corrections to the lighting of the Stamp Collector scene

I showed Andrew my lighting setup for the interior in his film and he really liked it. His ownly feedback was that he wanted the corners of the walls to be darker. Originally I didnt want to add an occlusion pass to the scene because he told me he was concerned with render times, but after talking about it again he said he wants me to add that pass. This was the result:


Andrew liked this but said that he wanted the top corners to be much darker than they currently are. I was having problems with making them darker because I had to delete the roof so that the occlusion in the ambient occlusion pass could enter the room and not leave me with a black image. Instead I then tried to delete a back wall instead of the roof but i still wasnt getting very dark top corners because of the light pouring in from the window. I felt I had to resort to a more un-orthodox method, I decided to make 2 large planes and got them to intersect the top corners of the walls. I then lowered the opacity on these so that they would cast a shadow:



This left VERY heavy shadows. I tried to make the material of the intersecting planes a ramp shader going from black to white (making the transparency systematically get more opaque as it gets to black) but because I was using depth map shadows this did not work. In the end Andrew told me that the room wont even be seen from this angle so it irradicates the problem straight away!!! but still I learned something today :P