The problem: A pesky patent, which had already caused issues between company founder John Carmack and software company Creative Labs. It’s all over a 3D shading technique, “Depth fail”, also known as “Carmack’s Reverse”. Turns out both companies stumbled upon the same technique, back in 1999. The ensuing drama saw Carmack and id forced to license the patent from Creative.
While that’s a totally suitable approach when releasing a game to retail, it makes things a little tricky when planning to release something as open source. Ten years after the game was completed, John Carmack has had to return to the drawing board to re-code this single element of a project that he’s releasing to improve the lives of gamers and programmers around the world.
It all sounded a bit doom and gloom, but Carmack’s a clever fellow and made a mere tweak or two to the code in order for it to pass the patent test. In his own words:
The workaround added four lines of code and changed two.
…and the end result is now happily sitting in our file library: Doom 3 Source Code, less than 10MB and all ready to go. The pack does not include any game data, because that’s still covered by the original end user license agreement of the game, but the behind-the-scenes stuff is there for you to poke around in.