Color of pitched surfaces

[Narska]

The same surface is either brighter or darker depending on its pitch. Notice the building with the pitched roof in the attached image.

What surface or rendering setting controls this effect so that I can make the surface more uniform in its appearance even when the orientation changes?

[Narska]

There was a 0 depth roof body that used for trimming what was causing this, even though the material was the same. Once it was put on a hidden layer it rendered properly.