ConnectedComponents
VTKExamples/Cxx/Graphs/ConnectedComponents
Description¶
This example constructs a graph with 4 vertices and 2 edges. V1 and V2 are not connected to V3 or V4. We wish to obtain all of the connected components of the graph. The output of the example is a list of component IDs. All vertices with the same ID can be reached from any vertex with the same ID.
Code¶
ConnectedComponents.cxx
#include <vtkSmartPointer.h> #include <vtkBoostConnectedComponents.h> #include <vtkDataArray.h> #include <vtkDataSetAttributes.h> #include <vtkGraph.h> #include <vtkIntArray.h> #include <vtkMutableUndirectedGraph.h> int main ( int, char *[] ) { vtkSmartPointer<vtkMutableUndirectedGraph> g = vtkSmartPointer<vtkMutableUndirectedGraph>::New(); vtkIdType v1 = g->AddVertex(); vtkIdType v2 = g->AddVertex(); vtkIdType v3 = g->AddVertex(); vtkIdType v4 = g->AddVertex(); g->AddEdge ( v1, v2 ); g->AddEdge ( v3, v4 ); vtkSmartPointer<vtkBoostConnectedComponents> connectedComponents = vtkSmartPointer<vtkBoostConnectedComponents>::New(); connectedComponents->SetInput(g); connectedComponents->Update(); vtkGraph* outputGraph = connectedComponents->GetOutput(); vtkIntArray* components = vtkIntArray::SafeDownCast( outputGraph->GetVertexData()->GetArray("component")); for(vtkIdType i = 0; i < components->GetNumberOfTuples(); i++) { int val = components->GetValue(i); std::cout << val << std::endl; } return EXIT_SUCCESS; }
CMakeLists.txt¶
cmake_minimum_required(VERSION 2.8) PROJECT(ConnectedComponents) find_package(VTK REQUIRED) include(${VTK_USE_FILE}) add_executable(ConnectedComponents MACOSX_BUNDLE ConnectedComponents.cxx) target_link_libraries(ConnectedComponents ${VTK_LIBRARIES})
Download and Build ConnectedComponents¶
Danger
The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.
Click here to download ConnectedComponents and its CMakeLists.txt file. Once the tarball ConnectedComponents.tar has been downloaded and extracted,
cd ConnectedComponents/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:
./ConnectedComponents
WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.