3D shadowing explored
GameDev.net has an interesting (but very technical) article up on the shadowing techniques being used in the new DOOM game, and also the Tenebrae Quake mod.
Shadows used to be just a patch of darkened texture, usually round in shape, which is projected onto the floor below characters or objects in a game. One must be ill informed or naïve to think that we can still get away with this kind of sloppy "hacks" in future 3D games. There used to be a time where shadows are just too expensive to be rendered properly in real-time, but with the ever-increasing power of graphics hardware, failure to provide proper shadows no longer meant mediocre implementations, it borders on being guilty of criminally under-utilizing the graphics hardware available.
Of course, until the vast majority of the gaming world has hardware capable of supporting advanced shadowing techniques, games built around them may not be financially successful. Counter-Strike is still incredibly popular today, and I would bet that a large part of that popularity stems from the fact that you can run the game with acceptable performance on even modest systems. Heck, I used to play CS on a Pentium 2 266 with a Voodoo2.
As details of the new DOOM trickle onto the web, it's looking more and more like the game will all but require very high-end hardware for acceptable frame rates with all the eye candy turned on, even at low resolutions. I can see a lot of people complaining about performance when the new DOOM is eventually released, but the game could drive a huge wave of PC graphics card upgrades.