Theater-goers who were fortunate enough to attend a recent production of Shakespeare's The Tempest got an unexpected treat when they witnessed the normally motionless backdrop come to life. The clouds appeared to be floating in the sky and a maiden walked through the scenery. A scene from IRT's 1995-96 production of The Tempest. Courtesy of Carl Pope Jr. The Indiana Repertory Theatre (IRT) in Indianapolis decided that photonics technology was the only way to go as it prepared for the complex play requiring numerous stage cues and background images. The theater's technical crew used Light Valve projection technology and digital imaging technology to bring its stage props and backdrops to life.Theaters have long experimented with simple slide projectors to project backdrops, but this type of technology produces images that are not only static and often grainy, but also expensive. It can take days to make changes, which involves reshooting and processing new film.To create the more fanciful, complex effects for its recent production of The Tempest, the IRT used a Barco Light Cannon driven by a Macintosh 7500 Power PC to generate "virtual" scenery. This combination made it easy to achieve a whole new world of realistic, full-motion effects.To obtain the images for the backdrop, IRT artistic director Libby Appel and scenic designer Karen TenEyck scanned in and edited about 160 images using off-the-shelf Director software. The computer allowed operators to quickly make changes in colors and sequence.The next hurdle was to find a special projector that could convert digitized computer data onto an 18-ft- tall 3 32-ft-wide screen at the rear of the stage. Enter the Barco Light Cannon. Instead of conventional cathode-ray tubes, the Light Cannon uses three 5.8-in.-diagonal liquid crystal display panels. To project the image on the screen, a lamp in the rear of the Light Cannon beams the light onto dichroic mirrors that split the light into individual red, green and blue beams. Each color travels through a high-resolution LCD panel that passes image-creating light -- hence the name Light Valve. The light is then recombined by dichroic mirrors to produce a crisp image that has lifelike color saturation and brightness.The computer does not control the timing at which the images appear on the screen. The stage manager calls cues for lighting, sound and video. On the director's cue, a simple mouse click begins a new sequence.Even these impressive examples of what the computer-driven Light Cannon projectors can do in theater environments don't begin to tap the technology's capabilities. In the future, a living actor could have a dialogue with an animated character, giving fantasy scenes a new degree of realism.Prospero may have used magic to command wind and sea, but this creative theater company conjured up its own high-tech spell. Shakespeare would have been amazed.