Adaptive records for volume irradiance caching

• Published in: The Visual computer Vol. 27; no. 6-8; pp. 655 - 664
• Main Authors: Ribardière, Mickaël, Carré, Samuel, Bouatouch, Kadi
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.06.2011; Springer Nature B.V; Springer Verlag
• Subjects: Algorithms; Artificial Intelligence; Caching; Computer Graphics; Computer Science; Data structures; Density; Graphics; Image Processing and Computer Vision; Interpolation; Irradiance; Original Article; Ray tracing; Rendering; Rendering; Participating media; Global illumination; Irradiance cache
• ISSN: 0178-2789; 1432-2315; 1432-8726
• DOI: 10.1007/s00371-011-0573-z

In this paper, we present a new irradiance caching scheme using Monte Carlo ray tracing for efficiently rendering participating media. The irradiance cache algorithm is extended to participating media. Our method allows to adjust the density of cached records depending on illumination changes. Direct and indirect contributions can be stored in the records but also multiple scattering. An adaptive shape of the influence zone of records, depending on geometrical features and irradiance variations, is introduced. To avoid a high density of cached records in low interest areas, a new method controls the density of the cache when adding new records. This record density control depends on the interpolation quality and on the photometric characteristics of the medium. Reducing the number of records accelerates both the computation pass and the rendering pass by decreasing the number of queries to the cache data structure (Kd-tree). Finally, instead of using an expensive ray marching to find records that cover the ray, we gather all the contributive records along the ray. With our method, pre-computing and rendering passes are significantly speeded-up.