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

[pof]

Hi David

the first polyline being:
   9 0 1 2 3 4 5 19 6 7
and the third polyline (actually it is a segment) being:
   2 18 0
I don't see why they shoud not merge together as (unless I misunderstand something):
   10 18 0 1 2 3 4 5 19 6 7

Am I wrong?


Le 09/12/2012 21:05, David Gobbi a écrit :
> Hi JD,
>
> It could only merge those two lines if it joined them with a "T".
> A polyline cannot have any branches.
>
>   - David
>
>
> On Sun, Dec 9, 2012 at 12:16 PM, pof <jd379252 at gmail.com> wrote:
>> 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;
>> }