We can now use this expression for s to interpolate arbitrary parameters, such
as texture indices (u, v), over our 3-space triangle. This is accomplished
substituting our solution for s given t into the parameter interploation.
Therefore, if we premultiply all parameters that we wish to
interpolate in 3-space by their corresponding w value and add a new plane equation to
interpolate the w values themselves, we can interpolate the numerators and denominator in screen-space.
We then need to perform a divide a each step to get to map the screen-space interpolants to their
corresponding 3-space values.
Once more, this is a simple modification to our existing triangle rasterizer.