Rotate a parent object so that a child's rotation matches a given rotation value.

Unity Engine
1

I have a setup where I have a game object that has an empty game object as a child. The child is at a different world rotation from that parent. What I want to do is rotate the parent so that the child’s rotation matches a given rotation value (I get that rotation value from a different empty game object).

I think this can be done using the Quaternion math, but I have no idea how to do it. Any tips would be appreciated!

Thanks,
Zach

2

If Qc is the child’s world Quaternion, and Qto is the quaternion that you’re trying to match the child’s orientation to, and Qp is the parent’s current world quaternion, then…

Q’p = Qp x (Qc-1 x Qto)

Quaternion Qto; // Rotation to match the child to.
parent.rotation = parent.rotation * (child.Inverse * Qto);
3

Edit: I got it working. I think what I’m seeing is an affect of how I’m calculating the rotation to match.

Thanks for your help!!

4

Sorry to bring this thread back from the dead, but is child.Inverse the same as Qaternion.Inverse(child.transform.rotation)?