[Insight-users] bug in DeformableModelSimplexMesh ?

[J.Menssen at cukz.umcn.nl]

Dear All

We are working on a segmentation algorithm using deformable models with
a refine mesh. The deformation and refinement is done  in a for loop.
Our application is based on the DeformableModel application as given in
the InsightApplications example DeformableModelSimplexMesh.
We modified the for loop in de DeformMesh method
(DeformableModelApplication.cxx) with a refinement of the mesh, but this
crashes. Below a part of (pseudo) code is given.. 
	
     for i=1:i<nr_iterations;i++
   {
      m_simplexMesh->DisconnectPipeline()
      m_deformFilter-SetInput(m_simplexMesh);
      m_deformFilter->Update(0;
      simplexMesh2 = m_deformFilter->GetOutput();
      
      m_refineMesh->SetInput(simplexMesh2);
      m_refineMesh->Update();
      m_simplexMesh=m_refineMesh->GetOutput();
  }
m_deformFilter is a
DeformableSimplexMesh3DGradientConstraintForceFilter, 
m_RefineMesh is a  itkSimplexMeshAdaptTopologyFilter
	
To isolate the bug, we started with a little modification of the
DeformMesh method in DeformableModelApplication.cxx. The modifications
are given below (line 522 in original file, InsightApplciations 3.16).
Running this code results also in a crash
*-----------------------------------------------------------------------
-----------------------------------------------------------------
SimplexMeshType::Pointer simplexMesh2 = m_SimplexMesh;
const unsigned int numberOfIterationsToGo =
atoi(m_IterationsValueInput->value()); 
for( unsigned int i=0; i<numberOfIterationsToGo; i++ )
{
      std::cout << " Iteration   " << i << std::endl;
    
//* -------------- start modified code
-------------------------------------------
	// THIS IS MODIFIED CODE THAT (WE THINK) DOESN'T VIOLATE THE ITK
RULES BUT THIS
 // CODE CRASHES

			m_SimplexMesh->DisconnectPipeline();
			m_DeformFilter->SetInput(m_SimplexMesh);
			m_DeformFilter->SetIterations(1);
			m_DeformFilter->Update();
			simplexMesh2 = m_DeformFilter->GetOutput();

			SimplexMesh2->DisconnectPipeline(0
			m_DeformFilter->SetInput(simplexMesh2);
			m_DeformFilter->SetIterations(1);
			m_DeformFilter->Update();
			m_SimplexMesh = m_DeformFilter->GetOutput();

// --------------------- end modified code
-------------------------------------- */

      m_SimplexMeshToShow  = m_SimplexMesh;
      this->RefreshMeshVisualization();
     
      // force a redraw
      axialView->redraw();
      coronalView->redraw();
      sagittalView->redraw();
      surfaceView->redraw();

      Fl::check(); 
 }
*-----------------------------------------------------------------------
--------------------------------------------------------------------

Error message (using Visual Studio 2005 and/or 2008) of the crash
Debug Assertion Failed !
	Expression map/set iterator not dereferencable 

Do we something wrong?  Using a for loop in a pipeline is dangerous but
in bug 0001080, we read it's possible to use a for loop. Also at the Old
Nabble forum  I read a message that is must be possible to use a for
loop.
(http://old.nabble.com/Using-image-iterators-combined-with-filters-in-a-
loop-td28684443.html)
Even if we changed the code in the original example
DeformableModelApplication according to the above  referenced Old Nabble
article the application crashes (see below)
      
m_DeformFilter->SetInput( m_SimplexMesh );

      m_DeformFilter->SetIterations(1); 
      m_DeformFilter->Update();

      m_SimplexMesh =  m_DeformFilter->GetOutput(); 
	m_SimplexMesh->DisconnectPipeline();


So is there a bug in the original ITK sources? As far as we now, ITK
doesn't allow to change the input of a filter and we think this is what
happened in the original DeformableSimplexMesh application.

Can someone help us with our problem ?


We tested with ITK 2.8, ITK 3.16 and 3.18 and all crashes
 Jan Menssen
Research assistant
Radboud University Nijmegen Medical Centre
Clinical Physics Lab - Peadiatrics
Huispost 833, route 833
P.O  box  9101 
6500 HB Nijmegen
Telefoon: +31 24 36 19063
E-mail J.Menssen at cukz.umcn.nl 
http://www.umcn.nl <http://www.umcn.nl/> 





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The Radboud University Nijmegen Medical Centre is listed in the Commercial Register of the Chamber of Commerce under file number 41055629.

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