How to calculate 3d camera's position from head position for hologram effect

In this video http://www.youtube.com/watch?v=Jd3-eiid-Uw a hologram type effect is achieved by moving a 3d camera in some sort of corresponding motion to that of the viewers head.

Given the position of viewers head relative to the screen how do you calculate the position of the camera开发者_如何学Go to achieve this effect? Also do you have to calculate the camera's fov and correct for shearing?

Johnny Chung Lee made the source code for that demo available from his website:

• http://johnnylee.net/projects/wii/