Irradiance Gradients in the Presence of
Participating Media and Occlusions
Wojciech Jarosz
Matthias Zwicker
Henrik Wann Jensen

University of California, San Diego

In Computer Graphics Forum (Proceedings of EGSR 2008)
Sarajevo, Bosnia-Herzegovina, June 23 - 25, 2008
All lighting on surfaces is indirect in this disco light scene. Our gradient method obtains the highest quality results by taking into account the participating media and occlusions. Previous methods suffer from artifacts by assuming all lighting arrives from surfaces (Ward and Heckbert '92) or by ignoring the contribution from occlusions (Jarosz et al. '08).

Abstract

In this paper we present a technique for computing translational gradients of indirect surface reflectance in scenes containing participating media and significant occlusions. These gradients describe how the incident radiance field changes with respect to translation on surfaces. Previous techniques for computing gradients ignore the effects of volume scattering and attenuation and assume that radiance is constant along rays connecting surfaces. We present a novel gradient formulation that correctly captures the influence of participating media. Our formulation accurately accounts for changes of occlusion, including the effect of surfaces occluding scattering media. We show how the proposed gradients can be used within an irradiance caching framework to more accurately handle scenes with participating media, providing significant improvements in interpolation quality.

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