# Making a Princess Dress Come to Life

By Robin Aronson |

Soon this dress will be on your floor!

Your kid prances around in a princess costume. Oh the Disney princesses! You wait two beats, watch as the dance gets boring and watch as that magic costume to gets chucked to the ground and turned into a plain old plaything yet again.  To you and me, a princess dress hitting the floor is same old, same old, to the animators of Tangled, Disney’s new take on Rapunzel, making a heap of cloth look real is a complex animation problem that took months to solve.

The problem, as described in Scientific American, was the layers of cloth the animators wanted to put on Rapunzel.  To make it look real, they got in touch with Eitan Grinspun of Columbia University’s school of engineering who studies what happens when cloth hits the ground.  (I’m not making that up.)  Apparently, there’s friction, elasticity (bendiness), and momentum to take into account as well as collisions between floor and cloth. But because Rapunzel’s fancy princess dress has more than one layer, the animation program would get overloaded with the information about all those collisions and go into “fail safe” mode, which prevented it from showing any more collisions. The solution?  They worked with the fail safe action that stopped the collision and made the fabric slide.

I’m sure there’s some kind of life lesson in that solution.  Short of that, no doubt the good folks at Disney will soon offer up a Rapunzel costume to buy for our kids and we’ll be able to decide for ourselves just how realistic the animated version of that princess dress hitting the ground really is.

Image: Courtesy of Disney

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Robin Aronson