ENH: Adding a tree layout example to VTK.

Examples/Infovis/Cxx/CMakeLists.txt

+PROJECT(Infovis)
+
+FIND_PACKAGE(VTK REQUIRED)
+IF(NOT VTK_USE_RENDERING)
+  MESSAGE(FATAL_ERROR "Example ${PROJECT_NAME} requires VTK_USE_RENDERING.")
+ENDIF(NOT VTK_USE_RENDERING)
+IF(NOT VTK_USE_INFOVIS)
+  MESSAGE(FATAL_ERROR "Example ${PROJECT_NAME} requires VTK_USE_INFOVIS.")
+ENDIF(NOT VTK_USE_INFOVIS)
+INCLUDE(${VTK_USE_FILE})
+
+ADD_EXECUTABLE(TreeLayout TreeLayout.cxx)
+TARGET_LINK_LIBRARIES(TreeLayout vtkInfovis vtkRendering vtkImaging vtkIO)

Examples/Infovis/Cxx/TreeLayout.cxx

+/*=========================================================================
+
+  Program:   Visualization Toolkit
+  Module:    TreeLayout.cxx
+
+  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
+  All rights reserved.
+  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notice for more information.
+
+=========================================================================*/
+//
+// This example shows how to create a simple tree view from an XML file.
+// You may specify the label array and color array from the command line.
+//
+
+#include "vtkActor.h"
+#include "vtkActor2D.h"
+#include "vtkDynamic2DLabelMapper.h"
+#include "vtkGlyph3D.h"
+#include "vtkGlyphSource2D.h"
+#include "vtkGraphLayout.h"
+#include "vtkGraphToPolyData.h"
+#include "vtkInteractorStyleImage.h"
+#include "vtkPointData.h"
+#include "vtkPolyDataMapper.h"
+#include "vtkProperty.h"
+#include "vtkRenderer.h"
+#include "vtkRenderWindow.h"
+#include "vtkRenderWindowInteractor.h"
+#include "vtkStringToNumeric.h"
+#include "vtkTextProperty.h"
+#include "vtkTreeLayoutStrategy.h"
+#include "vtkXMLTreeReader.h"
+
+void usage()
+{
+  cerr << endl;
+  cerr << "usage: TreeLayout filename [label_attribute] [color_attribute]" << endl;
+  cerr << "  filename is an xml file" << endl;
+  cerr << "  label_attribute is the attribute to use as labels." << endl;
+  cerr << "    Default is .tagname which labels using the element tag." << endl;
+  cerr << "  color_attribute is the attribute to color by (numeric)." << endl;
+  cerr << "    Default is no color." << endl;
+}
+
+int main(int argc, char* argv[])
+{
+  // Initialize parameters from the command line.
+  char* labelArray = ".tagname";
+  char* colorArray = NULL;
+  if (argc < 2)
+    {
+    usage();
+    return 0;
+    }
+  char* filename = argv[1];
+  if (argc >= 3)
+    {
+    labelArray = argv[2];
+    }
+  if (argc >= 4)
+    {
+    colorArray = argv[3];
+    }
+  
+  // Read in the XML file into a tree.
+  // This creates a tree with string columns for every attribute 
+  // present in the file, plus the special arrays named .tagname
+  // (containing the XML tag name) and .chardata (containg the
+  // character data within the tag).
+  vtkXMLTreeReader* reader = vtkXMLTreeReader::New();
+  reader->SetFileName(filename);
+  
+  // Automatically convert string columns containing numeric
+  // values into integer and double arrays.
+  vtkStringToNumeric* stringToNumeric = vtkStringToNumeric::New();
+  stringToNumeric->SetInputConnection(reader->GetOutputPort());
+  
+  // Retrieve the tree from the pipeline so we can check whether
+  // the specified label and color arrays exist.
+  stringToNumeric->Update();
+  vtkTree* tree = vtkTree::SafeDownCast(stringToNumeric->GetOutput());
+  if (tree->GetVertexData()->GetAbstractArray(labelArray) == NULL)
+    {
+    cerr << "ERROR: The label attribute " << labelArray << " is not defined in the file." << endl;
+    reader->Delete();
+    stringToNumeric->Delete();
+    usage();
+    return 0;
+    }
+  if (colorArray && 
+      tree->GetVertexData()->GetAbstractArray(colorArray) == NULL)
+    {
+    cerr << "ERROR: The color attribute " << colorArray << " is not defined in the file." << endl;
+    reader->Delete();
+    stringToNumeric->Delete();
+    usage();
+    return 0;
+    }
+  if (colorArray && 
+      vtkDataArray::SafeDownCast(tree->GetVertexData()->GetAbstractArray(colorArray)) == NULL)
+    {
+    cerr << "ERROR: The color attribute " << colorArray << " does not have numeric values." << endl;
+    reader->Delete();
+    stringToNumeric->Delete();
+    usage();
+    return 0;
+    }
+  
+  // If coloring the vertices, get the range of the color array.
+  double colorRange[2] = {0, 1};
+  if (colorArray)
+    {
+    vtkDataArray* color = vtkDataArray::SafeDownCast(
+      tree->GetVertexData()->GetAbstractArray(colorArray));
+    color->GetRange(colorRange);
+    }
+  
+  // Layout the tree using vtkGraphLayout.
+  vtkGraphLayout* layout = vtkGraphLayout::New();
+  layout->SetInputConnection(stringToNumeric->GetOutputPort());
+  
+  // Specify that we want to use the tree layout strategy.
+  vtkTreeLayoutStrategy* strategy = vtkTreeLayoutStrategy::New();
+  strategy->RadialOn();              // Radial layout (as opposed to standard top-down layout)
+  strategy->SetAngle(360.0);         // The tree fills a full circular arc.
+  layout->SetLayoutStrategy(strategy);
+  
+  // vtkGraphToPolyData converts a graph or tree to polydata.
+  vtkGraphToPolyData* graphToPoly = vtkGraphToPolyData::New();
+  graphToPoly->SetInputConnection(layout->GetOutputPort());
+
+  // Create the standard VTK polydata mapper and actor
+  // for the connections (edges) in the tree.
+  vtkPolyDataMapper* edgeMapper = vtkPolyDataMapper::New();
+  edgeMapper->SetInputConnection(graphToPoly->GetOutputPort());
+  vtkActor* edgeActor = vtkActor::New();
+  edgeActor->SetMapper(edgeMapper);
+  edgeActor->GetProperty()->SetColor(0.0, 0.5, 1.0);
+  
+  // Glyph the points of the tree polydata to create
+  // VTK_VERTEX cells at each vertex in the tree.
+  vtkGlyph3D* vertGlyph = vtkGlyph3D::New();
+  vertGlyph->SetInputConnection(0, graphToPoly->GetOutputPort());
+  vtkGlyphSource2D* glyphSource = vtkGlyphSource2D::New();
+  glyphSource->SetGlyphTypeToVertex();
+  vertGlyph->SetInputConnection(1, glyphSource->GetOutputPort());
+  
+  // Create a mapper for the vertices, and tell the mapper
+  // to use the specified color array.
+  vtkPolyDataMapper* vertMapper = vtkPolyDataMapper::New();
+  vertMapper->SetInputConnection(vertGlyph->GetOutputPort());
+  if (colorArray)
+    {
+    vertMapper->SetScalarModeToUsePointFieldData();
+    vertMapper->SelectColorArray(colorArray);
+    vertMapper->SetScalarRange(colorRange);
+    }
+    
+  // Create an actor for the vertices.  Move the actor forward
+  // in the z direction so it is drawn on top of the edge actor.
+  vtkActor* vertActor = vtkActor::New();
+  vertActor->SetMapper(vertMapper);
+  vertActor->GetProperty()->SetPointSize(5);
+  vertActor->SetPosition(0, 0, 0.001);
+  
+  // Use a dynamic label mapper to draw the labels.  This mapper
+  // does not allow labels to overlap, as long as the camera is
+  // not rotated from pointing down the z axis.
+  vtkDynamic2DLabelMapper* labelMapper = vtkDynamic2DLabelMapper::New();
+  labelMapper->SetInputConnection(graphToPoly->GetOutputPort());
+  labelMapper->GetLabelTextProperty()->SetJustificationToLeft();
+  labelMapper->GetLabelTextProperty()->SetColor(0, 0, 0);
+  if (labelArray)
+    {
+    labelMapper->SetLabelModeToLabelFieldData();
+    labelMapper->SetFieldDataName(labelArray);
+    }
+  vtkActor2D* labelActor = vtkActor2D::New();
+  labelActor->SetMapper(labelMapper);
+  
+  // Add the edges, vertices, and labels to the renderer.
+  vtkRenderer* ren = vtkRenderer::New();
+  ren->SetBackground(0.8, 0.8, 0.8);
+  ren->AddActor(edgeActor);
+  ren->AddActor(vertActor);
+  ren->AddActor(labelActor);
+  
+  // Setup the render window and interactor.
+  vtkRenderWindow* win = vtkRenderWindow::New();
+  win->AddRenderer(ren);
+  vtkRenderWindowInteractor* iren = vtkRenderWindowInteractor::New();
+  iren->SetRenderWindow(win);
+  
+  // Constrain movement to zoom and pan using the image interactor style.
+  vtkInteractorStyleImage* style = vtkInteractorStyleImage::New();
+  iren->SetInteractorStyle(style);
+  
+  // Start the main application loop.
+  iren->Initialize();
+  iren->Start();
+  
+  // Clean up.
+  style->Delete();
+  iren->Delete();
+  win->Delete();
+  ren->Delete();
+  labelActor->Delete();
+  labelMapper->Delete();
+  vertActor->Delete();
+  vertMapper->Delete();
+  glyphSource->Delete();
+  vertGlyph->Delete();
+  edgeMapper->Delete();
+  edgeActor->Delete();
+  graphToPoly->Delete();
+  strategy->Delete();
+  layout->Delete();
+  stringToNumeric->Delete();
+  reader->Delete();
+  
+  return 0;
+}