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I'm modelling a coat for a character, and I have those weird dark grey artefacts on some faces.

Here it is in edit Mode, Face select

Then in Object Mode

And this is what it look like in Edit Mode, Transparency On, Vertex Select

A few things :

As you can see, there's no overlapping faces, no triangles either, it has no modifier on it except for the mirror modifier.

I've already tried to :

  1. Shade it smooth or flat,
  2. Flip and Recalculate the Normals
  3. Apply all transforms in Object Mode, and
  4. Clean Up for Loose Edges/Vertices/Faces, and Merge By distance.
  5. I've also deleted and rebuilt those faces but those artefacts remains.

Any idea ?

Here's a blend file : https://blend-exchange.giantcowfilms.com/b/ykzVrBss

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    $\begingroup$ hello please share your file blend-exchange.giantcowfilms.com $\endgroup$ – moonboots Oct 21 '20 at 9:30
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    $\begingroup$ I would have guessed at normals though you seem to have already thought of that - maybe worth turning on Face Orientation in the Viewport Overlays menu just to check. If it's not that, you could try Apply(ctrl-a) in object mode, then Apply All Modifiers and/or Visual Geometry to Mesh. If either of these modifies your geometry and the new geometry looks like it's causing the shading that gives you somewhere to look, but without a blend file to examine I don't think we can give you a 100% cause since you've already eliminated all the obvious ones. $\endgroup$ – Ben Oct 21 '20 at 10:14
  • $\begingroup$ Here it is : blend-exchange.giantcowfilms.com/b/ykzVrBss Btw I know that my model is not perfect, but this topology should be enough to avoid those kind of artefacts, am I right ? Thanks for the help mates $\endgroup$ – Pdhm Oct 21 '20 at 10:37
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    $\begingroup$ Have you tried using the auto-smooth feature? $\endgroup$ – Edward Hurley Oct 21 '20 at 13:49
  • $\begingroup$ I don't know what is causing the issue, but if you want to just fix it here, I have found that you can just delete and re-add the vertices in the middle of the dark area, and it goes away. $\endgroup$ – person132 Oct 21 '20 at 16:59
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Clear (or edit) your custom split normals data from the Object properties->Geometry data section. These custom normals are causing this issue.

enter image description here

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  • $\begingroup$ THANK YOU. This is it ! In fact I rebuilt this coat from a previous one with cloth sim on it ! I didn't knew this feature even existed linked to a cloth simulation. What is it used for ? $\endgroup$ – Pdhm Oct 22 '20 at 11:01
  • $\begingroup$ It lets you add custom normals data from an arbitrary source - typically, a higher poly version of a mesh or simulation (cloth sim in this case), but several addons also do fancy things with it such as copying normals from a sphere to a sphere-plus-booleans that would otherwise have broken shading. The benefit of it being at the mesh level means it doesn't require a normal map or UV map to work and as you found to your detriment, it sticks around as long as the mesh does, which is actually good if you know they're being used. (side note: the UV map for that mesh was wild!) $\endgroup$ – Ben Oct 22 '20 at 11:25
  • $\begingroup$ Ok thanks for the infos ! And, about your side note, yes it was, and not only the UV Map hahaha. I learned Blender along the creation process of this coat. Thats why I had to remodel it :p $\endgroup$ – Pdhm Oct 27 '20 at 15:56

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