As I discovered, while trying to create very soft shadows from a large light source, by making a beauty dish (two dishes with a very bright light inside) out of a reflective umbrella model that Emmanuel kindly made for me to test. In the rendering process a light rays path is only being calculated once, after the ray has hit a surface it disappears, so light bouncing (scattering) isn't happening.
This might be the same reason your buildings entrance is appearing dark, because the light isn't being reflected back off the ground to help provide some fill light?
Here is the beauty dish model.
How it renders. I used Uber this time but all photo and advanced photo renders appear the same (from a light point of view) The frame at the side isn't illuminated by the light, the frame is a shiny surface and reflecting the illuminated dish.
I have written this next part to try and explain (for those who don't know) the effect of putting a single light source inside a beauty dish makes.
Since a single small distant light source will always cause objects to produce dark hard edge shadows (like the Sun does on a clear day) Putting a single light source inside a beauty dish. (by the way no direct light rays can hit an object from a beauty dish, only reflected light) The light rays bounce around the surfaces several times before finally exiting in multiple directions creating the effect of a much larger light source, because the light rays then hit the object from different controlled angles, the light rays overlap each other causing the same object to cast softer edge shadows as the light wraps around the objects surface, as can be seen here. Image produced in Art of Illusion.
Of course rendering the paths of multiple light rays and their surface interactions requires intensive calculations, producing much slower (final photo) rendering times.
db4tech
