CellEdgeNeighbors

VTKExamples/Cxx/PolyData/CellEdgeNeighbors


Description

Determine which cells share an edge with a specified cell.

Question

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Code

CellEdgeNeighbors.cxx

#include <vtkActor.h>
#include <vtkCell.h>
#include <vtkDataSetMapper.h>
#include <vtkExtractSelection.h>
#include <vtkIdList.h>
#include <vtkIdTypeArray.h>
#include <vtkNamedColors.h>
#include <vtkPolyData.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSelection.h>
#include <vtkSelectionNode.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkTriangleFilter.h>

#include <list>

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

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

  vtkIdType cellId = 0;

  auto cellPointIds = vtkSmartPointer<vtkIdList>::New();
  triangleFilter->GetOutput()->GetCellPoints(cellId, cellPointIds);

  std::list<vtkIdType> neighbors;

  for (vtkIdType i = 0; i < cellPointIds->GetNumberOfIds(); i++)
  {
    auto idList = vtkSmartPointer<vtkIdList>::New();

    // add one of the edge points
    idList->InsertNextId(cellPointIds->GetId(i));

    // add the other edge point
    if (i + 1 == cellPointIds->GetNumberOfIds())
    {
      idList->InsertNextId(cellPointIds->GetId(0));
    }
    else
    {
      idList->InsertNextId(cellPointIds->GetId(i + 1));
    }

    // get the neighbors of the cell
    auto neighborCellIds = vtkSmartPointer<vtkIdList>::New();

    triangleFilter->GetOutput()->GetCellNeighbors(cellId, idList,
                                                  neighborCellIds);

    for (vtkIdType j = 0; j < neighborCellIds->GetNumberOfIds(); j++)
    {
      neighbors.push_back(neighborCellIds->GetId(j));
    }
  }

  std::cout << "Edge neighbor ids are: " << std::endl;

  for (auto it1 = neighbors.begin(); it1 != neighbors.end(); ++it1)
  {
    std::cout << " " << *it1;
  }
  std::cout << std::endl;

  auto colors = vtkSmartPointer<vtkNamedColors>::New();

  auto sphereMapper = vtkSmartPointer<vtkDataSetMapper>::New();
  sphereMapper->SetInputConnection(sphereSource->GetOutputPort());
  sphereMapper->SetResolveCoincidentTopologyToPolygonOffset();

  auto sphereActor = vtkSmartPointer<vtkActor>::New();
  sphereActor->SetMapper(sphereMapper);
  sphereActor->GetProperty()->SetEdgeColor(
      colors->GetColor3d("Lamp_Black").GetData());
  sphereActor->GetProperty()->EdgeVisibilityOn();
  sphereActor->GetProperty()->SetLineWidth(5);

  auto mainCellMapper = vtkSmartPointer<vtkDataSetMapper>::New();

  auto neighborCellsMapper = vtkSmartPointer<vtkDataSetMapper>::New();

  // Create a dataset with the cell of interest
  {
    auto ids = vtkSmartPointer<vtkIdTypeArray>::New();
    ids->SetNumberOfComponents(1);
    ids->InsertNextValue(cellId);

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

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

    auto extractSelection = vtkSmartPointer<vtkExtractSelection>::New();
    extractSelection->SetInputConnection(0, sphereSource->GetOutputPort());
    extractSelection->SetInputData(1, selection);
    extractSelection->Update();

    mainCellMapper->SetInputConnection(extractSelection->GetOutputPort());
  }

  auto mainCellActor = vtkSmartPointer<vtkActor>::New();
  mainCellActor->SetMapper(mainCellMapper);
  mainCellActor->GetProperty()->SetColor(
      colors->GetColor3d("Tomato").GetData());

  // Create a dataset with the neighbor cells
  {
    auto ids = vtkSmartPointer<vtkIdTypeArray>::New();
    ids->SetNumberOfComponents(1);
    for (auto it1 = neighbors.begin(); it1 != neighbors.end(); ++it1)
    {
      ids->InsertNextValue(*it1);
    }

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

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

    auto extractSelection = vtkSmartPointer<vtkExtractSelection>::New();
    extractSelection->SetInputConnection(0, sphereSource->GetOutputPort());
    extractSelection->SetInputData(1, selection);
    extractSelection->Update();

    neighborCellsMapper->SetInputConnection(extractSelection->GetOutputPort());
  }

  auto neighborCellsActor = vtkSmartPointer<vtkActor>::New();
  neighborCellsActor->SetMapper(neighborCellsMapper);
  neighborCellsActor->GetProperty()->SetColor(
      colors->GetColor3d("Mint").GetData());

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

  // Add the actors to the scene
  renderer->AddActor(sphereActor);
  renderer->AddActor(mainCellActor);
  renderer->AddActor(neighborCellsActor);
  renderer->SetBackground(colors->GetColor3d("Slate_grey").GetData());

  // Render and interact
  renderWindow->SetSize(640, 480);
  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(CellEdgeNeighbors)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  vtkFiltersExtraction
  vtkFiltersSources
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping CellEdgeNeighbors: ${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(CellEdgeNeighbors MACOSX_BUNDLE CellEdgeNeighbors.cxx )
  target_link_libraries(CellEdgeNeighbors PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(CellEdgeNeighbors MACOSX_BUNDLE CellEdgeNeighbors.cxx )
  target_link_libraries(CellEdgeNeighbors PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS CellEdgeNeighbors
    MODULES ${VTK_LIBRARIES}
    )
endif () 

Download and Build CellEdgeNeighbors

Click here to download CellEdgeNeighbors and its CMakeLists.txt file. Once the tarball CellEdgeNeighbors.tar has been downloaded and extracted,

cd CellEdgeNeighbors/build 

If VTK is installed:

cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

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

Build the project:

make

and run it:

./CellEdgeNeighbors

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.