[vtkusers] Cross-platform rendering into an existing window

[Matt Leotta]

A group of us in Engineering at Brown University would like to start
using VTK for our 3D visualization needs.  However, we already have an
existing cross-platform GUI (using vgui in VXL) that provides us with an
OpenGL viewport and captures events.  We would like to render directly
into the viewport of this existing window and translate our existing
captured events into a form that can be handled by VTK.  I've seen some
examples of rendering into an existing window, but they seem to be
dependent on the specific toolkit in use.  

Can anyone suggest a way of doing this?  Do I need to write a
specialized subclass of vtkRenderWindow and/or
vtkRenderWindowInteractor?  Can I use vtkRenderer without a
vtkRenderWindow?  Is there a way to have a vtkRenderWindowInteractor
that handles manually triggered events but does not take over control of
capturing events?

Any advice would be greatly appreciated.  We have already (easily)
handled these issues for incorporating Open Inventor into our GUI. 
While we would prefer to use VTK, we will have to resort to using Open
Inventor if there is not simple way to incorporate VTK.

Thank You,

Matt Leotta
Brown University Division of Engineering