The attached image shows anomalies in the render which do not show up in the viewport - they look to me like a Fresnel effect.
I created a circular mesh for a tree skirt with solidify and subdiv modifiers. Below are samples from the viewport and three different shaders. I confirmed the normals were in the correct direction (up in this case) and tried reversing them, too. I also tested without modifiers and in numerous lighting conditions (HDRs, multiple and single point lights) and higher resolution (cycles) with the same result.
The subdiv modifier makes the anomalies smaller, but does not eliminate them. Lastly, the render artifacts also show up when using a solid color (i.e., no pattern).
Do they show up in viewport if you apply the solidify modifier? Is it turned off in viewport? Btw, Velvet, Oren-Nayar (Diffuse with roughness > 0) and Anisotropic shaders are not supported in Eevee yet. If not this, then please share the file as it’s really hard to just guess.
Thanks for the help - it solved my issue, indirectly. I was going to upload a trimmed-down version of the file and found a “back-up” copy of the mesh buried in my collections which was hidden in the viewport but not the render. It was this mesh, with no material, which was poking through in spots. Also, I am using cycles for this project, but added eevee just because the issue was showing up there, and wanted to eliminate the render engine as a culprit.
