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UNC Grad Student Untangles CGI Hair
Nov 29, 2010

Class project leads to key role in Disney's "Tangled"

For University of North Carolina-Chapel Hill alum Kelly Ward, Disney's newly released animated film "Tangled" could be considered her Mount Everest.

Everest stands 29,002 feet tall. Rapunzel's hair, for which the movie was titled, stretches a fraction of that - 70 feet - when fully unfurled.

But the technical feat of virtually rendering this flowing mound of hair for the big screen - in a form that appears both realistic, and at times, magical - was a challenge software engineers had never before attempted.

Without knowing it, Ward stumbled into base camp for that quest 10 years ago when she arrived UNC-CH as a graduate student in computer science.

It was at UNC that Ward met Dinesh Manocha and Ming Lin, two computer science faculty who would guide her into finding and following her own path, one that started when Ward decided she would try to make a single strand of hair move as her class project in Manocha's course "Geometric and Solid Modeling."

After Ward successfully accomplished her class project, she realized there was much more to learn-such as figuring out the complex computations required to create all 100,000 stands of hair on the human head and get them to move as they would in real life from the stroke of a hand, a toss of the head or a gust of wind.

The following summer, Ward resumed her work on hair modeling with guidance and support from Lin, who served as her graduate adviser.

Four years later, Lin gave a lecture at Walt Disney Animation Studios and talked about the remarkable progress Ward had made in animated hair modeling. That lecture led to Ward landing a job interview with Disney, and after she completed her Ph.D., Ward began work at Disney in September 2005.

It was during her job interview, Ward said, that Disney first discussed the possibility of working on a movie project based on "Rapunzel" the 17th-century German fairy tale about a young woman locked in a tower in the middle of the woods. The story is best known for the line, "Rapunzel, Rapunzel, let down your hair so that I may climb the golden stair."

Once hired, Ward spent five years working on a number of movies, including 2008's "Bolt."  That movie, and those preceding it, created the learning curve that helped make a movie like "Tangled" - in which hair is so central to the plot - possible, Ward said.

"We not only wanted the hair to be possible, we wanted it to be beautiful," she said. "We often looked at Rapunzel's hair as a character on its own. But Rapunzel is such a beautiful character herself - so young and expressive and full of life - we also wanted her hair to embody those same qualities."

Ward also had to make the hair defy the laws of physics by reducing the effects of gravity and friction while looking natural.

"Rapunzel is a petite girl," she said. "In real life, 70 feet of hair would weigh about 60 pounds, more weight than a real person would be able to move around as effortlessly as we allow Rapunzel to do in the movie."

"Throughout the movie, Rapunzel does a lot of running and jumping. She does cartwheels. The hair is everywhere and characters are always in her hair. Rolling in it. Combing it. Climbing it." If only climbing Everest seemed that effortless.

Watch video about Ward's achievements below, courtesy of Science Friday.

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