The patent dealt with a technique for rendering shadows called Carmack's Reverse, which was developed independently by both John Carmack and programmers at Creative Labs.
Teden pred izidom igre je postalo znano, da je na dogovor med id Software in Creative Labs o vključitvi zvočne tehnologije EAX v igri močno vplival programski patent, imenovan Carmack's Reverse, ki si ga je sicer lastilo slednje podjetje.