PBR damascus steel

electricsauce

I'm trying to make a pbr damascus steel material, but I'm a little stuck. Something about it doesn't look quite right and I don't have a sample nearby to reference. Anyone have any ideas on what I can improve? It's rendered in UE4 with a diffuse(only 2 colors), normal and roughness maps, and metallic set to 1. Thanks.

ZacD

First thing is it looks shiny and smooth.

Second I don't really see 2 major difference layers, it looks like there's grooves cut in, but not 2 different materials or layers.

Maybe lower the first try having a different values for BaseColor and Roughness, if that's not enough, use a texture for the metallic and try having it at 1 and .8.

Futzy

Looking at an image of this, it looks like you could define the striations - the very rough, contrasting gaps.

I don't know how you went about create the textures for this, but I played around with PS's clouds for a bit and came up with this, which also has the benefit of not needing to worry much about tiling the mess that's to be created.



Having the masks like this gives you freedom to do all sorts of stuff to take it further.

ZacD

Get rid of the normal map, or turn it way down. The surface is pretty flat.



I didn't read enough about damascus steel to learn if the darker material should act like a metal, I assumed it would act a bit like rust where it's a mix, but if you don't like that, lower the metalness of the darker bands.

ZacD

Sorry, I'm sleep deprived and I'm really messing up with the exact values, this looks better I think... I'll play with it more and try to get more physically correct values and things make sense.

s6

Damascus is created by combining two or more different metals in layers and compressing them together with heat, repeatedly folding and compressing it (among other methods). I believe Damascus was originally a single metal with unique properties, but all the reproductions of it aim to "mimic" it's visual qualities. To achieve this effect people purposely choose two contrasting metals.

My point being: In reality this surface is made up of two different metals, so it should be recreated in the same fashion. I don't have time at the current moment to make an example, but Zacs seems to be on track.

As ZacD said as well, your normals should be completely smooth or VERY faint. People usually make Damascus ingots then forge something out of it. When they forge, they tend to polish it afterwards to get a really smooth surface. Unless the surface hasn't been polished entirely and you have high and low spots kind of like wood grain.

almighty_gir

just doing a readup on wikipedia, it seems like the wave pattern is caused by nanotubes of carbon in the steel, which arrive due to using wood and leaves to help coke the metal as it's being made.

So replicating this "could" be as simple as just putting the waviness in the metalness map. In fact i wouldn't be surprised if this was the case.

electricsauce

I've noticed that there seems to be two distinct pattern types of the steel. One is very linear like the knife posted by futzy above, and the other has repeating circular patterns like this:




I removed the normal maps and toned the roughness way down. My understanding is that the metal setting should be 1 or 0 so I left it at 1. I made my maps by deforming a circle in substance designer so everything is tileable. Are the different types of steel differentiated by carbon content, or are there other minerals added in during the smelting process that change the physical characteristics of the metal?

EarthQuake

What Lee says makes sense. If the metal is polished to the same degree, really there should be no variance in the roughness.

almighty_gir

hehe so this will probably bake your noodle with regards to metalness:

Steel is not a "pure" metal, Steel is a combination of Iron and Carbon, a metal and a non-metal.

Now, generally speaking it's dense enough that metalness = 1 is true of steel. but if the waviness in damascus is down to visible carbon, or at the least, highly carbonised steel (which is probably more true than raw carbon, which would be too brittle) then you wouldn't want to use metalness = 0 for the carbon sections, use a grey value of your liking that helps get the look you're going for.

s6

I think it's important to differentiate between actual Damascus and the replication of it. The majority of Damascus I've seen isn't actually Damascus, but a replication.

http://www.minnesotafarriers.com/Damascus.htm

The pattern of Damascus all depends on how its forged. If it's only layered steels with different carbon levels, you will get a fairly linear pattern. If its twisted and compressed, you will get a more organic looking pattern. The more layers you use and compress the finer the "grain" will be. The less layers, the thicker it will be.

In any case, if you're going for the common type of Damascus, it should be as simple as defining two different types of metal in the same map.