# ReverseSense

VTKExamples/Cxx/PolyData/ReverseSense

### Code

ReverseSense.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPolyData.h>
    #include <vtkSphereSource.h>
    #include <vtkPointData.h>
    #include <vtkReverseSense.h>
    #include <vtkFloatArray.h>

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

      vtkSmartPointer<vtkFloatArray> pointNormals =
        vtkFloatArray::SafeDownCast(sphereSource->GetOutput()->GetPointData()->GetNormals());

      std::cout << std::endl << "Normals: " << std::endl;
      // Display the first few normals
      for(unsigned int i = 0; i < 5; i++)
      {
        double pN[3];
        pointNormals->GetTuple(i, pN);
        std::cout << "Point normal " << i << ": " << pN[0] << " " << pN[1] << " " << pN[2] << std::endl;
      }

      vtkSmartPointer<vtkReverseSense> reverseSense =
        vtkSmartPointer<vtkReverseSense>::New();
      reverseSense->SetInputConnection(sphereSource->GetOutputPort());
      reverseSense->ReverseNormalsOn();
      reverseSense->Update();

      vtkSmartPointer<vtkFloatArray> reversedNormals =
        vtkFloatArray::SafeDownCast(reverseSense->GetOutput()->GetPointData()->GetNormals());

      std::cout << std::endl << "Reversed: " << std::endl;
      // Display the first few normals to verify that they are flipped
      for(unsigned int i = 0; i < 5; i++)
      {
        double pN[3];
        reversedNormals->GetTuple(i, pN);
        std::cout << "Reversed normal " << i << ": " << pN[0] << " " << pN[1] << " " << pN[2] << std::endl;
      }

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(ReverseSense)

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

    add_executable(ReverseSense MACOSX_BUNDLE ReverseSense.cxx)

    target_link_libraries(ReverseSense ${VTK_LIBRARIES})

### Download and Build ReverseSense

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

    cd ReverseSense/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:

    ./ReverseSense

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.