案例查看地址：http://www.wjceo.com/blog/threejs/2018-05-03/157.html
简介
之前的阴影效果都是通过特定的法向贴图或者凹凸贴图再或者使用Three.js渲染生成的，这一节，我们使用另一种方法来创建阴影，也就是使用光照贴图。光照贴图是预先渲染好的的阴影，来模拟真实的阴影。 这种光照贴图的好处是我们再不损害渲染的性能的同时，还能够模拟出真实的阴影效果。缺点是，阴影的位置不会跟随模型的移动而改变。
案例实现
在这个案例当中，我们会看到非常真实的阴影效果。刚开始我是把两个立方体隐藏掉的，为了展现出光照贴图的效果。我将两个立方体隐藏掉，需要显示请点击右上角的showBox，实现方法很简单，将光照贴图赋值给linghtMap：
var groundGeom =
new THREE.PlaneGeometry
(10,
10,
1,
1);
var lightMap =
new THREE.TextureLoader().load(
'/lib/assets/textures/lightmap/lm-1.png');
var map =
new THREE.TextureLoader().load(
'/lib/assets/textures/general/floor-wood.jpg');
material =
new THREE.MeshLambertMaterial(
{
color:
0x777777,
lightMap: lightMap,
map:
map
});
groundGeom.faceVertexUvs
[1] = groundGeom.faceVertexUvs
[0];
var groundMesh =
new THREE.Mesh(groundGeom, material);
groundMesh.rotation.x = -Math.PI /
2;
scene.add(groundMesh);
为了能够保证当前的光照贴图纹理能够正常显示，我们使用的正常的贴图纹理的uv映射的值。 lightMapIntensity属性可以修改贴图纹理对模型的影响，默认值为1。我们直接写到了gui调试器里面，还有显示立方体的方法：
function initGui() {
gui = {
showBox:
function () {
var material =
new THREE.MeshPhongMaterial({color:
0x00ffff});
var geometryBig =
new THREE.CubeGeometry(
1.2,
1.2,
1.2);
var cubeBig =
new THREE.Mesh(geometryBig, material);
cubeBig.position.y +=
0.6;
scene.add(cubeBig);
var geometrySm =
new THREE.CubeGeometry(
0.7,
0.7,
0.7);
var cubeSm =
new THREE.Mesh(geometrySm, material);
cubeSm.position.
set(-
1.4,
0.35,
0);
scene.add(cubeSm);
},
lightMapIntensity:
1
};
var datGui =
new dat.GUI();
datGui.add(gui,
"showBox");
datGui.add(gui,
"lightMapIntensity",
0,
5).onChange(
function (e) {
material.lightMapIntensity = e;
});
}
案例代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title
</title>
<style type="text/css">
html, body {
margin: 0;
height: 100%;
}
canvas {
display: block;
}
</style>
</head>
<body onload="draw();">
</body>
<script src="https://cdn.bootcss.com/three.js/91/three.min.js"></script>
<script src="/lib/js/utils/ImageUtils.js"></script>
<script src="/lib/js/controls/OrbitControls.js"></script>
<script src="https://cdn.bootcss.com/stats.js/r17/Stats.min.js"></script>
<script src="https://cdn.bootcss.com/dat-gui/0.7.1/dat.gui.min.js"></script>
<script src="/lib/js/Detector.js"></script>
<script>
var renderer, camera, scene, gui, light, stats, controls, mesh, material;
function initRender() {
renderer = new THREE.WebGLRenderer({antialias: true});
renderer.setPixelRatio(window.devicePixelRatio);
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.setClearColor(0xeeeeee);
renderer.shadowMap.enabled = true;
document.body.appendChild(renderer.domElement);
}
function initCamera() {
camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 200);
camera.position.set(0, 12, 15 );
}
function initScene() {
scene = new THREE.Scene();
scene.background = new THREE.Color( 0xa0a0a0 );
scene.fog = new THREE.Fog( 0xa0a0a0, 50, 500 );
}
function initGui() {
gui = {
showBox:function () {
var material = new THREE.MeshPhongMaterial({color:0x00ffff});
var geometryBig = new THREE.CubeGeometry(1.2,1.2,1.2);
var cubeBig = new THREE.Mesh(geometryBig, material);
cubeBig.position.y += 0.6;
scene.add(cubeBig);
var geometrySm = new THREE.CubeGeometry(0.7, 0.7, 0.7);
var cubeSm = new THREE.Mesh(geometrySm, material);
cubeSm.position.set(-1.4, 0.35, 0);
scene.add(cubeSm);
},
lightMapIntensity:1
};
var datGui = new dat.GUI();
datGui.add(gui, "showBox");
datGui.add(gui, "lightMapIntensity", 0, 5).onChange(function (e) {
material.lightMapIntensity = e;
});
}
function initLight() {
scene.add(new THREE.AmbientLight(0x444444));
light = new THREE.DirectionalLight(0xffffff);
light.position.set(-20, 20, -20 );
light.castShadow = true;
light.shadow.camera.top = 10;
light.shadow.camera.bottom = -10;
light.shadow.camera.left = -10;
light.shadow.camera.right = 10;
light.castShadow = true;
scene.add(light);
}
function initModel() {
var helper = new THREE.AxesHelper(50);
scene.add(helper);
var groundGeom = new THREE.PlaneGeometry(10, 10, 1, 1);
var lightMap = new THREE.TextureLoader().load('/lib/assets/textures/lightmap/lm-1.png');
var map = new THREE.TextureLoader().load('/lib/assets/textures/general/floor-wood.jpg');
material = new THREE.MeshLambertMaterial(
{
color: 0x777777,
lightMap: lightMap,
map: map
});
groundGeom.faceVertexUvs[1] = groundGeom.faceVertexUvs[0];
var groundMesh = new THREE.Mesh(groundGeom, material);
groundMesh.rotation.x = -Math.PI / 2;
scene.add(groundMesh);
}
function initStats() {
stats = new Stats();
document.body.appendChild(stats.dom);
}
function initControls() {
controls = new THREE.OrbitControls(camera, renderer.domElement);
controls.enableDamping = true;
controls.enableZoom = true;
controls.autoRotate = false;
controls.autoRotateSpeed = 0.5;
controls.minDistance = 1;
controls.maxDistance = 2000;
controls.enablePan = true;
}
function render() {
}
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
renderer.setSize(window.innerWidth, window.innerHeight);
}
function animate() {
render();
stats.update();
controls.update();
renderer.render(scene, camera);
requestAnimationFrame(animate);
}
function draw() {
if (!Detector.webgl) Detector.addGetWebGLMessage();
initGui();
initRender();
initScene();
initCamera();
initLight();
initModel();
initControls();
initStats();
animate();
window.onresize = onWindowResize;
}
</script>
</html>
