what unit of angle in the file glTF?

Question

I'm trying to understand the format of glTF, tell me please what unit of angle in the file?

"nodes":[
{"name":"Bone2","rotation":[-0.6466940641403198,0,1.4359492797940017e-16,0.7627494931221008]},

Answer 1

Quaternion, looks like.

specification/2.0/schema/node.schema.json:

"rotation": {
    "type": "array",
    "description": "The node's unit quaternion rotation in the order (x, y, z, w), where w is the scalar.",
    "items": {
        "type": "number",
        "minimum": -1.0,
        "maximum": 1.0
    },
    "minItems": 4,
    "maxItems": 4,
    "default": [ 0.0, 0.0, 0.0, 1.0 ]
},