[vtkusers] extracting cells that uses 2 points

[Gonzalo Amadio]

Hello, I want to extract cells using two specified points. I was looking
into vtkPolyData and I found the function GetPointCells, but that is only
for one point. And I need it for two points instead of one.

So I used this example :
http://www.vtk.org/Wiki/VTK/Examples/Cxx/PolyData/ExtractCellsUsingPoints

I modified a little, instead of working with a spheresource I try to make
it work with a triangle strip (taken from this example :
http://www.vtk.org/Wiki/VTK/Examples/Cxx/GeometricObjects/TriangleStrip )

In this last example, there are 2 triangles, and (as in the code is
showed), I want the cell that uses the point 0.
But as shown in the result, it returns the 2 triangles instead of only one.

Maybe it is because the vtkTriangleStrip ? Is ok my idea?


Thank you.!



#include <vtkVersion.h>
#include <vtkSmartPointer.h>
#include <vtkInformation.h>
#include <vtkSphereSource.h>
#include <vtkExtractSelection.h>
#include <vtkSelection.h>
#include <vtkSelectionNode.h>
#include <vtkPolyData.h>
#include <vtkUnstructuredGrid.h>
#include <vtkIdTypeArray.h>
#include <vtkDataSetMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSphereSource.h>
#include <vtkVertexGlyphFilter.h>
#include <vtkTriangleStrip.h>
#include <vtkCellArray.h>

#include <vtkActor.h>
#include <vtkDataSetMapper.h>
#include <vtkPoints.h>


int main(int, char *[])
{

  vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint(0,0,0);
  points->InsertNextPoint(0,1,0);
  points->InsertNextPoint(1,0,0);
  points->InsertNextPoint(1.5,1,0);

  vtkSmartPointer<vtkTriangleStrip> triangleStrip =
vtkSmartPointer<vtkTriangleStrip>::New();
  triangleStrip->GetPointIds()->SetNumberOfIds(4);
  triangleStrip->GetPointIds()->SetId(0,0);
  triangleStrip->GetPointIds()->SetId(1,1);
  triangleStrip->GetPointIds()->SetId(2,2);
  triangleStrip->GetPointIds()->SetId(3,3);

  vtkSmartPointer<vtkCellArray> cells =
vtkSmartPointer<vtkCellArray>::New();
  cells->InsertNextCell(triangleStrip);

  vtkSmartPointer<vtkPolyData> polydata =
vtkSmartPointer<vtkPolyData>::New();
  polydata->SetPoints(points);
  polydata->SetStrips(cells);

  vtkSmartPointer<vtkIdTypeArray> ids =
vtkSmartPointer<vtkIdTypeArray>::New();
  ids->SetNumberOfComponents(1);
  ids->InsertNextValue(0);


  vtkSmartPointer<vtkSelectionNode> selectionNode =
    vtkSmartPointer<vtkSelectionNode>::New();
  selectionNode->SetFieldType(vtkSelectionNode::POINT);
  selectionNode->SetContentType(vtkSelectionNode::INDICES);
  selectionNode->SetSelectionList(ids);
  selectionNode->GetProperties()->Set(vtkSelectionNode::CONTAINING_CELLS(),
1);

  vtkSmartPointer<vtkSelection> selection =
    vtkSmartPointer<vtkSelection>::New();
  selection->AddNode(selectionNode);

  vtkSmartPointer<vtkExtractSelection> extractSelection =
vtkSmartPointer<vtkExtractSelection>::New();
  extractSelection->SetInput(0, polydata);
#if VTK_MAJOR_VERSION <= 5
  extractSelection->SetInput(1, selection);
#else
  extractSelection->SetInputData(1, selection);
#endif
  extractSelection->Update();

  // In selection
  vtkSmartPointer<vtkUnstructuredGrid> selected =
    vtkSmartPointer<vtkUnstructuredGrid>::New();
  selected->ShallowCopy(extractSelection->GetOutput());

  std::cout << "There are " << selected->GetNumberOfPoints()
            << " points in the selection." << std::endl;
  std::cout << "There are " << selected->GetNumberOfCells()
            << " cells in the selection." << std::endl;

  // Get points that are NOT in the selection
  selectionNode->GetProperties()->Set(vtkSelectionNode::INVERSE(), 1);
//invert the selection
  extractSelection->Update();

  vtkSmartPointer<vtkUnstructuredGrid> notSelected =
    vtkSmartPointer<vtkUnstructuredGrid>::New();
  notSelected->ShallowCopy(extractSelection->GetOutput());

  std::cout << "There are " << notSelected->GetNumberOfPoints()
            << " points NOT in the selection." << std::endl;
  std::cout << "There are " << notSelected->GetNumberOfCells()
            << " cells NOT in the selection." << std::endl;

  vtkSmartPointer<vtkDataSetMapper> inputMapper =
    vtkSmartPointer<vtkDataSetMapper>::New();
  inputMapper->SetInput(polydata);
  vtkSmartPointer<vtkActor> inputActor =
    vtkSmartPointer<vtkActor>::New();
  inputActor->SetMapper(inputMapper);

  vtkSmartPointer<vtkDataSetMapper> selectedMapper =
    vtkSmartPointer<vtkDataSetMapper>::New();
#if VTK_MAJOR_VERSION <= 5
  selectedMapper->SetInputConnection(selected->GetProducerPort());
#else
  selectedMapper->SetInputData(selected);
#endif
  vtkSmartPointer<vtkActor> selectedActor =
    vtkSmartPointer<vtkActor>::New();
  selectedActor->SetMapper(selectedMapper);

  vtkSmartPointer<vtkDataSetMapper> notSelectedMapper =
    vtkSmartPointer<vtkDataSetMapper>::New();
#if VTK_MAJOR_VERSION <= 5
  notSelectedMapper->SetInputConnection(notSelected->GetProducerPort());
#else
  notSelectedMapper->SetInputData(notSelected);
#endif
  vtkSmartPointer<vtkActor> notSelectedActor =
    vtkSmartPointer<vtkActor>::New();
  notSelectedActor->SetMapper(notSelectedMapper);

  // There will be one render window
  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->SetSize(900, 300);

  // And one interactor
  vtkSmartPointer<vtkRenderWindowInteractor> interactor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  interactor->SetRenderWindow(renderWindow);

  // Define viewport ranges
  // (xmin, ymin, xmax, ymax)
  double leftViewport[4] = {0.0, 0.0, 0.5, 1.0};
  double centerViewport[4] = {0.33, 0.0, .66, 1.0};
  double rightViewport[4] = {0.66, 0.0, 1.0, 1.0};

  // Setup the renderers
  vtkSmartPointer<vtkRenderer> leftRenderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(leftRenderer);
  leftRenderer->SetViewport(leftViewport);
  leftRenderer->SetBackground(.6, .5, .4);

  vtkSmartPointer<vtkRenderer> centerRenderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(centerRenderer);
  centerRenderer->SetViewport(centerViewport);
  centerRenderer->SetBackground(.3, .1, .4);

  vtkSmartPointer<vtkRenderer> rightRenderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(rightRenderer);
  rightRenderer->SetViewport(rightViewport);
  rightRenderer->SetBackground(.4, .5, .6);

  leftRenderer->AddActor(inputActor);
  centerRenderer->AddActor(selectedActor);
  rightRenderer->AddActor(notSelectedActor);

  leftRenderer->ResetCamera();
  centerRenderer->ResetCamera();
  rightRenderer->ResetCamera();

  renderWindow->Render();
  interactor->Start();

  return EXIT_SUCCESS;
}


-- 
--------
Gonzalo Amadio
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