Sky reflection on windows

[Anonymous]

Hi Everyone,

I get this big round dark area in the facade windows in the Cinerender image (see attached image). There is nothing in front of the building that should block the sky reflection. Anyone have any idea why this is happening? How do I get rid of this dark area and make the sky reflected properly on all window surfaces?

Thanks,

[Anonymous]

I think I've figured out. Looks like it has to do with the Ray Threshold parameter.
A spherical no-reflection area in a glass surface shows up or disappears depending on the ray threshold amount (see attached images).
I still don't know why it has to do this but I can move on now. Thanks,