Function TestDataSetGradient

Filters/General/Testing/Cxx/TestDataSetGradient.cxx:28–127

#include "vtkTestUtilities.h"

int TestDataSetGradient(int argc, char* argv[])
{
  char* fileName = vtkTestUtilities::ExpandDataFileName(argc, argv, "Data/hexa.vtk");

  // Read the data
  vtkSmartPointer<vtkUnstructuredGridReader> reader =
    vtkSmartPointer<vtkUnstructuredGridReader>::New();
  reader->SetFileName(fileName);
  delete[] fileName;

  // This class computes the gradient for each cell
  vtkSmartPointer<vtkDataSetGradient> gradient = vtkSmartPointer<vtkDataSetGradient>::New();
  gradient->SetInputConnection(reader->GetOutputPort());
  gradient->SetInputArrayToProcess(0, 0, 0, 0, "scalars");
  gradient->Update();

  // Create a polydata
  //  Points at the parametric center of each cell
  //  PointData contains the gradient
  vtkDoubleArray* gradientAtCenters =
    vtkDoubleArray::SafeDownCast(gradient->GetOutput()->GetCellData()->GetArray("gradient"));

  vtkSmartPointer<vtkDoubleArray> gradients = vtkSmartPointer<vtkDoubleArray>::New();
  gradients->ShallowCopy(gradientAtCenters);

  vtkSmartPointer<vtkPolyData> polyData = vtkSmartPointer<vtkPolyData>::New();
  vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
  points->SetNumberOfPoints(gradient->GetOutput()->GetNumberOfCells());

  vtkSmartPointer<vtkGenericCell> aCell = vtkSmartPointer<vtkGenericCell>::New();
  for (vtkIdType cellId = 0; cellId < gradient->GetOutput()->GetNumberOfCells(); ++cellId)
  {
    gradient->GetOutput()->GetCell(cellId, aCell);
    reader->GetOutput()->GetCell(cellId, aCell);

    double pcenter[3], center[3];
    aCell->GetParametricCenter(pcenter);
    std::vector<double> cweights(aCell->GetNumberOfPoints());
    int pSubId = 0;
    aCell->EvaluateLocation(pSubId, pcenter, center, &(*cweights.begin()));
    points->SetPoint(cellId, center);
  }
  polyData->SetPoints(points);
  polyData->GetPointData()->SetVectors(gradientAtCenters);

  // Select a small percentage of the gradients
  // Use 10% of the points
  int onRatio =
    reader->GetOutput()->GetNumberOfPoints() / (reader->GetOutput()->GetNumberOfPoints() * .1);

  vtkSmartPointer<vtkMaskPoints> maskPoints = vtkSmartPointer<vtkMaskPoints>::New();
  maskPoints->SetInputData(polyData);
  maskPoints->RandomModeOff();
  maskPoints->SetOnRatio(onRatio);

  // Create the Glyphs for the gradient
  vtkSmartPointer<vtkArrowSource> arrowSource = vtkSmartPointer<vtkArrowSource>::New();