The basics of the facial animation system did not change from the first movie to the sequel. The character technical directors, supervised by Lucia Modesto and Lawrence D. Cutler, essentially built a head in the computer, beginning with the skull and then layering on muscles and finally skin. The skin is programmed to respond to the manipulations of the muscles beneath in different combinations, enabling the animators to capture the desired expressions.
For “Shrek 2,” the technical directors added more muscles to the faces—Shrek’s face alone had 218 muscles—and also applied what they call “mega controls,” which allowed for such complex expressions as clenching the teeth, which subtly alters the entire face. Additionally, the TDs put more anatomical detail on the neck, which before had been little more than a tube beneath the skin, even giving the men an Adam’s apple that moves when they swallow.
Rendering realistic hair was another challenge that was made more demanding by the addition of so many human characters. Since all of the characters’ hair amounts to virtual wigs, an actual wigmaker came in to show the animation team how wigs are made and the color and shape patterns that go into creating various hairstyles. The animators, in turn, became what Bielenberg calls “virtual hair stylists,” learning not only how to style the hair, but also its properties when curly or straight, long or short, wet or dry, etc.
Appropriately dubbed the “wig system,” the process of computer animating hair combines dynamic motion—hair that automatically moves in reaction to the movement of the head and body—and manual control, which the animators generate. The system enables the animators to manipulate individual pieces or large sections of the hair and place them as needed. The lighting and effects departments were ultimately responsible for making the pieces look like strands of hair.
Some characters’ hair had specific obstacles to overcome. King Harold, for example, wears a crown, so his hair had to be made to react to the movement of the crown. As a result, when the crown shifts, the king’s hair deforms correspondingly. The queen’s hair is contained in a snood that presented a different challenge: The hair had a tendency to collide with and poke through the netting. The solution was to have the same system that is deforming the hair deform the netting, so everything moves together nice and neatly.
Animating Puss In Boots was a daunting challenge in and of itself, owing to the fact that he is covered in fur and has more moving parts than any of his human counterparts, including his tail, whiskers, sword, belt, and plumed hat. The number of controls required to animate Puss amounted to approximately four times that of any other character.
In “Shrek 2,” as in “Shrek,” Donkey’s fur was achieved using a program called a geometry shader, which determines how the hair—or in this case, fur—grows. Puss In Boots’ longer, fluffier fur—coupled with his wardrobe—required that the process be taken to the next generation.
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