[vtkusers] question on multiresolution volume rendering

[alext at win.tue.nl]

  Hello,

  I have a question on multiresolution volume rendering. 
  Basically I want to render a subsampled raycasted image, i.e. an image in
  which there's less than a ray per pixel. VTK does this e.g. when one
  manipulates volumes interactively with an interactor. However, the
  interactor decides itself which is the subsampling level, based on
  a desired frame rate. 
  I would like to be able to decide myself which is the subsampling rate.
  I have tried the following:

  vtkRenderer* ren = vtkRenderer::New();

  ren->GetRayCaster()->AutomaticScaleAdjustmentOff();

  int res_level = ... number between 0 and 4, this is the subsampling rate

  ren->GetRayCaster()->SetSelectedImageScaleIndex(res_level);

  ...add a raycasted vtkVolume to 'ren'....
  ...add a render window to 'ren'...
  ...ask the render window to Render()...


  The idea I had was to use an explicit setting of the image-scale-index
  on the vtkRayCaster of the renderer. This works OK under Windows + Linux
  but I quickly get garbled (half-rendered, half-garbage) images on an SGI O2.

  Is by chance something wrong in using the multiresolution feature of VTK
  as I did above? Do I forget to initialize something that, by chance, is ok
  under Linux/Windows, but might be garbage on the SGI? I tried to look at
  the source code to use the vtkRayCaster's image-scale features, but I'm
  not sure if I have to do the above or something else.

  Thanks very much for any help,

  Alex Telea

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 Dr. Alexandru C. Telea      | Technische Universiteit Eindhoven
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