It really doesn't take John Carmack to figure how the patented shadowing algorithm works. It's a very trivial modification of an older shadowing volume algorith

It really doesn't take John Carmack to figure how the patented shadowing algorithm works. It's a very trivial modification of an older shadowing volume algorithm where you slightly change depth test and stencil test settings to get more robust shadow volumes. I used this algorithm just the other day in some exercise work for uni studies. We actually had this algorithm as an example on one of the basic 3d graphics courses. When the d3 source is out, I might take the time to re-write the z-fail shadow volume code to doom3 and push it to a git server hosted in a country with sane patent laws. If I have very much time on my hands, I might try to do the shadow volume extrusion on the GPU with geometry shaders (a post-doom3 addition to GPU pipeline).