https://www.youtube.com/watch?v=pCQfpHsoykQ&ab_channel=TheOregonian

https://www.youtube.com/watch?v=ehi-vsRb4Ao&ab_channel=EVERYTHINGcpo%28%40Vaarticus%3B%40go.fast.r%29

還有簡單投影

https://www.youtube.com/watch?v=x6lXojghs3c&ab_channel=RonaldWalters