When will <model-viewer> support new material PBR properties?

[Dmitrijsmok]

Hey guys,
Is it possible to make model-viewer to enable/support Sheen.
This node is must-have for PBR fabric material
It is already supported for gLTF files and three.js:
https://threejs.org/examples/?q=sheen#webgl_materials_physical_sheen

[cdata]

In general we intend to support whatever Three.js supports regarding glTF. Three.js gains support for glTF PBR via updates to its GLTFLoader. Whatever the GLTFLoader produces,<model-viewer> will use.

Has sheen been specified and accepted for glTF? cc @donmccurdy

[donmccurdy]

Sheen is not specified in glTF yet, but it's coming.

Of the new material parameters planned for glTF, I think Clear Coat will be first.

[Dmitrijsmok]

Great, thank you, guys!