About mask maps textures

[Arex786]

As we all know, PBR textures bring the realism in the project. I want to know what channel, sh texture contains which PBR texture. 

e.g in Unity, a mask map contains a channel of RGB where R represent metallic map ,G represent occlusion map , B represents Detail mask and A represents Smoothness.

[silent]

Shading texture should contain following mappings:

Shading (R — metalness, G — roughness, B — specular) — for 3-channel shading textures (postfix: _sh)
Shading (R — metalness, G — roughness, B — specular, A — microfiber) — for 4-channel shading textures (postfix: _sh)

Thanks!