Method ComputeTopologicalDistance

Filters/Modeling/vtkSelectPolyData.cxx:398–488

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vtkIdType vtkSelectPolyData::ComputeTopologicalDistance(
  vtkPolyData* mesh, vtkIdList* edgePointIds, vtkIntArray* pointMarks, vtkIntArray* cellMarks)
{
  vtkIdType numPts = mesh->GetNumberOfPoints();
  vtkIdType numCells = mesh->GetNumberOfCells();

  // Next, prepare to mark off inside/outside and on boundary of loop.
  // Mark the boundary of the loop using point marks. Also initialize
  // the advancing front (used to mark traversal/compute scalars).
  // Prepare to compute the advancing front

  // Mark all points and cells as unvisited
  cellMarks->SetNumberOfValues(numCells);
  const int unvisited = VTK_INT_MAX;
  for (vtkIdType i = 0; i < numCells; i++)
  {
    cellMarks->SetValue(i, unvisited);
  }
  pointMarks->SetNumberOfValues(numPts);
  for (vtkIdType i = 0; i < numPts; i++)
  {
    pointMarks->SetValue(i, unvisited);
  }

  // Current and next front contain point IDs
  vtkSmartPointer<vtkIdList> currentFront = vtkSmartPointer<vtkIdList>::New();
  vtkSmartPointer<vtkIdList> nextFront = vtkSmartPointer<vtkIdList>::New();
  vtkIdType numMeshLoopPts = edgePointIds->GetNumberOfIds();
  for (vtkIdType i = 0; i < numMeshLoopPts; i++)
  {
    vtkIdType id = edgePointIds->GetId(i);
    pointMarks->SetValue(id, 0); // marks the start of the front
    currentFront->InsertNextId(id);
  }

  // Traverse the front as long as we can. We're basically computing a
  // topological distance.
  int maxFrontValue = 0;
  vtkIdType maxFrontCell = (-1);
  int currentFrontValue = 1;
  vtkIdType numPtsInFront = 0;
  while ((numPtsInFront = currentFront->GetNumberOfIds()))
  {
    // Process all triangles around the current front points
    for (vtkIdType i = 0; i < numPtsInFront; i++)
    {
      vtkIdType id = currentFront->GetId(i);
      vtkIdType* cells;
      vtkIdType ncells;
      mesh->GetPointCells(id, ncells, cells);
      for (vtkIdType j = 0; j < ncells; j++)
      {
        id = cells[j];
        if (cellMarks->GetValue(id) != unvisited)
        {
          // the cell is already visited
          continue;
        }