[Paraview] Image filters & extent

[Bryn Lloyd]

Hi,

I have been having trouble with writing image filter plugins. If the  
extent of the output image is larger than the input image extent, I  
get all sorts of problems.

I have tried using various parent classes, including  
vtkImageAlgorithm. Currently I am using vtkDataSetAlgorithm (I thought  
it would not try to be as "clever" as the vtkImageAlgorithm, but it  
seems to be the same thing).


1. The full extent is not visualized:
by setting the the extent of the output in RequestData I managed to  
get the visualization right:

   outInfo->Set( vtkStreamingDemandDrivenPipeline::WHOLE_EXTENT(),  
DataExtent, 6 );
   outInfo->Set( vtkStreamingDemandDrivenPipeline::UPDATE_EXTENT(),  
DataExtent, 6 );


2. Unfortunately, even with the addition above, the information  
(extent, dimensions etc.) are not shown correctly in the "Information  
tab" in paraview. Strangely enough, if I change a parameter of the  
filter and call Apply a second time, the values in the information tab  
are suddenly correct.


What I want is really a simple way to generate an output image with  
different size/extent than the input image, without having all this  
trouble setting pipeline information. Is there a way?

Thanks
Bryn