I'm trying to parent a packed object from sops to a packed fragment from a dop sim. essentially, it should follow the simulated position and rotate around and with the centroid of the simulated fragment.

I can use rest position to get the position to follow how I want it to. I can also use a centroid expression to get the center of rotation.

But I don't know how to get the packed object to rotate with the the fragment from the sim.

The sim gives me an orient attribute which is a vector4. and I tried to use the quaternion to angle/axis in vops but it only kind of works the the object doesn't rotate on the Z axis.

I guess I need a way to turn that vector4 into a 3 float vector that uses degrees so I can reference in a transform node roatation vector.

You should use the Transform Pieces sop. Here's a scene

Thanks that looks like it could be very helpful. I'll give it a shot as soon as I can.