Hi
Did you mean something like this if you did then you can get the sh3d file from here from it you should be able to figure out the walls and floors, each "step" is a room created in the individual area then exported and imported as an object. the beauty of using rooms in this way is that its shape, when drawn freehand is limited only by your imagination, or you can, as i did create walls any angle or arc, create a room in it then delete the walls.
Hope this helps, great idea doing a cinema, good luck
Mike