Interactive rendering of multiple scattering in participating media using separable phase function

This paper presents an interactive method to compute multiple scattering in non-homogeneous participating media with an effective phase function approximation. The volume is represented by grids, which allows us to render dynamic scenes. We achieve interactive computation rate by factorizing the phase function in transport equation with singular value decomposition (SVD) and keeping only the first few low-order approximation terms. These terms are paired 2D incident-direction texture maps and 2D outgoing-direction texture maps. The complicated integral calculation of in-scattering in each rendering pass is efficiently approximated by simply retrieving data from textures. Graphics hardware is also employed for on-the-fly computation. Using the proposed algorithm, we demonstrate rendering of multiple scattering in dynamic scenes at interactive rates.