THREE.js
可以这么理解three+js
，three
代表3
维世界，js
即javascript,
这是一个让我们可以在浏览器中绘制3D
效果的javascript
库，通过webgl
为html5 canvas
提供硬件3D
加速渲染，这样Web
开发人员就可以借助系统显卡来在浏览器里更流畅地展示3D
场景和模型了.
THREE.js
中有三个主要的概念，相机（Camera
）、场景（Scene
）、Renderer
（渲染器）
1.
照相机（Camera
）
学习Camera
之前我们先了解一下THREE.js
中使用的坐标系，如图所示：
构造函数
OrthographicCamera(left, right, top, bottom, near, far);
实例说明
camera = new THREE.OrthographicCamera(-2, 2, 1.5, -1.5, 1, 10);
camera.position.set(0, 0, 5);
var cubeGeometry = new THREE.CubeGeometry(1,1,1); //
创建一个正方体
var material = new THREE.MeshBasicMaterial({ color : 0xff0000, wireframe : true });
var cube = new THREE.Mesh(cubeGeometry, material);
scene.add(cube);
renderer.render(scene, camera);
但是这里有一个很奇怪的问题，命名创建的是一个长度为1
的正方体，为啥投影是长方体？这里canvas
面板的长宽比是2:1
，但是相机的（right-left
）/(top-bottom)
比例是4
：3
，因此
垂直方向上面被压缩了，所以显示的是一个长方体。
将（right-left
）/(top-bottom)
的比例同样调整为2:1
camera = new THREE.OrthographicCamera(-2, 2, 1, -1, 1, 10);
2.
光源(Light)
光是自然界中常见的现象，我们把正在发光的物体成为光源。与光相对立的是阴影，光被物体
遮挡住了便形成了阴影。根据光照的效果不同，THREE.js
中抽象除了几种不同的光源。
•
聚光灯(THREE.SpotLight)
•
平行光源(THREE.DirectionalLight)
•
环境光源(THREE.AmbientLight)
•
半球光源(THREE.HemisphereLight)
•
点光源(THREE.PointLight)
•
聚光灯(SpotLight)
聚光灯像某个方向进行照射的光源，其光照范围呈圆锥状。
构造函数
SpotLight(color, intensity,distance, angle, penumbra, decay);
color
：光的颜色
intensity
：光的强度
distance
：光能照射的最远的距离，按照光的强度按照距离呈线性衰减。
angle
：照射的中心点到圆锥上边距的夹角
decay
：光线衰减的速率
除了构造函数中的几个属性之外，SpotLight
还有一个很重要的属性target
，点光源聚焦的地方
，该属性值是一个Object3D
的实例，将target
的值设置为一个运动中的物体可以让点光源跟随物体的运动而运动。
THREE.js
中只有聚光灯(SpotLight)
和平行光源(DirectionalLight)
可以产生阴影，这里看看如何让聚光灯产生阴影。
1>.
告诉renderer
需要渲染阴影
var renderer = new THREE.WEBGLRenderer();
renderer.shadowMapEnabled = true; or renderer.shadowMap.enabled = true;
2>.
告诉THREE.js
哪些物体会投射阴影，
哪些物体会接收阴影
cubeMesh.castShadow = true; //cubeMesh
会在其他的物体上面投射阴影
floorMesh.receiveShadow = true; //floorMesh
会接收其他物体在其上投射的阴影
3>.
添加聚光灯
var spotLight = new THREE.SpotLight();
spotLight.angle = Math.PI / 8;
spotLight.exponent = 30;
spotLight.position = new THREE.Vector3(40, 60, -50);
scene.add(spotLight);
4>.
设置阴影相关的属性
spotLight.castShadow = true;
spotLight.shadow.camera.near = 500;
spotLight.shadow.camera.far = 4000;
spotLight.shadow.camera.fov = 30;
near, far, fov
设置投影的区域
5>.
设置阴影贴图大小
spotLight.shadow.mapSize.width = 1024;
spotLight.shadow.mapSize.height = 1024;
设置阴影贴图大小，如果发现阴影的边界呈块状，说明阴影贴图太小了，需要设置更大的值
总结实例:
<!DOCTYPE html>
<html>
<head>
<title>Example 03.04 - Directional Light</title>
<script type="text/javascript" src="../libs/three.js"></script>
<script type="text/javascript" src="../libs/jquery-1.9.0.js"></script>
<script type="text/javascript" src="../libs/stats.js"></script>
<script type="text/javascript" src="../libs/dat.gui.js"></script>
<style>
body {
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">
// once everything is loaded, we run our Three.js stuff.
$(function () {
var stats = initStats();
// 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
var renderer = new THREE.WebGLRenderer();
renderer.setClearColorHex(0xEEEEEE, 1.0);
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.shadowMapEnabled = true;
// create the ground plane
var planeGeometry = new THREE.PlaneGeometry(600, 200, 20, 20);
var planeMaterial = new THREE.MeshLambertMaterial({color: 0xffffff});
var plane = new THREE.Mesh(planeGeometry, planeMaterial);
plane.receiveShadow = true;
// rotate and position the plane
plane.rotation.x = -0.5 * Math.PI;
plane.position.x = 15
plane.position.y = -5
plane.position.z = 0
// add the plane to the scene
scene.add(plane);
// create a cube
var cubeGeometry = new THREE.CubeGeometry(4, 4, 4);
var cubeMaterial = new THREE.MeshLambertMaterial({color: 0xff3333});
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);
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 = -35;
camera.position.y = 30;
camera.position.z = 25;
camera.lookAt(new THREE.Vector3(10, 0, 0));
// add subtle ambient lighting
var ambiColor = "#1c1c1c";
var ambientLight = new THREE.AmbientLight(ambiColor);
scene.add(ambientLight);
var target = new THREE.Object3D();
target.position = new THREE.Vector3(5, 0, 0);
var pointColor = "#ff5808";
var directionalLight = new THREE.DirectionalLight(pointColor);
directionalLight.position.set(-40, 60, -10);
directionalLight.castShadow = true;
directionalLight.shadowCameraNear = 2;
directionalLight.shadowCameraFar = 200;
directionalLight.shadowCameraLeft = -50;
directionalLight.shadowCameraRight = 50;
directionalLight.shadowCameraTop = 50;
directionalLight.shadowCameraBottom = -50;
directionalLight.distance = 0;
directionalLight.intensity = 0.5;
directionalLight.shadowMapHeight = 1024;
directionalLight.shadowMapWidth = 1024;
scene.add(directionalLight);
// add a small sphere simulating the pointlight
var sphereLight = new THREE.SphereGeometry(0.2);
var sphereLightMaterial = new THREE.MeshBasicMaterial({color: 0xac6c25});
var sphereLightMesh = new THREE.Mesh(sphereLight, sphereLightMaterial);
sphereLightMesh.castShadow = true;
sphereLightMesh.position = new THREE.Vector3(3, 20, 3);
scene.add(sphereLightMesh);
// add the output of the renderer to the html element
$("#WebGL-output").append(renderer.domElement);
// call the render function
var step = 0;
// used to determine the switch point for the light animation
var invert = 1;
var phase = 0;
var controls = new function () {
this.rotationSpeed = 0.03;
this.bouncingSpeed = 0.03;
this.ambientColor = ambiColor;
this.pointColor = pointColor;
this.intensity = 0.5;
this.distance = 0;
this.exponent = 30;
this.angle = 0.1;
this.debug = false;
this.castShadow = true;
this.onlyShadow = false;
this.target = "Plane";
}
var gui = new dat.GUI();
gui.addColor(controls, 'ambientColor').onChange(function (e) {
ambientLight.color = new THREE.Color(e);
});
gui.addColor(controls, 'pointColor').onChange(function (e) {
directionalLight.color = new THREE.Color(e);
});
gui.add(controls, 'intensity', 0, 5).onChange(function (e) {
directionalLight.intensity = e;
});
gui.add(controls, 'distance', 0, 200).onChange(function (e) {
directionalLight.distance = e;
});
gui.add(controls, 'debug').onChange(function (e) {
directionalLight.shadowCameraVisible = e;
});
gui.add(controls, 'castShadow').onChange(function (e) {
directionalLight.castShadow = e;
});
gui.add(controls, 'onlyShadow').onChange(function (e) {
directionalLight.onlyShadow = e;
});
gui.add(controls, 'target', ['Plane', 'Sphere', 'Cube']).onChange(function (e) {
console.log(e);
switch (e) {
case "Plane":
directionalLight.target = plane;
break;
case "Sphere":
directionalLight.target = sphere;
break;
case "Cube":
directionalLight.target = cube;
break;
}
});
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)));
sphereLightMesh.position.z = -8;
sphereLightMesh.position.y = +(27 * (Math.sin(step / 3)));
sphereLightMesh.position.x = 10 + (26 * (Math.cos(step / 3)));
directionalLight.position = sphereLightMesh.position;
// 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';
$("#Stats-output").append(stats.domElement);
return stats;
}
});
</script>
</body>
</html>
