Spacetime Constraints：（时空的限制）.pdfVIP

Spacetime Constraints Andrew Witkin Michael Kass Schlumberger Palo Alto Research 3340 Hillview Avenue, Palo Alto, CA 94304 Abstract Siggraph ’87 [9]. Although Luxo, Jr. showed us that the team of animator, keyframe system, and renderer can be Spacetime constraints are a new method for creating char- a powerful one, the responsibility for defining the motion acter animation. The animator specifies what the character remains almost entirely with the animator. has to do, for instance, “jump from here to there, clearing a Some aspects of animation—personality and appeal, for hurdle in between;” how the motion should be performed, example—will surely be left to the animator’s artistry and for instance “don’t waste energy,” or “come down hard skill for a long time to come. However, many of the prin- enough to splatter whatever you land on;” the character’s ciples of animation are concerned with making the charac- physical structure —the geometry, mass, connectivity, etc. ter’s motion look real at a basic mechanical level that ought of the parts; and the physical resources available to the to admit to formal physical treatment. Consider for exam- character to accomplish the motion, for instance the char- ple a jump exhibiting anticipation, squash-and-stretch, and acter’s muscles, a floor to push off from, etc. The require- follow-through. Any creature—human or lamp—can only ments contained in this descri