I beleive what he may be trying to explain is that with our own eyes we see objects from 2 different view points, 1 from each eye, that are of cause a small distence apart.
When using the shutter glasses the eyes are alternatively blocked, while the other views an image, this image is from the camera view point in game, which when running in 3D mode the camera in the game will shift left and right a small distence to imitate the distence between our eyes, which in turn is interpreted by our brains as a 3D model.
If you where to look at the monitor without the use of shutter glasses, then you would notice the game would flicker left and right, each of which will display a slightly different image reletive to each view point.
So this 3dvision thingie actually goes in to the software and modifies it to put out 2 different images from what it was normally programmed to do ? - like creating an aditional camera, and moving the original one slightly to the side + moving the focus of the camera.
perhaps this is a very simple and universal thing to do on the game-programming level ?