Importance Sampling Microfacet-Based BSDFs using the Distribution of Visible Normals

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dc.contributor.authorHeitz, Ericen_US
dc.contributor.authord'Eon, Eugeneen_US
dc.contributor.editorWojciech Jarosz and Pieter Peersen_US
dc.date.accessioned2015-03-03T12:40:25Z
dc.date.available2015-03-03T12:40:25Z
dc.date.issued2014en_US
dc.description.abstractWe present a new approach to microfacet-based BSDF importance sampling. Previously proposed sampling schemes for popular analytic BSDFs typically begin by choosing a microfacet normal at random in a way that is independent of direction of incident light. To sample the full BSDF using these normals requires arbitrarily large sample weights leading to possible fireflies. Additionally, at grazing angles nearly half of the sampled normals face away from the incident ray and must be rejected, making the sampling scheme inefficient. Instead, we show how to use the distribution of visible normals directly to generate samples, where normals are weighted by their projection factor toward the incident direction. In this way, no backfacing normals are sampled and the sample weights contain only the shadowing factor of outgoing rays (and additionally a Fresnel term for conductors). Arbitrarily large sample weights are avoided and variance is reduced. Since the BSDF depends on the microsurface model, we describe our sampling algorithm for two models: the V-cavity and the Smith models. We demonstrate results for both isotropic and anisotropic rough conductors and dielectrics with Beckmann and GGX distributions.en_US
dc.description.seriesinformationComputer Graphics Forumen_US
dc.identifier.doi10.1111/cgf.12417en_US
dc.identifier.issn1467-8659en_US
dc.identifier.urihttps://doi.org/10.1111/cgf.12417en_US
dc.publisherThe Eurographics Association and John Wiley and Sons Ltd.en_US
dc.titleImportance Sampling Microfacet-Based BSDFs using the Distribution of Visible Normalsen_US
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33-Issue 4
EGSR14: 25th Eurographics Symposium on Rendering