WITH computer power, John Lasseter has created ``Billy'' - a gurgling, diaper-clad baby whose dimensionality and complex facial expressions put Bambi to shame. Billy crawls, drools, and sneezes as he plays with his toys - or rather, as he shakes, throws, and mercilessly gums them. This is too much for Tinny, a tiny wind-up toy, who decides he'd rather hide under the couch.
The two characters, appearing in this year's Oscar-winning animated short film ``Tin Toy,'' are helping to usher in computer animation as a legitimate art form.
``My work is basically an art form that grew out of a science,'' says ex-Disney animator Lasseter in a phone interview. Computer graphics, he says, is the science that's fueling advances in computer animation.
Lasseter's latest film ``reflects the maturing of the computer animation field,'' says Frederic Parke, director of the Computer Graphics Laboratory at New York Institute of Technology. While some form of computer animation has existed nearly as long as computers have, Lasseter's work is ``state of the art,'' especially in its animation of a human being, he says.
``Tin Toy'' isn't headed for the Saturday-morning TV circuit. Its purpose is to demonstrate new hardware and software developed by Pixar computer company in San Rafael, Calif., where Lasseter works. ``We wanted to experiment with doing a baby,'' he says. Commercial applications of computer animation can be seen in any number of ``flying logos'' now on television.
To produce the five-minute ``Tin Toy,'' Lasseter and his team constructed a clay model of a baby and ``digitized'' his head, body, and hands by placing the tip of a special wand on rows of points across the surface of the model. The computer recorded each location of the wand and formed its own three-dimensional model. More than 40 facial ``muscles'' were programmed into the computer model so that Lasseter could animate Billy's expressions.
``His baby is just fantastic,'' says Frank Thomas, an animator who worked for Disney for more than 40 years and is now retired. Mr. Thomas, who has experimented with computers, says he finds the new medium much more ``tedious'' than traditional animation.
Lasseter says it is hard work, but the process ``is not that much more time consuming'' than manual techniques. The only drawing involved, he says, is in the preliminary stages when he's thinking up the characters. ``You build a model in the computer, then animate that model,'' he says.
The final stage is called ``rendering,'' in which the artist indicates the color, texture, lighting, and shadows - the equivalent of ink and paint in traditional animation. In producing ``Tin Toy,'' the computer ``knows'' every surface - from the shiny plastic face of Tinny (the toy) to the paper box he came in, with its crinkled cellophane window. The afternoon sunlight, which streams in through window mullions, adds further realism and dimension.
ONCE this information was entered into the computer, it took about 45 minutes per frame (6,000-plus frames) for the computer to render the final scene.
Lasseter says technology takes ``a back seat'' to character and story: ``The heart in films is so important to me. You can make something really cute, but it may not have substance behind it.'' He draws upon the ``age-old principles'' of animation he learned at Disney. Tricks of timing, for example - deciding the speed of certain motions - give objects ``weight'' and help distinguish between bowling balls and balloons.
Frank Thomas calls Lasseter's work ``refreshing.'' Some other computer animators, he adds, ``are not entertainers, they're not in show business. ... They can make all kinds of glitzy, sparkling stuff, but it holds the audience only for about three minutes.''
Lasseter first became interested in computer animation at Disney when the studio was producing the 1982 movie ``Tron.'' He then went to Lucasfilm Ltd., where he helped design and animate the stained-glass knight in ``Young Sherlock Holmes'' three years later. After Pixar spun off from Lucasfilm three years ago, Lasseter and his colleagues produced two prize-winning animated films: ``Luxo Jr.'' and ``Red's Dream.''
On par with most computer-generated films, ``Tin Toy'' cost several thousand dollars per second of running time. ``Computer animation right now is expensive,'' says Lasseter, ``but it's getting cheaper.'' Rendering time grows less as computers get faster and include more memory, he says.
``Everything's becoming more practical and affordable,'' says Carl Machover, president-elect of the National Computer Graphics Association. Lasseter's work demonstrates that ``we've got an enormous tool kit available to us now.''
Will computers ever replace traditional animation?
Frank Thomas says no. By hand, ``you can draw tiny little moves that are almost impossible to get with computers,'' creating superior ``fluidity'' of motion. Each method requires totally different skills, too, he says.
Lasseter's ``Billy'' character is remarkable, but ``it's not what it ought to be or what it will be in few years,'' Thomas says. ``That's why it's worth proceeding with the computers.''