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."

The three computer graphic artists won an Academy Award in 2003 for their efforts, which led to astonishing, lifelike characters including Gollum in "The Lord of the Rings," Dobby in "Harry Potter and the Chamber of Secrets" and the characters in "Shrek 2."

Now beauty scientists are working on ways to use the concept for enhancing the appearance of real people.

Paul Matts, a London-based research scientist at Proctor & Gamble, and others are borrowing from the same medical technology to intricately map the differences between youthful and older skin. Again, the key finding is that appearance of a youthful glow or a pallid hue depends on how light is scattered just under the skin's surface.

With the help of medical technology, they've found that the distribution of three different light-absorbing molecules, known as chromophores, is what influences how light is scattered -- and how young or aged skin appears.

"The surprising thing is while we think of human appearance as complex, it's really driven by these three chromophores," said Matts. "It's the unique concentration and distribution of these chromophores that drives human appearance and has a profound impact on our judgment."

Medical researchers have used light-emitting instruments to focus on the three chromophores, which include melanin, hemoglobin and collagen, and their distribution to detect signs of skin cancer. Matts' team, meanwhile, has borrowed the technology to zero in on how the arrangement of chromophores affects appearance.

Matts and a team of investigators with the Rusham Park Technical Center in Surrey, England, analyzed the skin between the thumb and the first finger of 400 Caucasian women ranging in age from 10 to 70. They found those with younger skin show very evenly distributed chromophores, while those with older skin show uneven arrangements, even clumping.

"This is why you can take a photograph of someone and erase the lines and wrinkles in Photoshop and they'll still look old," he said. "They still look old because they still have this irregular arrangement of chromophores."

These "irregular arrangements" of chromophores are what lead to features such as spider veins, age spots and dulled skin.

Just as animators sought the ultimate mathematical model to mimic the way light plays off skin's subsurface, beauty scientists are seeking the ultimate technology (in the form of an ointment or perhaps a pill) to restore the even distribution of chromophores under the skin's surface. Traditional makeup can often dull a person's appearance because it causes light to scatter at the skin's surface instead of just beneath. But, Matts explains, scientists hope finding a way to redistribute chromophores under the skin could get at the cause of aged skin and restore a more natural look.

"Now that we understand these things, we can target them and leverage technology against them," he said.

Matts says he hopes to eventually analyze skin over the entire body to get a better sense of how skin ages throughout. Meanwhile, animators are also trying to push the envelope when it comes to generating lifelike skin on screen.

"People are looking at ways to model fine details now, like showing blood vessels under the skin," said Hanrahan. "These will involve more complex mathematical models."

Of course, skin is hardly the only feature that plays a key role in appearance. Hanrahan says he and other animators are also focusing on a different part of characters -- their hair. They're learning how to imitate the way light is reflected twice from hair -- once off its surface, creating a white highlight, and then after light has traveled through the hair shafts, creating a darker highlight.

So far, Hanrahan isn't aware of any crossover to the beauty industry, but as Marschner says, "There's always borrowing going on, and it often goes both ways."

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