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I'm modelling an indoor scene, but I'm getting these weird shadow-like areas. They can't be shadows though, as they are way too dark and move with my viewports position.

I checked my normals, but they seem all ok (blue) for the faces in the screenshots. I also checked for overlapping faces/edges/vertices but couldn't find any. I do have a couple ngons in the model, but not in the affected floor area of Example 2.

The mesh is "open"(?), so from outside you could see the "inside" of the mesh (red normals). Could this be the cause? I tried adding outside faces as well but it didn't fix the issue.

Any help would be appriciated!

Example 1 Example 2

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    $\begingroup$ I suspect it might be overlapping geometry - causing Z-fighting. Check your meshes and objects - do you have a duplicate mesh at the exact same point (try selecting one and move or hide it) or do your meshes have multiple overlapping faces? $\endgroup$ Nov 15, 2020 at 13:02
  • $\begingroup$ I checked the mesh, but there's definitely no overlap.No flickering or any other hint. Also when I box-select parts of the mesh, the numbers of selected faces etc. are as expected. $\endgroup$
    – rototof
    Nov 15, 2020 at 13:14
  • $\begingroup$ Are your objects scaled at extremes of scale (very large or very small) or positioned a long way away from the origin? Have you ‘Applied Scale’? You could try hiding (‘H’) each of the other objects one at a time to narrow down what’s affecting it. Have you tried switching between Eevee and Cycles to see if the same problem occurs - or between CPU and GPU rendering in Cycles? $\endgroup$ Nov 15, 2020 at 13:27
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    $\begingroup$ They are all to scale. The room is roughly 7m². I tried the rest of your suggestions, but as it turned out it was probably your first guess after all. I removed a couple of faces and rebuilt part of the mesh and it works now! Thanks! $\endgroup$
    – rototof
    Nov 15, 2020 at 14:35

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This can be the result of overlapping geometry - causing Z-fighting where two or more faces are in the exact same location and orientation. This can result in the faces shadowing each other and other artefacts such as banding.

Check your meshes and objects to see if you have a duplicate mesh at the exact same point (try selecting one and move or hide it to see if the other remains) or whether your mesh has multiple overlapping faces (move a vertex and see if another face is in the same place).

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