What are you using to make the normal maps? Newman had a similar issue and it turned out to be the way the normal map itself was being saved by the NVidia PSD plugin.
Normalmap plugin for Gimp, following the instructions in the
Gimp thread. I let the dds plugin handle the conversion (by saving to DXT5n), but now I tried converting manually (decompose, copy red to alpha, fill red & blue with black, save as png), and it's still the same.
I think it's more related to the method used by the shaders to invert the normals on the mirrored side of the ship. I don't know the shader code, but apparently the longitudinal specular highlights are a byproduct of the same mechanism that allows using mirrored UV maps on the models.
Yeah, but blender doesn't do this (I'm talking about the 3d view which uses glsl shaders, not rendering), and more importantly, not all ships in FSO seem to be affected. The Aeolus, the Leviathan/Fenris, the Poseidon and the Triton are fine, but the Aten, the Sobek, the Deimos the Iceni, and the Faustus are all showing the seam.
Yup I've had that happen a lot.
The only way I know how to fix this is a.) uvunwrap both sides seperately (they cannot share the same uvmap) or b.) in Max, detach the port side from the starboard side then reattach but do not combine vertices. (or do a bit of both)
Thanks for the suggestion, but I'd rather not do either. Unfortunately, b) doesn't get rid of the problem entirely and it creates an ugly seam. I tried disabling smoothing and merging all vertices, and it still shows up on some flat faces. I'm thinking of unmirroring only the flat surface on the top and bottom where the seam is, i.e. moving the UV seam from the middle a little bit to the right where there's a hard edge on the model, while keeping the disconnected parts sharing uvs. I might be able to get away with that without having to redraw the texture entirely, but I fear this will only move the lighting seam.
Edit: I remapped my model since the uv was crappy anyway, and this time I didn't split the large flat surfaces in the middle. After mapping one half I applied the mirror modifier then manually mirrored the UVs for one half of the surfaces in the middle and attached it to the other half, so most of the islands are still shared between the two halves. That solved the problem.
