Method RequestData

Infovis/Core/vtkCollapseGraph.cxx:104–192

}

int vtkCollapseGraph::RequestData(vtkInformation* vtkNotUsed(request),
  vtkInformationVector** inputVector, vtkInformationVector* outputVector)
{
  // Ensure we have valid inputs ...
  vtkGraph* const input_graph = vtkGraph::GetData(inputVector[0]);
  vtkGraph* const output_graph = vtkGraph::GetData(outputVector);

  vtkSmartPointer<vtkIdTypeArray> input_indices = vtkSmartPointer<vtkIdTypeArray>::New();
  vtkConvertSelection::GetSelectedVertices(
    vtkSelection::GetData(inputVector[1]), input_graph, input_indices);

  // Convert the input selection into an "expanding" array that contains "true" for each
  // vertex that is expanding (i.e. its neighbors are collapsing into it)
  std::vector<bool> expanding(input_graph->GetNumberOfVertices(), false);

  for (vtkIdType i = 0; i != input_indices->GetNumberOfTuples(); ++i)
  {
    expanding[input_indices->GetValue(i)] = true;
  }

  // Create a mapping from each child vertex to its expanding neighbor (if any)
  std::vector<vtkIdType> parent(input_graph->GetNumberOfVertices());
  vtkSmartPointer<vtkInEdgeIterator> in_edge_iterator = vtkSmartPointer<vtkInEdgeIterator>::New();
  for (vtkIdType vertex = 0; vertex != input_graph->GetNumberOfVertices(); ++vertex)
  {
    // By default, vertices map to themselves, i.e: they aren't collapsed
    parent[vertex] = vertex;

    if (expanding[vertex])
      continue;

    input_graph->GetInEdges(vertex, in_edge_iterator);
    while (in_edge_iterator->HasNext())
    {
      const vtkIdType adjacent_vertex = in_edge_iterator->Next().Source;
      if (expanding[adjacent_vertex])
      {
        parent[vertex] = adjacent_vertex;
        break;
      }
    }
  }

  // Create a mapping from vertex IDs in the original graph to vertex IDs in the output graph
  std::vector<vtkIdType> vertex_map(input_graph->GetNumberOfVertices(), -1);
  for (vtkIdType old_vertex = 0, new_vertex = 0; old_vertex != input_graph->GetNumberOfVertices();
       ++old_vertex)
  {
    if (parent[old_vertex] != old_vertex)
      continue;

    vertex_map[old_vertex] = new_vertex++;
  }

  // Create a new edge list, mapping each edge from children to parents, eliminating duplicates as
  // we go
  EdgeListT edge_list;