The problem I'm having is mapping a 3D triangle into 2 dimensions. I have three points in x,y,z form, and want to map them onto the plane described by the normal of the triangle, such that I end up with three points in x,y form.
My guess would be it'd assigning an arbitrary up vector... and then... doing something? Finding the distance traveled along the plane from one vertex to another...? What do I do, and how do I do it?