Shrek Animators, Dermatologists Share Beauty Secret

April 4, 2005 — -- Who knew that characters like Shrek and Gollum would share beauty secrets with leading skin-care scientists?

In fact, the same insight that has allowed animators to make digitally generated characters more lifelike on screen is now the interest of researchers aiming to create products that would help customers regain youthful, glowing skin.

The key lies in the way light enters and then scatters just below the skin's surface. Animators learned that mimicking this effect by applying mathematical models to animation programs can help spring an otherwise flat character to life.

"If you shine a laser pointer on a wall you'll see just a small spot of light. But shine it on your hand and you'll see a blob of red light because the light is spread around," said Stephen Marschner, a professor of computer graphics at Cornell University in Ithaca, N.Y. "That's what our model does."

Artists have long caught onto the translucent appearance of skin -- master painters learned to create the effect using layers and layers of paint, while wax museum artists found that adding a layer of translucent material to the outer layer of mannequins makes them appear more lifelike.

But it wasn't until medical researchers developed special laser tools designed to find skin disorders such as melanoma that animators, including Marschner, along with Pat Hanrahan of Stanford University and Henrik Wann Jensen, now at the University of California at San Diego, realized how to program for the same effect on screen with a fairly simple model.

"We came up with the idea from the medical community that if you shine a light source above and below the surface of the skin, it scatters below the surface in a way that mimics how light interacts with skin in real life," explained Hanrahan, who was working at Pixar Animation Studios when he first started thinking about what the animation community calls subsurface scattering in the early 1990s. "We wrote down the formula and it just spread like wildfire through all the studios."