normal map inverted in cycles I've been working on a piggy robot model in Blender for some time, and I'm having some issues texturing in Cycles, specifically with the normal map.
For some reason, Blender inverts half of my normal map on the model, which make the seams that are supposed to go inward are now sticking out (every line on the texture/normal map is supposed to be an indentation, like this, but without the lines being black, if you know what I mean:

And this is what happens when I try to apply the normal map:

Now I've tried to invert the green(y) and red(x) channel of my normal map in photoshop (with help of the nvidia plugin) but it turns the normal map slightly transparent, so when I use the png in blender, the whole texture becomes much darker (the material should be a glossy plastic material).
After that I tried to see if maybe changing the normal map node from 'tangent space' to 'blender object space', and that made the seams work, but also darkened the texture again, like this:


I'm kinda lost as to what I'm supposed to do now.
The normal map you are using is baked for tangent space. Blender tries to calculate the tangent and binormal vectors from a UV map. The problem here is that along UV seams the tangent direction can change. This is why you get weird shading along the UV seams.

A simple solution is to calculate the normalmap in Object space (use "Object Space", not "Blender Object Space" in the Cycles shader). However this will not work if your object gets deformed, for example by animation bones. Also there still seem to be some artifacs and the normals seem not to be calulated smoothly (see red box below).



Using the displacement texture directly instead of the normal map gives you perfectly smooth shading, so I think you should it instead.

Apart from the texture issues your object also has a bunch of flipped normals: inside the nostrils, the eye sockets and inside the holes where the ears are attatched to the head.