[vtk-developers] RE: Problem when creating vtkImageData by hand

[David Cole]

The bug number in the bug tracker is:
http://public.kitware.com/Bug/bug.php?op=show&bugid=2169&pos=0 
<http://public.kitware.com/Bug/bug.php?op=show&bugid=2169&pos=0>

It links back to this approximate discussion on the list:
http://public.kitware.com/pipermail/vtk-developers/2005-August/thread.html#3634

Will Schroeder wrote:

> Prabhu-
>
> I wanted to update you on this test. It has uncovered some issues in 
> the pipeline and we are evaluating options for a fix. In the mean 
> time, we have made a one-line fix that avoids cloning the output of 
> the reader to create the image data. I know this is not what is 
> intended, but we are trying to clear the dashboard while we resolve 
> the issue...we have entered a bug in the tracker.
>
> Will
>
> At 10:35 AM 8/18/2005, you wrote:
>
>> >>>>> "Brad" == Brad King <brad.king at kitware.com> writes:
>>
>>     Brad> Prabhu Ramachandran wrote:
>>     >>>>>>> "Dean" == Dean Inglis <dean.inglis at camris.ca> writes:
>>     >>
>>     Dean> and removed the outline filter from the pipeline and
>>     Dean> everything runs fine.  As soon as I add the outline filter,
>>     Dean> I get the same weird results.  I haven't figured out if this
>>     Dean> is a pipeline problem, IPW problem or outline filter
>>     Dean> pb.... :{
>>     >>
>>     >> Thanks for the confirmation of the problem!  This means there
>>     >> is a nasty bug lurking somewhere in there.
>>
>>     Brad> I've found the problem.  The vtkOutlineFilter derives from
>>     Brad> vtkPolyDataAlgorithm.
>>     Brad> vtkPolyDataAlgorithm::RequestUpdateExtent sets
>>     Brad> RequestExactExtent to 1 so that it requests the exact
>>     Brad> unstructured extent.  However when the input of
>> [...]
>>     Brad> Since vtkTrivialProducer has only one copy of the data it
>>     Brad> will never actually generate or re-initialize its output.
>>     Brad> However when RequestExactExtent is on then the executive
>>     Brad> crops the data and it is lost forever!
>>
>> I don't understand this.  Shouldn't this work because the pipeline is
>> "branched" in the sense that the resliced output is used by one actor
>> and the original (intact) data is used by the outline filter.  Why
>> should the cropping propagate upstream at all and affect all branches
>> of the pipeline?
>>
>> cheers,
>> prabhu
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>
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