Method RequestData

Filters/General/vtkGradientFilter.cxx:264–380

------------------------------------------------------------------------------

//------------------------------------------------------------------------------
int vtkGradientFilter::RequestData(vtkInformation* vtkNotUsed(request),
  vtkInformationVector** inputVector, vtkInformationVector* outputVector)
{
  vtkDebugMacro("RequestData");

  vtkInformation* inInfo = inputVector[0]->GetInformationObject(0);
  vtkInformation* outInfo = outputVector->GetInformationObject(0);

  vtkDataSet* input = vtkDataSet::SafeDownCast(inInfo->Get(vtkDataObject::DATA_OBJECT()));
  vtkDataSet* output = vtkDataSet::SafeDownCast(outInfo->Get(vtkDataObject::DATA_OBJECT()));
  vtkDataArray* array = this->GetInputArrayToProcess(0, inputVector);

  if (input->GetNumberOfCells() == 0)
  {
    // need cells to compute the gradient so if we don't have cells. we can't compute anything.
    // if we have points and an array with values provide a warning letting the user know that
    // no gradient will be computed because of the lack of cells. otherwise the dataset is
    // assumed empty and we can skip providing a warning message to the user.
    if (input->GetNumberOfPoints() && array && array->GetNumberOfTuples())
    {
      vtkWarningMacro("Cannot compute gradient for datasets without cells");
    }
    output->ShallowCopy(input);
    return 1;
  }

  if (array == nullptr)
  {
    vtkErrorMacro("No input array. If this dataset is part of a composite dataset"
      << " check to make sure that all non-empty blocks have this array.");
    return 0;
  }
  if (array->GetNumberOfComponents() == 0)
  {
    vtkErrorMacro("Input array must have at least one component.");
    return 0;
  }

  // we can only compute vorticity and Q criterion if the input
  // array has 3 components. if we can't compute them because of
  // this we only mark internally the we aren't computing them
  // since we don't want to change the state of the filter.
  bool computeVorticity = this->ComputeVorticity != 0;
  bool computeDivergence = this->ComputeDivergence != 0;
  bool computeQCriterion = this->ComputeQCriterion != 0;
  if ((this->ComputeQCriterion || this->ComputeVorticity || this->ComputeDivergence) &&
    array->GetNumberOfComponents() != 3)
  {
    vtkWarningMacro("Input array must have exactly three components with "
      << "ComputeDivergence, ComputeVorticity or ComputeQCriterion flag enabled."
      << "Skipping divergence, vorticity and Q-criterion computation.");
    computeVorticity = false;
    computeQCriterion = false;
    computeDivergence = false;
  }

  int fieldAssociation;
  if (vtkGradientFilterHasArray(input->GetPointData(), array))