What is the underlying type of `orientation`?

The documentation says that it’s a “property, but Property is only an abstract class that is inherited by 7 different children, each with children of their own, none of which describe what I can assign to entity.orientation! By trial and error, I have discovered that Matrix4 works, Quaternion works, but Matrix3 doesn’t, (unless, maddeningly, you first construct a Quaternion from it). What is orientation actually stored as? Which frame is orientation relative to? How many licks does it take to get to the center of a tootsie-pop?

I believe Quaternion is the official type. I definitely agree it and other entity property types are sparsely documented. Transforms.headingPitchRollQuaternion is commonly used with this property and give you some clues about the default reference frames.

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Thanks so much @Gabby_Getz! Do you know which frame the orientation is with respect to? Physical accuracy is important to what I’m doing, so I need to make sure I have my reference frames straight. If there’s not an answer that anyone on the CesiumJS team is aware of, I can do some experimentation and get back to this post later.

The documentation commonly refers to “the ellipsoid’s fixed reference frame” as the reference frame which the entity API’s orientation is relative to, with the default ellipsoid being WGS84.

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