[vtkusers] Multiple Rendering Windows Sharing a Common Camera (Interactor)

[Chih-Wei Chiu]

I want to have many scalar/vector fields rendered in their own rendering
window, but they all use the same camera. That is, when I roate the camera
in one window, the other windows rotates simultaneously, and vice versa.

It seems impossible under current VTK implementation, since an interactor
can only have one rendering window
(vtkRenderingWindowInteractor::SetRenderingWindow() instead of
vtkRenderingWindowInteractor::AddRenderingWindow() ).

What should I do?