How can I copy camera transform to an actor ?

Hello,
I want to have an actor thet represents the camera with the same orientation and position than the camera.
I would like to attach objects to this “root camera” actor to simplify the positionning of different elements that needs to be attached to the camera.

I have tried to get the camera orientation and position and affect it to the vtkActor but it is not working. A simple cube attached to the “root camera” actor is not staying at the good place.

So, can you tell me how to do that ?

Thank in advance