Exploiting Visibility Correlation in Direct Illumination

The visibility function in direct illumination describes the binary visibility over a light source, e.g., an environment map. Intuitively, the visibility is often strongly correlated between nearby locations in time and space, but exploiting this correlation without introducing noticeable errors is a hard problem. In this paper, we first study the statistical characteristics of the visibility function. Then, we propose a robust and unbiased method for using estimated visibility information to improve the quality of Monte Carlo evaluation of direct illumination. Our method is based on the theory of control variates, and it can be used on top of existing state‐of‐the‐art schemes for importance sampling. The visibility estimation is obtained by sparsely sampling and caching the 4D visibility field in a compact bitwise representation. In addition to Monte Carlo rendering, the stored visibility information can be used in a number of other applications, for example, ambient occlusion and lighting design.

[1]  J. Zára,et al.  Making radiance and irradiance caching practical: adaptive caching and neighbor clamping , 2006, EGSR '06.

[2]  Yves D. Willems,et al.  A 5D Tree to Reduce the Variance of Monte Carlo Ray Tracing , 1995, Rendering Techniques.

[3]  Tomas Akenine-Möller,et al.  Practical Product Importance Sampling for Direct Illumination , 2008, Comput. Graph. Forum.

[4]  Gregory J. Ward,et al.  Adaptive Shadow Testing for Ray Tracing , 1994 .

[5]  Arnauld Lamorlette,et al.  An approximate global illumination system for computer generated films , 2004, ACM Trans. Graph..

[6]  Sergey Zhukov,et al.  An Ambient Light Illumination Model , 1998, Rendering Techniques.

[7]  László Szirmay-Kalos,et al.  Global Illumination as a Combination of Continuous Random Walk and Finite‐Element Based Iteration , 2001, Comput. Graph. Forum.

[8]  Maneesh Agrawala,et al.  Efficient Shadows for Sampled Environment Maps , 2006, J. Graph. Tools.

[9]  Bo Hu,et al.  Optimizing Control Variate Estimators for Rendering , 2006, Comput. Graph. Forum.

[10]  Adam Arbree,et al.  Multidimensional lightcuts , 2006, ACM Trans. Graph..

[11]  Paul S. Heckbert,et al.  Irradiance gradients , 2008, SIGGRAPH '08.

[12]  Wolfgang Heidrich,et al.  Correlated visibility sampling for direct illumination , 2005, SIGGRAPH '05.

[13]  Leonidas J. Guibas,et al.  Optimally combining sampling techniques for Monte Carlo rendering , 1995, SIGGRAPH.

[14]  Wolfgang Heidrich,et al.  Bidirectional importance sampling for direct illumination , 2005, EGSR '05.

[15]  Tomas Akenine-Möller,et al.  Wavelet importance sampling: efficiently evaluating products of complex functions , 2005, ACM Trans. Graph..

[16]  Sumanta N. Pattanaik,et al.  Radiance caching for efficient global illumination computation , 2008, IEEE Transactions on Visualization and Computer Graphics.

[17]  Donald P. Greenberg,et al.  Accurate direct illumination using iterative adaptive sampling , 2006, IEEE Transactions on Visualization and Computer Graphics.

[18]  Donald P. Greenberg,et al.  Local Illumination Environments for Direct Lighting Acceleration , 2002, Rendering Techniques.

[19]  Mateu Sbert,et al.  An Information Theory Framework for the Analysis of Scene Complexity , 1999, Comput. Graph. Forum.

[20]  James T. Kajiya,et al.  The rendering equation , 1986, SIGGRAPH.

[21]  Mateu Sbert,et al.  Combined Correlated and Importance Sampling in Direct Light Source Computation and Environment Mapping , 2004, Comput. Graph. Forum.

[22]  Yves D. Willems,et al.  The Ambient Term as a Variance Reducing Technique for Monte Carlo Ray Tracing , 1995 .

[23]  Wolfgang Heidrich,et al.  Sequential Sampling for Dynamic Environment Map Illumination , 2022 .

[24]  Peter Shirley,et al.  Monte Carlo techniques for direct lighting calculations , 1996, TOGS.

[25]  JaroszWojciech,et al.  Wavelet importance sampling , 2005 .

[26]  Sumanta N. Pattanaik,et al.  Temporal Radiance Caching , 2007, IEEE Trans. Vis. Comput. Graph..

[27]  Adam Arbree,et al.  To appear in the ACM SIGGRAPH conference proceedings Lightcuts: A Scalable Approach to Illumination , 2022 .

[28]  Laurent Moll,et al.  Efficient image-based methods for rendering soft shadows , 2000, SIGGRAPH.

[29]  Parris K. Egbert,et al.  Two Stage Importance Sampling for Direct Lighting , 2006, Rendering Techniques.

[30]  Gregory J. Ward,et al.  A ray tracing solution for diffuse interreflection , 2008, SIGGRAPH '08.

[31]  Parris K. Egbert,et al.  Importance resampling for global illumination , 2005, EGSR '05.

[32]  Donald P. Greenberg,et al.  Direct illumination with lazy visibility evaluation , 1999, SIGGRAPH.

[33]  H. Jensen.  Realistic Image Synthesis Using Photon Mapping , 2001 .

[34]  Mark Meyer,et al.  Statistical acceleration for animated global illumination , 2006, SIGGRAPH 2006.