# MeshQuality

VTKExamples/Cxx/PolyData/MeshQuality

### Description

This example uses one of many selectable methods to determine the quality of a mesh. In this case, we have selected to use the area of the triangles. We show how to retrieve the quality metric computed on each triangle after the process is completed.

### Code

MeshQuality.cxx

    #include <vtkVersion.h>
    #include <vtkPolyData.h>
    #include <vtkPointData.h>
    #include <vtkCellData.h>
    #include <vtkDoubleArray.h>
    #include <vtkDataSet.h>
    #include <vtkMeshQuality.h>
    #include <vtkSmartPointer.h>
    #include <vtkSphereSource.h>
    #include <vtkTriangleFilter.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>

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

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

      vtkPolyData* mesh = triangleFilter->GetOutput();
      std::cout << "There are " << mesh->GetNumberOfCells() << " cells." << std::endl;

      vtkSmartPointer<vtkMeshQuality> qualityFilter =
        vtkSmartPointer<vtkMeshQuality>::New();
    #if VTK_MAJOR_VERSION <= 5
      qualityFilter->SetInputConnection(mesh->GetProducerPort());
    #else
      qualityFilter->SetInputData(mesh);
    #endif
      qualityFilter->SetTriangleQualityMeasureToArea();
      qualityFilter->Update();

      vtkSmartPointer<vtkDoubleArray> qualityArray =
        vtkDoubleArray::SafeDownCast(qualityFilter->GetOutput()->GetCellData()->GetArray("Quality"));

      std::cout << "There are " << qualityArray->GetNumberOfTuples() << " values." << std::endl;

      for(vtkIdType i = 0; i < qualityArray->GetNumberOfTuples(); i++)
      {
        double val = qualityArray->GetValue(i);
        std::cout << "value " << i << " : " << val << std::endl;
      }

      vtkSmartPointer<vtkPolyData> polydata =
        vtkSmartPointer<vtkPolyData>::New();
      polydata->ShallowCopy(qualityFilter->GetOutput());

      // Visualize
      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
    #if VTK_MAJOR_VERSION <= 5
      mapper->SetInputConnection(polydata->GetProducerPort());
    #else
      mapper->SetInputData(polydata);
    #endif
      mapper->SetScalarRange(polydata->GetScalarRange());

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

      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      renderer->AddActor(actor);
      renderer->SetBackground(.3, .6, .3); // Background color green

      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(MeshQuality)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(MeshQuality MACOSX_BUNDLE MeshQuality.cxx )

    target_link_libraries(MeshQuality ${VTK_LIBRARIES})

### Download and Build MeshQuality

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

    cd MeshQuality/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:

    ./MeshQuality

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.