This thread seems to relate to a similar or related issue: Another gltf import question - #9 by derelict
From reading that thread I get the sense that importing GLTF and using files is a bit of a hassle.
This ‘sideOrientation’ parameter has barely any documentation, this is all the info there is be it in Material, MeshBuilders, etc.
https://doc.babylonjs.com/typedoc/classes/babylon.material#sideorientation
sideOrientation: number
Stores the value for side orientation
So, yeah, alright we know it’s of type number, and kinda vaguely what it is/does. Any info on how to actually use/set/get this parameter?