VelocityOrientationProperty reference frame?

Does the VelocityOrientationProperty compute the quaternion in ECF (Earth Fixed Frame)? I want to have my model point along the velocity but cancel out the pitch so that the model does not nose up/down when changing altitude. I’m having trouble getting the correct result and I don’t know if my original assumption of the reference frame for the quaternion is correct.

Yes, it is using the fixed frame. You should be able query VelocityOrientationProperty for the quat, turn it into HPR with HeadingPitchRoll.fromQuaternion set the pitch to 0 and then get a Quat back via Quaternion.fromHeadingPitchRoll

Ok, good. The process you described is what I’m trying to do but if I directly convert the quaternion to HPR; isn’t that HPR relative to the fixed frame still? Don’t I need to take the original quaternion and represent that in eastNorthUp first so that I can cancel out the pitch in eastNorthUp?

The entity’s position property will also contain a reference to the reference frame. That’s the reference frame that the original Quaternion will be in.