Dune, I am sure you`ve got something figured out by now.
Anyways, here is what I noticed: I had my camera set up in the middle room.
Since it has no floor with normals pointing inward the light somehow bleeds through
the edge of the polygon. The higher the AA the less that happens. But rendering time
is increasing of course. Obviously, not a good solution.
Here is what I did:
I masked off the planet with a simple shader which covers an area a little big larger
than the box, so that the planets surface is black. Then I put a plane into this room
which is exactely the size of the room. That is my new groundfloor, textured and
displaced and so on. No more bleeding through at the bottom of the box.
On the other hand if a doublesided box works I would do it this way in the modelling
phase anyway. The thickness in the doorframe and the window in the roof looks
much better this way in my opinion.
In the pictures I uploaded I used a spotlight inside the room to lighten up the walls and
the ceiling. It is closely placed beneath the ceiling, pointing down. Outer Radius of the
light cone set to 179.9 and the inner radius to about 40 or 50 to have a nice smooth transition.
Then it is just a question of fiddling with all the settings of the spotlight to find something
which works. Strength, Max Distance, Falloff Power, the cone angles and the Penumbra Gamma.
GI is set to default settings. After the spotlight is adjusted to a nice overall lighting I used the
strength on surfaces parameter in the Enviro light to brighten up the room as needed.
But that takes away some contrast.
Maybe this is useful somehow.
cheers, Klaus (sorry, for the lenghty post)