However, there is not always a lot of communication between traditional animators and computer animators. Many old-school animators still live under the misunderstanding that computer animation is far too technically complex to be any fun to do. They envision bleary-eyed computer programmers typing "move arm 45.93 degrees to the left, 19.17 degrees up." Or they think it is far too simple, anticipating college kids with no idea about the principles of animation, hitting a button that says, "Happy walk, 16 frames."

Of course, neither of these horrifying visions is true. Today's character animation programs are all designed with traditionally trained artists in mind and try to make the jump from 2D to 3D as painless as possible. At the same time, although these programs are extremely powerful and offer enormous control over animation, modeling, lighting and so on, they still require that an educated artist sits in front of the computer and makes the decisions on every little nuance of movement.

Mary Lynn Machado, a technical director at Rhythm & Hues studio in Los Angeles, works on a Silicon Graphics Octane computer workstation to create models for animation.

The Technical Stuff
Okay, so how do you actually animate on a computer? Although the techniques and terms described here vary a little from program to program, the principles and the process are basically the same. Digital character animation can be described as a hybrid mix between puppet animation and cel animation. It is similar to puppet animation in that you are dealing with a three dimensional character that can be looked at from every possible angle, and that you are posing it in three dimensional space. The similarity with hand drawn animation lies in the fact that you work according to the pose to pose principle, creating key frames that resemble key poses in drawn animation. You control the way the computer creates the inbetweens, just like an animator will write instructions to his inbetweener in the corner of each drawing.

Modeling
Before any animation can be done, a model has to be created. At larger studios, this is usually done by modeling technical directors (TD's), who do not do any animation. A computer model can be constructed from geometric primitives, like spheres boxes and cylinders, but that's not much help when it comes to creating organic looking characters. Usually the modeler will use splines, which are lines whose curvature is adjusted with little handles on the control vertices which are located at the start and end points of the spline. By connecting numerous splines and dragging them around in three dimensions, a computer model is created. The model may be entirely created in the computer, or based on a three dimensional scan of a clay model.

Bones
A problem in many computer animation programs is that they don't allow you to have continuous skin between separate body parts. Therefore, the hand, the forearm, the upper arm, etc. have to exist as separate objects that are not connected. A limited number of programs, however, allow you to create the character in one piece. This is known as a mesh. This mesh only provides the "skin" of the character and is hollow inside. To move the different parts of the body separately, you then have to construct a virtual skeleton inside the mesh and connect parts of the mesh to each individual bone. Thus, when you move the forearm bone, the control vertices associated with that bone will move the body accordingly.

Key Frames
The first principle that a computer animator has to learn is key framing. A key frame in computer animation is a frame on which the animator has specified the start or end of a movement, or a change of direction. As an example, to move the arm of a character, the animator will set a key on frame 10 (A), indicating that this is where the movement begins. Then he jumps forward to frame 20 (B) and creates a new key, on which he puts the arm into its end position. Thus, from frames 11 to 19 the arm will be moving from position A to position B.