[barrkel]

Duke Nukem 3D used a 2.5D engine; it was like Doom, in that the map was strictly 2D with ceiling and floor heights: http://en.wikipedia.org/wiki/Build_engine

I can't agree with you that FPSes haven't changed since then; it's only true if you are very selective about what you consider important about a FPS. What you have said implies that you don't care about story line, realism of physics simulation, gameplay, etc., which I'm quite certain is simply not objectively true of the gaming marketplace. Even if you think it's the "3D" that matters, then things were vastly better in Quake than Duke Nukem, where you could look directly up and down without bad distortion etc.

And then, one needs to ask, what quality is it of the 3D that matters? Simple things like decent texture scaling (trilinear filtered mipmapping, anisotropic filtering etc.) and antialiasing make a big difference, but are often only viable at high resolution in 6-month old games with the latest hardware, such are the demands of the processing.

[mryall]

> I can't agree with that FPSes haven't changed since then

Yeah, I found Portal by Valve Software a couple of years ago the same groundbreaking experience in terms of gameplay that I felt with those first 3D games. Some of my friends said the same about HalfLife before it.

[wmil]

It was a 2.5D engine, but there were a lot of hacks put in to make it feel more 3D.

For instance you couldn't do proper floors above floors, but there were some rendering tricks you could use to do bridges.

It also supported slanted floors, which helps level designers more than you realize. Also there were invisible teleports to fake a real 3d layout.

But the most important part was that the level designers were very good at using those tricks to hide the limits of the engine.