What extactly is the unused checkbox for?

Lately I've been reading around the forums and people are getting trouble with their shaders and a lot of the time the solution is to uncheck the unused check box on the bitmaps. So I decided that I should save myself some time and go through all the bitmaps I have and uncheck the appropriate area. Anyway, it seems that the default bitmaps that actually came with the game seem to be grayed out with the box checked. So that leads to the question in the title. What exactly is the unused check box for?

I'm not too sure, but I think it tells the map compiler to skip it when compiling and instead check the shared maps for it when ingame. If the bitmap is not located in the shared map files, it will not show up ingame. All of the default bitmaps are contained in shared map which is why it doesn't matter if it is unused checked or not, same for many other tags.

Ok. Thanks. I wanted to know if i was wasting my time or messing up all my bitmaps. I'm Glad to see I wasn't doing either. *sigh of relief*

it's for stuff like fog planes.

(i think, thats what i used it for anyway)