I'm using the box to cutout internal walls to give a view through the house. If they are windows, then I understand why they are letting light through. I was hoping however that they would block the light from internal light sources like a normal wall. I've seen it done in 3ds Max and was hoping it was achievable here. If not, that's cool, when I get my final images I can edit them in Photoshop to achieve what I want.