[vtkusers] Zooming the vtkImageViewer

[David Gobbi]

Hi Eduard,

This varies from machine to machine, and from OpenGL implementation
to OpenGL implementation.

On a typical PC with a commodity 3D-accelerated board, using 
textures in a vtkRenderWindow is faster than using vtkImageWindow
(sometimes MUCH faster).  Why?  For one, textures use AGP,
while glDrawPixels almost never uses AGP.  Also, textures are
cached in video memory so Zoom is essentially free.

On any recent professional 3D system (PC or UNIX workstation)
textures work just as fast as the vtkImageWindow - there should
really be no difference.

On old systems (no accelerated texture mapping, this even 
includes many modern SGI Octanes) then texture mapping is of
course much slower.

 - David

--
  David Gobbi, MSc                    dgobbi at irus.rri.on.ca
  Advanced Imaging Research Group
  Robarts Research Institute, University of Western Ontario

On Tue, 11 Apr 2000, Eduard Schreibmann wrote:

> 
> 
> It is much slower, and the quality of the final image is poorer .
> Using vkRenderWindow instead of  vtkImageWindow is 2-4 times slower .
> 
> 
> Brian Alexander Todd wrote:
> 
> > Erik,
> >
> > Another possibility is to texture your image onto
> > a plane and use a vtkRenderWindow instead of
> > vtkImageWindow.  Then zooming is all taken care of
> > for you.
> >
> > Brian
> >
> > At 08:58 AM 6/8/00 +0100, Matt Clarkson wrote:
> > >You do this by connecting the volume
> > >to a vtkImageReslice filter, and extracting
> > >a 2D slice and connecting this to the viewer.
> > >You set the vtkImageReslice filter
> > >to extract a 2D image, ie. Set the extent to
> > >0 255 0 255 0 0
> > >
> > >The vtkImageReslice can then be adjusted to give
> > >different fields of view. Effectively you are resampling
> > >a 2D image each time rather than a 3D volume
> > >
> > >I didnt know that the image viewer had a camera
> > >as such.
> > >
> > >Anyway, hope this helps
> > >
> > >Matt
> > >
> > >
> > >Erik Sobel wrote:
> > >>
> > >> Does anyone know how to zoom an image in a vtkImageViewer (without
> > >> resampling the volume - since this messes up other parts of my
> > >> pipeline)?   Is it possible to just grab the camera used by the
> > >> vtkImageViewer and zoom it?
> > >>
> > >> Thanks,
> > >> Erik
> > >>
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> > >--
> > >Computational Imaging Science Group
> > >Radiological Sciences,
> > >Guy's Hospital
> > >London Bridge
> > >London
> > >SE1
> > >9RT
> > >Tel: +44 (0)20 7955 2380
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> > >E-mail: m.clarkson at umds.ac.uk
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> > >
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