ot long ago you might have called it magic. Today it's called CGI, computer generated imagery. This electronic world of make-believe - where real animals talk and statues come alive - is revolutionizing Hollywood's special effects. Super-fast graphics computer, new creative software, and high-resolution pictures are rapidly taking us to a point where unreal looks real. Let's take a look at how Rhythm & Hues, one of Hollywood's top CGI studio is working on this art form, based on bits and bytes of computer technology.
In the Disney movie, Hocus Pocus, witches turned a boy into a cat. But this was no ordinary feline. What the filmmakers sought to create was a compelling character with life-like human qualities.

But some of the most believable animal action has been done using CGI. Some of it is real, such as a talking mule which was simply chewing peanut butter - but some of it is not.
For Focus Pocus, Bert Terreri, special effects supervisor at Rhythm and Hues, worked on the Disney sound stage with animation supervisor, Chris Bailey, to ensure that the live action would work with the computer-generated cat's head. They had to try to get the cat to look in the general direction it was supposed to talk in - and to make sure the shot was long enough for the dialog.
Meanwhile, back at Rhythm & Hues, modeling manager Keith Hunter worked with a sculpted, clay cat's head, modeled from

The film studio approach Rhythm & Hues, whose repertoire included the otherworldly creature in Star Trek Deep Space Nine and the missile encounter in Flight of the Intruder, among others. But Hocus Pocus was the company's toughest challenge yet. Its producers wanted something unique in the history of motion pictures, a completely believable, photo-realistic, talking cat. The challenge of this project was to create a life-like, computer-generated cat's head, animate it with facial expressions, and then place it on to the body of the real cat in the movie. A blending of live action and computer - generated imagery.
Talking animals are nothing new to movies. Earlier techniques included rotoscope animation.

Movie Magic explores the conception, creation and execution of Hollywood's most fantastic special effects. To learn more about computer generated imagery, animation and pyrotechnics, watch Movie Magic, Tuesday at 6 PM on Discovery Channel.

photos of live cats. He traced it into the computer using a special platform which surrounds the model in a magnetic field.This process called digital encoding takes thousands of points from the model and plots them on a sort of three-dimensional grid in the computer. Each point is assigned a unique number. The computer keeps track of where each point is, in relation to the others.
So in the end Hunter got a sculpture in the computer that looked like the real model. The 3D wire frame image was stored in the computer, where animators manipulated it for individual shots in the movie.