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I've searched all over the internet for this and nothing has come up. Everything is about spec maps which I don't want.

I would like to know how to apply a gloss map to a material in Blender Cycles.

I have a marble texture with an image texture input to a diffuse texture, and a glossy shader with a white colour. Both are being put into a mix shader.

I have downloaded a gloss map but I don't know how to apply it.

Any help would be greatly appreciated.

Thanks in advance.

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A gloss map is a map of specular power, the inverse of a roughness map. Read it as non-color, then subtract it from 1 (but see below) via a math node and plug it into the roughness value of any/all shaders.

There is no single, standardized format for gloss/roughness/specular power-- there are instead a lot of different ways to map from color to gloss, depending on engine. So in order to use a gloss map correctly, you have to know the engine for which it was made, and then you have to know how that engine interprets gloss.

Or you could just wing it. Start with the simple inversion I mentioned above.

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  • $\begingroup$ Isn't a specular map a map of "specular power"? Meaning, the specular map is how much light is reflected and the glossiness map is how clear that reflection is, right? The roughness map is the inverse of the glossiness, it's how foggy the reflection is. I usually just plug the glossiness in an "invert" node and then plug it in roughness, usually looks fine. $\endgroup$
    – Alexandre Marcati
    Commented Sep 20, 2021 at 3:01
  • $\begingroup$ @Alexandre Marcati "specular power" is a measure of how clear the reflection is; the word "power" comes from specular equations like C*dot(normal, half-vector)^P where S is specular color and P is specular power, acting as surface smoothness. The specular color in those situations directly (linearly) controls how much light is reflected. $\endgroup$
    – Nathan
    Commented Sep 22, 2021 at 15:08
  • $\begingroup$ I see... But if the glossiness/roughness map is a map of specular power, what is the specular map? $\endgroup$
    – Alexandre Marcati
    Commented Sep 22, 2021 at 16:09
  • $\begingroup$ @AlexandreMarcati It is typically a map of specular color-- the C term in the equation I gave above. (There are occasions when it might be a mapping of Fresnel response, as when it is used as the input to a Specular input on a Principled BSDF.) (Oops, I called it both S and C, but too late to edit.) $\endgroup$
    – Nathan
    Commented Sep 22, 2021 at 16:22

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