Improved Irradance Computation by Importance Sampling

In this paper we consider the task of refining a low-resolution radiosity solution by using final gather. This final gather can be done by using Monte-Carlo methods. We show how to built an adequate probability density function (pdf) such that the involved variance is greatly reduced and thus we can reduce the number of samples to take, keeping the error. The proposed pdf uses information gathered during the computation of low-resolution radiosity. This data includes an approximation to the distribution of irradiance landing on a patch and coming from other patches. Once this distribution is (approximately) known, we can use it to built an importance-based pdf for final gather, such that just a few tens of samples can be taken to accurately compute irradiance.

[1]  Peter Shirley,et al.  A ray tracing method for illumination calculation in diffuse-specular scenes , 1990 .

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

[3]  Donald P. Greenberg,et al.  Modeling the interaction of light between diffuse surfaces , 1984, SIGGRAPH.

[4]  Michael F. Cohen,et al.  Radiosity and realistic image synthesis , 1993 .

[5]  Peter Shirley,et al.  A Two-Pass Solution to the Rendering Equation with a Source Visibility Process , 1995, Rendering Techniques.

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

[7]  Holly Rushmeier,et al.  Realistic image synthesis for scenes with radiatively participating media , 1988 .

[8]  Arjan J. F. Kok,et al.  Source Selection for the Direct Lighting Computation in Global Illumination , 1994 .

[9]  Carlos Ureña,et al.  A formalization and classification of global illumination methods , 1997, Comput. Graph..

[10]  James Arvo,et al.  Stratified sampling of spherical triangles , 1995, SIGGRAPH.

[11]  Brigitta Lange,et al.  Rayvolution: An Evolutionary Ray Tracing Algorithm , 1995 .

[12]  Harold R. Zatz.  Galerkin radiosity: a higher order solution method for global illumination , 1993, SIGGRAPH.

[13]  Dani Lischinski,et al.  Discontinuity meshing for accurate radiosity , 1992, IEEE Computer Graphics and Applications.

[14]  Andrew S. Glassner,et al.  Principles of Digital Image Synthesis , 1995 .

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

[16]  Pat Hanrahan,et al.  Wavelet radiosity , 1993, SIGGRAPH.