Computer Viewing

The goal of perspective projection is to transform 3D coordinates (x,y,z) into 2D coordinates on the projection plane. Most graphics systems put the center of projection at (0,0,0) and project 3D points onto the plane z=d, and the projection formulas are: xp = x * d / z, and yp = y * d / z.

a) Some graphics systems put the center of projection at (0,0,-d) and project 3D points onto the plane z=0. Draw side-view diagrams to show what this would look like.

b) What would the projection formulas for (xp, yp) be in this case?