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  1. #1
    MSgt. Shooter Person
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    Mar 2012
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    33

    Default Blender normal issue

    I'm trying to import a brain model from blender into UDK, but for some reason UDK is inverting 1/2 of my normal map. They were generated and applied in Blender. Any ideas? Thanks.


  2. #2

    Default

    Did you use normal map compression?

  3. #3
    MSgt. Shooter Person
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    Germany
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    Default

    First of all you should use smoothing groups on your mesh and also take this into account when baking the normal map.

    Blender normal maps have the green channel inverted. You can either fix this in an image editing program like photoshop/gimp or in the material editor by multiplying your normal map sampler by a Canstant3Vector (1,-1,1).

    Besides there is a UV seam across your mesh that causes normal map errors because the high and low poly model don't match exactly. You should also fix that in PS/gimp.
    Last edited by mAlkAv!An; 06-21-2012 at 02:52 AM.
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  4. #4
    Boomshot
    Join Date
    May 2011
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    Chicago
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    2,215

    Default

    Also, did you possibly mirror the right side to the left while modeling by duplicating it and scaling it to -1 in the corresponding axis? If so, your normals may be reversed on the left side. Though if this material isn't two sided then we'd be able to see through the left side to the back of the mesh.

  5. #5
    MSgt. Shooter Person
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    Mar 2012
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    Default

    I'm not using any texture compression that I'm aware of. I did use a mirror modifier when building the low poly (The high poly was done in sculptris with a mirror) but I applied it and recalculated the normals before baking. I've tried a few different methods of UV unwrapping, including letting Blender do it automatically, but I still get a similar problem. I'm going to try exporting in a couple different formats then converting using the autodesk fbx converter and see if that helps.

    Thanks for the tip on the green channel. I tried multiplying it by (1, -1, 1) but it didn't help.

  6. #6

    Default

    When you import a normal map, you MUST change the compression type to TC_NormalMap, by default it is TC_Default and that will not interpret your normal map correctly

  7. #7
    MSgt. Shooter Person
    Join Date
    Mar 2012
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    Default

    I think I have it now. I ended up recalculating the normals using xnormal, but I was still having the problem. For some reason the nmap looks correct in the content browser, but when it is imported into the material editor the green channel is obviously inverted. Thanks for the help.

  8. #8
    MSgt. Shooter Person
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    Germany
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    Default

    That's allright. If you use TC_Normalmap compression the material editor node preview have to look like this.

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