Problem With Metallic PBR: Doesn't Look Like Expected

[Aleksei]

Hi!
I'm exporting textures from Substance painter for Metallic PBR workflow. I and see inconsistency in look of materials when rendering it with Octane. Which, I thought, should be impossible in a true PBR workflow.
In particular, I've noticed problem with the roughness channel. I export it from Substance Painter as 16bit grayscale image with Linear profile:

Setting for roughness channel in Substance Painter

01.png (5.33 KiB) Viewed 1937 times

In Octane I add this texture to the Universal material like this:

Import settings in the Universal material

I here I set Gamma to 1, because it's Linear profile. But, to say the truth, I'm always confused with those profiles. That's why I also tried 2.2 gamma. And here are the results:

Reference look in Substance Painter (pay attention to the roughness):

Reference look

Roughness gamma 1:



Roughness gamma 2.2:



As you can see in both cases (gamma 1 & 2.2) there is no match to the original PBR look from Substance Painter. But this cannot happen in the PBR. That's why I think maybe I'm doing something wrong at some stage? Please, advice.

Of course, by trial and error, while manually adjusting the channel's gamma I could achieve the material look which is close to the reference one. I've stopped at 1.5 gamma. But why 1.5? This is not how the PBR workflow should look like.

Roughness gamma 1.5 (random guess):

[funk]

Are you setting the BRDF/BSDF to GGX?

[Aleksei]

Em... no. Should I? And what's that?

[funk]

Em... no. Should I? And what's that?

Yes you should. It's under Universal material > BSDF.

[Aleksei]

Yes you should. It's under Universal material > BSDF.

Oh, wow, thank you. It works perfectly. Now I see why I didn't know about that: unfortunately, they didn't cover this setting in the Octane Documentation for Universal material (for Cinema 4D) which I read. Just now I found one mention of the GGX very well hidden in the tutorials.

[funk]

Great! I'm glad that sorted things out for you