three.js 源码注释(四十四)Light/DirectionalLight.js

时间:2021-09-28 03:17:11
/**
*
* DirectionalLight方法 根据设置灯光的颜属性color, 强度属性intensity创建平行光光源。
* DirectionalLight 对象的功能函数采用定义构造的函数原型对象来实现。
* NOTE: SpotLight类型灯光实现了阴影,但是需要在场景中使用MeshLambertMaterial或者MeshPhongMaterial
* Example:
* var light = new THREE.SpotLight(0xff0000,1,100,Math.PI /2,5); //创建灯光对象
* light.position.set(50,50,30); //设置位置
* light.castShadow = true; //开启阴影
* light.shadowMapWidth = 1024; //阴影贴图宽度设置为1024像素
* light.shadowMapHeight = 1024; //阴影贴图高度设置为1024像素
* light.shadowCameraNear = 500; //阴影的平截头体区域near属性
* light.shadowCameraFar = 4000; //阴影的平截头体区域far属性
* light.shadowCameraFov = 30; //阴影的平截头体区域fov属性
* scene.add(lignt); //加入场景
*/
// <summary>DirectionalLight</summary>
// <param name="color" type="THREE.Color">灯光的颜色属性
// <param name="intensity" type="Number">灯光的强度,默认是1
// <returns type="DirectionalLight">返回DirectionalLight,平行光光源.</returns>
THREE.DirectionalLight = function ( color, intensity ) {

THREE.Light.call( this, color ); //调用Light对象的call方法,将原本属于Light的方法交给当前对象DirectionalLight来使用.
this.position.set( 0, 1, 0 ); //灯光的位置属性初始化为,0,1,0
this.target = new THREE.Object3D(); //创建一个目标点对象,目标点对象是一个Object3D对象.

this.intensity = ( intensity !== undefined ) ? intensity : 1; //灯光的颜色属性,如果不指定,初始化为1.(光线的密度,默认为1。因为RGB的三个值均在0~255之间,不能反映出光照的强度变化,光照越强,物体表面就更明亮。)

this.castShadow = false; //布尔值,默认为false,如果设置为true,对于所有表面都会逐像元地计算其在光照方向上是否被遮挡,这会消耗大量的计算。
this.onlyShadow = false; //布尔值,控制是否只产生阴影而不“照亮”物体,默认为false。这种模式也许有什么特殊应用吧。


this.shadowCameraNear = 50; //shadowCameraNear属性,正交投影立方体近端,定义一个范围(正交投影立方体),不计算在范围之外的物体的阴影,near默认是50
this.shadowCameraFar = 5000; //shadowCameraFar属性,正交投影立方体远端,定义一个范围(正交投影立方体),不计算在范围之外的物体的阴影,far默认是5000

this.shadowCameraLeft = - 500; //shadowCameraLeft属性,正交投影立方体左端,定义一个范围(正交投影立方体),不计算在范围之外的物体的阴影,left默认是500
this.shadowCameraRight = 500; //shadowCameraRight属性,正交投影立方体右端,定义一个范围(正交投影立方体),不计算在范围之外的物体的阴影,right默认是500
this.shadowCameraTop = 500; //shadowCameraTop属性,正交投影立方体上端,定义一个范围(正交投影立方体),不计算在范围之外的物体的阴影,top默认是500
this.shadowCameraBottom = - 500; //shadowCameraBottom属性,正交投影立方体下端,定义一个范围(正交投影立方体),不计算在范围之外的物体的阴影,Bottom默认是500

this.shadowCameraVisible = false; //shadowCameraVisible设置为true,会在场景中显示灯光的框架,方便调试

this.shadowBias = 0; //阴影贴图的偏移,
this.shadowDarkness = 0.5; //阴影对物体亮度的影响,默认是0.5

this.shadowMapWidth = 512; //阴影贴图宽度,单位像素,默认512
this.shadowMapHeight = 512; //阴影贴图高度,单位像素,默认512

/*对于平行光,WebGL可以使用级联阴影贴图(或成为平行分割阴影贴图)有很好的阴影质量,特别是远距离观看。
级联阴影通过分割可视区域逐步部分变大,并使用相同的大小,在每个阴影贴图。结果是物体接近观看者将比更远的物体获得更多的阴影贴图像素。
对于平行光阴影的质量和性能,阴影的距离是非常重要的。就像阴影级联数,阴影距离可以在质量设置中设置,很容易降低阴影范围,以减少硬件性能消耗。
在阴影距离结束处,阴影将淡出,更远的物体将没有阴影。大多数情况下在场景中更远地方的阴影不会引人注目!*/

this.shadowCascade = false; //阴影级联

this.shadowCascadeOffset = new THREE.Vector3( 0, 0, - 1000 ); //阴影级联偏移距离
this.shadowCascadeCount = 2; //当使用2个阴影级联时,整个阴影距离内,默认被分为两块,靠近观察者较小的块和远处较大的块

this.shadowCascadeBias = [ 0, 0, 0 ]; //阴影级联偏移数组
this.shadowCascadeWidth = [ 512, 512, 512 ]; //阴影级联宽度数组
this.shadowCascadeHeight = [ 512, 512, 512 ]; //阴影级联高度数组

this.shadowCascadeNearZ = [ - 1.000, 0.990, 0.998 ]; //阴影级联近处
this.shadowCascadeFarZ = [ 0.990, 0.998, 1.000 ]; //阴影级联远处

this.shadowCascadeArray = []; //阴影级联数组

//TODO: 下面这些完全没弄明白,以后补上详细的注释

this.shadowMap = null; //指定阴影贴图,WebGLRenderTarget对象,这里好像很复杂,完全没弄明白,以后补上详细的注释.
this.shadowMapSize = null; //阴影图的大小,注意,这里应符合OpenGL中对纹理的要求(2的n次方+2n)
this.shadowCamera = null; //阴影贴图相机,THREE.PerspectiveCamera对象,
this.shadowMatrix = null; //阴影贴图矩阵

};

/**
*下面是DirectionalLight对象提供的功能函数定义,一部分通过prototype继承自Light方法
**/
THREE.DirectionalLight.prototype = Object.create( THREE.Light.prototype ); //DirectionalLight对象从THREE.Light的原型继承所有属性方法

/*clone方法
*clone方法克隆DirectionalLight对象
*/
// <summary>clone</summary>
// <returns type="SpotLight">返回克隆的DirectionalLight对象</returns>
THREE.DirectionalLight.prototype.clone = function () {

var light = new THREE.DirectionalLight();
THREE.Light.prototype.clone.call( this, light ); //调用THREE.Light.clone方法,克隆平行光对象
//复制当前灯光对象的属性
light.target = this.target.clone();
light.intensity = this.intensity;
light.castShadow = this.castShadow;
light.onlyShadow = this.onlyShadow;

//
light.shadowCameraNear = this.shadowCameraNear;
light.shadowCameraFar = this.shadowCameraFar;

light.shadowCameraLeft = this.shadowCameraLeft;
light.shadowCameraRight = this.shadowCameraRight;
light.shadowCameraTop = this.shadowCameraTop;
light.shadowCameraBottom = this.shadowCameraBottom;

light.shadowCameraVisible = this.shadowCameraVisible;

light.shadowBias = this.shadowBias;
light.shadowDarkness = this.shadowDarkness;

light.shadowMapWidth = this.shadowMapWidth;
light.shadowMapHeight = this.shadowMapHeight;

//
light.shadowCascade = this.shadowCascade;

light.shadowCascadeOffset.copy( this.shadowCascadeOffset );
light.shadowCascadeCount = this.shadowCascadeCount;

light.shadowCascadeBias = this.shadowCascadeBias.slice( 0 );
light.shadowCascadeWidth = this.shadowCascadeWidth.slice( 0 );
light.shadowCascadeHeight = this.shadowCascadeHeight.slice( 0 );

light.shadowCascadeNearZ = this.shadowCascadeNearZ.slice( 0 );
light.shadowCascadeFarZ = this.shadowCascadeFarZ.slice( 0 );

return light; //返回克隆的平行光的对象

};