Chapter 1:Create You First 3D Scene With Three.js

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1,各浏览器对WebGL的支持

手机浏览器对WebGL的支持：

书的源码：https://github.com/josdirksen/learning-threejs

第一次用浏览器打开代码可能无法正常显示，好像要对浏览器做一些设置额。

创建第一个3D场景包括这几样东西：

<!DOCTYPE html>

<html>

<head>

    <title>Example 01.06 - Screen size change</title>

    <script type="text/javascript" src="../libs/three.js"></script>

    <script type="text/javascript" src="../libs/stats.js"></script>//shows the frames per second(fps) for animation

    <script type="text/javascript" src="../libs/dat.gui.js"></script>//allows you to very easily create a simple user interface component that can change variables in your code

    <style>

        body {

            /* set margin to 0 and overflow to hidden, to go fullscreen */

            margin: 0;

            overflow: hidden;

        }

    </style>

</head>

<body>

<div id="Stats-output">

</div>

<!-- Div which will hold the Output -->

<div id="WebGL-output">

</div>

<!-- Javascript code that runs our Three.js examples -->

<script type="text/javascript">

    var camera;

    var scene;

    var renderer;

    // once everything is loaded, we run our Three.js stuff.

    function init() {

　　　　

        var stats = initStats();

        // create a scene, that will hold all our elements such as objects, cameras and lights.

        scene = new THREE.Scene();

        // create a camera, which defines where we're looking at. 第一个参数是摄像机的角度，其他因素不变的情况下角度越大，看到的场景越小，第二个是场景的比例，第三个是near，第四个是far我们能看到的是near和far之间的内容

        camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 1000);

        // create a render and set the size

        renderer = new THREE.WebGLRenderer();

        renderer.setClearColor(new THREE.Color(0xEEEEEE, 1.0));

        renderer.setSize(window.innerWidth, window.innerHeight);

        renderer.shadowMapEnabled = true;//默认是不开启阴影效果的，如果要显示阴影在这里要把它设为true;

        // create the ground plane

        var planeGeometry = new THREE.PlaneGeometry(60, 20, 1, 1);//创建一个长为60，宽为20的长方形，后面那两个参数是可选的，分别为widthsegements,heightsegements

        var planeMaterial = new THREE.MeshLambertMaterial({color: 0xffffff});//设置材质，并初始化材质颜色

        var plane = new THREE.Mesh(planeGeometry, planeMaterial); //把二者合并为一个mesh对象

        plane.receiveShadow = true;//接收阴影

        // rotate and position the plane

        plane.rotation.x = -0.5 * Math.PI;

        plane.position.x = 15;

        plane.position.y = 0;

        plane.position.z = 0;

        // add the plane to the scene

        scene.add(plane);

        // create a cube

        var cubeGeometry = new THREE.BoxGeometry(4, 4, 4);//新建一个立方体，参数为width,height,depth,后面还有三个可选参数，分别为widthsegments,heightsegments,depthsegments

        var cubeMaterial = new THREE.MeshLambertMaterial({color: 0xff0000});

        var cube = new THREE.Mesh(cubeGeometry, cubeMaterial);

        cube.castShadow = true;

        // position the cube

        cube.position.x = -4;

        cube.position.y = 3;

        cube.position.z = 0;

        // add the cube to the scene

        scene.add(cube);

        var sphereGeometry = new THREE.SphereGeometry(4, 20, 20);//SphereGeometry(radius, widthSegments, heightSegments, phiStart, phiLength, thetaStart, thetaLength)

var sphereMaterial = new THREE.MeshLambertMaterial({color: 0x7777ff});

        var sphere = new THREE.Mesh(sphereGeometry, sphereMaterial);

        // position the sphere

        sphere.position.x = 20;

        sphere.position.y = 0;

        sphere.position.z = 2;

        sphere.castShadow = true;

        // add the sphere to the scene

        scene.add(sphere);

        // position and point the camera to the center of the scene

        camera.position.x = -30;

        camera.position.y = 40;

        camera.position.z = 30;

        camera.lookAt(scene.position);

        // add subtle ambient lighting

        var ambientLight = new THREE.AmbientLight(0x0c0c0c);

        scene.add(ambientLight);

        // add spotlight for the shadows

        var spotLight = new THREE.SpotLight(0xffffff);

        spotLight.position.set(-40, 60, -10);

        spotLight.castShadow = true;

        scene.add(spotLight);

        // add the output of the renderer to the html element

        document.getElementById("WebGL-output").appendChild(renderer.domElement);

        // call the render function

        var step = 0;

        var controls = new function () {

            this.rotationSpeed = 0.02;

            this.bouncingSpeed = 0.03;

        };

        var gui = new dat.GUI();

        gui.add(controls, 'rotationSpeed', 0, 0.5);

        gui.add(controls, 'bouncingSpeed', 0, 0.5);

        render();

        function render() {

            stats.update();

            // rotate the cube around its axes

            cube.rotation.x += controls.rotationSpeed;

            cube.rotation.y += controls.rotationSpeed;

            cube.rotation.z += controls.rotationSpeed;

            // bounce the sphere up and down

            step += controls.bouncingSpeed;

            sphere.position.x = 20 + ( 10 * (Math.cos(step)));

            sphere.position.y = 2 + ( 10 * Math.abs(Math.sin(step)));

            // render using requestAnimationFrame

            requestAnimationFrame(render);

            renderer.render(scene, camera);

        }

        function initStats() {

            var stats = new Stats();

            stats.setMode(0); // 0: fps, 1: ms

            // Align top-left

            stats.domElement.style.position = 'absolute';

            stats.domElement.style.left = '0px';

            stats.domElement.style.top = '0px';

            document.getElementById("Stats-output").appendChild(stats.domElement);

            return stats;

        }

    }

    function onResize() {

        camera.aspect = window.innerWidth / window.innerHeight;

        camera.updateProjectionMatrix();

        renderer.setSize(window.innerWidth, window.innerHeight);

    }

    window.onload = init;

    // listen to the resize events

    window.addEventListener('resize', onResize, false);

</script>

</body>

</html>