{
    "nodes": [
        {
            "name": "skinning",
            "mesh": 0,
            "skin": 0,
        }
    ],

    "meshes":[
        {
        }
    ],

    "skins":[
        {
            "inverseBindMatrices": 12,
            "joints": [1, 2, 3 ...]
        }
    ],
}

SkinnedMeshRenderer.rootBone

This may not used as skinning root.

• Used as BoundingBox center. Relative to Update When Offscreen checkbox
• Used as skin bone for bones without weight