Method EvaluateGradient

Common/DataModel/vtkImplicitDataSet.cxx:99–149

Evaluate implicit function gradient.

// Evaluate implicit function gradient.
void vtkImplicitDataSet::EvaluateGradient(double x[3], double n[3])
{
  vtkDataArray* scalars;
  vtkCell* cell;
  vtkIdType id;
  int subId, i, numPts;
  double pcoords[3];

  // See if a dataset has been specified
  if (!this->DataSet || !(scalars = this->DataSet->GetPointData()->GetScalars()))
  {
    vtkErrorMacro(
      << "Can't evaluate gradient: either data set is missing or data set has no point data");
    for (i = 0; i < 3; i++)
    {
      n[i] = this->OutGradient[i];
    }
    return;
  }

  if (this->DataSet->GetMaxCellSize() > this->Size)
  {
    delete[] this->Weights;
    this->Weights = new double[this->DataSet->GetMaxCellSize()];
    this->Size = this->DataSet->GetMaxCellSize();
  }

  // Find the cell that contains xyz and get it
  cell =
    this->DataSet->FindAndGetCell(x, nullptr, -1, VTK_DBL_EPSILON, subId, pcoords, this->Weights);

  if (cell)
  { // Interpolate the point data
    numPts = cell->GetNumberOfPoints();

    for (i = 0; i < numPts; i++) // Weights used to hold scalar values
    {
      id = cell->PointIds->GetId(i);
      this->Weights[i] = scalars->GetComponent(id, 0);
    }
    cell->Derivatives(subId, pcoords, this->Weights, 1, n);
  }

  else
  { // use outside value
    for (i = 0; i < 3; i++)
    {
      n[i] = this->OutGradient[i];
    }
  }
}

void vtkImplicitDataSet::PrintSelf(ostream& os, vtkIndent indent)
{