体积光，体积雾——链接
http://www.lsngo.net/2017/10/22/unityshader_volumetriclight/?gqfwls=qb0ac3
https://zhuanlan.zhihu.com/p/21425792
https://www.cnblogs.com/minggoddess/p/10102269.html 体积雾
https://blog.csdn.net/FeiBin2013/article/details/80383235 雾
https://blog.csdn.net/feibin2013/article/details/80391024 雾
https://blog.csdn.net/feibin2013/article/details/80383235 雾
https://www.jianshu.com/p/d01373c79f3b 雾
http://www.manew.com/thread-141101-1-1.html 光
https://zhuanlan.zhihu.com/p/21425792 光
https://zhuanlan.zhihu.com/p/30944509 光
https://yq.aliyun.com/articles/622307 光
https://blog.csdn.net/puppet_master/article/details/79859678 综合
https://developer.nvidia.com/gpugems/GPUGems3/gpugems3_ch13.html 光
https://developer.nvidia.com/gpugems/GPUGems/gpugems_ch39.html
https://zhuanlan.zhihu.com/p/32425359
https://blogs.unity3d.com/2012/03/23/shadowgun-optimizing-for-mobile-sample-level/
https://blog.csdn.net/candycat1992/article/details/42061701
GodRay现象的原理，丁达尔效应。胶体中的粒子对光线进行了散射形成光亮的通路。
BillBoard特效贴片
Volume Shadow沿光方向挤出顶点
Radial Blur Postprocessing基于后处理的实现
Ray-Marching基于光线追踪的实现
根据远近控制淡入淡出比较简单，只要设置两个距离的参数，根据距离去计算即可。如果感觉效果不够强，就乘方一下。