The book Masters of Doom gives more information. It's a good read about the early days of id and the gaming industry in general. Carmack would go on 'research

The book Masters of Doom gives more information. It's a good read about the early days of id and the gaming industry in general. Carmack would go on 'research getaways' to hack on the Quake 3 engine. He did this because, at the time, the id office was not conducive to his work style. "Trinity" was the codename for the Quake 3 engine.