Substance Painter to VRay Reflection artifacts

[yaschancool]

Hi,
So I have these strange reflection artifacts.
I am using Substance Painter and export with the VRAY preset, and use 16bit PNG.
I setup the materials in slate editor using VRAY HDRI loader with UDIMs and set the gamma to 'none' to every map except diffuse.
My Max has gamma and LUT enabled.

So, I get these reflection artifacts in some of the curved surfaces that look like oil spill.

My question is, what would cause this? it looks normal in SP.

If I export roughness maps from SP and use roughness setting in VRayMtl , I never get this error.

I am currently working with a massive VFX model which has the materials set up already from SP using the VRay Preset.
The maps look fine so far in the renderer using the studios default HDRI but I worry something like this would happen if the lighting would change.

I wonder if I am doing it right, and had I better to get the maps re-exported using the roughness preset?

Thanks in advance
Jaakko

[Ihno]

The Vray export uses an IOR map are you using it?
That might be the problem, it needs to be remapped since it works between 0 and 1(because it's not float) and realistic ior's are >1.
Go in the output settings of the IOR map in the max mtl editor and raise the rgb offset to one.
But I think the whole preset is obsolete nowdays.. Why not simply export the pbr maps directly and use them in vray?

[yaschancool]

Yes I used the IOR map. Thats pretty interesting, indeed.
Thats what I ended up doing, just exported the PBR roughness maps and made VrayMtl to use roughness. Solved it.

About that, it is little weird that I cant just connect Roughness to 'roughness" in VrayMtl as doing so does nothing. I have to expose the slots and instancing the map to the roughness there. In slate editor it still weirdly connects it to the glossiness map, although this seems to work.
For someone new this can be a show stopper, someone please fix that?

[Ihno]

The roughness parameter in vray is diffuse roughness it can be used to simulate dusty materials for example.
The glossiness is the one to use.
But in the Vray mtl unter BRDF change the radiobutton to "use roughness". This simply inverts the glossiness, so you can use roughness maps.

[yaschancool]

Thank you Inho!
So the diffuse roughness is not the standard PBR roughness, I see. So I can just plug in the roughness maps to the glossines and invert with the radiobutton.
Thanks for clarifying this.