Function TraverseLoop

Filters/Modeling/vtkContourLoopExtraction.cxx:73–117

March along connected lines to the end---------------------------------- pts[0] is assumed to be the starting point and already inserted.

// March along connected lines to the end----------------------------------
// pts[0] is assumed to be the starting point and already inserted.
vtkIdType TraverseLoop(double dir, vtkPolyData* polyData, vtkIdType lineId, vtkIdType start,
  LoopPointType& sortedPoints, std::vector<signed char>& visited, vtkDataArray* scalars,
  double range[2])
{
  vtkIdType last = start, numInserted = 0;
  double t = 0.0;
  bool terminated = false;
  vtkIdType ncells;
  vtkIdType npts;
  const vtkIdType* pts;
  vtkIdType* cells;
  vtkIdType nei;
  vtkIdType lastCell = lineId;
  polyData->GetCellPoints(lineId, npts, pts);

  // Recall that we are working with 2-pt lines
  while (!terminated)
  {
    last = (pts[0] != last ? pts[0] : pts[1]);
    numInserted++;
    t = dir * static_cast<double>(numInserted);
    sortedPoints.emplace_back(t, last);
    UpdateRange(scalars, last, range);

    polyData->GetPointCells(last, ncells, cells);
    if (ncells == 1 || last == start) // this is the last point
    {
      return last;
    }
    else if (ncells == 2) // continue along loop
    {
      nei = (cells[0] != lastCell ? cells[0] : cells[1]);
      polyData->GetCellPoints(nei, npts, pts);
      visited[nei] = 1;
      lastCell = nei;
    }
    else // non-manifold, for now just quit (TODO: break apart loops)
    {
      terminated = true;
      break;
    }
  }

  return last;
}

// March along connected lines to the end----------------------------------
void OutputPolygon(LoopPointType& sortedPoints, vtkPoints* inPts, vtkCellArray* outLines,