Time Restricted Parallel Ray Tracing

Ray tracing is certainly one of the fundamental algorithms in the world of computer graphics. Given enough time, processing power, and highly detailed geometry, the algorithm can produce wonderfully realistic renderings. However, these requirements, especially the first two, can cause a number of headaches for individuals interested in creating renderings. This paper focuses on including the dynamic of time while ray tracing. Time is a restriction on everything in the natural world, and ray tracing is no different. One could forsee many circumstances in which an individual would want to produce an image within a certain duration. Real-time ray tracing for video games or interactive systems is one such use. In a video game situation it is conceivable that gamers may want a rendering system in which they don’t have to set their graphics rendering options to attain a specific frame rate; instead the ray tracer would achieve whatever quality the computer system is capable of. We do not frame our exploration within any sepcific domain; rather, we simply examine the issues raised when guaranteed delivery of a rendering is required by a given time. There are two ways to view the inclusion of a time restriction in a ray tracing scheme. The first is to view the time limitation as a guideline or a goal to achieve over the average case (if rendering multiple frames consecutively). This level of restriction gives more leeway to the algorithm, as it may adapt to the input geometry and spend more time on more complex scenes while spending less on simpler scenes. The second method, and the one which we have adopted for this text, involves setting a hard cap on the time required to ray trace a scene regardless of its complexity. While certainly less general and adaptive than the previously described method, the method is much simpler. Striving for an average framerate introduces questions regarding the tradeoff between saving time for a later run or perfecting the tiniest of shadings on the most insignificant of objects in a scene.