How 3D effect work?

Our ability to see stereo-vision comes from each of our eyes seeing a slightly different view of the world. Our brain integrates these two images into one three-dimensional picture.

The key element in producing the stereoscopic depth effect is parallax. Parallax is the horizontal distance between corresponding left and right image points. The stereoscopic image is composed of two images generated from two related perspective viewpoints, and the viewpoints are responsible for the parallax content of a view. For more information check Creating Good Stereo-Vision Images and Stereographics Handbook by Lenny Lipton. Sci. Virtual-worlds newsgroup web site has useful FAQs about 3D technology.