Ok, google to the rescue again... from what's written below it seems that a GeForce4 and a 2.66GHz machine will be easily enough to play it. You might not have every single visual feature on, but it will play well.
From http://www.insidemacgames.com/news/story.php?ArticleID=3578
quote:
Chief among the known improvements to this title are in the area of graphics. A real-time lighting model is being implemented that will apply to everything in the game, characters and environments alike. One demo sequence of the engine shows a ceiling fan casting a real-time moving shadow. Every pixel in the game will be at least bump-mapped, and some will require up to 50 passes for current graphics cards to render. id is currently shooting for a photo-realistic quality game, and the hardware requirements alone will be terrifying -- as John Carmack notes that a GeForce 3 will be required to get an average of just 30 fps.
From http://www.insidemacgames.com/news/story.php?ArticleID=8076
quote:
Those looking forward to the release of DOOM 3, but still wondering of their machines will be capable of handling the game might want to check out a recent news post at 3D Action Planet. The post contains information, straight from id Software's John Carmack, of the PC version's current minimum specs. Here's the info:
1GHz CPU
256MB RAM
GF1 or Radeon 7xxx series card
There's an article here: http://www.beyond3d.com/interviews/carmackdoom3/
quote:
(question)GeForce1/GeForce2/Radeon7500. All would be able to run DOOM3 at lower resolutions with fewer per pixel lights per frame. What about per pixel normalized LightDirection? No cube maps and LightDirection can be stored in diffuse or specular color component of vertex but I'd appreciate a clarification/confirmation from you.
(john carmack)That is actually on my list of things to benchmark, but I rather doubt it will make a difference. I don't think there are enough combiners on a GF1/2 to do it, and I don't expect much of a speedup by skipping a rather low-res cube map access on GF3/4.