Shading issue

[dadaromeo]

Can someone gives me a hint of what is going on, please?

[PetrT]

Pehaps some normal issues
Auto smooth is off or on-?
May be recalculation is needed or edge split modificator
Picture is to small to see all details of issue
Did you try Eevee in this case?

[dadaromeo]

Yes auto smooth is on and the angle set to 30. But changing the angle doesn't change the issue.
No, I didn't try Eevee, can't render in it (don't have a graphics card).

Yeah, it's probably normal issues because these artefacts only appear when smooth shading it pressed. With flat shading, everything looks fine. I think it's the way LuxCore is "averaging" things, that may constraints users to have irreproachable geometry. And may be it's something a user should be aware of.

The issue isn't just about this model. I've replaced the model with a somehow "stylized" dummy cube and the artefacts appear but, subtle.

[Sharlybg]

Please can you select your original model "" the screw machine""" and apply scale transformation with CTRL+A ? and see if it change the result.

[CodeHD]

One more idea: Do you use Blenders custom split normals in your mesh?
LuxCore supports it only since v2.4.I don't think it would explain all of your problems, but if not you could try using them and see if that fixes those spots.

[PetrT]

did you try edge split modifcator or try to remove auto smooth?

[dadaromeo]

Please can you select your original model "" the screw machine""" and apply scale transformation with CTRL+A ? and see if it change the result.

Scale transformation is already applied.

did you try edge split modifcator or try to remove auto smooth?

The Edge Split Modifier works at some extend.

One more idea: Do you use Blenders custom split normals in your mesh?
LuxCore supports it only since v2.4.I don't think it would explain all of your problems, but if not you could try using them and see if that fixes those spots.

I checked and Custom Split Normals was already added to the mesh. I clear it and the artefacts don't show up again even tough I add the Custom Split Normals back . Any explanation?

Thank you all for all your tips.

[CodeHD]

I checked and Custom Split Normals was already added to the mesh. I clear it and the artefacts don't show up again even tough I add the Custom Split Normals back . Any explanation?

Thank you all for all your tips.

Glad we could help!

I have observed that with custom split normals, the auto smooth option gets checked automatically (and is n fact necessary). Otherwise I too observe the artefacts you showed.

Perhaps your mesh previously had split normals, but auto smooth was not active? When clearing and re-setting, it would probably have been activated.