the AddObserver is member function of vtkObject, however when I try to do:<br>
<br>
spherePickTestActor-&gt;AddObserver(vtkCommand::RightButtonPressEvent,interactorCallBack);<br><div id=":11i">
spherePickTestActor-&gt;AddObserver(vtkCommand::RightButtonReleaseEvent, interactorCallBack);<br>
<br>
it does not work, I can only make callback of &quot;vtkRenderWindowInteractor&quot;<br>
and &quot;vtkInteractorObserver and its subclasses&quot; successfully worked,<br>
something like:<br>
<br>
renWinInteractor-&gt;AddObserver(vtkCommand::RightButtonPressEvent,<br>
interactorCallBack);<br>
<br>
is it the nature of the design or did I do anything wrong?  Please help and<br>
thanks a lot!<br>
<br>
<br>
Truly,<br>
<br>
<br>
Phoenix<br>
</div>