(Source: artbistro.monster.com) Last month, two weeks before the main event, the Academy of Motion Pictures Arts and Sciences awarded 15 scientific and technical awards to 46 men who pioneered advances in moviemaking technology. Among the awards mis year was a Scientific and Engineering award given to Per Christensen, Michael Bunnell, and Christophe Hcry for developing point-based rendering for indirect illumination and ambient occlusion. The first film to use this rendering technique, Pirates of the Caribbean: Dead Man’s Chest, won an Oscar for the visual effects created at Industrial Light & Magic. Now available in Pixars RenderMan and widely adopted by visual effects studios, the point-cloud rendering technique has helped studios create realistic CCi characters, objects, and environments in more than 30 films.

Simply put, the technique is a fast, point-based method, for computing diffuse global illumination (color bleeding). This point- cloud solution is as much as 10 times faster than raytracing, uses less memory, has no noise, and the amount of time it takes .to calculate does not increase when surfaces are displacement-mapped, have complex shadcrs, or are lit by complex light sources. It owes its existence to a unique interplay berween researchers in a hardware company, a software company, and two visual effects studios.

Bunnell’s Gem of an Idea

The idea originated with Michael Bunnell, now president of Fantasy IjI), a game company he founded. Nvidia had just introduced its programmable graphics processing unit (GPU), and Bunnell was working in the company’s shader compiler group. “It was a new thing and an exciting time,” he says. “We were translating human-written shaders into code that could run directly on the graphics processing chip.”

Real-time rendering made possible by the CiPU opened the door to more realistic images for interactive games and more iterative shading and Sighting in postproduction houses. Bunnell pushed his excitement out into the world by writing a chapter for the first CiPU (iems book on shadow mapping and anti-aliasing techniques.

“It wasn’t a new technique,” Bunnell says. “It was about doing something on a graphics chip in a reasonable number of steps.”

Bunnell was more interested, though, in subdivision surfacing, in tessellation that breaks a curved surface into the triangles needed for rendering, and he began working on ways to render curved surfaces in real, time. The demo group at Nvidia used his code for a product launch, and then asked if he could do something more: real- time ambient occlusion.

Ambient occlusion darkens areas on CG objects that we can see, but rhat light doesn it reach – the soft shadow under a windowsill, for example, or a characters nose. It is calculated knowing the geometry, not light, and in some ways is self-shadowing.

Full Article:  ArtBistro.monster.com



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