Various Coatings on Metals in a Metalness UE4 Workflow
polycounter lvl 3
I've read through the PBR bible stickied here; it's fantastic and has helped a lot. The majority of my work, both at work and at home, is making weapons or vehicles, and as such I deal with a ton of different metals and their coatings, and I'm getting hung up on what is a "metal" and what is not. I'm hoping you folks can help.
(imgur is blocked here, sorry for links instead of embedded images
)
Bare steel - http://www.steadfastcycles.com/cart/images/$(KGrHqF,!h8E2I+UCyWsBNvIoSGMD!~~_12.jpg
This would get a value 1 (white) in the metalness map because it's bare, exposed steel and the diffuse map would be have light grays and some variance. I don't know the numbers, but it would be in the lower values for roughness, being fairly glossy, but not enough to get a mirror finish.
'Hydrated Iron Oxide' aka Rust - http://www.allmacwallpaper.com/get/MacBook-Air-13-inch-wallpapers/Rusted-metal-1440x900/1778-4.jpg
At the risk of sounding pretentious with fancy names, it does make a difference as rust is not the only iron oxide. More on that in a bit. Anyway, the rust itself here would get almost a 0 in the metalness map, **maybe** a bit of value for the thinner parts. Some of the raised bits of tread aren't rusted and would get close to a 1 here. The diffuse would be orange-red-browns for the rusted areas, and the exposed metal pieces should be a mid-to-light grays for the steel underneath. Roughness is near white for the rust and darker for the still-shiny bits of steel poking through.
Hopefully I'm on the right track here or I'm in bigger trouble than I thought. So now we get to where I'm having trouble.
Bluing - http://www.employees.org/~beetle/guns/33b.jpg
This is also an iron oxide similar to rust but chemically different, named 'magnetite.' Where does this go on the metalness spectrum? Iron oxide is not a conductor, but I've had some good results putting some value in the metalness map and I don't know why. There are also a bunch of different kinds of bluing yielding a bunch of different results: https://en.wikipedia.org/wiki/Bluing_%28steel%29 what would you guys do for some of these materials?
Parkerizing - http://www.hallowellco.com/colt1911-887377-left.jpg
Parkerizing is a phosphate oxide and after studying it for awhile, I'm a bit surer in my opinions that it should not be in the metalness map, though again, I've had good results with slight above zero values here, it makes it feel a bit 'wetter' and 'alive,' but I'm curious what you all do.
Anodizing - https://en.wikipedia.org/wiki/Anodizing#/media/File:Cheap_carabiners.JPG
Mostly used on aluminum, anodizing creates a thin even coat of aluminum oxide on the surface of the metal. It's also more porous than pure aluminum, and can accept dyes of various colors. What would you all do for something like this? My inclincation is to call this 'metal' and put it in the metalness map; if I didn't, how would I distinguish this piece from a shiny piece of blue plastic next to it?
Galvanizing - https://en.wikipedia.org/wiki/File:Galvanized_surface.jpg
Usually steel dipped in molten zinc, how would you treat galvanizing? The crystal shapes here can range from an inch or so to microscopic (http://shabbirtoolsmart.com/wp-content/uploads/2015/03/hot-dip-galvanized-bolt-nut-500x500.jpg) like here. Zinc is technically a metal, though the pictures here make it seem like light doesn't treat it like one. Maybe that's just because its really rough and it's hard to tell?
There are a bunch of other kinds of coatings I'm still trying to research - the most pressing right now are the ones on this M2 machine gun I attached here (couldn't re-find the link). It looks like a parkerizing, though without being certain, I'm having a tough time replicating it. What do you all think?
(imgur is blocked here, sorry for links instead of embedded images
)Bare steel - http://www.steadfastcycles.com/cart/images/$(KGrHqF,!h8E2I+UCyWsBNvIoSGMD!~~_12.jpg
This would get a value 1 (white) in the metalness map because it's bare, exposed steel and the diffuse map would be have light grays and some variance. I don't know the numbers, but it would be in the lower values for roughness, being fairly glossy, but not enough to get a mirror finish.
'Hydrated Iron Oxide' aka Rust - http://www.allmacwallpaper.com/get/MacBook-Air-13-inch-wallpapers/Rusted-metal-1440x900/1778-4.jpg
At the risk of sounding pretentious with fancy names, it does make a difference as rust is not the only iron oxide. More on that in a bit. Anyway, the rust itself here would get almost a 0 in the metalness map, **maybe** a bit of value for the thinner parts. Some of the raised bits of tread aren't rusted and would get close to a 1 here. The diffuse would be orange-red-browns for the rusted areas, and the exposed metal pieces should be a mid-to-light grays for the steel underneath. Roughness is near white for the rust and darker for the still-shiny bits of steel poking through.
Hopefully I'm on the right track here or I'm in bigger trouble than I thought. So now we get to where I'm having trouble.
Bluing - http://www.employees.org/~beetle/guns/33b.jpg
This is also an iron oxide similar to rust but chemically different, named 'magnetite.' Where does this go on the metalness spectrum? Iron oxide is not a conductor, but I've had some good results putting some value in the metalness map and I don't know why. There are also a bunch of different kinds of bluing yielding a bunch of different results: https://en.wikipedia.org/wiki/Bluing_%28steel%29 what would you guys do for some of these materials?
Parkerizing - http://www.hallowellco.com/colt1911-887377-left.jpg
Parkerizing is a phosphate oxide and after studying it for awhile, I'm a bit surer in my opinions that it should not be in the metalness map, though again, I've had good results with slight above zero values here, it makes it feel a bit 'wetter' and 'alive,' but I'm curious what you all do.
Anodizing - https://en.wikipedia.org/wiki/Anodizing#/media/File:Cheap_carabiners.JPG
Mostly used on aluminum, anodizing creates a thin even coat of aluminum oxide on the surface of the metal. It's also more porous than pure aluminum, and can accept dyes of various colors. What would you all do for something like this? My inclincation is to call this 'metal' and put it in the metalness map; if I didn't, how would I distinguish this piece from a shiny piece of blue plastic next to it?
Galvanizing - https://en.wikipedia.org/wiki/File:Galvanized_surface.jpg
Usually steel dipped in molten zinc, how would you treat galvanizing? The crystal shapes here can range from an inch or so to microscopic (http://shabbirtoolsmart.com/wp-content/uploads/2015/03/hot-dip-galvanized-bolt-nut-500x500.jpg) like here. Zinc is technically a metal, though the pictures here make it seem like light doesn't treat it like one. Maybe that's just because its really rough and it's hard to tell?
There are a bunch of other kinds of coatings I'm still trying to research - the most pressing right now are the ones on this M2 machine gun I attached here (couldn't re-find the link). It looks like a parkerizing, though without being certain, I'm having a tough time replicating it. What do you all think?