目前爲止,three.js 庫中提供的所有的基本幾何體部分都已經介紹完了。今天開始我們要介紹 three.js 中提供的一些相對高級且特別的幾何體對象,譬如 ConvexGeometry(凸面體)、LathGeometry(掃描體)、TubeGeometry(管狀體)、ExtrudeGeometry(拉伸體)、TextGeometry(三維文字)及 ParametricGeometry(等式體)等。
首先,我們來介紹一下 ConvexGeometry 凸面體。通過 ConvexGeometry 我們可以在一組給定點的外圍建立一個凸包。所謂凸包,是指包圍這組點的最小圖形。下面我給出一個具體示例,代碼如下所示:
<!DOCTYPE html>
<html>
<head>
<title>示例 06.01 - ConvexGeometry</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="../build/js/QuickHull.js"></script>
<script src="../build/js/geometries/ConvexGeometry.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 convex;
var spGroup;
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.MeshBasicMaterial({color: 0x00ff00, transparent: true, opacity: 0.2, 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.redraw = function(e) {updateMesh()};
}
/** 定義 dat.GUI 對象,並綁定 guiParams 的幾個屬性 */
var gui = new dat.GUI();
gui.add(guiParams, 'redraw');
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 === spGroup) {
//mesh.rotation.x = step;
mesh.rotation.y = step;
//mesh.rotation.z = step;
}
});
}
function updateMesh() {
scene.remove(spGroup);
// 定義 convex
var points = generatePoints();
var convexGeometry = new THREE.ConvexGeometry(points);
convex = new THREE.SceneUtils.createMultiMaterialObject(convexGeometry, meshMaterial);
convex.children[1].castShadow = true; // convex.children[0] 的材質是 MeshNormalMaterial,不能投射陰影
//convex.position.set(0, guiParams.radius * 2 + 3, 0);
spGroup.add(convex);
scene.add(spGroup);
}
/** 隨機生成 20 個點 */
function generatePoints() {
var points = [];
for (var i = 0; i < 20; i++) {
var randomX = -15 + Math.round(Math.random() * 30);
//var randomY = -15 + Math.round(Math.random() * 30);
var randomY = Math.round(Math.random() * 30);
var randomZ = -15 + Math.round(Math.random() * 30);
points.push(new THREE.Vector3(randomX, randomY, randomZ));
}
spGroup = new THREE.Object3D();
var material = new THREE.MeshBasicMaterial( {color: 0xff0000, transparent: false} );
// 添加 20 個小球體
points.forEach(function(point) {
var spGeometry = new THREE.SphereGeometry(0.2);
var spMesh = new THREE.Mesh(spGeometry, material);
spMesh.position.set(point.x, point.y, point.z);
spGroup.add(spMesh);
});
return points;
}
</script>
</body>
</html>
在這個例子中,我們在 generatePoints() 函數中隨機生成了一組長度爲 20 的點(THREE.Vector3),然後利用這組點創建了一個 ConvexGeometry。我們可以通過右上角的 redraw(重新繪製)按鈕來重新生成 20 個新點並構造新的凸包。另外,爲了更好的觀察,我們爲每一個點添加了一個 SphereGeometry 小球體。爲了更好的控制整個圖形,我們把所有的小球體以及構造的凸包都添加到了一個叫 spGroup 的組中,這樣我們就可以很容易的把它們當做一個整體來進行旋轉了。
未完待續···