初探threeJs，进入web3D的世界。

最近开始看了webGL的一些知识，了解了相关的计算机图形基础知识，突然发现这些知识和之前大学学过得3Dmax有很多共性的地方，比如场景，模型、材质、灯光、摄像机等等。突然发现之前自己学的东西并不是全部没用，理解起来也有一定帮帮助。

运行结果：

代码如下：

let i = 0;
function init() {
    // create a scene, that will hold all our elements such as objects, cameras and lights.
    var scene = new THREE.Scene();

    // create a camera, which defines where we're looking at.
    var camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 1000);

    // create a render and set the size
    // 设置渲染面板属性
    var renderer = new THREE.WebGLRenderer();
    renderer.setClearColor(new THREE.Color(0xcccccc));  // 设置渲染面板颜色
    renderer.setSize(window.innerWidth, window.innerHeight);    // 设置渲染面板长宽

    // // show axes in the screen
    // 显示三维坐标轴
    var axes = new THREE.AxesHelper(20);
    scene.add(axes);

    // create the ground plane
    // var planeGeometry = new THREE.PlaneGeometry(60, 20);
    // var planeMaterial = new THREE.MeshBasicMaterial({
    //     color: 0xAAAAAA
    // });
    // var plane = new THREE.Mesh(planeGeometry, planeMaterial);

    // // rotate and position the plane
    // plane.rotation.x = -0.5 * Math.PI;
    // plane.position.set(15, 0, 0);

    // // add the plane to the scene
    // scene.add(plane);

    // create a cube
    

    // position the cube
    // cube.position.set(-4, 3, 0);
    // add the cube to the scene
    

    // create a sphere
    // var sphereGeometry = new THREE.SphereGeometry(4, 20, 20);
    // var sphereMaterial = new THREE.MeshBasicMaterial({
    //     color: 0x7777FF,
    //     wireframe: true
    // });
    // var sphere = new THREE.Mesh(sphereGeometry, sphereMaterial);

    // // position the sphere
    // sphere.position.set(20, 4, 2);

    // // add the sphere to the scene
    // scene.add(sphere);

    // position and point the camera to the center of the scene
    camera.position.set(-30, 40, 30);
    camera.lookAt(scene.position);

    // add the output of the renderer to the html element
    document.getElementById("webgl-output").appendChild(renderer.domElement);

    // render the scene
    let addT = null;
    let redt = null;
    let timeAdd = null;
    let timeDel = null;
    let step = 1;
    let frequ = 100;
    // 数值增加到制定数字
    function add (dis) {
        clearInterval(timeDel);
        timeAdd = setInterval(() => {
            if (i < dis) {
                i++;
                intCub();
            } else {
                clearInterval(timeAdd);
                // del(0);
            }
            console.log(i);
        }, frequ);
    };
    // 数值减少到制定数字
    function del (dis) {
        clearInterval(timeAdd);
        timeDel = setInterval(() => {
            if (i > dis) {
                i--;
                intCub();
            } else {
                val = dis;
                clearInterval(timeDel);
                add(50)
            }
            console.log(i);
        }, frequ);
    };
    function intCub () {
        let random = parseInt(1 + (4 - 1) * (Math.random()));   // 随机数用于正方体的长宽高
        let randomC = parseInt(1 + (2 - 1) * (Math.random()));  // 随机数用于球形的半径
        let colorRandomNum = parseInt(1 + (7 - 1) * (Math.random()));  // 随机数用于赋值后续的物体的材质颜色
        let randomColor = [0xF7CE18, 0x2550EC, 0x57E10C, 0xEB6F0A, 0xEB0AE9, 0x820745, 0x8D11D8];

        // 配置灯光
        let light = new THREE.AmbientLight(0xFF0000);
        light.position.set(100, 100, 200);
                
        // 生成正方体
        var cubeGeometry = new THREE.BoxGeometry(random, random, random);   // 长宽高
        // 给正方体网格添加材质
        var cubeMaterial = new THREE.MeshBasicMaterial({
            color: randomColor[colorRandomNum],
            wireframe: false  // 是否显示网格状态
        });
        var cube = new THREE.Mesh(cubeGeometry, cubeMaterial);  // 将材质贴到模型上

        // 生成原型
        var sphereGeometry = new THREE.SphereGeometry(randomC, 200, 200);  // 半径和网格数，网格数表示球体的粗糙程度
        var sphereMaterial = new THREE.MeshBasicMaterial({
            color: randomColor[colorRandomNum],
            wireframe: false   // 是否显示网格状态
        });
        var sphere = new THREE.Mesh(sphereGeometry, sphereMaterial);  // 将材质贴到模型上

        // position the sphere
        // 设置球体的位置
        sphere.position.set(parseInt(-10 + (25 - 1) * (Math.random())), parseInt(-10 + (25 - 1) * (Math.random())), parseInt(-10 + (25 - 1) * (Math.random())));
        
        // 设置正方体的位置
        cube.position.set(parseInt(-10 + (25 - 1) * (Math.random())), parseInt(-10 + (25 - 1) * (Math.random())), parseInt(-10 + (25 - 1) * (Math.random())));
        // add the sphere to the scene
        // 将贴好材质的模型和灯光添加到场景
        scene.add(sphere);  
        scene.add(cube);
        scene.add(light);
        renderer.render(scene, camera); // 渲染场景中的模型
    };
    // 运行渲染
    add (50);
}