Character Motion Systems

30 10 2008

Reference: Character Motion Systems


The use of motion capture for computer character animation is relatively new, having begun in the late 1970’s, and only now beginning to become widespread.

Motion capture is the recording of human body movement (or other movement) for immediate or delayed analysis and playback. The information captured can be as general as the simple position of the body in space or as complex as the deformations of the face and muscle masses. Motion capture for computer character animation involves the mapping of human motion onto the motion of a computer character.

The mapping can be direct, such as human arm motion controlling a character’s arm motion, or indirect, such as human hand and finger patterns controlling a character’s skin color or emotional state.

The idea of copying human motion for animated characters is, of course, not new. To get convincing motion for the human characters in Snow White, Disney studios traced animation over film footage of live actors playing out the scenes. This method, called rotoscoping, has been successfully used for human characters ever since. In the late 1970’s, when it began to be feasible to animate characters by computer, animators adapted traditional techniques, including rotoscoping. At the New York Institute of Technology Computer Graphics Lab, Rebecca Allen used a half-silvered mirror to superimpose videotapes of real dancers onto the computer screen to pose a computer generated dancer for Twyla Tharp’s “The Catherine Wheel.”

The computer used these poses as keys for generating a smooth animation. Rotoscoping is by no means an automatic process, and the complexity of human motion required for “The Catherine Wheel,” necessitated the setting of keys every few frames. As such, rotoscoping can be thought of as a primitive form or precursor to motion capture, where the motion is “captured” painstakingly by hand.