Raw list of all features is on the API:
- PBRMaterial - Babylon.js Documentation
- PBRMetallicRoughnessMaterial - Babylon.js Documentation
- PBRSpecularGlossinessMaterial - Babylon.js Documentation
Visualizing exportable channels from 3D modeler could be (in theory) seen on the exporter doc’ (example with Maya), but it’s possible some informations are still lacking (for Blender exporter doc’ it’s the case - for Blender 2.8 it’s normal as it’s still in beta).