ConnectivityFilterDemo

VTKExamples/Cxx/Filtering/ConnectivityFilterDemo


Description

This example uses vtkPolyDataConnectivity to separate an input vtkPolyData into disconnected regions. Each region is assigned a unique color. A number of vtkNamedColors are used to fill part of the vtkLookupTable. If the number of extracted regions is more that the number of specified colors, the remaining colors are generated with a random number generator.

The default representation is surface. If the user types a "w" in the render window, the view will be rendered as a wireframe. The renderer will use hidden line removal.

The example supports any vtkPolyData reader.

Info

ConnectivityFilter illustrates vtkConnectivityFilter on a simple 2 region dataset.

Question

If you have a simple question about this example contact us at VTKExamplesProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

Code

ConnectivityFilterDemo.cxx

#include <vtkSmartPointer.h>
#include <vtkPolyDataConnectivityFilter.h>

#include <vtkSphereSource.h>
#include <vtkDataSetMapper.h>

#include <vtkLookupTable.h>
#include <vtkCamera.h>
#include <vtkActor.h>
#include <vtkProperty.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkAppendPolyData.h>
#include <vtkScalarsToColors.h>
#include <vtkNamedColors.h>

// Readers
#include <vtkBYUReader.h>
#include <vtkOBJReader.h>
#include <vtkPLYReader.h>
#include <vtkPolyDataReader.h>
#include <vtkSTLReader.h>
#include <vtkXMLPolyDataReader.h>

#include <vtkPolyData.h>
#include <vtkSphereSource.h>

#include <algorithm> // For transform()
#include <string> // For find_last_of()
#include <cctype> // For to_lower

#include <random>

namespace
{
vtkSmartPointer<vtkPolyData> ReadPolyData(std::string const& fileName);
}

int main(int argc, char*argv[])
{
  vtkSmartPointer<vtkPolyData> polyData =
    ReadPolyData(argc > 1 ? argv[1] : "");

  auto connectivityFilter =
    vtkSmartPointer<vtkPolyDataConnectivityFilter>::New();
  connectivityFilter->SetInputData(polyData);
  connectivityFilter->SetExtractionModeToAllRegions();
  connectivityFilter->ColorRegionsOn();
  connectivityFilter->Update();

  // Visualize
  int numberOfRegions = connectivityFilter->GetNumberOfExtractedRegions();
  if (argc > 1)
    {
      std::cout << argv[1] << " contains " << numberOfRegions << " regions" << std::endl;
    }
    else
    {
      std::cout << "Generated data" << " contains " << numberOfRegions << " regions" << std::endl;
    }
  auto lut =
    vtkSmartPointer<vtkLookupTable>::New();
  lut->SetNumberOfTableValues(std::max(numberOfRegions, 10));
  lut->Build();

  // Fill in a few known colors, the rest will be generated if needed
  auto colors =
    vtkSmartPointer<vtkNamedColors>::New();
  lut->SetTableValue(0, colors->GetColor4d("Gold").GetData());
  lut->SetTableValue(1, colors->GetColor4d("Banana").GetData());
  lut->SetTableValue(2, colors->GetColor4d("Tomato").GetData());
  lut->SetTableValue(3, colors->GetColor4d("Wheat").GetData());
  lut->SetTableValue(4, colors->GetColor4d("Lavender").GetData());
  lut->SetTableValue(5, colors->GetColor4d("Flesh").GetData());
  lut->SetTableValue(6, colors->GetColor4d("Raspberry").GetData());
  lut->SetTableValue(7, colors->GetColor4d("Salmon").GetData());
  lut->SetTableValue(8, colors->GetColor4d("Mint").GetData());
  lut->SetTableValue(9, colors->GetColor4d("Peacock").GetData());

  // If the number of regions os larger than the number of specified colors,
  // generate some random colors.
  if (numberOfRegions > 9)
  {
    std::mt19937 mt(4355412); //Standard mersenne_twister_engine
    std::uniform_real_distribution<double> distribution(.4, 1.0);
    for (auto i = 10; i < numberOfRegions; ++i)
    {
      lut->SetTableValue(i, distribution(mt), distribution(mt), distribution(mt), 1.0);
    }
  }
  auto mapper =
    vtkSmartPointer<vtkDataSetMapper>::New();
  mapper->SetInputConnection(connectivityFilter->GetOutputPort());
  mapper->SetScalarRange(0, connectivityFilter->GetNumberOfExtractedRegions() - 1);
  mapper->SetLookupTable(lut);
  mapper->Update();

  auto  actor =
    vtkSmartPointer<vtkActor>::New();
  actor->SetMapper(mapper);

  auto  renderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderer->AddActor(actor);
  renderer->UseHiddenLineRemovalOn();
  renderer->SetBackground(colors->GetColor3d("Silver").GetData());

  auto  renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(640, 480);

  // Pick a good view
  renderer->GetActiveCamera()->SetFocalPoint(0.0, 0.0, 0.0);
  renderer->GetActiveCamera()->SetPosition(0.0, 1.0, 0.0);
  renderer->GetActiveCamera()->SetViewUp(0.0, 0.0, 1.0);
  renderer->GetActiveCamera()->Azimuth(30.0);
  renderer->GetActiveCamera()->Elevation(45.0);
  renderer->ResetCamera();
  renderer->GetActiveCamera()->Dolly(1.25);
  renderer->ResetCameraClippingRange();
  renderWindow->Render();

  auto  interactor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  interactor->SetRenderWindow(renderWindow);
  interactor->Initialize();
  interactor->Start();

  return EXIT_SUCCESS;
}
namespace {
vtkSmartPointer<vtkPolyData> ReadPolyData(std::string const& fileName)
{
  vtkSmartPointer<vtkPolyData> polyData;
  std::string extension = "";
  if (fileName.find_last_of(".") != std::string::npos)
  {
    extension = fileName.substr(fileName.find_last_of("."));
  }
  // Make the extension lowercase
  std::transform(extension.begin(), extension.end(), extension.begin(),
                 ::tolower);
  if (extension == ".ply")
  {
    auto reader = vtkSmartPointer<vtkPLYReader>::New();
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtp")
  {
    auto reader = vtkSmartPointer<vtkXMLPolyDataReader>::New();
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".obj")
  {
    auto reader = vtkSmartPointer<vtkOBJReader>::New();
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".stl")
  {
    auto reader = vtkSmartPointer<vtkSTLReader>::New();
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtk")
  {
    auto reader = vtkSmartPointer<vtkPolyDataReader>::New();
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".g")
  {
    auto reader = vtkSmartPointer<vtkBYUReader>::New();
    reader->SetGeometryFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else
  {
    // Return a polydata sphere if the extension is unknown.
    auto source = vtkSmartPointer<vtkSphereSource>::New();
    source->SetThetaResolution(20);
    source->SetPhiResolution(11);
    source->Update();
    polyData = source->GetOutput();
  }
  return polyData;
}
} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ConnectivityFilterDemo)

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

Download and Build ConnectivityFilterDemo

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

cd ConnectivityFilterDemo/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:

./ConnectivityFilterDemo

WINDOWS USERS

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