Question regarding normal maps and sharing unwrap space.

[NiGHTS2o06]

Hey guys.

OK so ive got a model whereby the chest area is unique to both the left and right sides however the back comprises of shared texture space (see below):



Now ive created a normal map and to try and eliminate seams ive copied the right side of the map over to the left to ideally eliminate the seam that should be present due to the unique scuplting on both sides (see below):



However, seams are still present in the render and I dont really know how I can eradicate this problem.



Im not sure if giving the back its own unique texture space is the solution as the resolution is 512*512 and im trying for maximum optimisation to collaborate with an relatively asymmetrical model.

Does anyone know of a work around for this. Thanks.

[EricChadwick]

Looks like you're using Max, which version?

Where did you generate the normal map, in RTT, or another program? What is your material setup? Are you using Normal Bump? Are you using scanline renderer?

RTT, Standard material with NormalBump, and scanline should all work OK together, without requiring any painting touchup.

Does the sleeve UV touch it there? Might need to paint into the the sleeve area too. Can you show a screenshot of just the normalmap on the model, no lighting?

[NiGHTS2o06]

Ok, ive fixed that problem (created unique UVW space for the entire body, means smaller texture size in chunks but fixes the problem) however heres an issue thats annoying:



The first image is a viewport image of the actual coloured normal, the second is the normal in viewport with DX shaders turned on and the last one is a normal render. The seams appear in the viewport but not on the render which....is strange since I want to print screen final images of the model instead of rendering them. Any thoughts?

[EricChadwick]

Yeah, none of the dx shaders that ship with Max actually solve normalmap seams. Only shipped shader that solves tangentspace seams is Normal Bump with scanline renderer.

Fortunately there are some third-party shaders that do it right.
http://wiki.polycount.net/Normal_Map#ShadersAndSeams

Hope this helps, let me know how it goes.

BTW, you don't have to use unique mapping, you can still mirror UVs if you want. Just move the mirrored bits 1 unit over on U or V, so only a single non-overlapping copy of the forward-facing UVs is left in the 0-1 UV box. Hope that makes sense. More info in that link above.

[NiGHTS2o06]

Ok the secondary problem was fixed using the links for those shaders (thanks for that) however the inital problem still exists. I was moving the mirrored bits 1 UV box along (upwards as shown in the very top pic) however that seam is still present.

NOTE: Ive also tried moving the UV where no seam was present (i.e. the opposite side of the jacket) and replacing it with the UV unwrap where the seam was present and welding the vertices to the front of the jacket however this didnt remove the seam at all.

[EricChadwick]

Sorry, I'm confused about which problems you're saying are solved vs. not solved.

You should not paint out the color differences across UV seams, they are there to work with the normal/tangent/bitangent information stored in the vertices.
http://wiki.polycount.net/Normal_Map...sAndBitangents
If you paint the edges to be the same color, you will actually introduce seams when the model is using a shader that properly uses the tangents/bitangents.

However if you cannot use one of these "correct" shaders, like you're going out to a game engine that doesn't use the tangents, then you would want to paint out the seams as best as you can, though some seams will still be unavoidable with this method.

Here's a tutorial about how to paint out seams on mirrored tangent space normal maps. Note: this method only solves seams along horizontal or vertical UV seams, not across anything angled. Always good to have more tricks though: http://boards.polycount.net/showthread.php?t=51088

[NiGHTS2o06]

Sorry, the problem that was solved was the use of an external shader for viewport normal mapping (as opposed to rendering).

The problem that wasnt solved was the mirrored UV coordinates for a normal map. The processes I followed were:

1) Create the low and high poly models.

2) UVW unwrap the model, offsetting mirrored UVW coordinates by 1 in the U (or V) axis.

3) Bake normal map and apply. The result is the third image on the first post.

I then attempted to delete the mirrored polys, copy and weld the polys again from the side that mapped and rendered properly and offset in the UV field by 1. Same results as above.

[EricChadwick]

After step 3, if you're using one of those correctly-written shaders, then it should work fine. I don't know where your process is breaking down, sorry. If the shader solved your seams, it should also solve your mirror seams.