Specular map in the MeshStandardMaterial

Some 3d rendering engines support the use of specular maps. These are grayscale maps that range from 0 to 0.5 and that control the amount of specular highlight on different areas of the model. They are generated the same way AO maps are but are then mapped to the 0 to 0.5 range and their goal is to reduce specularity inside cavities and folds, which is a phenomenon that actually happens in the real world.
Sketchfab has this feature where the AO map can directly be used to reduce specular highlights.
Is such a feature available or being developed for Three.js ? Or is there any other shader hack that would allow me to reduce specular highlights through the use of a map, while staying inside a PBR workflow ? Thanks a lot, love three.js

I know this post says that specular maps and PBR workflows are redundant but they actually aren’t. Specular maps can reduce specular highlights (which is not the same as increasing roughness! (roughness spreads the specular highlights but it shouldn’t be spread it should only be darkened))

I think it would make sense to support specular on MeshPhysicalMaterial, the more advanced extension of MeshStandardMaterial. A version of that will eventually be supported in the glTF metal/rough workflow: https://github.com/KhronosGroup/glTF/pull/1719. I don’t think this is being worked on right now, though.

You’re right, it would make sense to add it to MeshPhysicalMaterial, especially since MeshPhysicalMaterial already supports reflectivity but it only takes a 0-1 float for argument. Adding something like reflectivityMap which would take a grayscale map as an input would be the solution. Is there a way I could add this reflectivityMap property on my own ? Thanks a lot!