Why diffuse+glossy give a very ugly net shadow depending on the camera?

I have no lamps, just only an environment texture that is ok (hdr ecc).

I have simply only a Diffuse + Glossy (with high roughness) shader that are connected with a Mix shader, and here in the image you can see other variations of this problem with also normal maps and Frenel applied. The one with less bad effect is because it’s subdivided 4 times but still it is visible!
So why in the world this happens!? What is the cause? And what is the basic workflow to avoid this?

How are we supposed to know with so little information? Please ALWAYS supply an example .blend file with any support question.

Fresnel - You have a glossy mixed &n controlled by fresnel or using Principled…

IkariShinji, I can’t upload the file because it has an environmental texture from Substance Painter and it is 15 MB with it.
Parameters in the properties are as default, except for CPU that is now GPU and the samples are increased for the preview (nothing else has been altered). Plus: I am not using modifiers, and the material is only one.
The nodes in question are, as I said: Diffuse + Glossy in the Mix node, with some variations in the previews that you can see here (some textures applied; Fresnel applied; Bumps applied ecc).
The right-bottom preview is really only composed by colored Diffuse + Glossy (with roughness) into a Mix shader, going into the output node, and -nothing- else. Because of this, I thought that this was a very much common problem, since my settings are ultra-basic…

Burnin I can’t understand what are you suggesting… As I have said I have already added Fresnel in one of the 3 previews. (PS: I don’t want to use the Principled node because I want to learn how to use all behind it, before using it).

Then delete the environment map and upload that file. Or use pasteall.

The problem might very well be the mesh itself, so there is no use in describing one or the other render setting. All we need to know is in the file.

show pic without the environ map
does it do the same effect ?

Pastall is limited around 7 MB I think
but without the enviro map should be a lot smaller !

upload the file without the enviro map
at least we can test it

happy bl

30 MB, according to their website.

I suspect the normals are inverted, and that odd reflection is in fact the fresnel total internal reflection.
Try to recalculate the normals or flip them.

Thanks for the tip it has been increase a lot more then before LOL

happy cl

It’s 7 MB for images, but 30 MB for .blend-files.

Hey guys thanks to all but now I have solved.
In the low poly model I had 2 loops for each horizontal ring (I have just beveled them), but adding a third loop inside the two, the problem disappears! Just, I can’t understand why it didn’t worked with the subdivision surface before (2nd preview), since it adds loops too…