Okay, rephrasing my question

i dont quite get how the matrix is formed between xyz coordinates to uv screen coordinate. Like how does xyz values gets projected to uv coordinate in specific way so to create the sense of depth needed in perspective in way so it doesnt messed up/looks natural.

like x =x+z, u=x/z, cos and sin in matrices. i cant quite piture it.

help understanding, in a way of pixe by pixels/grid by grid of sort...