I have a large space station scene, where there are giant mirrors that are sources of reflected light, and to emulate this, I made directional lights attached to the mirrors with cookies to make them look like the reflections of the sun in the mirrors. I have a few of these mirrors, lighting different parts of the station, and to keep the directional lights in check, I divided up the station into layers, so certain mirrors shine light on only certain sections. This works all well and good for the actual lights, but when I pre-calculate the realtime GI, suddenly parts of the station are getting reflected light from "mirrors" that are nowhere near them!
In other words: How can I make the GI from directional lights respect the layer mask I set on their source lights?? I'd prefer not having the directional lights affect parts of my scene they shouldn't be affecting!
(And if anyone has any better ways of reflecting sunlight onto a large scene via massive mirrors, I'm open to that too.)