VertexConnectivity

#include <vtkSmartPointer.h>
#include <vtkIdList.h>
#include <vtkPolyData.h>
#include <vtkCellData.h>
#include <vtkDoubleArray.h>
#include <vtkDataSet.h>
#include <vtkSphereSource.h>
#include <vtkTriangleFilter.h>
#include <vtkExtractEdges.h>
#include <vtkDataSetMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkIdTypeArray.h>
#include <vtkSelectionNode.h>
#include <vtkSelection.h>
#include <vtkExtractSelection.h>
#include <vtkProperty.h>
#include <vtkVertexGlyphFilter.h>

vtkSmartPointer<vtkIdList> GetConnectedVertices(vtkSmartPointer<vtkPolyData> mesh, int id);

int main(int, char *[])
{
  vtkSmartPointer<vtkSphereSource> sphereSource =
      vtkSmartPointer<vtkSphereSource>::New();
  sphereSource->Update();

  vtkSmartPointer<vtkTriangleFilter> triangleFilter =
      vtkSmartPointer<vtkTriangleFilter>::New();
  triangleFilter->SetInputConnection(sphereSource->GetOutputPort());
  triangleFilter->Update();

  vtkSmartPointer<vtkExtractEdges> extractEdges =
    vtkSmartPointer<vtkExtractEdges>::New();
  extractEdges->SetInputConnection(triangleFilter->GetOutputPort());
  extractEdges->Update();

  vtkSmartPointer<vtkPolyData> mesh = extractEdges->GetOutput();

  vtkSmartPointer<vtkIdList> connectedVertices = GetConnectedVertices(mesh, 0);

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

  std::cout << "Connected vertices: ";
  for(vtkIdType i = 0; i < connectedVertices->GetNumberOfIds(); i++)
  {
    std::cout << connectedVertices->GetId(i) << " ";
    ids->InsertNextValue(connectedVertices->GetId(i));
  }
  std::cout << std::endl;

  vtkSmartPointer<vtkDataSetMapper> connectedVertexMapper =
    vtkSmartPointer<vtkDataSetMapper>::New();

  {
    vtkSmartPointer<vtkSelectionNode> selectionNode =
      vtkSmartPointer<vtkSelectionNode>::New();
    selectionNode->SetFieldType(vtkSelectionNode::POINT);
    selectionNode->SetContentType(vtkSelectionNode::INDICES);
    selectionNode->SetSelectionList(ids);

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

    vtkSmartPointer<vtkExtractSelection> extractSelection =
        vtkSmartPointer<vtkExtractSelection>::New();

    extractSelection->SetInputConnection(0, extractEdges->GetOutputPort());
    extractSelection->SetInputData(1, selection);
    extractSelection->Update();

    vtkSmartPointer<vtkVertexGlyphFilter> glyphFilter =
      vtkSmartPointer<vtkVertexGlyphFilter>::New();
    glyphFilter->SetInputConnection(extractSelection->GetOutputPort());
    glyphFilter->Update();

    connectedVertexMapper->SetInputConnection(glyphFilter->GetOutputPort());
  }

  vtkSmartPointer<vtkActor> connectedVertexActor =
    vtkSmartPointer<vtkActor>::New();
  connectedVertexActor->SetMapper(connectedVertexMapper);
  connectedVertexActor->GetProperty()->SetColor(1,0,0);
  connectedVertexActor->GetProperty()->SetPointSize(5);

  vtkSmartPointer<vtkDataSetMapper> queryVertexMapper =
    vtkSmartPointer<vtkDataSetMapper>::New();

  {
    vtkSmartPointer<vtkIdTypeArray> ids2 =
      vtkSmartPointer<vtkIdTypeArray>::New();
    ids2->SetNumberOfComponents(1);
    ids2->InsertNextValue(0);

    vtkSmartPointer<vtkSelectionNode> selectionNode =
      vtkSmartPointer<vtkSelectionNode>::New();
    selectionNode->SetFieldType(vtkSelectionNode::POINT);
    selectionNode->SetContentType(vtkSelectionNode::INDICES);
    selectionNode->SetSelectionList(ids2);

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

    vtkSmartPointer<vtkExtractSelection> extractSelection =
        vtkSmartPointer<vtkExtractSelection>::New();

    extractSelection->SetInputConnection(0, extractEdges->GetOutputPort());
    extractSelection->SetInputData(1, selection);
    extractSelection->Update();

    vtkSmartPointer<vtkVertexGlyphFilter> glyphFilter =
      vtkSmartPointer<vtkVertexGlyphFilter>::New();
    glyphFilter->SetInputConnection(extractSelection->GetOutputPort());
    glyphFilter->Update();

    queryVertexMapper->SetInputConnection(glyphFilter->GetOutputPort());
  }

  vtkSmartPointer<vtkActor> queryVertexActor =
    vtkSmartPointer<vtkActor>::New();
  queryVertexActor->SetMapper(queryVertexMapper);
  queryVertexActor->GetProperty()->SetColor(0,1,0);
  queryVertexActor->GetProperty()->SetPointSize(5);

  vtkSmartPointer<vtkDataSetMapper> sphereMapper =
    vtkSmartPointer<vtkDataSetMapper>::New();
  sphereMapper->SetInputConnection(extractEdges->GetOutputPort());
  vtkSmartPointer<vtkActor> sphereActor =
    vtkSmartPointer<vtkActor>::New();
  sphereActor->SetMapper(sphereMapper);

    //Create a renderer, render window, and interactor
  vtkSmartPointer<vtkRenderer> renderer =
    vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetRenderWindow(renderWindow);

  //Add the actors to the scene
  renderer->AddActor(sphereActor);
  renderer->AddActor(queryVertexActor);
  renderer->AddActor(connectedVertexActor);
  renderer->SetBackground(.3, .2, .1); // Background color dark red

  //Render and interact
  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

vtkSmartPointer<vtkIdList> GetConnectedVertices(vtkSmartPointer<vtkPolyData> mesh, int id)
{
  vtkSmartPointer<vtkIdList> connectedVertices =
      vtkSmartPointer<vtkIdList>::New();

  //get all cells that vertex 'id' is a part of
  vtkSmartPointer<vtkIdList> cellIdList =
      vtkSmartPointer<vtkIdList>::New();
  mesh->GetPointCells(id, cellIdList);

  /*
  cout << "Vertex 0 is used in cells ";
  for(vtkIdType i = 0; i < cellIdList->GetNumberOfIds(); i++)
    {
    cout << cellIdList->GetId(i) << ", ";
    }
  cout << endl;
  */

  for(vtkIdType i = 0; i < cellIdList->GetNumberOfIds(); i++)
  {
    //cout << "id " << i << " : " << cellIdList->GetId(i) << endl;

    vtkSmartPointer<vtkIdList> pointIdList =
      vtkSmartPointer<vtkIdList>::New();
    mesh->GetCellPoints(cellIdList->GetId(i), pointIdList);

    //cout << "End points are " << pointIdList->GetId(0) << " and " << pointIdList->GetId(1) << endl;

    if(pointIdList->GetId(0) != id)
    {
      //cout << "Connected to " << pointIdList->GetId(0) << endl;
      connectedVertices->InsertNextId(pointIdList->GetId(0));
    }
    else
    {
      //cout << "Connected to " << pointIdList->GetId(1) << endl;
      connectedVertices->InsertNextId(pointIdList->GetId(1));
    }
  }

  return connectedVertices;
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(VertexConnectivity)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  vtkFiltersExtraction
  vtkFiltersGeneral
  vtkFiltersSources
  vtkInteractionStyle
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping VertexConnectivity: ${VTK_NOT_FOUND_MESSAGE}")
  return ()
endif()
message (STATUS "VTK_VERSION: ${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
  # old system
  include(${VTK_USE_FILE})
  add_executable(VertexConnectivity MACOSX_BUNDLE VertexConnectivity.cxx )
  target_link_libraries(VertexConnectivity PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(VertexConnectivity MACOSX_BUNDLE VertexConnectivity.cxx )
  target_link_libraries(VertexConnectivity PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS VertexConnectivity
    MODULES ${VTK_LIBRARIES}
    )
endif () 

cd VertexConnectivity/build 

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./VertexConnectivity