Interesting, so it was apparently similar to the Build engine used by Duke Nukem 3D.
Was it written from scratch by someone at LucasArts or was it based on the Build engine?
The TFE Discord channel has people with a wealth of knowledge on this stuff. IIRC Lucas Arts designed it from the ground up, borrowing a few ideas and techniques from ID and inventing a few of their own.
Remember playing a lot of Dark Forces, but noticed on newer machines that it just didn't seem to run all that well.
Will have to give this replacement a go and see how it stacks up.
I've been playing it in DOSBox for some time. This is quite a magnificent rework. Mouse look is game changing!