CellPointNeighbors

VTKExamples/Cxx/PolyData/CellPointNeighbors


Description

Determine which cells share at least a single point with a specified cell.

Code

CellPointNeighbors.cxx

#include <vtkSmartPointer.h>

#include <vtkSphereSource.h>
#include <vtkPolyData.h>
#include <vtkIdList.h>
#include <vtkCell.h>
#include <vtkTriangleFilter.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 <vtkNamedColors.h>

#include <list>

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

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

  // Find all cells connected to point 0
  vtkIdType cellId = 0;

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

  // neighbor cells may be listed multiple times
  // use std::set instead of std::list if you want a unique list of neighbors
  std::list<vtkIdType> neighbors;

  /*For each vertice of the cell, we calculate which cells uses that point.
   So if we make this, for each vertice, we have all the neighbors.
   In the case we use ''cellPointIds'' as a parameter of ''GeteCellNeighbors'',
   we will obtain an empty set. Because the only cell that is using that set of points
   is the current one. That is why we have to make each vertice at time.*/

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

    //get the neighbors of the cell
    vtkSmartPointer<vtkIdList> 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 << "Point neighbor ids are: " << std::endl;

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

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

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

  vtkSmartPointer<vtkActor> sphereActor =
    vtkSmartPointer<vtkActor>::New();
  sphereActor->SetMapper(sphereMapper);
  sphereActor->GetProperty()->SetEdgeColor(colors->GetColor3d("Lamp_Black").GetData());
  sphereActor->GetProperty()->EdgeVisibilityOn();
  sphereActor->GetProperty()->SetLineWidth(3);

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

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

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

    vtkSmartPointer<vtkSelectionNode> selectionNode =
      vtkSmartPointer<vtkSelectionNode>::New();
    selectionNode->SetFieldType(vtkSelectionNode::CELL);
    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, sphereSource->GetOutputPort());
    extractSelection->SetInputData(1, selection);
    extractSelection->Update();

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

  }

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

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

    vtkSmartPointer<vtkSelectionNode> selectionNode =
      vtkSmartPointer<vtkSelectionNode>::New();
    selectionNode->SetFieldType(vtkSelectionNode::CELL);
    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, sphereSource->GetOutputPort());
    extractSelection->SetInputData(1, selection);
    extractSelection->Update();

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

  }

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

  //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(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(CellPointNeighbors)

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

Download and Build CellPointNeighbors

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

cd CellPointNeighbors/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:

./CellPointNeighbors

WINDOWS USERS

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