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Virtual skin looking even better

It you get a close look at some of the creatures of the night in the Van Helsing movie, you might notice how realistic their skin looks.

The reason is a program that works out how light affects surfaces like skin to make computer-generated characters look more believable.

The software was first used on Gollum in the Lord of the Rings trilogy and is now a staple of blockbusters packed with visual effects.

The man behind the technique, Dr Henrik Jensen of the University of California at San Diego, was recently rewarded for his contribution to Hollywood.

In February he received a Technical Achievement Award from the people who hand out the Oscars.

Game developers are now looking at the techniques to create more realistic looking characters in the next generation of video games.

Convincing looks

The secret in making virtual skin seem real is all to do with light. Dr Jensen found that light did not just bounce from surfaces such as marble and skin.

Instead light beams penetrate below the surface and scatter at different points.

"I was involved in a project where we wanted to simulate weathering of marble," recalls Dr Jensen of his time at the Massachusetts Institute of Technology in 1998.

"One night I illuminated the marble material with a laser-pointer and I noticed how the marble started glowing and how the red light from the laser-pointer even caused a glow on the backside of the material."

This led him to study how light scattered inside materials like marble. The breakthrough came three years later while at Stanford University.

Dr Jensen managed to come up with a mathematical formula that calculates how light is absorbed and dispersed beneath materials like marble or skin.

"The development of the mathematical model was the most difficult aspect of the project," he told BBC News Online.

"It required a number of new algorithms and techniques not previously seen in computer graphics."

Quickly adopted

The software offered the visual effects industry the means to move away from computer-generated faces that looked plastic and unconvincing on the silver screen.

"For skin it has turned out to be a key missing piece in today's visual effects," said Dr Jensen, "and for this reason it has been adopted quickly by the visual effects industry.

"It was used on Gollum in the Lord of the Rings trilogy, and it was used in Harry Potter 2 on Dobby, in Hulk, and in Terminator 3.

"Currently, it is being used in almost all visual effects for movies and there are a number of game companies looking at how to adapt the technique for games as well."

Dr Jensen is now working on refining the technique so that it can capture the subtle details in the skin on a human face.

He also hopes that in the future it will be more widely used in architectural design and art restoration to make virtual buildings leap out of the computer screen.

Posted by thinkum at May 6, 2004 01:03 PM