[bananaboy]

It barely resembles id tech 3 at this point (I am an engine and pipeline programmer at Sledgehammer Games). There are very very few remnants of it in the codebase. I occasionally do some spelunking to see what’s left and these days it’s just the occasional comment and function names (although the content of the functions will have changed significantly).

[asdff]

I'm guessing its cheaper to iterate the old engine like this than to try and rebuild a new one from scratch one day, then move everyone onto that new engine and have them be as familiar as they were with the old one made of a couple decades of mostly duct tape it sounds like now.

[bananaboy]

Exactly! Armchair enthusiasts and gamers and such will talk about some game release and its "new engine" but throwing away the entire codebase is rarely a sensible choice financially speaking.