> (if my memory is correct, oddly the engine uses quads rather than triangles)

I'm also working off a near 30-year-old memory but I recall quads not being unusual around this time. I remember a preview of Tomb Raider 3 in Official Playstation Magazine making a big deal out of the updated engine using triangles instead of quads to draw things. This was around 1998, so a couple of years after Quake came out.