Somehow, Creative Labs obtained a patent on a shadowing technique that is sometimes referred to as "Carmack's Reverse" in programming circles. Instead of fighting the patent, id Software has made an agreement with Creative, and Beyond3D received a clarification from John Carmack:
The patent situation well and truly sucks.
We were prepared to use a two-pass algorithm that gave equivalent results at a speed hit, but we negotiated the deal with Creative so that we were able to use the zfail method without having to actually pay any cash. It was tempting to take a stand and say that our products were never going to use any advanced Creative/3dlabs products because of their position on patenting gaming software algorithms, but that would only have hurt the users.
This is upsetting for programmers who were planning on using the same technique. The patent probably doesn't affect Europeans, I'm not sure about Canadians.