It goes without saying that, in any animated film, the voice is only a portion of each character's performance. The performances in "Shrek" were greatly enhanced by PDI/DreamWorks' proprietary facial animation system, representing a giant leap forward from its first application in "Antz." Whereas "Antz" was almost entirely populated by, well, ants, "Shrek" is the first computer animated film to star humans, including the title character.
According to supervising animator Raman Hui, "Shrek is an ogre, but at the same time, he has the same range of emotions as any of us. In fact, the most challenging animation to do was when Shrek is hiding what he is really feeling...saying one thing but thinking something else. Animators are just like actors; it's up to us to put all those emotions into the face."
The facial animation system in "Shrek" enabled Hui and his team to convey complex emotions and expressions through a remarkable layering system that is based on real human anatomy. The application of the system begins with the character technical directors, supervised by Lucia Modesto and Luca Prasso. Essentially, the skull of the character is formed in the computer, and covered with computer recreations of the actual muscles of the face. The skin is then layered over and programmed to respond to the manipulations of the muscles as would a human face, complete with wrinkles, laugh lines and other imperfections.
Hundreds of controls are wired into the face like human nerves, enabling the animators to go far beyond the speech phonemes for the correct lip synch. By applying a wide range of command combinations in different percentages, they could achieve expressions as varied as for any human actor. However, with facial sizes and characteristics as diverse as those of Shrek, Donkey, Fiona and Farquaad, specific adjustments had to be made to accomplish the desired expressions for each character. The same commands that formed a smile for one could result in something quite different for another.
For animating entire characters in "Shrek," the team at PDI/Dream Works reasoned that the techniques used in their facial animation system could be applied to the whole body structure. Once again, the skeletal system formed the core, layered over with muscles, skin and, in this case, clothing. A breakthrough program that the software developers dubbed a "Shaper" was used to achieve realistic deformations of the skin, as well as the clothing.
Basically, a Shaper is a layering process that deforms the surface from the inside out. When you modify the innermost layer, the change extends outward to ultimately change the exterior shape. It is taken from the same principle that causes your arm muscle to flex when you bend your arm. Applying the Shaper, the animators could not only get realistic deformations of the skin, but wrinkles in the "costumes" as they reacted to the way the characters moved.
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