoints );

				//

				var extrudeSettings = {
					steps: 200,
					bevelEnabled: false,
					extrudePath: randomSpline
				};


				var pts = [], numPts = 5;
                //畫五角星，也就是兩個不同半徑的圓
				for ( var i = 0; i < numPts * 2; i ++ ) {

					var l = i % 2 == 1 ? 10 : 20;

					var a = i / numPts * Math.PI;

					pts.push( new THREE.Vector2( Math.cos( a ) * l, Math.sin( a ) * l ) );

				}

				var shape = new THREE.Shape( pts );

				var geometry = new THREE.ExtrudeBufferGeometry( shape, extrudeSettings );

				var material2 = new THREE.MeshLambertMaterial( { color: 0xff8000, wireframe: false } );

				var mesh = new THREE.Mesh( geometry, material2 );

				scene.add( mesh );


				var materials = [ material, material2 ];

				var extrudeSettings = {
					depth: 20,
					steps: 1,
					bevelEnabled: true,
					bevelThickness: 2,
					bevelSize: 4,
					bevelSegments: 1
				};

				var geometry = new THREE.ExtrudeBufferGeometry( shape, extrudeSettings );

				var mesh = new THREE.Mesh( geometry, materials );

				mesh.position.set( 50, 100, 50 );

				scene.ad			d( mesh );

}
 

 animate() 方法

function animate() {

	requestAnimationFrame( animate );

    //控制器變化更新檢視
	controls.update();
	renderer.render( scene, camera );

}