[vtkusers] Segmentation fault

[Shawn Waldon]

Hi Goodwin,

It shouldn't be causing the segfault.  That line will create a new smart
pointer and set its internal pointer to the reader's output, incrementing
the reference count.
See
http://www.vtk.org/Wiki/VTK/Tutorials/SmartPointers#Getting_an_Object_with_a_Smart_Pointerfor
details.  If the reference increment is unnecessary, then it is still
only a small performance gain and not a segfault causing bug.

My guess for the segfault is what Bill said: the normals are in a
vtkDoubleArray not a vtkFloatArray so SafeDownCast is returning NULL.

HTH,

Shawn


On Mon, Apr 7, 2014 at 1:11 PM, Goodwin Lawlor <
goodwin.lawlor.lists at gmail.com> wrote:

> Hi Elena,
>
> I coud be wrong but I dont think this is correct:
>
>  vtkSmartPointer<vtkPolyData> polydata = reader->GetOutput();
>
>
> reader->GetOutput() returns a regular pointer to a vtkPolydata not a smart
> pointer.
>
> Try:
>
> vtkPolyData *polydata = reader->GetOutput();
>
> instead.
>
> hth
>
> Goodwin
>
>
>
>
> On Mon, Apr 7, 2014 at 4:00 PM, elena bresciani <
> elena.bresciani87 at gmail.com> wrote:
>
>> Hello everybody!
>>
>> I need your help with a segmentation fault error.
>> Using gdb I understood where it is generated but I don't know how to
>> modify the code to make it run.
>>
>> Here's the portion of the code that I'm talking about:
>>
>>
>> *vtkSmartPointer<vtkPolyData> polydata = reader->GetOutput();*
>> (the reader is a vtkXMLPolyDataReader)
>>
>>
>>
>> *vtkFloatArray *PointNormalArray = vtkFloatArray::SafeDownCast(
>> polydata->GetPointData()->GetNormals() ) ; for(vtkIdType i = 0; i <
>> PointNormalArray->GetNumberOfTuples(); i++) {....}*
>>
>> everytime I call GetNumberOfTuples I have this error so I think the
>> problem is on PointNormalArray.
>>
>> Can somebody help me?
>>
>> Thanks in advance
>>
>> Elena
>>
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-- 
Shawn Waldon
Graduate Research Assistant
Department of Computer Science
University of North Carolina at Chapel Hill
swaldon at cs.unc.edu
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