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 assign 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?