[vtkusers] question on multiresolution volume rendering

[Lisa S. Avila]

Hello Alex,

Your selected image scale index should be a number between 0 and 3 (not 4). 
This is because index 4 is used for the automatic adjustment.

Lisa


At 01:06 PM 6/14/2001, alext at win.tue.nl wrote:


>   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
>
>-----------------------------------------------------------------
>  Dr. Alexandru C. Telea      | Technische Universiteit Eindhoven
>                              |
>  E-mail   : alext at win.tue.nl | Dept. of Mathematics and
>  Office   :  HG 7.71         | Computer Science
>  Tel.     : +31 40 247 5008  | PO Box 513
>  Secretary: +31 40 247 4416  | 5600 MB Eindhoven
>  Fax      : +31 40 246 8508  | The Netherlands
>                              |
>  URL      : http://www.win.tue.nl/math/an/alext
>-----------------------------------------------------------------
>
>
>
>
>
>
>_______________________________________________
>This is the private VTK discussion list.
>Please keep messages on-topic. Check the FAQ at: 
><http://public.kitware.com/cgi-bin/vtkfaq>
>Follow this link to subscribe/unsubscribe:
>http://public.kitware.com/mailman/listinfo/vtkusers