Point in triangle test
https://blackpawn.com/texts/pointinpoly/
Perspective-Correct Interpolation
https://www.comp.nus.edu.sg/~lowkl/publications/lowk_persp_interp_techrep.pdf
Clipping
https://www.cs.uic.edu/~jbell/CourseNotes/ComputerGraphics/Clipping.html
OpenGL Programming Guide