I need to use some textures made in the Specular-Glossiness workflow in the MegaSplat terrain asset, but it turns out that the asset is only compatible with the Metallic-Roughness workflow, and the creator told me there is no simple way to convert a gloss map to a roughness map because gloss i not a PBR concept? (i did not know that)
Isn’t Gloss map just a different name for Smoothness map, which is just a different PBR workflow?
Is there any really good tutorial on how to convert a gloss map to roughness? (I’m not skilled at photoshop (like at all…))
I also don’t know how converting from Specular to Metalic is done but i understand it’s easier with certain pieces of Software?
Plz help 
I’m not a pro about the subject, but I think this video has the information you are looking for. He talks about gloss map near the end 1/3 of the video but the information in the entire video is good knowledge to have.
They explain it in this post:
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If you use Substance Painter, you can use this filter:
The really simple way to do it is to invert the gloss map and use this for Roughness - you may need to do a bit of an adjustment on the levels to get it to look perfect. Keep in mind that a rough surface (like rock or bricks) will have more white in it and a smooth surface like glass or chrome will be completely black or close to it.
The specular map usually has the metallic highlights in it (scratches and nicks) so you can also Add this to the gloss map before you invert it if you want to get those extra details in there. It depends on how well the specular was created, but overlaying them works pretty well to get the right blend. Any area that is scratched in a specular map should be highlighted in white, but in a roughness map this would cause them to not shine, so you want them to be black hence overlay and then invert. It kind of depends on whether you want the nicks and scratches to catch the light, or be dull. If you want them to be dull, then you would want to invert the spec before overlaying.
Then for metallic, anything that is metal should be pure white, anything non-metal is black. It’s really that simple. A lot of people will use the metallic to try to tweak the look of their roughness map by using a greyscale texture, but you shouldn’t do it that way as it is physically incorrect. A metallic or metalness map should always be black and white as there aren’t any materials in the real world that are partially metal. If it doesn’t look shiny enough, then you adjust your roughness map to be darker in those areas and it will, in turn, make the metal shine more and vice versa.
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Probably searching for Substance Designer tutorial and making it using notes.
I wanted to update my post here with a VERY simplified version of getting a roughness out of your specular and gloss textures:
- Add the Specular map (Linear Dodge) to your gloss map.
- Merge the layers and invert them.
- Remove the color (saturation = 0).
**Pay attention to how the specular looks before combining because sometimes the better option is to Multiply the specular with the Gloss which will stop it from blooming too much. In a specular map, the brightest areas are shiny but in a roughness map, the dark areas are so make sure the white parts from the specular are darker in your roughness (keeping in mind the gloss will flatten out some of the values).
My original thought that Metallic should only be black and white isn’t quite right because you can use greys to control the intensity. Technically this should be done with the roughness to be true PBR, but it’s an easier way to tune your materials artistically. You’ll notice that Substance will create greyscale metallic textures, not just black and white.