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 by substituting our solution for s given t into the parameter interpolation.

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.