1. Fast Approximation of Multiple Scattering in Inhomogeneous Participating Media Szirmay-Kalos László Liktor Gábor Tamás Umenhoffer Tóth Balázs EG 2009

2. AbsroptionOut-scatteringIn-scattering Emission GI in Participating Media path: ds Incident radiancia: L(s) Outgoing radiancia: L(s+ds) Camera screen

3. Importance of approximate solutions Real-time visualization Bootstrap for an “accurate” method –Monte Carlo (main part separation) –Iteration (initial state)

4. Previous approaches Direct term only Homogeneous case, diffusion approx. r

5. Spherical layers: Idea Direct term –Other directions are irrelevant Direct + Indirect –Other rays face similar conditions Solve diff. equation for each ray assuming spherical symmetry

6. Spherical layers: algorithm Ray marching for sample directions Resampling of the result at voxels

7. Results: head Direct term 100 iterations 25 iterations Proposed estimation

8. Conclusions 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