Method CellBoundary

Common/DataModel/vtkPolygon.cxx:1756–1820

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

//------------------------------------------------------------------------------
int vtkPolygon::CellBoundary(int vtkNotUsed(subId), const double pcoords[3], vtkIdList* pts)
{
  int i, numPts = this->PointIds->GetNumberOfIds();
  double x[3];
  int closestPoint = 0, previousPoint, nextPoint;
  double largestWeight = 0.0;
  double p0[3], p10[3], l10, p20[3], l20, n[3];

  pts->Reset();
  std::vector<double> weights(numPts);

  // determine global coordinates given parametric coordinates
  this->ParameterizePolygon(p0, p10, l10, p20, l20, n);
  for (i = 0; i < 3; i++)
  {
    x[i] = p0[i] + pcoords[0] * p10[i] + pcoords[1] * p20[i];
  }

  // find edge with largest and next largest weight values. This will be
  // the closest edge.
  this->InterpolateFunctions(x, weights.data());
  for (i = 0; i < numPts; i++)
  {
    if (weights[i] > largestWeight)
    {
      closestPoint = i;
      largestWeight = weights[i];
    }
  }

  pts->InsertId(0, this->PointIds->GetId(closestPoint));

  previousPoint = closestPoint - 1;
  nextPoint = closestPoint + 1;
  if (previousPoint < 0)
  {
    previousPoint = numPts - 1;
  }
  if (nextPoint >= numPts)
  {
    nextPoint = 0;
  }

  if (weights[previousPoint] > weights[nextPoint])
  {
    pts->InsertId(1, this->PointIds->GetId(previousPoint));
  }
  else
  {
    pts->InsertId(1, this->PointIds->GetId(nextPoint));
  }

  // determine whether point is inside of polygon
  if (pcoords[0] >= 0.0 && pcoords[0] <= 1.0 && pcoords[1] >= 0.0 && pcoords[1] <= 1.0 &&
    (this->PointInPolygon(x, this->Points->GetNumberOfPoints(),
       static_cast<vtkDoubleArray*>(this->Points->GetData())->GetPointer(0), this->GetBounds(),
       n) == VTK_POLYGON_INSIDE))
  {