[vtkusers] Bug in vtkStripper on a very simple case ?

[pof]

Hi all,

I get a strange result (which may be a bug) using vtk stripper, i.e. it 
does not merge LINES as polylines as it is expected to.
In this example (see below an extract of the polydata produced by 
vtkStripper), only 2 polylines should be obtained, but vtkStripper 
forgot to merge the first and the third line together, though they 
obviously share point with Id=0 (btw, the fact that only Id 0 remains 
unmerged might not be pure luck).

LINES 3 24
9 0 1 2 3 4 5 19 6 7
10 9 8 17 13 12 15 14 11 10 16
2 18 0
Does anybody have an idea or an explanation?
Thanks
JD

PS: Here below is the complete source file that generates these data and 
in which vtkStripper is used.

//////////////////////////////////////////////////////
// Example modified from IntersectionPolyDataFilter.cxx
//////////////////////////////////////////////////////
#include <vtkActor.h>
#include <vtkIntersectionPolyDataFilter.h>
#include <vtkPolyDataMapper.h>
#include <vtkPolyDataWriter.h>
#include <vtkProperty.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkCellArray.h>
#include <vtkStripper.h>

int main(int argc, char *argv[])
{
   vtkSmartPointer<vtkSphereSource> sphereSource1 = 
vtkSmartPointer<vtkSphereSource>::New();
   sphereSource1->SetCenter(0.0, 0.0, 0.0);
   sphereSource1->SetRadius(2.0f);
   sphereSource1->SetPhiResolution(20);
   sphereSource1->SetThetaResolution(20);
   sphereSource1->Update();
   vtkSmartPointer<vtkPolyDataMapper> sphere1Mapper = 
vtkSmartPointer<vtkPolyDataMapper>::New();
   sphere1Mapper->SetInputConnection( sphereSource1->GetOutputPort() );
   sphere1Mapper->ScalarVisibilityOff();
   vtkSmartPointer<vtkActor> sphere1Actor = 
vtkSmartPointer<vtkActor>::New();
   sphere1Actor->SetMapper( sphere1Mapper );
   sphere1Actor->GetProperty()->SetOpacity(.3);
   sphere1Actor->GetProperty()->SetColor(1,0,0);

   /////////////////////////
   // BEGIN MODIFICATIONS //
   /////////////////////////
   // Create a planar object
   // Define 4 vertices
   vtkSmartPointer<vtkPoints> PlanePoints = 
vtkSmartPointer<vtkPoints>::New();
   vtkSmartPointer<vtkCellArray> PlaneCells = 
vtkSmartPointer<vtkCellArray>::New();
   PlanePoints->InsertNextPoint(-3, -1, 0);
   PlanePoints->InsertNextPoint(3, -1, 0);
   PlanePoints->InsertNextPoint(-3, 1, 0);
   PlanePoints->InsertNextPoint(3, 1, 0);
   // Create 2 trianglar faces
   PlaneCells->InsertNextCell(3);
   PlaneCells->InsertCellPoint(0);
   PlaneCells->InsertCellPoint(1);
   PlaneCells->InsertCellPoint(2);
   PlaneCells->InsertNextCell(3);
   PlaneCells->InsertCellPoint(1);
   PlaneCells->InsertCellPoint(3);
   PlaneCells->InsertCellPoint(2);
   // Create the polydata from points and faces
   vtkSmartPointer<vtkPolyData> ProtectionWall = 
vtkSmartPointer<vtkPolyData>::New();
   ProtectionWall->SetPoints(PlanePoints);
   ProtectionWall->SetPolys(PlaneCells);
   /////////////////////////
   // END MODIFICATIONS //
   /////////////////////////

   vtkSmartPointer<vtkPolyDataMapper> planeMapper = 
vtkSmartPointer<vtkPolyDataMapper>::New();
   planeMapper->SetInputConnection( ProtectionWall->GetProducerPort() );
   planeMapper->ScalarVisibilityOff();

   vtkSmartPointer<vtkActor> planeActor = vtkSmartPointer<vtkActor>::New();
   planeActor->SetMapper( planeMapper );
   planeActor->GetProperty()->SetOpacity(.3);
   planeActor->GetProperty()->SetColor(0,1,0);

   // Get intersection segments (LINES) using the 
vtkIntersectionPolyDataFilter
   vtkSmartPointer<vtkIntersectionPolyDataFilter> 
intersectionPolyDataFilter = 
vtkSmartPointer<vtkIntersectionPolyDataFilter>::New();
   intersectionPolyDataFilter->SplitFirstOutputOff();
   intersectionPolyDataFilter->SplitSecondOutputOff();
   intersectionPolyDataFilter->SetInputConnection( 0, 
sphereSource1->GetOutputPort() );
   intersectionPolyDataFilter->SetInputConnection( 1, 
ProtectionWall->GetProducerPort() );
   intersectionPolyDataFilter->Update();

   /////////////////////////
   // BEGIN MODIFICATIONS //
   /////////////////////////
   // Try to get the polylines (there should be 2) from the segments (LINES)
   vtkSmartPointer<vtkStripper> stripper = 
vtkSmartPointer<vtkStripper>::New();
stripper->SetInputConnection(intersectionPolyDataFilter->GetOutputPort());
   stripper->Update();
   // Save resulting polydata on a file, in which we see that there are 
3 polylines (actually the second polyline is ok,
   // but the first and third polylines should have been further merged
   vtkSmartPointer<vtkPolyDataWriter> wr = 
vtkSmartPointer<vtkPolyDataWriter>::New();
   wr->SetFileName("polylines.txt");
   wr->SetInputConnection(stripper->GetOutputPort());
   wr->Write();
   ///////////////////////
   // END MODIFICATIONS //
   ///////////////////////

   vtkSmartPointer<vtkPolyDataMapper> intersectionMapper = 
vtkSmartPointer<vtkPolyDataMapper>::New();
   intersectionMapper->SetInputConnection( stripper->GetOutputPort() );
   intersectionMapper->ScalarVisibilityOff();

   vtkSmartPointer<vtkActor> intersectionActor = 
vtkSmartPointer<vtkActor>::New();
   intersectionActor->SetMapper( intersectionMapper );

   vtkSmartPointer<vtkRenderer> renderer = 
vtkSmartPointer<vtkRenderer>::New();
   renderer->AddViewProp(sphere1Actor);
   renderer->AddViewProp(planeActor);
   renderer->AddViewProp(intersectionActor);

   vtkSmartPointer<vtkRenderWindow> renderWindow = 
vtkSmartPointer<vtkRenderWindow>::New();
   renderWindow->AddRenderer( renderer );

   vtkSmartPointer<vtkRenderWindowInteractor> renWinInteractor =
     vtkSmartPointer<vtkRenderWindowInteractor>::New();
   renWinInteractor->SetRenderWindow( renderWindow );

   renderWindow->Render();
   renderWindow->SetSize(600, 600);
   renderer->SetBackground(0.1, 0.2, 0.4);
   renWinInteractor->Start();

   return EXIT_SUCCESS;
}