this post was submitted on 11 May 2026
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Why am I getting seams on my normals? (media.piefed.ca)
submitted 2 weeks ago* (last edited 2 weeks ago) by PlzGibHugs@piefed.ca to c/blender@lemmy.world
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Some spots are fine, others have seams. There are marked seams on the mesh, but the UV map is seamless, and removing the marked seams seems to have no impact.

Edit: No seam visible when looking at normals or tangent via a geometry node, nor when looking at the UV map applied to the model as color. I'm pretty sure it has to be something to do with the UV mapping node.

Edit 2: I've uploaded the file here.

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[โ€“] PlzGibHugs@piefed.ca 2 points 2 weeks ago (1 children)

I've uploaded it here.

[โ€“] TacticalToothbrush@discuss.tchncs.de 2 points 2 weeks ago

This is not my area of expertise so I can't be of much help.

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Because they're tangent space normals, and where there are seams, tangent space changes sharply. It is not that the normals (world space or object space) are discontinuous; it is that the tangent space is discontinuous, and so the tangent space normals are discontinuous, even though the world space normals are not. (Tangent space is a space where the +Z vector points in the direction of the sampled normal and the +X vector points in the direction of increasing U, from your UV map. The normal map color is a remapped vector intended to be interpreted in this tangent space. The direction of increasing U changes sharply across seams. Which is okay.)

Seems different on this case where normal map is continuous but tangent normal is not. I guess you can unwrap the ring in one piece to have only one seam and hide it somehow.