Ray Tracing Dynamic Scenes with Shadows on the GPU

We present fast ray tracing of dynamic scenes in this paper with primary and shadow rays. We present a GPUfriendly strategy to bring coherency to shadow rays, based on previous work on grids as acceleration structures. We introduce indirect mapping of threads to rays to improve the performance of ray tracing on the GPU for the traversal and intersection steps. We also construct a light frustum in a spherical space for shadow rays. A grid structure is constructed each frame for the light frustum and traversed coherently. This involves careful mapping of the primary ray information to the light space and balancing the work load of the threads. Using the finegrained parallelism of GPU, we reorder the shadow rays to make them coherent and process multiple thread blocks to each cell to balance the work load. Spherical mapping is key to handling light sources placed anywhere in the scene by reducing the triangle count and improving performance in shadow checking. In addition it also allows us to introduce spotlights in raytracing. In practice, we attain interactive performance for moderately large models which change dynamically in the scene.