Do these metals exist in real life?

JordanN

Hey Polycount, I got a question regarding the roughness found in metalness.

COMPLETELY DISREGARDING non-metal/dielectric detail like rust,dirt,scratches etc, are there any real life metals that have completely blurred to no reflections at all?

See the middle and far right teapots as examples. 


I understand metal on its own is naturally shiny so I tend to use only the first teapot example as a base, but I wonder if there are examples for the other two or should I just ignore them?

ActionDawg

Metal isn't naturally shiny, it's naturally reflective. One of the things PBR aims to do is decouple the micro-surface's finish (roughness/gloss) from the amount of light that gets reflected, aka you can edit them independently as you theoretically could in real life. There's always a consistent amount of energy reflected no matter if the surface is shiny or as rough as possible.

So to answer the original question yeah, metal can get that rough, but it always maintains the same reflection unless it oxidizes. I can't think of any good examples offhand that reach the look of 100% roughness other than maybe really fine metal foam, but galvanized metal can be very rough.

radiancef0rge

Yes they exist. What is probably throwing your eyes off is the teapot on the right has no normal information. 
A very rough surface like such would have quite a bit of surface detail. Sand blasted metal would appear this way. 

JordanN

Interesting.

So I have one more question. Does this mean metal can have a range of roughness values depending on how beat up/or intertwined it is with other materials, or should there only be one constant value?

I remember this giving me trouble before when I made an oil barrel prop. Whereas I now understand the other residual factors like sand or paint runoff add depth and roughness, does the metal that partially comes in contact with these elements have its roughness changed or is it all still reflective?

Klawd

Of course it can, portions of it that have seen more friction will usually be more reflective. Paint on top of a metal piece will have its metalness and roughness properties, different from the material underneath, and they cover it. Same goes for sand, dust, dirt, and anything that you can find on a metal barrel.

radiancef0rge

So I have one more question. Does this mean metal can have a range of roughness values depending on how beat up/or intertwined it is with other materials, or should there only be one constant value?

Yeah, it can have lots of different roughness values, for example an area on the metal that was sand blasted may have a higher roughness than an area that was scratched with a stone. 

 does the metal that partially comes in contact with these elements have its roughness changed or is it all still reflective?

Sure, roughness can change. 

Two things to clarify based on your questions: 

• Its important to remember that referring to how rough or glossy something is - is not reflectivity. Reflectivity is Specular which should look like a material ID map. You should refer to the material attribute you are inquiring about as roughness, or glossiness. 
• Roughness is one of the maps you have more freedom with. Imagine you have a large piece of plastic and you scratch it with different objects, a knife, a rock, some sand. Each of those areas are going to penetrate deeper into the plastic. A light will dissipate differently in each of those areas. Another way to visualize this would be scratching the plastic with different number sand paper, the level of courseness of the sand paper will define how wide the highlight is. Because of this, you have the opportunity to use this texture map to tell your own story with that texture map as you can make up the narrative of the surface. 

I'm not trying to pimp my own work here, however it seems relevant to the oil barrel example. Albedo on the left, then specular, then gloss, then normal. Notice how simple the specular and albedo are, and then how much detail is in gloss and normal. 

Hopefully that answers some of your questions. 

zachagreg

Klawd said:

Of course it can, portions of it that have seen more friction will usually be more reflective. Paint on top of a metal piece will have its metalness and roughness properties, different from the material underneath, and they cover it. Same goes for sand, dust, dirt, and anything that you can find on a metal barrel.

I think this is the most important part. Think of the barrel as not just metal but all of the different materials that are present on the barrel as Klawd said each one will have it's on metalness and roughness values rather than one over the entire surface. The variation of these values on any singular object is what gives different light and surrounding reflections as well as visual interest. Best practice would be to look at the object and see how it the materials layer on top of each other and then mimic that in your texturing. Metal>Paint>Rust>Dirt, etc.