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