But as any animator knows, the different body parts of a character don't start and stop moving all at the same time. Therefore, the animator will generally set keys for the different body parts on different frames, so that the shoulder moves from frame 10 to 20, whereas the elbows starts moving on frame 12 and stops on frame 23. Of course, he can then go on and refine the timing by shifting the position of key frames. A good program will also allow him to copy and paste key frames between shots and even between characters. The exact position of a character's hand in one shot may prove useful as a starting point for posing the hand of another character in a completely different shot.

Function Curves
Function curves are one of the most important tools a computer animator has. The term varies from program to program. Motion graph, velocity and channels are just some of the names used. Using function curves you can edit the slow in and slow out between key frames. By default the inbetweens created by animation software give you smooth, mechanical inbetweens that do not change speed. This is why so much computer animation looks weightless and slick, as if the characters are floating in outer space where there is no gravity. To avoid this problem, the animator needs to spend a large amount of time adjusting the exact shape of the function curve between each key frame. This determines the exact amount of movement per inbetween.

Below: Two examples of the computer animator's "palette." The wireframe model can be seen on the lower left, with the fully rendered character on the upper right. The charts on the upper left and lower right enable the animator to control motion and sequencing. These screenshots were created with Softimage for Windows 95/NT.