Realistic image synthesis with hybrid photon maps

Abstract

In the scope of the current research, authors have developed an approach to accelerate the synthesis of realistic images with bidirectional ray tracing based on the consecutive usage of the photon maps and backward photon (imphoton) maps. In the presented approach the photon maps are used to account for the possible sources of caustic illumination, while the imphoton maps are used to account the indirect illumination. The caustic photon maps are built for points of the first diffuse event after the occurrence of at least one specular event at the path of the forward ray. As the caustic illumination is accounted in the photon maps it became possible to shift the imphoton maps farther from the first diffuse event of the backward ray and build the imphoton maps for the second diffuse event. The algorithm was optimized to be used on a modern multiprocessor workstation with the non-uniform memory access pattern. By using the three-level threads hierarchy that combines synchronous, semi-synchronous, and asynchronous components authors have achieved an additional image synthesis speedup. The ray tracing methods were based on physically correct laws of light propagation, which allows performing physically correct modeling and image synthesis for optically complex scenes containing optical devices. The presented image synthesis methods were implemented and integrated into the computer system of photorealistic rendering. The sample rendering results are presented.