Формирование эффективной пространственной структуры фотонных карт для ускорения процесса рендеринга

Abstract

The analysis of realistic rendering methods from the point of view of the efficiency of calculation of secondary and caustic illumination is carried out. A method of bidirectional stochastic ray tracing using photonic maps is proposed, which ensures high efficiency of calculation of caustic illumination. The main approaches of using the photon maps method are considered: the construction of photon maps on the traces of forward rays and on the traces of backward rays. The advantages and disadvantages of these methods are revealed. The method of bidirectional stochastic ray tracing using backward photon maps is chosen as the basic solution. Profiling of this solution was carried out based on the Lumicept software package. The main problems associated with slowing down the rendering process have been identified. For most scenes, half of the rendering time was spent processing requests to the photon map: searching for nearby photons within the cell of the spatial structure and searching for the intersection of the ray with the integrating photon spheres. Several solutions for spatial partitioning of photonic maps were analyzed: a regular mesh, a regular mesh with a hash table and a binary tree. The advantages and disadvantages of the solutions under consideration are revealed and a combined solution is proposed that combines the adaptability of splitting a binary tree and the access efficiency provided by hash tables. A combined solution has been implemented in the Lumicept software package, which will increase the overall rendering efficiency by 30%.