Zhang approached the problem by looking at the muscle groups that most commonly make skin move, such as those in the shoulder, neck, arms, thighs, and calves. He then used software to analyze the shapes of these muscles and simplify them into ellipses. “The muscles are not biologically correct,” Zhang says. “They are estimated shapes.” But when the muscles are simplified, he says, an animator doesn’t need detailed knowledge of their shapes to make their movements look real. In addition, using simplified shapes cuts down on the computational power the process requires.
In informal subjective surveys, people found that characters created using the new algorithm were more realistic than those created using the traditional skin-based method. However, the algorithm does not produce better results in all cases; it works best for characters with more defined muscles, Zhang says. In characters with fewer muscles and smoother bodies, it doesn’t predict the skin changes very well.
The researchers’ algorithm is a “refinement” of the tools already available to animators, says Michel Besner, a senior director of product management at Autodesk, a manufacturer of design software and technology. And it could make their jobs easier. “When we ask an artist to do more quality [animations] it forces them to become doctors,” he says.
The Bournemouth researchers are tackling an important problem in animation, agrees Karan Singh, professor of computer science at the University of Toronto, who calls the group’s algorithm “an incremental contribution on what exists.” The research is similar to the work that he and colleagues have done, says Singh, but the new approach has even broader applications than his work.
Zhang’s algorithm is still in the early stages and needs to be integrated into software with an easy user interface. The researchers’ goals are not necessarily to produce a product immediately, though. They plan to further reduce the amount of computation needed to animate a muscle, and improve the realism in the skin of less muscular characters.