[vtkusers] Segmentation fault

Discussion:

elena bresciani

2014-04-07 15:00:08 UTC

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

Bill Lorensen

2014-04-07 15:18:23 UTC

Permalink

Have you applied
reader->Update();

before you request the reader's output?

On Mon, Apr 7, 2014 at 11:00 AM, elena bresciani

Post by elena bresciani
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.
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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elena bresciani

2014-04-07 15:32:03 UTC

Permalink

yes

Post by Bill Lorensen
Have you applied
reader->Update();
before you request the reader's output?
On Mon, Apr 7, 2014 at 11:00 AM, elena bresciani

Post by elena bresciani
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

Post by elena bresciani
the code to make it run.
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++)

{....}

Post by elena bresciani
everytime I call GetNumberOfTuples I have this error so I think the

problem

Post by elena bresciani
is on PointNormalArray.
Can somebody help me?
Thanks in advance
Elena
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Bill Lorensen

2014-04-07 17:00:06 UTC

Permalink

Perhaps the reader is returning normals as doubles?

On Mon, Apr 7, 2014 at 11:32 AM, elena bresciani

yes

Post by Bill Lorensen
Have you applied
reader->Update();
before you request the reader's output?
On Mon, Apr 7, 2014 at 11:00 AM, elena bresciani

--
Unpaid intern in BillsBasement at noware dot com

Goodwin Lawlor

2014-04-07 17:11:21 UTC

Permalink

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

Post by elena bresciani
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.
*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
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
http://www.vtk.org/Wiki/VTK_FAQ
http://www.vtk.org/mailman/listinfo/vtkusers

Shawn Waldon

2014-04-07 17:17:26 UTC

Permalink

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 <

Post by Goodwin Lawlor
Hi Elena,
vtkSmartPointer<vtkPolyData> polydata = reader->GetOutput();
reader->GetOutput() returns a regular pointer to a vtkPolydata not a smart
pointer.
vtkPolyData *polydata = reader->GetOutput();
instead.
hth
Goodwin
On Mon, Apr 7, 2014 at 4:00 PM, elena bresciani <

Post by elena bresciani
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.
*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
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
http://www.vtk.org/Wiki/VTK_FAQ
http://www.vtk.org/mailman/listinfo/vtkusers

_______________________________________________
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--
Shawn Waldon
Graduate Research Assistant
Department of Computer Science
University of North Carolina at Chapel Hill
***@cs.unc.edu

Goodwin Lawlor

2014-04-07 17:31:26 UTC

Permalink

Thanks for that link Shawn and setting me straight (I did day I could be
wrong ;-))

My logic was that if you had to do:

vtkSmartPointer<vtkPolyData> polydata = vtkSmartPointer<vtkPolyData>::New();

then initializing a smart pointer not created with the form on the RHS
above wouldn't work...

Goodwin

Post by 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 <

Post by Goodwin Lawlor
Hi Elena,
vtkSmartPointer<vtkPolyData> polydata = reader->GetOutput();
reader->GetOutput() returns a regular pointer to a vtkPolydata not a
smart pointer.
vtkPolyData *polydata = reader->GetOutput();
instead.
hth
Goodwin
On Mon, Apr 7, 2014 at 4:00 PM, elena bresciani <

Post by elena bresciani
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.
*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
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
http://www.vtk.org/Wiki/VTK_FAQ
http://www.vtk.org/mailman/listinfo/vtkusers

--
Shawn Waldon
Graduate Research Assistant
Department of Computer Science
University of North Carolina at Chapel Hill

elena bresciani

2014-04-08 07:19:31 UTC

Permalink

Thank you guys,

I tried changing the type of PointNormalArray in vtkDoubleArray

*vtkDoubleArray *PointNormalArray = vtkDoubleArray::SafeDownCast(
polydata->GetPointData()->GetNormals() ) ; *

but I still have the segfault.

Elena

Post by Goodwin Lawlor
Thanks for that link Shawn and setting me straight (I did day I could be
wrong ;-))
vtkSmartPointer<vtkPolyData> polydata =
vtkSmartPointer<vtkPolyData>::New();
then initializing a smart pointer not created with the form on the RHS
above wouldn't work...
Goodwin

Post by Goodwin Lawlor
Hi Elena,
vtkSmartPointer<vtkPolyData> polydata = reader->GetOutput();
reader->GetOutput() returns a regular pointer to a vtkPolydata not a
smart pointer.
vtkPolyData *polydata = reader->GetOutput();
instead.
hth
Goodwin
On Mon, Apr 7, 2014 at 4:00 PM, elena bresciani <

Post by elena bresciani
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.
*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
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
http://www.vtk.org/Wiki/VTK_FAQ
http://www.vtk.org/mailman/listinfo/vtkusers

--
Shawn Waldon
Graduate Research Assistant
Department of Computer Science
University of North Carolina at Chapel Hill

Bill Lorensen

2014-04-08 11:58:32 UTC

Permalink

Please post a small, complete, compilable example that illustrates your problem.

On Tue, Apr 8, 2014 at 3:19 AM, elena bresciani

Post by elena bresciani
Thank you guys,
I tried changing the type of PointNormalArray in vtkDoubleArray
vtkDoubleArray *PointNormalArray = vtkDoubleArray::SafeDownCast(
polydata->GetPointData()->GetNormals() ) ;
but I still have the segfault.
Elena

Post by 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_Pointer
for 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

Post by Goodwin Lawlor
Hi Elena,

Post by elena bresciani
vtkSmartPointer<vtkPolyData> polydata = reader->GetOutput();

reader->GetOutput() returns a regular pointer to a vtkPolydata not a
smart pointer.
vtkPolyData *polydata = reader->GetOutput();
instead.
hth
Goodwin
On Mon, Apr 7, 2014 at 4:00 PM, elena bresciani

Post by elena bresciani
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.
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
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
http://www.vtk.org/Wiki/VTK_FAQ
http://www.vtk.org/mailman/listinfo/vtkusers

--
Shawn Waldon
Graduate Research Assistant
Department of Computer Science
University of North Carolina at Chapel Hill

--
Unpaid intern in BillsBasement at noware dot com

elena bresciani

2014-04-08 12:33:55 UTC

Permalink

Here it is, I omitted the inclusion of the header files and the output
section

int main ( int argc, char *argv[] )
{

std::string filename = argv[1];

// Read data from the file
vtkSmartPointer<vtkXMLPolyDataReader> reader =
vtkSmartPointer<vtkXMLPolyDataReader>::New();
reader->SetFileName(filename.c_str());
reader->Update();

// polydata object
vtkSmartPointer<vtkPolyData> polydata = reader->GetOutput();

// get normals
vtkDoubleArray *pointNormalsArray = vtkDoubleArray::SafeDownCast
(polydata->GetPointData()->GetNormals());

vtkSmartPointer<vtkPolyData> newpolydata =
vtkSmartPointer<vtkPolyData>::New();
vtkSmartPointer<vtkPoints> newPoints =
vtkSmartPointer<vtkPoints>::New();

// for every point p1 in the polydata find the point p2 which lies on
the normal at a distance D from p1

for(vtkIdType i = 0; i < pointNormalsArray->GetNumberOfTuples(); i++)

{
double p1[3];
polydata->GetPoint(i,p1); //prendo il punto

double pN[3];
pointNormalsArray->GetTuple(i, pN);

double p2[3];
double D=2*atoi(argv[3]);
p2[0]=p1[0]-pN[0]*D;
p2[1]=p1[1]-pN[1]*D;
p2[2]=p1[2]-pN[2]*D;

vtkIdType pid[1];
pid[0]=newPoints->InsertNextPoint(p2);

}

//set points to polydata
newpolydata->SetPoints(newPoints);

return EXIT_SUCCESS;
}

Post by Bill Lorensen
Please post a small, complete, compilable example that illustrates your problem.
On Tue, Apr 8, 2014 at 3:19 AM, elena bresciani

Post by Shawn Waldon
Hi Goodwin,
It shouldn't be causing the segfault. That line will create a new

smart