Bridge Sampling for Connections via Multiple Scattering Events

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dc.contributor.authorSchüßler, Vincenten_US
dc.contributor.authorHanika, Johannesen_US
dc.contributor.authorDachsbacher, Carstenen_US
dc.contributor.editorGarces, Elenaen_US
dc.contributor.editorHaines, Ericen_US
dc.date.accessioned2024-06-25T10:20:23Z
dc.date.available2024-06-25T10:20:23Z
dc.date.issued2024
dc.description.abstractExplicit sampling of and connecting to light sources is often essential for reducing variance in Monte Carlo rendering. In dense, forward-scattering participating media, its benefit declines, as significant transport happens over longer multiple-scattering paths around the straight connection to the light. Sampling these paths is challenging, as their contribution is shaped by the product of reciprocal squared distance terms and the phase functions. Previous work demonstrates that sampling several of these terms jointly is crucial. However, these methods are tied to low-order scattering or struggle with highly-peaked phase functions. We present a method for sampling a bridge: a subpath of arbitrary vertex count connecting two vertices. Its probability density is proportional to all phase functions at inner vertices and reciprocal squared distance terms. To achieve this, we importance sample the phase functions first, and subsequently all distances at once. For the latter, we sample an independent, preliminary distance for each edge of the bridge, and afterwards scale the bridge such that it matches the connection distance. The scale factor can be marginalized out analytically to obtain the probability density of the bridge. This approach leads to a simple algorithm and can construct bridges of any vertex count. For the case of one or two inserted vertices, we also show an alternative without scaling or marginalization. For practical path sampling, we present a method to sample the number of bridge vertices whose distribution depends on the connection distance, the phase function, and the collision coefficient. While our importance sampling treats media as homogeneous we demonstrate its effectiveness on heterogeneous media.en_US
dc.description.number4
dc.description.sectionheadersLight and Reflection
dc.description.seriesinformationComputer Graphics Forum
dc.description.volume43
dc.identifier.doi10.1111/cgf.15160
dc.identifier.issn1467-8659
dc.identifier.pages13 pages
dc.identifier.urihttps://doi.org/10.1111/cgf.15160
dc.identifier.urihttps://diglib.eg.org/handle/10.1111/cgf15160
dc.publisherThe Eurographics Association and John Wiley & Sons Ltd.en_US
dc.rightsAttribution 4.0 International License
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.subjectCCS Concepts: Computing methodologies → Rendering; Ray tracing
dc.subjectComputing methodologies → Rendering
dc.subjectRay tracing
dc.titleBridge Sampling for Connections via Multiple Scattering Eventsen_US
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