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ConnectivityFilterDemo

vtk-examples/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 question about this example, please use the VTK Discourse Forum

Code

ConnectivityFilterDemo.cxx

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkDataSetMapper.h>
#include <vtkLookupTable.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPolyDataConnectivityFilter.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.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 <cctype>    // For to_lower
#include <string>    // For find_last_of()

#include <random>

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

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

  vtkNew<vtkPolyDataConnectivityFilter> connectivityFilter;
  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;
  }
  vtkNew<vtkLookupTable> lut;
  lut->SetNumberOfTableValues(std::max(numberOfRegions, 10));
  lut->Build();

  // Fill in a few known colors, the rest will be generated if needed.
  vtkNew<vtkNamedColors> colors;
  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);
    }
  }
  vtkNew<vtkDataSetMapper> mapper;
  mapper->SetInputConnection(connectivityFilter->GetOutputPort());
  mapper->SetScalarRange(0,
                         connectivityFilter->GetNumberOfExtractedRegions() - 1);
  mapper->SetLookupTable(lut);
  mapper->Update();

  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);

  vtkNew<vtkRenderer> renderer;
  renderer->AddActor(actor);
  renderer->UseHiddenLineRemovalOn();
  renderer->SetBackground(colors->GetColor3d("Silver").GetData());

  vtkNew<vtkRenderWindow> renderWindow;
  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->SetWindowName("ConnectivityFilterDemo");
  renderWindow->Render();

  vtkNew<vtkRenderWindowInteractor> interactor;
  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 3.12 FATAL_ERROR)

project(ConnectivityFilterDemo)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ConnectivityFilterDemo: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
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}
)

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.