A Flexible Algorithm for Multiprocessor Ray Tracing

Ray tracing programs are widely used to generate photo-realistic images, but the high computation time may discourage their implementation on single-processor machines; moreover, cost reduction of multi-processor general purpose architectures makes parallel rendering an attractive field of research. We propose a new algorithm which addresses the main issues of a parallel implementation of ray tracing on a message-passing-based machine. We adopt efficient strategies for dynamic workload distribution among processors, task synchronization and communication delay reduction. The resulting implementation is highly flexible, since any number of processors can be employed without introducing synchronization problems. We show an implementation of our algorithm on an nCUBE 2 supercomputer which is a general purpose parallel architecture with distributed memory. A theoretical evaluation of our algorithm allows us to identify a decreasing function for rendering times; the considered examples confirm the theoretical expectations showing that the efficiency of our system may reach up to the 91% of the value achievable by dividing the sequential rendering time by the number of processors employed.