Three dimensional data sets are becoming widespread in scientific simulations and analysis of physical systems. Applications ranging from fluid simulations to medical imaging require understanding of three dimensional (3D) data. Researchers often produce images from the data to aid in understanding. In the resulting images, monocular depth cues such as object size, parallax motion, and shading help to interpret 3D data. However, viewing 3D data is enhanced by using stereo pairs so that binocular depth cues are available. There are several schemes for producing stereo pairs on the screen of a workstation (e.g. liquid crystal shutters, vibrating mirrors or cylinderical lens). We describe here a liquid crystal shutter system which is easy and inexpensive to construct.

vibrating mirrors or cylinderical lens). We describe here a liquid crystal shutter system which is easy and inexpensive to construct. Using liquid-crystal shutter glasses designed for video games, it is possible to construct an inexpensive stereo viewing interface to any personal computer or workstation which has hardware double-buffering of the display screen and which can produce an RS-232 character. The resulting display exhibits strong stereo depth cues. Flicker is noticeable and depends on the refresh rate of the monitor as well as the speed with which the double-buffered display can be changed. On the IBM RISC System 6000, equipped with the GL display card (part number xxx), the flicker is moderate, the brightness good, and the stereo effect very stable. The description given here will assume an IBM RISC System 6000. There are two parts to the system: the software to display two images in the double buffer and the hardware which converts an RS-232 character to the waveform necessary to drive the liquid-crystal glasses. Clearly the software will have to be modified for other systems, although it should run virtually unmodified on Silicon Graphics machines, such as the Personal IRIS.