Catálogo de publicaciones - libros

Multiple importance sampling is a tool to weight the results of different samplers with the goal of a minimal variance for the sampled function. If applied to light transport paths, this tool enables techniques such as bidirectional path tracing and vertex connection and merging. The latter generalizes the path probability measure to merges—also known as photon mapping. Unfortunately, the resulting heuristic can fail, resulting in a noticeable increase of noise. This chapter provides an insight into why things go wrong and proposes a simple-to-implement heuristic that is closer to an optimal solution and more reliable over different scenes. The trick is to use footprint estimates of sub-paths to predict the true variance reduction that is introduced by reusing all the photons.

We present an algorithm for perspective-correct, real-time specular illumination for surfaces of varying glossiness in dynamic environments. Our algorithm leverages properties from earlier techniques (e.g., radiance probes and screenspace reflections) while reducing the amount of visual errors by adding ray tracing to the rendering pipeline. Our algorithm extends previous work by allowing accurate reflections for all surfaces regardless of the material, and it has global coherence (i.e., there are no visible discontinuities). With radiance caching, multiple samples can be efficiently computed as the radiance computation is decoupled from the final shading. The radiance cache is also used to approximate the specular term for the roughest surfaces without any ray tracing.