VTK/Examples/Cxx/PolyData/PolyDataPointNormals

#include <vtkCellData.h>
#include <vtkCellArray.h>
#include <vtkDoubleArray.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPointData.h>
#include <vtkSmartPointer.h>
 
int main(int, char *[])
{
  ///////// Set Point Normals ///////////
  // Create 3 points
  vtkSmartPointer<vtkPoints> points =
    vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint(1.0, 0.0, 0.0);
  points->InsertNextPoint(0.0, 0.0, 0.0);
  points->InsertNextPoint(0.0, 1.0, 0.0);
 
  // Add the points to a polydata
  vtkSmartPointer<vtkPolyData> polydata =
    vtkSmartPointer<vtkPolyData>::New();
  polydata->SetPoints(points);
 
  // Set point normals
  vtkSmartPointer<vtkDoubleArray> pointNormalsArray = 
    vtkSmartPointer<vtkDoubleArray>::New();
  pointNormalsArray->SetNumberOfComponents(3); //3d normals (ie x,y,z)
  pointNormalsArray->SetNumberOfTuples(polydata->GetNumberOfPoints());
 
  // Construct the normal vectors
  double pN1[3] = {1.0, 0.0, 0.0};
  double pN2[3] = {0.0, 1.0, 0.0};
  double pN3[3] = {0.0, 0.0, 1.0};
 
  // Add the data to the normals array
  pointNormalsArray->SetTuple(0, pN1) ;
  pointNormalsArray->SetTuple(1, pN2) ;
  pointNormalsArray->SetTuple(2, pN3) ;
 
  // Add the normals to the points in the polydata
  polydata->GetPointData()->SetNormals(pointNormalsArray);
 
  ///////// Get Point Normals ///////////
  vtkSmartPointer<vtkDoubleArray> pointNormalsRetrieved = 
    vtkDoubleArray::SafeDownCast(polydata->GetPointData()->GetNormals());
  if(pointNormalsRetrieved)
    { 
    std::cout << "There are " << pointNormalsRetrieved->GetNumberOfTuples() 
              << " point normals." << std::endl;
 
    for(vtkIdType i = 0; i < pointNormalsRetrieved->GetNumberOfTuples(); i++)
      {
      double pN[3];
      pointNormalsRetrieved->GetTuple(i, pN);
      std::cout << "Point normal " << i << ": " 
                << pN[0] << " " << pN[1] << " " << pN[2] << std::endl;
      }
 
    }//end if(pointNormalsRetrieved)
  else
    {
    std::cout << "No point normals." << std::endl;
    }
 
  return EXIT_SUCCESS;
}