[vtkusers] vtkFixedPointVolumeRayCastMapper and vtkInteractor

[Frank Gao]

Hi All,

I just did some experiments with volume mappers and interactors. I expect to
do the rendering, and use mouse to move/rotate/zoom images using
vtkInteractorStyleTrackball. Images with low LOD should be displayed when
the mouse is being held and moved.

Would someone please help with the following issues:
* With vtkVolumeRayCastMapper, how can I change/adjust the LOD so that the
display is a little better when mouse is being moved?
* With vtkFixedPointVolumeRayCastMapper, there is no image display before
the mouse is stopped and released. How could I make it happen? Adding
vtkLODProp3D does not seem to be helpful.
* With vtkOpenGLVolumeTextureMapper2D, there is no intermediate display too,
but I can define a vtkLODProp3D, and make it work. Is there any easier way
to approach the behavior?

Thanks in advance,

Frank Gao