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Why did U4 use roughness/metallic vs Specular/Glossiness?

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    #16
    When describing PBR which uses Metallic/Roughness it just makes more sense and its a good way to help re-train for PBR thinking, it's good not to think that those two maps are just splat the Spec/Gloss maps in, you can almost get away with inverting the Gloss for Roughness but it is a different way of thinking and its good to break from the old way and have a new 'Standard', I sense that the Metallic/Roughness is the one that is gonna stick. I am a Unity Alpha/Beta tester and I have had long conversations about changing the naming in Unity 5

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      #17
      Based off a a podcast I heard with some of the Marmoset guys (I believe there was an Unreal representative present) they stated that roughness / metalness and spec / gloss are interchangeable terms for all intents and purposes. They chose to change the names primarily to keep from confusing people over which shading "standard", if you will, is in use. Roughness / metalness are just more accurate descriptions of what is happening with real materials.

      Please correct me if this is spreading misinformation, but it was my understanding of what they said. (Couldn't locate the link for that podcast... )
      Last edited by Kadeschui; 08-26-2014, 01:25 PM.

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        #18
        The biggest different though is in the usage and why the naming is important.

        Glossiness 0=not glossy, 1=glossy
        Roughness 0=not rough(glossy), 1=rough (glossy)

        Specular is a not well defined process, you can use it to change specular colour and intensity
        Metallness is quite different from specular colour in that it defines where the specular colour inherits from the underlying albedo where the intensity is a function of the energy conservation of PBR

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          #19
          There are some notes from the 'Real Shading in Unreal Engine 4' presentation at Siggraph 2013 which should provide some insight. Check out the 'Material Model' section on page 9 which discusses the reasoning behind 'Roughness' and the omission of the 'Specular' parameter.

          It's available from the excellent https://www.unrealengine.com/resources page (or directly from https://de45xmedrsdbp.cloudfront.net...s-26915738.pdf).

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            #20
            Originally posted by AdamZ View Post
            Why did Unreal choose one over the other?
            Couple reasons I imagine. Metal/Rough are both gray scale images in PBR. Spec/Gloss in a PBR workflow requires that Spec be RGB. This is because it's Diffuse texture only holds the color information for non-metals and is black where it's metal. The Specular texture is black everywhere except where the metal is, then displays the color of the metal where there is metal. That is two extra channels, and more confusion.

            The other reason is Base Color/Albedo. Metal/Rough enforces a strictly PBR safe color texture. Spec/Gloss as a shader is still somewhat behind, even as a PBR workflow, if only because it relies upon the old Diffuse shader.

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              #21
              Metal/Roughness, has its benefits, but it also limited our ability to create materials that doesn't exist in reality. And I believe a lot of people really like to do that.
              Brent Liu
              ::TeaCrab::
              https://www.artstation.com/artist/remotecrab131

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                #22
                Yeah, metalness saves texture memory vs the specular PBR workflow.

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                  #23
                  Originally posted by RemoteCrab131 View Post
                  Metal/Roughness, has its benefits, but it also limited our ability to create materials that doesn't exist in reality. And I believe a lot of people really like to do that.
                  Yep, we even thought about go back to UE3 for this...

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