Chapter 3. Character Animation

27 10 2008

The Biped & Quadped

Character animation with 3d software is a relatively new art form. In 3d, animating a character is quite different from animation a bouncing ball or a car rolling down a street, a living creature has limbs that move in various ways. When it walks or runs, at least one body part (such as the left or right foot) reacts with the ground at any given time.

Throughout the 1990s three different approaches were developed to make 3d character animation possible: jointed characters, model control, and skeletons.

Jointed Characters

The first approach was to create jointed characters, similar to a marionette. The parts were linked together in a hierarchy; moving the torso would move the entire character in space, than the arms and legs could be rotated separately. This solution is still in use for many types of animation, but it has limitations. The joints are nearly always visible, or become visible as soon as the character starts to move.

Model Controls

To get around the problems of joints, another approach was developed for one-piece character models. An animator could place controls at key points on a character’s body and use the controls to push and pull parts of the mesh, Although this technique makes it possible to animate a character smoothly, it is also a tedious and difficult. A great nimber of controls is necessary to make the character deform correctly and when animated the character can seem to be made out of rubber or clay.

Skeletons and Skinning

A third approach was developed that mirrors real life more closely. A skeletal structure is placed inside the character model. When the skeleton is animated, its acts like bones inside a body and cause the character model to deform accordingly. This technique requires tools to make the skeleton affect the character model appropriately. For example, the skeletons upper arm bone must affect just the characters upper arm and no other body part.