Well. I'm starting to have my reservations about this project. Yesterday, I've made an experiment by making a sketch of a shaft. However, it seems that the lights outside the shaft were not behaving as I predicted. The light just gone through the ceilings, lighting the the ceilings above.
Attached is the mess I've done. Of course the doors won't be stacked as a single object. This is just trial and error (being the error quite evident. I've tried several configurations with the lights, without results).
My guess is that the ceilings have to cause 100% dark shadows, but unfortunately that is a light property. I mean, the shadows cannot be 100% black, because there is always the reflected light, but the ceilings must cause total occlusion. The only way to minimize the blackness of the shadows case I choose the shadows to be 100% dark is to use more than one light per floor (which I was going to use, anyway). Is there any other solution?
Also, I had to change the lights from volume to ray trace, or the rendering would appear to be scratched. Anyone noticed this problem with volume lights before?