Material的lightMap属性，是光照贴图，使用光照贴图可以模拟出真实的阴影效果，但是阴影的位置不能随着随着物体的移动而移动。
1、示例
示例
http://ithanmang.com/threeJs/home/201809/20180905/06-lightMap-texture.html
效果
下面的阴影是通过光照贴图加载进来的，如下面的关照贴图
2、使用步骤
2.1、创建实例
let lm = new THREE.TextureLoader().load('../../textures/lightmap/lm-1.png');
planeGround.material.lightMap = lm;将平面的材质的lightMap设置
2.3、指定UV映射
planeGround.geometry.faceVertexUvs[1] = planeGround.geometry.faceVertexUvs[0];为光照贴图指定uv映射，将纹理的那一部分映射到表面，只有这样才能将关照贴图与其它贴图分别开来。
3、示例代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<link rel="icon" href="../../../three.png">
<title>使用光照贴图创建假阴影</title>
<style>
body {
margin: 0;
overflow: hidden; /* 溢出隐藏 */
}
#loading {
position: fixed;
top: 50%;
left: 50%;
color: #FFFFFF;
font-size: 20px;
margin-top: -30px;
margin-left: -40px;
}
</style>
<script src="../../libs/build/three-r93.js"></script>
<script src="../../libs/examples/js/Detector.js"></script>
<script src="../../libs/examples/js/libs/dat.gui.min.js"></script>
<script src="../../libs/examples/js/libs/stats.min.js"></script>
<script src="../../libs/examples/js/controls/OrbitControls.js"></script>
</head>
<body>
<p id="loading">loading......</p>
<script>
let scene, camera, renderer, controls, guiControls;
let stats = initStats();
/* 场景 */
function initScene() {
scene = new THREE.Scene();
scene.background = new THREE.Color(0x050505);
}
/* 相机 */
function initCamera() {
camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 10000);
camera.position.set(0, 50, -90);
camera.lookAt(new THREE.Vector3(0, 0, 0));
}
/* 渲染器 */
function initRender() {
renderer = new THREE.WebGLRenderer({antialias: true});
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
}
/* 灯光 */
function initLight() {
scene.add(new THREE.AmbientLight(0x0c0c0c));
let spotLight1 = new THREE.SpotLight(0xffffff);
spotLight1.position.set(-400, -400, -400);
let spotLight2 = new THREE.SpotLight(0xffffff);
spotLight2.position.set(400, 400, 400);
scene.add(spotLight1);
scene.add(spotLight2);
}
/* 控制器 */
function initControls() {
/* 地图控件 */
controls = new THREE.OrbitControls(camera, renderer.domElement);
/* 属性参数 */
}
/* 调试插件 */
function initGui() {
guiControls = new function () {
this.normalScale = 1;
};
let gui = new dat.GUI();
gui.add(guiControls, 'normalScale', -2, 2).onChange(function (e) {
box1.material.normalScale.set(e, e);
});
}
/* 场景中的内容 */
let box1;
let box2;
function initContent() {
let planeGround = createMesh(new THREE.PlaneGeometry(95, 95, 1, 1), 'floor-wood.jpg');
box1 = createMesh(new THREE.BoxGeometry(10, 10, 10), 'plaster.jpg', 'plaster-normal.jpg');
box2 = createMesh(new THREE.BoxGeometry(10, 10, 10), 'plaster.jpg');
let lm = new THREE.TextureLoader().load('../../textures/lightmap/lm-1.png');
box1.translateX(10);
box2.translateX(-10);
box1.translateY(10);
box2.translateY(10);
planeGround.rotateX(Math.PI * -0.5);
planeGround.material.lightMap = lm;
planeGround.geometry.faceVertexUvs[1] = planeGround.geometry.faceVertexUvs[0];
scene.add(planeGround);
scene.add(box1);
scene.add(box2);
}
/* 移除加载元素 */
function removeLoading() {
document.getElementById('loading').style.display = 'none';
}
/* 创建带有纹理的网格 */
function createMesh(geometry, imageUrl, normalMap) {
let loader = new THREE.TextureLoader();
let texture = loader.load('../../textures/general/' + imageUrl);
let material = new THREE.MeshPhongMaterial();
material.map = texture;
if (normalMap !== undefined) {
let normal = loader.load('../../textures/general/' + normalMap, function () {
removeLoading();
});
material.normalMap = normal;
}
let mesh = new THREE.Mesh(geometry, material);
return mesh;
}
/* 性能插件 */
function initStats() {
let stats = new Stats();
document.body.appendChild(stats.domElement);
return stats;
}
/* 窗口变动触发 */
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
renderer.setSize(window.innerWidth, window.innerHeight);
}
/* 数据更新 */
function update() {
stats.update();
controls.update();
if (box1 && box2) {
box1.rotateY(0.01);
box2.rotateY(0.01);
}
}
/* 初始化 */
function init() {
if (!Detector.webgl) Detector.addGetWebGLMessage();
initScene();
initCamera();
initRender();
initLight();
initControls();
initContent();
initGui();
/* 监听事件 */
window.addEventListener('resize', onWindowResize, false);
}
/* 循环渲染 */
function animate() {
requestAnimationFrame(animate);
renderer.render(scene, camera);
update();
}
/* 初始加载 */
(function () {
console.log("three init start...");
init();
animate();
console.log("three init end...");
})();
</script>
</body>
</html>