complex physical phenomena such as light absorption and scattering. The radiance transmitted through a medium then depends on the variations of scattering and extinction along potentially complex light paths, yielding soft light shafts and shadowing (Figure 1). Computing light scattering in these media usually requires complex offline computations [Cerezo et al. 2005]. Some real-time applications are based on heavy precomputations [Zhou et al. 2008]. Some others introduce restrictions such as approximate diffusion schemes, or specific volume representations.