The voxels are created in a plane which is aligned to the vector halfway between the camera and the light. When the camera and light are facing the same way, rendering happens front to back, and when facing towards each other, rendering happens back to front. Therefore you may notice a static particle set “changing” when moving a light or camera if your voxel size is large. This shouldn’t be an issue with smaller voxels and larger filter radii. Are you expecting artifacts from this approach?