Metalness Outline

ghaztehschmexeh

So I get this weird thing happening when I use metalness maps. It appears as a white outline around metal areas. It's especially more annoying in areas where metal/non-metal is quite noisy (rubbed, worn areas etc). I thought maybe it was to do with areas which were accidentally not 0 or 1 (partially translucent brushes); clamping the levels improves the outline slightly but degrades the quality overall. Interestingly enough I don't see this issue at all in substance painter. Any way to fix/reduce this?

Thanks

pixel.DW

This is a known artifact that comes with working with metalness/roughness. It is more noticeable the lower the texel density. Unfotunately there's not much you can do other than increasing your texture resolution.

I highly recommend checking out the Allegorithmic PBR Guide. It answers this question and a bunch of others.

EarthQuake

Yep, this is a problem with the metalness workflow, and storing both diffuse and specular content in the same map.

More here: http://www.marmoset.co/toolbag/learn/pbr-conversion

ghaztehschmexeh

ah I thought it might be. Why do I not notice the effect in substance painter then? Perhaps it doesn't actually use a metalness map, I have only played with it a little. Increasing the resolution isn't really an option, it's already at 4k guess I'll swap to a reflectivity workflow.

Fabian Fischer

ghaztehschmexeh wrote: »

ah I thought it might be. Why do I not notice the effect in substance painter then? Perhaps it doesn't actually use a metalness map, I have only played with it a little. Increasing the resolution isn't really an option, it's already at 4k guess I'll swap to a reflectivity workflow.

It's not that much noticeable but the Spec/Gloss workflow also have those borders. They are black instead of white but they are there.

ghaztehschmexeh

Fabian Fischer wrote: »

It's not that much noticeable but the Spec/Gloss workflow also have those borders. They are black instead of white but they are there.

Well if that is the case it probably won't show too much on this weapon because of the black paint. Shouldn't take too long for me to convert because I'm using dDo to manage my PS documents.

EarthQuake

Fabian Fischer wrote: »

It's not that much noticeable but the Spec/Gloss workflow also have those borders. They are black instead of white but they are there.

This has not been my experience. Do you have some reference to show this?

From what I understand, the cause is storing both content types in the same texture, and the interpolation at the edges causing the issue. As the specular worklow uses explicit maps for both albedo an reflectivity, there is no edge artifact problem.

From the tutorial linked above:


I don't see any black lines here. You can see some dark shading along certain edges, but that comes from the normal map detail (there is a slight bevel there), the same is visible in the metalness content as well.

Jerc

It's less visible on a surface that's already dark like in your example but if you do it on a rather bright surface, you'll see a darker outline on a smooth transition from non metal to metal:



The diffuse is getting darker on those edges and the reflectivity is getting brighter, so you end up with the same issue as when transitioning from metal to non metal with the metalness workflow. It's arguably less noticeable than the white outline you get with metalness depending on the asset though.

ghaztehschmexeh

Thanks for all the great info. In this case I will swap to using reflectivity. Obviously when using a specific engine you don't really get a choice. In those cases I guess you would just have to place scratches etc strategically so they aren't too close to the camera?

Swizzle

If you're using antialiasing in your metalness map, you can often do a levels adjustment to fake it so that the halo around the metal parts is less visible. This can lead to other small artifacts (such as a halo of highly reflective non-metals), so I'd suggest using it sparingly.