https://qiita.com/bokkuri_orz/items/08cbaeae6a34fed7f903
https://www.cnblogs.com/sifenkesi/p/4721649.html
https://docs.unity3d.com/Manual/SL-PlatformDifferences.html
https://blog.csdn.net/puppet_master/article/details/52819874
https://www.jianshu.com/p/4e8162ed0c8d
https://www.cnblogs.com/murongxiaopifu/p/7050233.html
http://gad.qq.com/article/detail/29392
http://gad.qq.com/article/detail/32341
https://blog.csdn.net/puppet_master/article/details/52819874
https://zhuanlan.zhihu.com/p/37624886
Demo
https://forum.unity.com/threads/how-do-i-render-my-own-shadow-map.471293/
Shader Replacement
https://docs.unity3d.com/Manual/SL-ShaderReplacement.html
深度贴图shader
https://docs.unity3d.com/Manual/SL-DepthTextures.html