Ok this one is REALLY wierd…
So I had two objects that I joined together. I had the same surface applied to both. I then went to bake full render, and one of them bakes to uv map and other comes out black. Both are part of the same object as I said. This makes no sense to me at all.
Help? :S
Maybe you need to remake the UV?
Done so tones of times. Still no fix. (re textured and unwrapped again)
Check to see if there are two UV Textures assigned to the same object. Maybe it’s using only one of the mapping channels. If that’s the case then you need to join the UV Textures as well.
Thanks! That was the fix. 