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.

John Carmack

Thanks stelth.