[vtkusers] vtkSelection with GLOBALIDS, vtkExtractSelection returns empty

[John Platt]

Hi,

Try changing your selection array from vtkIntArray to vtkIdTypeArray and check that the filters copy the GLOBALIDS (the default is not to copy or interpolate).

John.
  ----- Original Message ----- 
  From: da xu 
  To: vtkusers at vtk.org 
  Sent: Wednesday, July 08, 2009 8:12 AM
  Subject: [vtkusers] vtkSelection with GLOBALIDS,vtkExtractSelection returns empty


  Hey all,

  I am trying to extract a section of my datasets using vtkSelection. I currently have a GUI that the user clicks on to select a start and end point using vtkPointPicker, returning the PointID. With a starting POINTID and ending POINTID, i then use a vtkSelection with field type POINT, ContentType GLOBALIDS to extract a dataset containing the points (with vtkSelectionNode's SetSelectionList correctly set I believe). However, I always end up extracting an empty grid.

  I can't figure out if:
   My vtkSelectionNode is set up incorrectly
   I'm using vtkExtractSelection incorrectly.
   The vtkPointPicker doesnt actually get GLOBALIDS ?
   Missing an update somewhere?

  Here is the code:

  // Set up vtkSelectionNode
      vtkSelection* selection = vtkSelection::New();
      vtkSelectionNode* selectionNode = vtkSelectionNode::New();
      selectionNode->SetFieldType(
  vtkSelectionNode::POINT);
      selectionNode->SetContentType(vtkSelectionNode::GLOBALIDS);

  // Populate the selection node with our GLOBALIDS (obtained from vtkPointPicker)
      vtkIntArray* intarray = vtkIntArray::New();
      for (int a = first; a < second; a++)
      {
          intarray->InsertNextValue(a);
      }
      selectionNode->SetSelectionList(intarray);
      selection->AddNode(selectionNode);

  // Some setup stuff, Our source data is from a multiblock data set
      vtkMultiBlockDataSet *extractFrom = vtkMultiBlockDataSet::SafeDownCast(m_v_modules.at(0)->getDataObject());
      int nblocks = extractFrom->GetNumberOfBlocks();

      vtkGeometryFilter *filter = vtkGeometryFilter::New();
      vtkDataSetMapper *mapper = vtkDataSetMapper::New();
      int counter=0;
      vtkExtractSelection* extractSelection = vtkExtractSelection::New();

  // Iterate through our datasets (structured grids) and apply vtkExtractSelection to them. Always extracts empty!
      vtkCompositeDataIterator *iter = extractFrom->NewIterator();
      iter->InitTraversal();

      int totalpoints = 0;
      while (!iter->IsDoneWithTraversal())
      {
          vtkDataSet* ds = vtkDataSet::SafeDownCast(iter->GetCurrentDataObject());
          if (ds)
          {
              const char* name = ds->GetClassName();    /// Temp debugger
              extractSelection->RemoveAllInputs();
              extractSelection->SetInput(0, ds);    /// Set the vtkDataSet for extraction
              extractSelection->SetInput(1, selection);    /// Set the vtkSelection for extraction
              vtkDataObject* extracted = extractSelection->GetOutput();
              extractSelection->Update();
              const char* name2 = extracted->GetClassName();    /// Temp debugger
              
              vtkUnstructuredGrid* unstructGridTest = vtkUnstructuredGrid::SafeDownCast(extracted);
              int ntemp1 = unstructGridTest->GetNumberOfPoints();
              totalpoints += ntemp1;
              counter++;
          }
          iter->GoToNextItem();
      }



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