GGX BRDF yields large black spots with bump map

[Drachen]

I've been using a Vray Blend Mtl with 3 layers (Grant Warwick method) with Ward BRDF to create a stainless steel shader. I've been using a Composite map in the bump slot to create both the grain of the metal and the "wobble" in the reflection seen in large sheets of stainless steel (think elevator doors, refrigerators, etc) Bump is very high (165) to achieve this. Here it is with and without the wobble for comparison



I've been wanting to replicate this with a single Vray Mtl with the GGX BRDF for awhile, but my early tests showed some problems. The same Composite Bump map used with the layered approach yields large black spots in the reflection. I can eliminate them by significantly reducing the bump (down to 45) but this eliminates most of the wobble. There is enough for me to proceed in production, but I'd like to see if there are suggestions for fixing this. Here is the GGX material with the full strength composite bump, reduced composite bump, and reduced bump with only grain.



Any suggestions/insight would be welome, along with any critiques of the material itself. There is no rust/grime/scratches because this is for use in product visualization.
Thanks,

Lee

[super gnu]

just a quick thought, do you have "fix dark glossy edges" turned on in your ggx material?

[Drachen]

Yes that is enabled. I have also replicated this with multiple HDRI's in the scene, one of which is an outdoor with bright blue sky, and I still get solid black areas.

[rossen.dimov]

In current nightly builds GTR/GGX Microfacet brdf ignores 'fix dark edges', since it doesn't make sense for any microfacet brdf.
In current stable build (3.20) 'fix dark edges' ON produces physically incorrect results.
On the other hand those black regions seem not right and if you could post scene files we will look into them.

[vlado]

As Rossen noted, best to post the scene so that we can look at what's wrong.

Best regards,
Vlado

[Drachen]

Here's the scene file. The HDRI that I am using is 134 mb so I did not include it. I have tested the scene with several HDRI's and they all produce this error.

Thanks,
Lee

[rossen.dimov]

Thank you for the scene. We found a problem on our side, which we are considering how to fix and it will most likely take some time. Until then, please use the workaround you've already found.