Title: Skeletons for your spineless avatar
Author: Gedalia Pasternak
Created: May 6, 1999
Modified: June 22,1999

What Biped Lacks:

A good facial animation system

One question that that I want to addresses: Why does character studio lack a facial animation system? it seems like a obvious thing to do. Traditionally character animation facial animation has been accomplished via a morph or shape animation system . What this means is that the artist would physically transform the vertices of a face and then save the information into the object. These targets could then be used as weights are superimposed upon each other. That is, a face could have a smile and a raised eyebrow stored and the artist mixes them together creating compound expression. Muscle simulations would make most artists twitch.)

It works for Jar Jar, why shouldn't we do it? This is a technique that will only work on one model because you can't share the topology between two dissimilar meshes. There are two possible solutions for our animation system conundrum.

  1. We create a shape based animation system. Encoding the various facial transforms and then allow users to alter the basic mesh and create new avatars with the basic expressions hard coded in. This solution seems plausible but really limits the flexibility of the animation system in the avatars.
  2. The second solution and used to create our own type of biped specifically for humanoid faces. This allows any character that is properly set up to share animations with each other as well as interface properly with the system, this seems like a better solution, however not a simple one. What does that imply? There are quite a number of different types of muscles in the face. Fred Park has created a muscle simulation that deals may mainly with the muscles that contract. With this facial expression model one can raise ones eyebrows, smile, frown and furrow the brow. 

The structures necessary for this to work:

Upper facial node

  • Upper eyelid
  • Eyeball
  • Lower eyelid
  • Frontalis
  • Corrugator
  • Orbicularis Oculi

Lower facial node

  • Tongue node
  • Jaw bone
  • Labii superioris
  • Obricularis Oris
  • Zygomatic Major
  • Mentalis


The yellow lines indicate muscles. a structure like this will have to be placed as part of the skeleton. so that the facial simulator has something to work with.

Facial Structure in 3ds Max Necessary for:

Jaw articulation
Eye lid articulation
Eye Movement

Results (of the structure to the right) (movie removed for space reasons.

 NOTE: This took me approximately 6 hours to do. This is partly due to the fact that the automatic tools in character studio are geared to towards envelopes that are going to be applied to legs. The face on the other hand is an extremely elastic structure with a lot of fine motion and interaction, with very little gross distortions. Another issue they came up is that it is much too easy to be forced to start from scratch using character studio. In the process of animating a character you very often discover a flaw in the mesh that needs to be corrected. The correction can actually wind up erasing the vertex weighting that has been performed.

It is possible the could create our own enveloping tools more geared towards facial features then large joints. For instance the mouth would be a better represented by an oval shape. The first co-ordinate representing the weight of the jaw's influence and the 2nd the weight of the static root node.