[vtk-developers] Re: ReleaseDataFlag

[Tim Hutton]

Thanks Charles, that works nicely.

Just a thought, are the VTK classes tested against this problem? If I has 
submitted one of my filters then it might have been a user that ran against 
this problem.

Mental note to self: always check classes with GlobalDataReleaseFlagOn 
before submitting.

Tim.

At 14:46 25/03/2002 -0500, Charles Law wrote:
>Try copying (ShallowCopy) the input before you use it as input to the 
>transform filter.
>
>vtkPolyData *tmp = vtkPolyData::New();
>tmp->ShallowCopy(this->GetInput());
>
>...
>
>trans->SetInput(tmp);
>
>...
>
>
>At 05:16 PM 3/25/2002 +0000, Tim Hutton wrote:
>>Maybe this is more an issue for developers, apologies for the cross-posting.
>>
>>I'm confused about the ReleaseDataFlag. A couple of my own filters were 
>>using a lot of memory, so I called 
>>vtkDataObject::SetGlobalReleaseDataFlag(1) to try to release memory from 
>>earlier in the pipeline that was no longer needed. This works 
>>spectacularly for one of them, everything was fine. For the other, 
>>however, I got problems because towards the end of the Execute() function 
>>the data in this->GetInput() had been released and had gone! I think the 
>>problem is captured in this sketch:
>>
>>void MyFilter::Execute()
>>{
>>
>>...
>>
>>this->GetInput()->GetCell(id); // fine, since data not released
>>
>>...
>>
>>vtkTransformPolyDataFilter trans
>>trans->SetInput(this->GetInput());
>>
>>...
>>
>>trans->Update();
>>
>>... // use output of trans
>>
>>this->GetInput()->GetCell(id); // ERROR! data has been released!
>>
>>}
>>
>>When trans has finished, it checks to see if it can release its data. The 
>>global flag says yes, so it releases this->GetInput() which is disastrous.
>>
>>How do I stop the data being released mid-Execute? Using 
>>ReleaseDataFlagOff() calls doesn't work because the global flag overrides 
>>them! (see vtkDataObject::ShouldIReleaseData)
>>
>>I'm using the latest CVS of VTK4 on win2k with visualc++6.
>>
>>Thanks,
>>
>>Tim.
>>---------------------------------------------------------------------------
>>Tim Hutton,                        http://www.eastman.ucl.ac.uk/~dmi/MINORI
>>Research Fellow & PhD student,                   T.Hutton at eastman.ucl.ac.uk
>>MINORI Project, Biomedical Informatics Unit,     Tel: [+44] (0)20 7915 2344
>>Eastman Dental Institute, UCL,                   Fax: [+44] (0)20 7915 2303
>>256 Gray's Inn Road, London WC1X 8LD, UK      Mobile: [+44] (0)7748 678 832
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>