On one screen, a swirling storm cloud slowly twists itself into the characteristic funnel shape of a killer tornado. On another, molecules the size of baseballs jostle frantically for position, each seeking out a comfortable docking site on another's surface. On a third screen, a small child in bright white diapers rises on stubby legs and toddles across a room.
These remarkable moving images and hundreds like them on display last week in Philadelphia at the tenth annual exposition of the National Computer Graphics Association are more than pretty pictures. Each represents a three- dimensional microcosm, stored within the memory of a computer, that human operators can turn, twist and reshape all they want. When special goggles, bodysuits and gloves are used to display and manipulate the images, those microcosms can become so real that viewers feel they have stepped through a kind of electronic looking glass into a completely artificial, computer- generated world.
Three-dimensional computer graphics, the technique by which digital machines generate realistic-looking objects and move them as fast as they would move in real life, has come of age. Architects are using 3-D technology to let clients walk through buildings before they are constructed. Scientists employ it to visualize phenomena too fast, too small or too explosive to be seen firsthand. Industry is relying on it to speed up design and production cycles.
As 27,000 artists, engineers and enthusiasts gathered for their big show, the computer-graphics experts had special reason to celebrate. Late last month two of their own, John Lasseter and William Reeves of Pixar, a computer manufacturer in San Rafael, Calif., won the first Academy Award given for a totally computer-generated film -- a short subject called Tin Toy that starred a rambunctious baby and a windup music man. Says Jaron Lanier, founder of VPL Research, a small Redwood City, Calif., company that makes the equipment used to help people enter a computer-generated world: "This is the year that this stuff is finally starting to work."
Behind the burst of activity is a dramatic advance in computer technology. Over the years, computer scientists have devised an impressive array of mathematical techniques, or algorithms, for rendering 3-D images on a 2-D computer screen. Traditionally, these algorithms -- for drawing things in perspective, for example, removing surfaces hidden from the viewer's line of sight or painting finished objects with texture and shade -- have been encoded in programs and stored in computers as software. As such, they used up massive quantities of computer time. To draw a simple object ten times a second, the minimum needed to create the illusion of motion, took 1 billion calculations a second. The highly polished images that won Tin Toy its Oscar took some 12 trillion calculations each.