Author Topic: Specular vs Metalness: Interchangeable Gloss/Roughness maps?  (Read 367 times)

Hi there,

I've been doing some research on the differences between Specular and Metalness and I have a good understanding now of their pros and cons.

My question; In general are the gloss maps from a specular workflow generally interchangeable/sufficient as a roughness map (after inversion) for a metalness workflow or does the missing specular/reflection map contain too much needed information? Is it a case of 'depends on the artist that made the maps' or a more generalised thing?

Would I be able to take a bunch of materials made in the specular workflow and use them in a metalness one by just ditching the specular map and inverting the gloss map? (Obviously speaking dielectric mats, not metallic).

Thanks for any insight you may have.

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Would I be able to take a bunch of materials made in the specular workflow and use them in a metalness one by just ditching the specular map and inverting the gloss map? (Obviously speaking dielectric mats, not metallic).

This is correct.
In the roughness workflow all dielectrics are given the same standard specular value automatically, so you can indeed ditch the specular map entirely for dielectrics.

And roughness is indeed the exact inverse of Gloss. In designer you can just use an invert grayscale and that's it.
But you have to be careful when inverting roughness in other software like photoshop. Photoshop automatically applies gamma correction (when using default color management settings), so you can end up with incorrect results here.
Esger van der Post.
Game design student and texturing addict.

Hey, thanks for getting back to me.

My concern is that in some cases, there appears to be a lot going on in the spec maps. I have to assume that the artist did that for a reason? Is it possible for someone using the specular workflow to rely heavily on the spec map rather than the gloss for a lot things? Therefor wouldn't removing it lose a lot of the 'magic' of the material?

There shouldn't be an awful lot going on in the specular map of dielectric materials, other than very subtle changes in color and brightness. But you will indeed lose these subtleties when converting to metallic. That's the downside of the metallic workflow.

If you're seeing bright colors on the specular map, than these are metals, and these parts should be converted as such to the basecolor and metallic maps. Unlike dielectrics, these metallic areas rely a lot on the color of the specular map. That's why these colors get transferred to the basecolor in the metallic workflow.

There's a nice article about this by marmoset btw, in case you haven't seen it already. https://marmoset.co/posts/pbr-texture-conversion/#spectometal. They refer to dielectrics as 'insulators' btw.

Esger van der Post.
Game design student and texturing addict.

Thanks Bud, that article is great actually. I think it'll answer any remaining questions I have.

Thanks a lot for your help.

Regards
Bill