学习threeJS(三)--光源

1、光源的类型

• AmbientLight(环境光)
• PointLight(点光源)
• SpotLight(聚光灯光源，锥形光源)
• DirectionLight(方向光，太阳光，平行光)
• HemisphereLight(半球光)
• AreaLight(面光源)
• LensFlare(镜头炫光)

2、基础光源

一、AmbientLight

没有特定来源，不会产生阴影，不能单独使用，与其余光源一块儿使用，目的是弱化阴影或添加颜色。

var ambientLight = new THREE.AmbientLight('#0c0c0c');
scene.add(ambientLight);

不须要指定光源位置

二、PointLight

new THREE.PointLight(color颜色,  intensity强度,  distance距离,  position位置, visible光源开闭)

var pointColor = '#ccffcc';
  var pointLight = new THREE.PointLight(pointColor, 2, 100);
  pointLight.position.x = -20;
  pointLight.position.y = 10;
  pointLight.position.z = 0;
  pointLight.visible = true;
  scene.add(pointLight);

*点光源不会产生投影，由于点光源向全部方向发射光，计算负担太重。

三、SpotLight

• castShadow 是否生成阴影
• shadowCameraNear 投影近点
• shadowCameraFar 投影远点
• shadowCameraFov 投影视场（我理解为视角）
• target 目标，决定光照方向
• shadowBias 阴影偏移
• angle 角度、光柱的宽度
• exponent 光强衰减指数
• onlyShadow 没有光照只有阴影
• shadowCameraVisible 投影方式可见
• shadowDarkness 阴影暗度--场景渲染以后不能修改
• shadowMapWidth 阴影映射宽度（像素）
• shadowMapHeight 阴影映射高度（像素）

var spotLight = new THREE.SpotLight('#FFFFFF');
spotLight.position.set(-40, 60, -10);
spotLight.castShadow = true;
spotLight.target = plane;
scene.add(spotLight);

若想指向其余地方，空间其余点位，能够建立一个空的THREE.Object3D()实例

var target = new THREE.Object3D();
target.position = new THREE.Vector3(5, 0, 0);

spotlight.target  = target;

其余属性有待研究

四、DirectinalLight

var directionalLight = new THREE.DirectionalLight('#FFFFFF');
directionalLight.position.set(-20, 50, -20);
directionalLight.castShadow = true;
directionalLight.shadowCameraNear = 2;
directionalLight.shadowCameraFar = 200;
directionalLight.shadowCameraTop = 50;
directionalLight.shadowCameraBottom = -50;
directionalLight.shadowCameraLeft = -50;
directionalLight.shadowCameraRight = 50;
scene.add(directionalLight);

3、特殊光源

待更