When the animated heroes of Pixar鈥檚 upcoming movie Cars speed around a racetrack, their metallic bodies will gleam in the lights like none before.
The four-wheeled characters have been given a little extra sparkle using a software technique called ray tracing, which projects thousands of imaginary light rays onto each object to mimic the way light interacts with surfaces. Cars, due to be released this summer, will be the first feature-length film to use the technique throughout, making its animated vehicles appear more realistic.
The cars start as animated virtual 3D objects labelled with their desired surface texture 鈥� how shiny they should be, for instance. Pixar鈥檚 software applies ray-tracing algorithms that calculate the path of each light ray as it bounces off objects within the scene, to add highlights, shadows and complex reflections. As a result, an animated car鈥檚 reflection shows up in shop windows as it passes, while the shops are reflected on the vehicle鈥檚 windscreen and bodywork. 鈥淎t any point on the surface we calculated hundreds or thousands of rays,鈥� says Eben Ostby, Pixar鈥檚 supervising technical director. 鈥淭he more rays, the richer and more realistic the scene becomes.鈥�
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While the technique has been used for years by digital artists and lens designers, the huge number of calculations needed to create the hundreds of thousands of frames in a feature film has limited its use in movies up to now. Pixar used 3000 computers churning through the calculations day and night, but even so it still took days to render some frames.
