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blender to substance painter issue baking discontinuous seams in world space normal

I am struggling with an issue when exporting to substance painter.

whenever I export my model into substance and bake it, all the world space normals have discontinued UV seams, this means triplanar projection and smart materials all have seams as well.
I have been trying various methods to find out how to get around this but each time the seams are clearly visible and are affecting the way substance painter smart materials apply to the model with harsh seams and bad mapping.

I will try and cover what I have tried thus far.
I have tried high to low poly baking, cages, edge split modifier, triangulating before export, normal smoothing 180, clearing all edge sharpness or adding edge sharp to UV borders and re-working UV map multiple times.
Some of these has changed the bake slightly but not gotten rid of the seams. from what I have read on various forums it has something to do with smoothing groups and UV seams but I have not yet seen a good solution.
I have included bellow a test piece that shows the issue in a png and includes a blend file and FBX export.
any help would be much appreciated as this is really putting a block in my asset workflow.

The only thing I can add is that if I use "smart UV project" in blender it solves the issue, but this means I can't set my own UV cuts/islands and i have to rely on what the blender script spits out which I don't like for neat UVs

Please note the test piece is a small piece of a much bigger mesh so the unwrap is small but as it should be and will be baked at 4k.


thank you

Replies

  • Brandon.LaFrance
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    Brandon.LaFrance Polycount Sponsor
    I took a look. You simply don't have enough resolution in the texture to support the detail. If you examine your UVs you'll see that this part is only using a small fraction of the UV map. At a 1k texture resolution, there are simply too few pixels to get a smooth transition across UV seams. The solution in this case is to either scale the UVs to use more of the texture map, or increase your texture resolution in Painter. This is why "Smart UV Project" solved your issue. It creates UVs that fill the entire UV space.

    Not related to your issue, but thought I should mention it. There isn't really a need to use the edge split modifier. I think that was a work-around used before Blender supported custom normals. Now, my general workflow is to simply set all faces to smooth, enable auto smooth set to an angle of 180, and mark sharp edges in edit mode. In general, wherever you've marked a hard edge, you should have a UV split with some edge padding. The reverse is not necessarily true - a UV split does not necessitate a hard edge. Don't want to get too far into the weeds, as that's an entire topic on its own, but I encourage you to reference this excellent thread to learn more:

    https://polycount.com/discussion/107196/youre-making-me-hard-making-sense-of-hard-edges-uvs-normal-maps-and-vertex-counts/p1
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