From what I've seen, with global illumination, the floors and ceilings need to not be continuous. It creates unrealistic light leaks as the resolution of the baked illumination may vary from system to system. If each surface is non continuous then the light will terminate on the edges as well. I'm not 100 percent sure though, but I'm hoping I'm planning it correctly. It is more authentic that way and I get texture space for each room if I want it. I'm really liking the character of the building though as it's coming through.

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