Computer And Video Games has a preview of Doom 3, including an interview with John Carmack. It may require registration for full reading. Some excerpts:
When it was time to look at the Doom 3 stuff, I investigated five different directions for rendering post-Quake III. Some of them would have given much higher quality renderings of static environments. It's not an exaggeration that we can do photo-realistic renderings of static environments and move through them. But, when you then paste dynamic objects on to those static scenes, they're clearly in this separate plane. You've got your moving thingy and your environment. And I thought it was more important as a game technology, which is about interactive things, that we followed this other opportunity. Instead of pursuing ultimate detail on the environments, we could unify all the lighting and surfaces, which is the big thing for Doom 3. So that was the core decision to be made, and I look back at that and, more than any other game I've done, I think those initial decisions and the initial technology layout were exactly right.
There was an important paper that came out at SIGGRAPH a few years ago by someone at SGI [Silicon Graphics]. He presented one real-time renderer and he presented something that showed the decomposition of Renderman shaders into multi-pass stuff that required floating-point and pixel stuff. It was amusing because I remember people completely discounting that paper, which I think is going to be looked back at as one of the most seminal things in interactive graphics. People were saying the Renderman shader was ridiculous - it took 500 passes to do this simple shader. People just hit this number - 500 passes, and clicked it out of their brain as not relevant. But a pixel in Doom 3 may have 80 textures combined on to it.
And I think the push for people to innovate in gameplay - I'm not sure that I particularly agree with it. You don't go around constantly coming up with new basketball games.
In other words: real-time Pixar in 5 years.
(From Gamers.at, via Tobi. And thanks to Clemens for copying the interview so I could put excerpts in here.)