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Could someone explain metalness maps to me?

polycounter lvl 8
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Stirls polycounter lvl 8
My lead tells me they're a game-changer, and I'm not quite sure I have grasped the concept of them fully. What are the benefits of metalness compared to specular?

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  • Gazu
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    Gazu polycounter lvl 11
    I know that im not the most experienced polycount user, but i can tell you that the metallness map is the map which you can use to make parts of your map or the whole map look like metall.

    metall= white
    non metall= black

    Greetings
  • Stirls
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    Stirls polycounter lvl 8
    Experienced PC or not, it's still helpful. Thanks for the reply. I figured that both could be used, but the game is mostly metallic stuff!
  • stevston89
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    stevston89 interpolator
    Some background first. The metalness map was made to save the use of another full color map for specular/ reflectance. Metal has no diffuse so for the most part when texturing metal you can put black in the diffuse. Also most every other material except metal falls with in the same specular intensity. So the made the metalness map.

    First what it does is it take the metal area ( white in the metalness maps) and it makes the diffuse black. Then it takes what you paint in the diffuse in the metalness areas as the specular power/color control. Everything that is not a metal gets a standard specular power and no color.

    To make maps using this you simply use the metalness map to separate out what you want to be a metal. Then in the diffuse instead of paint diffuse for the metal you paint what you want for the specular power/ color. The mask should pretty much black and white. If you have gray values you will get some weirdness.
  • JedTheKrampus
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    JedTheKrampus polycounter lvl 8
    Also note that in a few cases a grey value for metalness is OK and should be considered, e.g. if your material is a copper patina it will probably be somewhere in between. But don't quote me on that! :p
  • EarthQuake
    Also note that in a few cases a grey value for metalness is OK and should be considered, e.g. if your material is a copper patina it will probably be somewhere in between. But don't quote me on that! :p

    Generally rust, patina, any sort of heavily oxidized metal can be represented as a non-metal, and shouldn't use grey values. A transition area between raw metals and oxidization makes sense, but rust etc can easily be considered as a non-metal, think of it more as "used to be metal".
  • passerby
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    passerby polycounter lvl 12
    Or think of rust like paint, it is covering the metal so is non metal
  • sargentcrunch
  • EarthQuake
    perna wrote: »
    I see how people can get confused when there's this sort of cross-talk going on.

    People here are saying "rust", yet talking about different effects.
    Sure, a surface that is 100% rust could get away with not using metalness, but you have surfaces that are lightly rusted, with metal showing through, and you have streaks of rust running down pure metal surfaces as well, and these all need grey values.

    I think the only real difference is I'm talking about it in terms of materials, ie: X pixel is A material and Y pixel is B material, while you're talking specifically about a certain effect. Depending on the effect, the transition area may be wider or smaller, or stronger/weaker, though generally even a light coating of oxidization on top of metal means its going to reflect like an insulator, not a raw metal. I definitely agree that without some grey values, transitions between certain types of effects can be really harsh.

    Looking at reference here, in the majority of cases where you would see rust leaks, the leaks are going to be on painted metal (metals that rust easily tend to be painted), so its non-metal(rust), and non-metal(paint), though of course there could be a few spots of freshly chipped paint where the metal has not yet rusted, which would make sense to tag as metallic.

    Often times if you've got a bare metal that has sat out long enough to show significant rust, even in the areas where its not clearly "rusty" will tend to be worn/oxidized enough that you should be able to get away with tagging it as a non-metal, as the difference in reflectance between that and a raw, bare metal is quite big, and these sorts of materials tend to have a lot of diffuse detail (gunk built up over time etc). One of the big problems using a partial metalness value in those situations is now you're depending on the albedo to be both diffuse and specular, which often require opposite or at least totally different values. Full color spec tends to be more flexible if in these cases.

    Per: It would be cool if you could post an example of a case where you can only represent a certain type of material with grey metalness values, as I'm struggling to think of a real compelling example. I've often mentioned that it can sometimes be ok to use gray values, but I always struggle to come up with a clear example why.

    GoddessofCopper.JPG

    Maybe something like this, but even here when we break it down to the pixel level, most of the texture would be 0 or 1 with some grey values in the transition areas from copper to patina. Even in the patches that the patina isn't as strong, those can generally be represented as a non-metal.

    Perhaps a material where the oxidization/material buildup is so small/light that it only creates minor variation, in which case I think you could probably just tag it as metal, and add the variation into the abledo (and probably gloss) inputs to show that effect.
  • s6
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    s6 polycounter lvl 10
  • ZacD
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    ZacD ngon master
    What about when you have a dried colored liquid on a metal, like a stain, or oil, something that is going to be somewhat transparent.
  • EarthQuake
    perna wrote: »
    So, you'll have rust forming in a "noise" pattern. When observing this with a microscope, we'll see microscopic dots with very low metalness in areas of very high metalness. Of course, when we zoom out, these merge and become partial/transparent/transition pixels, which of course can't be represented without partial values... unless we "cheat" with the other maps, of course, but that's still a cheat and a workaround, and not a true representation of what happens in the real world.

    Yeah absolutely, we won't ever really have the resolution to represent how fine the granularity is between different material types, so you'll often want some mid-values for transitioning between metal and rust. I agree with pretty much your whole post here, I think any differences we've got are down to semantics etc.
  • Stirls
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    Stirls polycounter lvl 8
    Good to see I've inspired some very interesting conversation here. Starting to get a grasp of how it works.

    My characters I've designed for this game boast very colourful sets of armour on the diffuse, and I'm being told that metalness will work best for these guys. However, a few posts I've read here say that it mutes the diffuse/albedo.

    I am having a bit of trouble getting a nice metalness map going. Any tips?
  • EarthQuake
    Post some images of what you're having trouble with, its hard to give any tips if we don't know what the problem is.

    As far as colorful sets of armor, that is very vague. Are they colorful because they are copper, brass, gold? If so, metalness should be 1 and you should have the appropriate specular color for those materials in the albedo. If they are colorful because they are painted, then that would be a metalness value of 0.
  • passerby
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    passerby polycounter lvl 12
    for your mid values, i would still use a pure white on your metallic map, since that makes the same areas of your albedo map, act like a reflectance map. So you can get your midtones by using a lower value on your albedo on metal surfaces.
  • oXYnary
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    oXYnary polycounter lvl 18
    What about grey for metal discolorization. Not from rust, but say heat.
    bho2.jpg

    That transition area especially..
  • passerby
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    passerby polycounter lvl 12
    personally if i was usign the metalness workflow for that i would declare metal in the metallic map, but lower the discoloued parts in the albedo/reflectance and colour them there.

    I find these are cases where the metalness workflow gets to be a pain in the ass, since you got no way to manage reflectance and albedo at once.
  • 3D4D
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    3D4D polycounter lvl 6
    Hi
    Please help, im a bit new to this. I've been looking a marmoset toolbag. Is a Reflectivity map the same a Metalness Map, they are listed as the same tab. I've been looking at there "material values chart" and Reflectivity values dont seem to range from white to black like they would when creating Metalness Maps
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