[vtkusers] Re: Need some help with vtkGraph representation and visualisation pipeline of graphs.

[Geoframer]

Thanx Jeff,

That clarification really helps! - Geofram

On 5/7/07, Jeff Baumes <jeff.baumes at kitware.com> wrote:
>
> Geofram,
>
> There are a few different ways to display a random graph in VTK.  One
> way is to set to vertex locations manually:
>
> <code>
> import vtk
> import random
>
> points = vtk.vtkPoints()
> for i in range(500):
>     points.InsertPoint(i, random.random(),random.random(),random.random())
>
> graph = vtk.vtkGraph()
> graph.SetPoints(points)
> graph.SetNumberOfVertices(500)
>
> for i in range(499):
>     graph.AddEdge(i,i+1)
>
> graphtopoly = vtk.vtkGraphToPolyData()
> graphtopoly.SetInput(graph)
>
> mapper = vtk.vtkPolyDataMapper()
> mapper.SetInputConnection(graphtopoly.GetOutputPort())
>
> graphactor = vtk.vtkActor()
> graphactor.SetMapper(mapper)
>
> ren = vtk.vtkRenderer()
> ren.AddActor(graphactor)
> win = vtk.vtkRenderWindow()
> win.AddRenderer(ren)
> interact = vtk.vtkRenderWindowInteractor()
> interact.SetRenderWindow(win)
> win.GetInteractor().Initialize()
> win.GetInteractor().Start()
> </code>
>
> The next is to use a random graph layout:
> <code>
> import vtk
>
> graph = vtk.vtkGraph()
> graph.SetNumberOfVertices(500)
>
> for i in range(499):
>     graph.AddEdge(i,i+1)
>
> layout = vtk.vtkRandomLayoutStrategy()
> layout.ThreeDimensionalLayoutOn()
>
> graphlayout = vtk.vtkGraphLayout()
> graphlayout.SetInput(graph)
> graphlayout.SetLayoutStrategy(layout)
>
> graphtopoly = vtk.vtkGraphToPolyData()
> graphtopoly.SetInputConnection(graphlayout.GetOutputPort())
>
> mapper = vtk.vtkPolyDataMapper()
> mapper.SetInputConnection(graphtopoly.GetOutputPort())
>
> graphactor = vtk.vtkActor()
> graphactor.SetMapper(mapper)
>
> ren = vtk.vtkRenderer()
> ren.AddActor(graphactor)
> win = vtk.vtkRenderWindow()
> win.AddRenderer(ren)
> interact = vtk.vtkRenderWindowInteractor()
> interact.SetRenderWindow(win)
> win.GetInteractor().Initialize()
> win.GetInteractor().Start()
> </code>
>
> The last way is to use the graph layout viewer, which creates the
> pipeline/mappers/actors for you:
>
> <code>
> import vtk
>
> graph = vtk.vtkGraph()
> graph.SetNumberOfVertices(500)
>
> for i in range(499):
>     graph.AddEdge(i,i+1)
>
> viewer = vtk.infovis.vtkGraphLayoutViewer()
> viewer.SetInput(graph)
> viewer.SetLayoutStrategy('Random');
>
> ren = vtk.vtkRenderer()
> win = vtk.vtkRenderWindow()
> win.AddRenderer(ren)
> interact = vtk.vtkRenderWindowInteractor()
> interact.SetRenderWindow(win)
> viewer.SetRenderWindow(win)
> win.GetInteractor().Initialize()
> win.GetInteractor().Start()
> </code>
>
> A few notes:
> 1. The vtkGraphLayoutViewer always assigns new coordinates to vertices
> based on a layout strategy.  The default behavior is to perform a
> force directed layout (that is why your graph was showing up as flat
> ... the layout spread out the graph in the x and y axes).
> 2. vtkGraphLayoutViewer turns edges into lines and also glyphs the
> vertices.  vtkGraphToPolyData only turns edges into lines.  You need
> to use vtkGlyph3D to display vertices if you are not using the viewer.
>
> Hope this helps!
> Jeff
>
> --
> Jeff Baumes
> R&D Engineer, Kitware Inc.
> (518) 371-3971 x132
> jeff.baumes at kitware.com
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