AO Maps Baking with Dark Islands
There is a particular problem with regards to baking AO maps that seems to come up quite regularly in my projects. This problem is not what I would consider to be a bug in Blender but more along the lines of a user error and as such is easily fixable. You might have encountered the same problem too, as a result here is an easy fix.
Problem: Geometry Appears Dark In Texture Mode
This issue first becomes evident when a texture is applied to a model. Sometimes the texture will appear to be darker in certain areas than would be expected.
This can be seen before an Ambient Occlusion (AO) Map is baked out, however becomes even more prevalent when the AO map is finally baked.
In this example baking the AO map has resulted in extremely Dark and Black Islands in areas where little to no Occlusion has occurred.
Fix: Apply Transform
Closer inspection of the geometry reveals that one the axes of the Scale transform has been flipped, resulting in a negative Scale.
In this event the solution would be to select the geometry in the 3D viewport and go to
Object > Apply > Scale
The effect of Applying a Transform in this case is to retain the objects current Transform History (which ultimately results in the object’s Position, Orientation and Size as it is seen in the 3D viewport) and simultaneously to reset the numerical values representing these properties to their defaults.
Once this has been done, re-baking an AO map will result in a Render as expected.