https://www.cnblogs.com/yymn/p/4661898.html
https://www.zhihu.com/question/22298352/answer/228543288
https://zhuanlan.zhihu.com/p/41212352
https://blog.csdn.net/chaipp0607/article/details/72236892
https://blog.csdn.net/zouxy09/article/details/49080029
好网站:!!
https://graphics.stanford.edu/