Distributed Ray Tracing

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Distributed Ray Tracing

This technique is just a rollover from the previous techniques. Distributed ray tracing was used for effects such as depth of field, filtering, motion blur, and texture interpolation. It was developed because many times images rendered with only one ray per pixel would have a few calculation problems which made rendered images appear unclear with tiny artifacts also known as noise . To fix the problem, researchers realized that instead of tracing one single ray to determine the intensity of a pixel, many rays would be traced instead to calculate the right pixel intensity. The tracing of a ray to a pixel is called s am pling . When a series of sampled rays equals the same value consecutively, this is s upersampling . Many researchers incorporated supersampling into their applications because it guaranteed a pixel's color by testing many samples of the same pixel to ensure that the correct color was returned.

NOTE

NOTE

Distributed ray tracing was intro duced in 1984 by Robert L.Cook, Thomas Porter,and Loren Carpenter.

Other problems soon were seen in supersampling that needed to be addressed. If many tested samples differed in value, researchers needed to somehow dive deeper into finding a method to subdividing each pixel into small components . A new technique called adaptive supersampling was invented. It kept applications testing until the average became fluent. The idea behind adaptive supersampling was to break up an ever-changing value into smaller regions and test each region as a whole value. This made rendered images appear much clearer but this wasn't perfect. You would have to test a large number of samples to generate a very detailed image. This suddenly became worse if the resolution of the image was significant in size. A higher resolution required lots of processing power that, in the end, made 3D rendering applications slow. Take a look at Figure 5.9 for an example of ray tracing. The image conveys multiple diffuse interactions as well as specu-lar reflection and indirect illumination . These effects are easily achieved using ray tracing.

Figure 5.9. Example of ray tracing that displays multiple diffuse interactions.

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