7.AmbientLight（环境光）-影响整个场景的光源
奚翰海
AmbientLight光源的颜色会影响整个场景。而且AmbientLight的光线没有特定的来源，而且这个光源也不会影响阴影的生成。不能将AmbientLight作为场景中的唯一光源。在使用其他光源（例如Spotlight和DirectionalLight）的同时使用AmbientLight，目的是弱化阴影或添加一些颜色。如下例所示，可以使用一个简单的用户界面来修改添加到场景中的环境光。
<!DOCTYPE html>
<html>
<head>
<title>Example 03.01 - Ambient Light</title>
<script type="text/javascript" src="../libs/three.js"></script>
<script type="text/javascript" src="../libs/stats.js"></script>
<script type="text/javascript" src="../libs/dat.gui.js"></script>
<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">
// 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.
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.setClearColor(new THREE.Color(0xEEEEEE, 1.0));
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.shadowMapEnabled = true;
// create the ground plane
var planeGeometry = new THREE.PlaneGeometry(60, 20, 1, 1);
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 = 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);
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);
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 = -25;
camera.position.y = 30;
camera.position.z = 25;
camera.lookAt(new THREE.Vector3(10, 0, 0));
// add subtle ambient lighting
var ambiColor = "#0c0c0c";
var ambientLight = new THREE.AmbientLight(ambiColor);
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;
this.ambientColor = ambiColor;
this.disableSpotlight = false;
};
var gui = new dat.GUI();
gui.addColor(controls, 'ambientColor').onChange(function (e) {
ambientLight.color = new THREE.Color(e);
});
gui.add(controls, 'disableSpotlight').onChange(function (e) {
spotLight.visible = !e;
});
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;
}
}
window.onload = init
</script>
</body>
</html>
在这个例子中，使用SpotLight来照亮物体，并生成阴影。
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