Computer Graphics

Participating Media

Transport through a volume rather than across a surface.

Colour is the family; a dashed line is the second member of it.

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G delta-tracking Delta Tracking volumetric-path-tracing Volumetric Path Tracing delta-tracking->volumetric-path-tracing heterogeneous media have no closed-form transmittance henyey-greenstein Henyey-Greenstein Phase Function phase-function Phase Function henyey-greenstein->phase-function one anisotropy parameter spans forward to backward microflake Microflake Theory microflake->phase-function oriented flakes give the medium a direction participating-media Participating Media scattering Scattering participating-media->scattering phase-function->participating-media radiative-transfer-equation Radiative Transfer Equation radiative-transfer-equation->participating-media rendering-equation The Rendering Equation radiative-transfer-equation->rendering-equation transport along a ray, not just across surfaces ratio-tracking Ratio Tracking ratio-tracking->delta-tracking the binary accept/reject outcome is high variance sggx SGGX Microflake Distribution sggx->microflake microflake distribution closed under linear transforms volumetric-path-tracing->radiative-transfer-equation solves it by random walks through the medium path-tracing Path Tracing volumetric-path-tracing->path-tracing paths can scatter inside a volume, not only at surfaces

9 nodes

Henyey-Greenstein Phase Function

A one-parameter phase function, originally fitted to interstellar dust, whose single anisotropy value spans strong forward through isotropic to backw… · 1941

Microflake Theory

Applies microfacet reasoning to volumes: the medium is filled with oriented flakes rather than isotropic particles, so anisotropic materials like clo… · 2010

Ratio Tracking

Instead of accepting or rejecting each collision outright, accumulates a continuous transmittance ratio, which removes the binary outcome that makes… · 2014

SGGX Microflake Distribution

A microflake distribution parameterized by a symmetric matrix, so it stays in the same family under linear transforms and can be filtered and interpo… · 2015

Delta Tracking

Fills a heterogeneous medium with fictitious matter up to a uniform majorant so distances can be sampled analytically, then randomly rejects the fict…

Participating Media

Volumes that absorb, emit and scatter light along a ray rather than only at surfaces: smoke, fog, clouds, skin interiors.

Phase Function

The volumetric analogue of a BRDF: the angular distribution of light after a single scattering event in a medium.

Radiative Transfer Equation

The volumetric counterpart of the rendering equation, describing how radiance changes along a ray through absorption, out-scattering, in- scattering…

Volumetric Path Tracing

Extends path tracing with sampled scattering events inside media, choosing a distance along each ray and then a new direction from the phase function.