PolyDataConnectivityFilter LargestRegion

VTKEx/Cxx/PolyData/PolyDataConnectivityFilter_LargestRegion

Description

This example uses vtkPolyDataConnectivityFilter to keep the largest connected region of a mesh. Note that this is based on the number of points, not the actual area of the region.

The original vtkPolyData is red, on top. The extracted region is yellow, on the bottom.

Note

Contrast this with PolyDataConnectivityFilter_SpecifiedRegion.

Note

Contributed by: Jinyoung Hwang

Other languages

See (CSharp)

Question

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

Code

PolyDataConnectivityFilter_LargestRegion.cxx

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

#include <vtkSphereSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkProperty.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkAppendPolyData.h>

#include <vtkNamedColors.h>

int main(int, char *[])
{
  vtkSmartPointer<vtkNamedColors> colors =
    vtkSmartPointer<vtkNamedColors>::New();

  // Small sphere
  vtkSmartPointer<vtkSphereSource> sphereSource1 = 
    vtkSmartPointer<vtkSphereSource>::New();
  sphereSource1->SetRadius(5);

  // Large sphere
  vtkSmartPointer<vtkSphereSource> sphereSource2 = 
    vtkSmartPointer<vtkSphereSource>::New();
  sphereSource2->SetRadius(10);
  sphereSource2->SetCenter(25,0,0);
  sphereSource2->SetThetaResolution(10);
  sphereSource2->SetPhiResolution(10);

  vtkSmartPointer<vtkAppendPolyData> appendFilter = 
    vtkSmartPointer<vtkAppendPolyData>::New();
  appendFilter->AddInputConnection(sphereSource1->GetOutputPort());
  appendFilter->AddInputConnection(sphereSource2->GetOutputPort());

  vtkSmartPointer<vtkPolyDataConnectivityFilter> connectivityFilter = 
    vtkSmartPointer<vtkPolyDataConnectivityFilter>::New();
  connectivityFilter->SetInputConnection(appendFilter->GetOutputPort());
  connectivityFilter->SetExtractionModeToLargestRegion(); 

  // Create a mapper and actor for original data
  vtkSmartPointer<vtkPolyDataMapper> originalMapper = 
    vtkSmartPointer<vtkPolyDataMapper>::New();
  originalMapper->SetInputConnection(appendFilter->GetOutputPort());

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

  // Create a mapper and actor for extracted data
  vtkSmartPointer<vtkPolyDataMapper> extractedMapper = 
    vtkSmartPointer<vtkPolyDataMapper>::New();
  extractedMapper->SetInputConnection(connectivityFilter->GetOutputPort());
  extractedMapper->Update();

  vtkSmartPointer<vtkActor> extractedActor = 
    vtkSmartPointer<vtkActor>::New();
  extractedActor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());
  extractedActor->SetMapper(extractedMapper);
  extractedActor->SetPosition(0,-20,0);

  // Visualization
  vtkSmartPointer<vtkRenderer> renderer = 
    vtkSmartPointer<vtkRenderer>::New();
  renderer->AddActor(originalActor);
  renderer->AddActor(extractedActor);
  renderer->GradientBackgroundOn();
  renderer->SetBackground (colors->GetColor3d("Gold").GetData());
  renderer->SetBackground2 (colors->GetColor3d("Silver").GetData());

  vtkSmartPointer<vtkRenderWindow> renderWindow = 
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);

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

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(PolyDataConnectivityFilter_LargestRegion)

find_package(VTK COMPONENTS 
  vtkvtkCommonColor
  vtkvtkCommonCore
  vtkvtkFiltersCore
  vtkvtkFiltersSources
  vtkvtkInteractionStyle
  vtkvtkRenderingContextOpenGL2
  vtkvtkRenderingCore
  vtkvtkRenderingFreeType
  vtkvtkRenderingGL2PSOpenGL2
  vtkvtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping PolyDataConnectivityFilter_LargestRegion: ${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(PolyDataConnectivityFilter_LargestRegion MACOSX_BUNDLE PolyDataConnectivityFilter_LargestRegion.cxx )
  target_link_libraries(PolyDataConnectivityFilter_LargestRegion PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(PolyDataConnectivityFilter_LargestRegion MACOSX_BUNDLE PolyDataConnectivityFilter_LargestRegion.cxx )
  target_link_libraries(PolyDataConnectivityFilter_LargestRegion PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS PolyDataConnectivityFilter_LargestRegion
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build PolyDataConnectivityFilter_LargestRegion

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

cd PolyDataConnectivityFilter_LargestRegion/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:

./PolyDataConnectivityFilter_LargestRegion

WINDOWS USERS

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