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Something is causing my mesh to show strange shadows along edges in render mode, but not in the material preview. I don't know what's causing it or how to fix it, so I'm hoping someone here has an idea.

Things I've tried so far that haven't worked:
• recalculating normals
• resetting vectors
• clearing custom normal split data
• disabling all modifiers
• hiding all other objects
• merging by distance and checking for non-manifold geometry
• shading flat, then smooth again (shadows are even worse when shaded flat)

If I import the same mesh in a new scene, this also happens, but I can't find any doubled faces, vertices, etc. in the mesh that could cause this.

Mesh in material preview: enter image description here

Mesh in shaded mode: enter image description here

Mesh in shaded mode & in edit mode: enter image description here

Mesh in shaded mode with flat shading on the object: enter image description here

Here's a minimal scene showing the problem:

Aci
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  • First thing to eliminate.. do you have any objects ( copies? ) hidden in the viewport, but not disabled from rendering? – Robin Betts Jan 16 '23 at 10:26
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    Yes, but I'm viewing it in the viewport, so this is the only object (and the light source) that is visible – Aci Jan 16 '23 at 10:27
  • Ahh, OK, thanks. Maybe share a minimal version showing the problem, following the instructions on https://blend-exchange.com/ . – Robin Betts Jan 16 '23 at 10:35
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    Thanks, I added the file to the post! – Aci Jan 16 '23 at 10:45
  • Hi, Aci, I'm sorry to say, I can't reproduce this effect, in the 'Test' file you provided. I tried a few things to make it go wrong, and haven't found one... I guess we'll wait and see whether anyone else can, while checking configuration.. graphics drivers? – Robin Betts Jan 16 '23 at 12:10
  • Did you use the cycles render engine? I've tried opening the scene using maya, and in Arnold I see a similar effect, but in eevee it's barely noticeable. A bright material also helps, in the example you sent you used a darker red-ish one that might help hide it. When you're that far zoomed out it can also be hard to see, the file should start you out looking right at the area where the issue occurs, and if you go to rendered view right after opening it up, you should be able to see it. – Aci Jan 16 '23 at 12:29
  • For sure. (Just checked again) Cycles, GPU, CPU, De-noising in/out. Ramming the lighting up to excess, setting camera and viewport clipping-ranges too high, blowing out shadow-termination offsets.. clearing custom normals ... I just can't get it to go ! – Robin Betts Jan 16 '23 at 13:02
  • What version of blender are you using? And what graphics card? Did you change anything in the initial test scene? I've tested it on three different PCs with different versions of Blender, in Maya and on all of them I've had the same issue.

    I also have noticed that removing or rotating the sunlight can change the effect though, so it seems to be hard shadows being calculated wrong somehow.

     – Aci Jan 16 '23 at 13:26
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    Ahhh! got it to go! It looks to me like shadow termination.. the adjustment is the Object tab, Shading panel. Cost: a little blowing out of shadows. You may also try an extra level of subdiv. for render only, if needed, to prevent your viewport from creaking. See also, for example, here .. If we've found it, this Q may get clobbered as a duplicate .. :( .. :D – Robin Betts Jan 16 '23 at 17:16
  • Thanks, that solved it! Appreciate the help! ^^ – Aci Jan 17 '23 at 11:03
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    Great! I hope you don't mind, nothing personal, but since this is the fix, I'm going to close this Q as a duplicate. We try to keep searches in the archive as simple as possible. – Robin Betts Jan 17 '23 at 11:32

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