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Fast Approximation Fast Approximation of Multiple of Multiple Scattering in Scattering in Inhomogeneous Inhomogeneous Participating MediaParticipating Media
Szirmay-Kalos László Liktor GáborTamás UmenhofferTóth Balázs
EG 2009
AbsroptionOut-scatteringIn-scatteringEmission
GI in Participating GI in Participating MediaMedia
path: dsIncident radiancia:
L(s)
Outgoing radiancia:
L(s+ds)
Camera
screen
Importance of Importance of approximate solutionsapproximate solutions Real-time
visualization Bootstrap for an
“accurate” method– Monte Carlo
(main part separation)
– Iteration (initial state)
Previous approachesPrevious approaches
Direct term only
Homogeneous case, diffusion approx.
2
00
4
d)(exp)(
r
ssrL
r
t
r
rrL et
20
)4(
exp'3)(
r
Spherical layers: IdeaSpherical layers: Idea
Direct term– Other directions are
irrelevant Direct + Indirect
– Other rays face similar conditions
Solve diff. equation for each ray assuming spherical symmetry2
00
4
d)(exp)(
r
ssrL
r
t
Spherical layers: Spherical layers: algorithmalgorithm
Ray marching for sample directions
Resampling of the result at voxels
Results: headResults: headDirect term
100 iterations 25 iterations
Proposed
estimation
ConclusionsConclusions
Fast approximation of the global illumination solution
Assumes spherical symmetry Cost is the same as of the direct
term Computes also the scattered term Applications
– Fast visualization– Initial state for a precise solver