@smorrell 2) Other ray tracing software (like Radiance) can take into account specular/semi-specular and transmissive surfaces and spectrum. I wonder if I could combine the strengths of AGi32 with your model, because AGi32 doesnt have scattered voxels.
Here is an example of an outdoor parking lot in AGI32 with a lambertian reflectance of 0.16 for the ground and 0.2 for the building.