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博主的案例並不難，只是爲了更好的給想入門threeJS的同學一點點經驗！！！！！
涉及的知識點博主已經從three源碼庫裏面摘要出來放在對應的註釋裏面！
前面學習了常見的幾種格式的模型加載，只要選擇對應的加載器加載，獲取對應的geometry和material就基本可以還原模型了！
後面博主會考慮把loader加載的模型格式補全！
今天我們學習geometry類的BufferGeometry，buffergeometry是自由度最高的一種geometry，它可以自定義頂點、顏色、法線等屬性！
本案例是根據頂點索引生成三角形再組合成一個面
圖示:
代碼：
<html>
<head>
<title>threeJS21-geometry-buffergeometry-indexed</title>
<style>
body {
background-color: #000;
margin: 0px;
overflow: hidden;
}
#WebGL {
width: 100%;
height: 100%;
position: absolute;
left: 0;
top: 0;
z-index: 999;
}
</style>
</head>
<body>
<script src="http://libs.baidu.com/jquery/2.0.0/jquery.js"></script>
<script src="../../../build/three.js"></script>
<script src="../../js/controls/OrbitControls.js"></script>
<div id="WebGL"></div>
<script>
'use strict';
var container, camera, scene, renderer, geometry, material, animate, controls; //常用變量
var spotLight, mshStdBox, mesh; //自定義對象變量
var target = new THREE.Vector3(0, 30, 0);
var webGLW = $('#WebGL').width();
var webGLH = $('#WebGL').height();
init();
animate();
function init() {
container = document.getElementById('WebGL');
scene = new THREE.Scene();
scene.background = new THREE.Color(0xcfcfcf);
scene.fog = new THREE.Fog(0xa0a0a0, 200, 1000); //霧
camera = new THREE.PerspectiveCamera(40, window.innerWidth / window.innerHeight, 0.1, 1000);
camera.position.set(0, 60, -100);
camera.lookAt(target);
var ambient = new THREE.AmbientLight(0xffffff);
scene.add(ambient);
lights(); //燈光：聚光燈
// lightsHelper(spotLight); //燈光顯示助手
plane() //// 地面
loadModel(); //添加模型
rendererScene(); //場景渲染
OrbitControls(camera, renderer); //OrbitControls控件模塊，90版本鼠標右鍵上下是移動，96版本之後右鍵上下是縮放
window.addEventListener('resize', onWindowResize, false); //監聽屏幕變化
}
function plane() {
// 地面
let grid_mesh = new THREE.Mesh(new THREE.PlaneBufferGeometry(2000, 2000), new THREE.MeshPhongMaterial({
color: 0x999999,
depthWrite: false
}));
grid_mesh.rotation.x = -Math.PI / 2;
grid_mesh.receiveShadow = true;
scene.add(grid_mesh);
var grid = new THREE.GridHelper(2000, 20, 0x000000, 0x000000);
grid.material.opacity = 0.2;
grid.material.transparent = true;
scene.add(grid);
}
function lights() {
// SpotLight( color：顏色, intensity：強度, distance：發光距離, angle：角度, penumbra：邊緣範圍, decay：衰減 )
spotLight = new THREE.SpotLight(0xffffff, 1);
spotLight.position.set(10, 120, -30);
spotLight.angle = Math.PI / 4;
spotLight.penumbra = 0.05; //邊緣範圍，反比
spotLight.decay = 2; //衰減係數，反比
spotLight.distance = 400; //發光距離
spotLight.castShadow = true; //陰影
spotLight.shadow.mapSize.width = 1024;
spotLight.shadow.mapSize.height = 1024;
spotLight.shadow.camera.near = 10; //近截面
spotLight.shadow.camera.far = 250;
scene.add(spotLight);
}
function lightsHelper(lightsObject) {
// 聚光燈顯示助手SpotLightHelper( light:燈光, color：顏色 )
var lightHelper = new THREE.SpotLightHelper(lightsObject, 0xdfdfdf);
scene.add(lightHelper);
var mesh = new THREE.Mesh(new THREE.PlaneBufferGeometry(200, 200), new THREE.MeshPhongMaterial({
color: 0x9cfcf99,
depthWrite: false
}));
mesh.rotation.x = -Math.PI / 2;
mesh.position.set(0, -20, 0)
mesh.receiveShadow = true;
scene.add(mesh);
}
function loadModel() { //模型
var geometry = new THREE.BufferGeometry();
var indices = [];
var vertices = [];
var normals = [];
var colors = [];
var size = 50;
var segments = 10;
var halfSize = size / 2;
var segmentSize = size / segments;
// 爲簡單網格幾何體生成頂點、法線和顏色數據
for (var i = 0; i <= segments; i++) {
var y = (i * segmentSize) - halfSize;
for (var j = 0; j <= segments; j++) {
var x = (j * segmentSize) - halfSize;
vertices.push(x, -y, 0);
normals.push(0, 0, 1);
var r = (x / size) + 0.5;
var g = (y / size) + 0.5;
colors.push(r, g, 1);
}
}
// 生成索引（元素數組緩衝區的數據）
for (var i = 0; i < segments; i++) {
for (var j = 0; j < segments; j++) {
var a = i * (segments + 1) + (j + 1);
var b = i * (segments + 1) + j;
var c = (i + 1) * (segments + 1) + j;
var d = (i + 1) * (segments + 1) + (j + 1);
// 每次迭代生成兩個面（三角形）
indices.push(a, b, d); // 第一個面
indices.push(b, c, d); // 第二個面
}
}
geometry.setIndex(indices); //設置索引
// addAttribute ( name : String, attribute : BufferAttribute )
geometry.addAttribute('position', new THREE.Float32BufferAttribute(vertices, 3));
geometry.addAttribute('normal', new THREE.Float32BufferAttribute(normals, 3));
geometry.addAttribute('color', new THREE.Float32BufferAttribute(colors, 3));
var material = new THREE.MeshPhongMaterial({
specular: 0x111111,
shininess: 250,
side: THREE.DoubleSide,
vertexColors: THREE.VertexColors
});
mesh = new THREE.Mesh(geometry, material);
mesh.position.set(0, 30, 0)
scene.add(mesh);
}
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
renderer.setSize(window.innerWidth, window.innerHeight);
}
function rendererScene() {
renderer = new THREE.WebGLRenderer({
antialias: true
});
renderer.setPixelRatio(window.devicePixelRatio);
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.shadowMap.enabled = true;
renderer.shadowMap.type = THREE.PCFSoftShadowMap;
renderer.gammaInput = true;
renderer.gammaOutput = true;
container.appendChild(renderer.domElement);
}
function OrbitControls(camera, renderer) {
//OrbitControls控件操作模塊
controls = new THREE.OrbitControls(camera, renderer.domElement);
controls.target = target; //控制的target
controls.autoRotate = true; //是否自動旋轉
controls.autoRotateSpeed = 0.5; //自動旋轉速度，正比
}
function animate() {
requestAnimationFrame(animate);
if (controls) controls.update();
renderer.render(scene, camera);
};
</script>
</body>
</html>