For a single screen, each frame of the 3D movie must contain two (left and right eye) images. In the Nortel Networks VR Theatre, two screens at right angles require double the effort - four images making up a single frame of the 3D movie. The graphics computer (1) sends two images (a left-right pair) to each of the two projectors (2a and 2b) which back-project the images onto the semi-transparent screens (3a and 3b). The computer also communicates with a transmitter (4) which emits an infra-red signal telling the glasses worn by the audience which image (left or right) is currently being displayed on the screens.
The computer driving the system is a high-end PC with dual graphics cards producing synchronised left and right screen 800x600 resolution images at 120Hz. At a desired 30 stereo frames per second, that's a whopping 170 megabytes per second of image data or nearly 70 gigabytes for the six and one half-minute show. Rather than prerecord this data and play it back via a fast disc system, the full 3D worlds depicted in the show reside in main memory. Correct left and right eye views for each screen are then computed in real-time from twin cameras spaced 5 cm apart, the average human eye separation.