Previously when using light cache, there could be artifacts caused when voxel points that were sampled outside the volume object's geometry got interpolated into the rest of the volume. This commit adds a (similar to a dilate) filter pass after creating the light cache, that fills these empty areas with the average of their surrounding voxels. http://mke3.net/blender/devel/rendering/volumetrics/vol_lightcache_filter.jpg