[vtkusers] Cameras in vtkQGL and vtkandqt compared with Vtk

[Kent Vander Velden]

  My application uses both Qt (a widget library) and Vtk.  I have used
Qt widgets that provide a Vtk render window called vtkandqt and vtkQGL.
Both of these work well, but there is a slight difference from the vtk
interpretor that is included with Vtk31.  The difference is most noticeable
if viewing a simple cone.  If you rotate the cone to face the user and then
start zooming, the qt widgets start clipping the front of the cone off
well before the interpretor does.  This behavior is quite bad for my
application.  There seems to be some crazy stuff as well, like the rear
being clipped even though objects are moving towards the camera (or the
camera is moving towards the objects).

  I have tried reseting the camera and the clipping range, and that seems to
work with most of the objects that I view, but larger objects (which are still
smaller than the thickness of the clipping range) fail to rotate properly.

  If anyone has experience with these widgets and know how to fix the problem
please let me know.  Neither of these widgets use vtkRenderWindowInteractor
and reimplement the basic functionality in their code.  Obviously there are
some differing details.

  Alternatively, if anyone has an idea of what might be going on in general
also let me know and maybe I can use those suggestions to find the difference.

  Thanks!

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Kent Vander Velden
kent at iastate.edu