Facial animation by computer is a complex subject
involving advanced
techniques in human-computer interaction, physical and geometrical
simulation, computer graphics and also image recognition. A living
face (human or animal) in motion is a complex animated structure in
which fine details, rigid and deformable structures run together
producing a variety of expressions. The choice of a specific facial
model is dictated by the particular effects one expects to achieve
during animation. See
[28][108][75][80][148][134][146][133][144][124][66][89][101][81][119][138][98][103][105][72].
As discussed above, all human faces possess the same physiological
organization of bones, muscles and skin. People smile in the same
way-contracting the big zygomatic and the lips corner elevator.
Nevertheless, all faces are different.
The complexity of facial animation is due mainly to the fact that there is no unique model integrating all primary and secondary effects perceived on a face: each particular aspect requires specific modeling (facial animation, wrinkles, speech, etc.) and all aspects intersect each other in a complicated manner. This is why the design of highly structured facial animation systems in which all aspects of facial animation are clearly integrated is an important issue. High level tools allow the design of facial animation from a generic point of view; that is, independent of a given geometry. Since it is now possible to obtain several geometric data bases representing faces, the design of facial animation would be greatly simplified if one could utilize expressions libraries that could be applied to any face.