Imperfect voxelized shadow volumes

Voxelized shadow volumes (VSVs) [Wyman 2011] are a discretized view-dependent shadow volume representation, but are limited to point or directional lights. We extend them, allowing dynamic volumetric visibility from area lights using imperfect shadow volumes. As with imperfect shadow maps [Ritschel et al. 2008], area lights can use coarser spacial sampling without significantly degrading quality. Combining coarser resolution with a parallel shadow volume construction enables interactive rendering of dynamic volumetric shadows from area lights in homogeneous single-scattering media, at around 4x the cost of hard volumetric shadows.