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#!/usr/bin/env python
# Python examples script that uses the R calculator filter to find the
# maxiumum spanning tree of a random input graph by inverting the edge
# weights of the graph in R. The MST algorithm then finds the maximum
# spanning tree instead of the minimum spanning tree.
# VTK must be built with VTK_USE_GNU_R turned on for this example to work!
from vtk import *
if __name__ == "__main__":
# Generate a random graph with 20 vertices and a random number of edges
source = vtkRandomGraphSource()
source.SetNumberOfVertices(20)
source.SetEdgeProbability(0.2)
source.SetUseEdgeProbability(True)
source.SetStartWithTree(True)
source.IncludeEdgeWeightsOn()
source.AllowParallelEdgesOn()
# Create RCalculatorFilter for interaction with R
rcalculator = vtkRCalculatorFilter()
rcalculator.SetInputConnection(source.GetOutputPort())
# Display R output on the terminal
rcalculator.SetRoutput(1)
# Copy edge weight array to R as variable ew
rcalculator.PutArray("edge weight","ew")
# Invert the edge weight data.
rcalculator.SetRscript("ew = 1.0/ew\n")
# Copy edge weight array back to VTK.
rcalculator.GetArray("edge weight","ew")
# Find the minimal spanning tree (will be maximal spanning tree)
mstTreeSelection = vtkBoostKruskalMinimumSpanningTree()
mstTreeSelection.SetInputConnection(rcalculator.GetOutputPort())
mstTreeSelection.SetEdgeWeightArrayName("edge weight")
mstTreeSelection.NegateEdgeWeightsOn()
mstTreeSelection.Update()
# Create a graph layout view
view = vtkGraphLayoutView()
view.AddRepresentationFromInputConnection(rcalculator.GetOutputPort())
view.SetColorVertices(True)
view.SetEdgeLabelArrayName("edge weight")
view.SetEdgeLabelVisibility(True)
view.SetEdgeColorArrayName("edge weight")
view.SetColorEdges(True)
view.SetLayoutStrategyToSimple2D()
view.SetVertexLabelFontSize(14)
view.SetEdgeLabelFontSize(12)
# Make sure the representation is using a pedigree id selection
view.GetRepresentation(0).SetSelectionType(2)
# Set the selection to be the MST
view.GetRepresentation(0).GetAnnotationLink().SetCurrentSelection(mstTreeSelection.GetOutput())
# Set the theme on the view
theme = vtkViewTheme.CreateMellowTheme()
theme.SetLineWidth(5)
theme.SetPointSize(10)
theme.SetCellOpacity(1)
theme.SetSelectedCellColor(1,0,1)
view.ApplyViewTheme(theme)
theme.FastDelete()
view.GetRenderWindow().SetSize(600, 600)
view.ResetCamera()
view.Render()
view.GetInteractor().Start()
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