Hello everyone !

I would like to mirror the mesh of a hairstyle because I think it would look way better ! :lovestruc
I'm using TSRW and Milkshape : I'm used to exporting the mesh as .wso, loading it in Milkshape and then : Vertex - Mirror Left <--> Right.
Then I import the modified mesh back in TSRW and everything looks fine.

But not this time : there are shadows and lighting problem. A part of the mesh is black and it is very polygonal

How could I solve this problem ? Is there another way to mirror a mesh ?

After you have mirrored a mesh you need to alligne its normals.
You best do this by selecting each smoothing group(if its has multiple) in the groups tab and alligne its nomals using Demon's alligne normals tool.(repeat for the others)

If it doesn't have a 2nd smoothing group for the inside layer then you best tick autosmooth before mirroring.
Mirror and fix any seams with Demon alligne normals tool by selecting the outside layer faces only(tick ignore backfaces when selecting)

Thank you very much for your fast answer !
I did what you said and now the hair looks way better : the textures look fine and the hair isn't black anymore.
But now there are little "black stains" on the hair, I mean some little shadow issues. I really don't know how to fix this problem...

that happens when you alligne the normals on both the outside and inside layer, you need to alligne them seperate.
I think you best mirror them with autosmooth on.

Wow, thank you so so much BloomsBase !!
I checked the Autosmooth box, mirrored the mesh and imported it back to TSRW and now the hair looks wonderful ! :lovestruc
Thanks a billion for your help !!