When using a baked normal map it is inverted on half my model I am having a problem when baking and then using a normal map.

I have a high res and low res model and am using the "Bake selected to active" feature.

I am using BI to bake the image as I cannot seem to get cycles bake to work. I am then applying the normal map in Cycles through a Normal Map node plugged into a Diffuse.

As you can see, the baked image itself looks OK and symmetrical. When I use it, however, half my model seems to have the normals inverted. I previously had a mirror modifier while modelling and I suspect that is involved, but it was applied before I started the bake. I also checked all my normals on the model and they face the right way.

I can't figure it out and its driving me mad! Help!


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EDIT: On further investigation I can see that the problem lies with my baked normal map. If you look closely at it you can see that it is not baking correctly as it is uneven. So my bake is wrong, I just don't know why.
If you made the UV's while the mirror modifier was active then the UV's for both sides should be overlapped, the bake is only correct for one half of the model.  

If you hover over the UVImage Editor and press Ctrl+P (Unpack), you should end up with distinct islands for all the geometry.

Now you should re-bake.