The key is low cost and high performance, according to PSC scientist Joel Stiles, an associate professor in the Mellon College of Science at Carnegie Mellon. Joel Stiles, a medical doctor, physiologist and neuroscientist, and colleague Stuart Pomerantz, a programming expert, created the new system, called the PSC Stereo Animation System (PSC-SAS). "If you make good stereo content and have a good display system", stated Joel Stiles, "stereo viewing works fabulously. But it's tremendously underused, because few people have put all the pieces together in an optimum way. Our system provides theater-quality stereo viewing of complex animations at extremely high performance-cost ratio."
With PSC-SAS, images display on a screen, as in normal movie viewing, and the viewer wears light, comfortable glasses, like polarized sunglasses, making the system easily adaptable to in-theater or home viewing. Many stereo-viewing systems, in contrast, rely on special goggles, connected to a computer that can be used by only one person at a time while looking at a computer monitor.
To date, PSC-SAS has been used mainly in scientific settings, for 3D display of dynamic data, compiled as movies, from computational simulations of biomolecules, cellular physiology and other applications, where being able to see depth enhances the ability to understand and analyse complex phenomena. The reaction among scientists, according to Joel Stiles and Stuart Pomerantz, has been remarkable.
"Many scientists and other professionals who have seen various types of stereo display", explained Dr. Stiles, "are jaded. They think it sort of works, but it's basically a toy. When they see our system, they say wow and they're reaching out to touch what they see, because it looks so real as it hangs there in space."
All stereo-viewing systems achieve the effect of depth by displaying a slightly different image to each eye. PSC-SAS is distinctive in providing high-quality content in movie-form with "passive" stereo display technology. Most scientific systems and computer games are "active" stereo, relying on goggles that are, in effect, shutter glasses, controlling what each eye sees by electronically switching between the right and left eye at a rate faster than the wearer perceives.
Active stereo can provide high-quality effects, but it has several disadvantages. Prominently, it may present a health and safety problem. In some people, the rapid on-off flashing seen by each eye may become uncomfortable, and flashing lights can sometimes trigger an epileptic reaction. Visualization professionals generally limit their use to relatively short periods at a time. Active stereo, furthermore, is prohibitive for theater viewing, because of the cost of providing computerized goggles to everyone in the theater. The goggles, moreover, are heavy, need batteries and a link to a computer to keep them synchronized.
A more recent technology - "glasses-free" stereo on computer monitors - offers limited resolution and requires the viewer's head to remain in a particular location to see the effect. With PSC-SAS, two projectors display a right and left-eye image on the screen simultaneously, overlaid on each other, based on the well understood phenomenon of polarized light, so that one image is polarized at a 90 degree angle to the other. Polarized glasses allow the left and right eyes to perceive the two distinct images separately. With this approach, many viewers at one time can see stereo depth.
"One lens is polarized in one direction", stated Stuart Pomerantz, "and the other in the opposite direction. As long as the filters on the projectors match the filters on the glasses, you can deliver one image to the right eye and another to the left. It's an old trick."
PSC-SAS implements the old trick with stereo-movie content created by software called DReAMM, developed by Dr. Stiles, coupled to playback software called PSC-MP, developed by Stuart Pomerantz. To accommodate the high resolution of scientific images, PSC-SAS relies on sophisticated compression techniques that reduce file size, but only to a degree that the eye can't detect as different from the original. PSC-MP delivers the polarized images to the dual projectors in synchrony at high realism. It decodes and transmits data at 100 megabits per second, 20 times faster than DVD data rates, for high-definition quality at 30 frames per second.
The result - vivid colour and sharp, unpixelated images without uncomfortable, unsafe goggles - also comes at reasonable cost. Dr. Stiles estimates a total expense of $12.000 for the hardware components of PSC-SAS, available off-the-shelf, easily within the range of today's home theater market. A non-depolarizing screen, two computer projectors, a dual-processor PC, and a pair of polarized glasses - bring your own popcorn.
PSC-SAS is available for licensing and commercialization through the Carnegie Mellon University Innovation Transfer Center. The Pittsburgh Supercomputing Center is a joint effort of Carnegie Mellon University and the University of Pittsburgh together with Westinghouse Electric Company. It was established in 1986 and is supported by several federal agencies, the Commonwealth of Pennsylvania and private industry.