About that performance hit
If you follow these things at all, you probably know that it doesn't take a terribly expensive video card to drive a 1680x1050 display in the latest games. Of course, stereoscopic 3D will necessarily involve some sort of performance hit, because you've basically got to render the each frame twice, once for each eye, in order to achieve a given frame rate. Handicapping the magnitude of this performance hit is difficult. Nvidia claims it does some nifty things in its drivers, including "smart culling," in order to keep performance up, but it's very light on the details. Going on what little information I had, I decided to play it what I thought was fairly safe and test 3D Vision with a GeForce GTX 260 graphics card (the version with 216 SPs). The GTX 260 is pretty fast, after all, and not a bad value at present.

Well, that didn't work out too well. Some games felt sluggish with stereoscopic 3D enabled, even at 1680x1050, and even with features like high-quality shadows sometimes disabled. I really didn't want slow frame rates to spoil the effect for my test subjects, so I tried swapping in a GeForce GTX 285 instead. When that wasn't enough, I just went whole hog and plugged in a second GTX 285. That did the trick, but it ought to have—we're talking about a pair of $350 graphics cards.

Since this is hardware review site, I'm required by OSHA and the FDA to supply you with some benchmark numbers to prove my point. (Well, OK, the numbers don't have to prove a point, but they're required anyhow.) I tested on the same basic system config documented here, using a single GeForce GTX 285 graphics card, both with and without stereoscopic 3D enabled. I then tested with two GTX 285s in SLI and 3D Vision enabled, as well. Here's what I found:

As you can see, the performance hit is sizeable—maybe even bigger than the hit Michael Phelps took off of that bong. In Left 4 Dead, the extra work required for stereoscopic 3D doesn't present much of a problem for the GTX 285; it still averages nearly 60 FPS. The performance drag is considerable, though: one GTX 285 without 3D Vision is faster than two GTX 285s with it.

Fallout 3 is similar in this respect. A single GTX 285 without stereoscopy is quite a bit faster than two GTX 285 cards with it. Even more unfortunately, SLI is no help at all in Crysis Warhead. Once you turn on 3D Vision, frame rates take a nosedive, regardless.

Of course, the performance hit will vary from one game to the next, and Nvidia claims it's working on refining its 3D Vision profiles for improved performance as well as better compatibility. Still, right now, the stakes are pretty easy to see: if you want stereoscopic 3D, you're going to have to fork out for a pretty beefy graphics subsystem, as well. This isn't an issue one can ignore, because smooth frame rates are an incredibly vital component of perceived image quality in a game. As fundamental as depth is to our visual systems, the illusion of motion is even more crucial.