John Carmack published an update on Twitter regarding the source code of Doom 3. id Software promised the code will be released soon, but there are still some legal hurdles as a certain shadowing technique used in Doom 3 is patented by Creative.
The Tech Report recalls an alternative to this shadowing technique patent was a two-pass algorithm that gave equivalent results at a speed hit. Carmack's tweet suggests he may replace the code owned by Creative with the alternative technique.
John Carmack's latest tweet about the subject reveals that a software patent issue has held up the release—and is forcing Carmack to re-write some of the code:
Lawyers are still skittish about the patent issue around "Carmack's reverse", so I am going to write some new code for the doom3 release.
The patent for "Carmack's reverse," a shadowing technique, happens to be owned by Creative (yes, the SoundBlaster folks). Back in 2004, id Software and Creative came to an agreement that allowed Carmack to use, uh, his technique in Doom 3 for free, so long as he implemented support for Creative's EAX audio technology in the game. At the time, Carmack stated that the alternative was to use a "two-pass algorithm that gave equivalent results at a speed hit."