Dissertations details

  • Estratégias de Paralelização do Algoritmo de Ray Tracing
  • Apr 1997
  • Image rendering using ray tracing enjoys the benefits of a simple algorithm, capable of increased realism but, unfortunately, very expensive. This high computation cost, seconded by an inherent parallelism, turns this algorithm into a natural candidate for parallel and/or distributed solutions. This dissertation addresses the various aspects of development of parallel ray tracing algorithms targeted at local networks with standard \unix\ environments. First we discuss ray tracing in general and methods currently available to improve execution times. Next we present one of such optimization techniques, used in our prototype, corresponding to a variation of \textsl{Spatial Enumeration}. This optimization method discretizes space by means of a hierarchy of uniformly subdivided grids that, with proper parametrization, enjoys compactness and adaptability associated with octrees, maintaining fast processing of uniform spatial subdivision. Parallel rendering is addressed next, beginning with a discussion of parallel ray tracing in respect to the available parallelization strategies: \emph{Control-oriented parallelization} and \emph{Data-oriented parallelization}. This work studied both and produced two architectures which are described in great detail. In this study we find that control-oriented parallelization is globally superior to its counterpart. The architecture designed according to that strategy is the most versatile and the one that obtained the best overall results. Its main characteristic relies on the emulation of a shared virtual memory among different processors, achieved by mapping a NFS file to memory. In spite of its simplicity, this mechanism showed to be sufficient to attend good results. Additionally, with the illusion of a shared memory simplier algorithms are possible requiring considerable less development time.
  • Departamento de Informática, FCT/UNL
  • Sérgio Duarte