Nvision 2008: Real-time HD Ray tracing

According to David Luebke, a SGI Reality Workstation was necessary to do an unspectacular Ray tracing demo in 1998. Today this would be possible with CUDA and their much cheaper GPUs. Together with his colleague Steven Parker, he developed a technology demo, in which a sports car is speeding through a city. The demo premiered at Siggraph and was on display at Nvision, too. In a lecture Luebke and Parker revealed some background info. "Some people say that Ray tracing is beautiful and Rasterizing is ugly”, said David Luebke. "I say: Both are ugly in their own way. Common rasterized 3D graphic is fast indeed, but requires some effort for visual special effects.”

Luebke's and Parker's Ray tracing demo has two million, whereas the car and the environment have one million each - approximately the numbers that the Unreal Engine 3 can display. For this process Nvidia's Quadro Plex 2100 D4 Visual Computing System with four GPUs is used. The system displays the vehicle and the city at a resolution of 1,920 x 1,080 pixels with 30 frames per second. Color Shader, shadows, reflections and refractions are calculated with five "jumps” per light ray. Bump mapping, variable light sources and up to 4x adaptive Anti Aliasing are additional features of the demo. The objects were created with Maya and imported into the Ray tracing engine with the application Collada.

Texture and Vertex Buffer are filled in OpenGL at first. Then they are transferred to the Ray tracing system that is written in CUDA and calculates the individual light rays. Depending on the light source Light or Miss Shaders are used. If a light ray is bouncing off of a surface, the specific Material Shader of that surface is activated. Finally the Ray tracing system gives the data to a visualization and post-processing unit, which is written in OpenGL again.



David Luebke thinks the simplified rendering with less algorithms and an easier combination of special effects to be advantages of the ray tracing system. ”Even in Hollywood productions the effect specialists don't use Ray tracing exclusively, because of speed”, Luebke explains. ”My advice to all graphics experts: Use both systems, Rendering and Ray tracing.” Among the biggest customers of graphics companies that specialized on Ray tracing are, according to Luebke, automobile corporations that want to simulate their future cars as realistic as possible. "Game developers leer at the Holy Grail of Ray tracing: indirect lighting”, says Luebke. Soft shadows and reflections enable to create an even more realistic game world.