Practical Hessian-Based Error Control for Irradiance Caching

Project Members

Jorge Schwarzhaupt (University of California, San Diego)
Henrik Wann Jensen (University of California, San Diego)
Wojciech Jarosz (Disney Research Zurich)

In ACM Transactions on Graphics (Proceedings of ACM SIGGRAPH Asia 2012)

Our new Occlusion Hessian significantly outperforms both the Pure and the Bounded Split-Sphere (clamped to the gradient and 150px max spacing) for irradiance caching. It also performs significantly better than the recently published occlusion-unaware Hessian error metrics by Jarosz et al. 2012.


This paper introduces a new error metric for irradiance caching that significantly outperforms the classic Split-Sphere heuristic. Our new error metric builds on recent work using second order gradients (Hessians) as a principled error bound for the irradiance. We add occlusion information to the Hessian computation, which greatly improves the accuracy of the Hessian in complex scenes, and this makes it possible for the first time to use a radiometric error metric for irradiance caching. We enhance the metric making it based on the relative error in the irradiance as well as robust in the presence of black occluders. The resulting error metric is efficient to compute, numerically robust, supports elliptical error bounds and arbitrary hemispherical sample distributions, and unlike the Split-Sphere heuristic it is not necessary to arbitrarily clamp the computed error thresholds. Our results demonstrate that the new error metric outperforms existing error metrics based on the Split-Sphere model and occlusion-unaware Hessians.



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Practical Hessian-Based Error Control for Irradiance Caching
November 30, 2012
Paper File [pdf, 30.21 MB]

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