[vtkusers] Interactively updating the edge colors of a graph

[Jeff Baumes]

Steffen,

Thanks for your detailed report. The issue was that the filter that updated
colors (vtkApplyColors) did not update when the underlying lookup table is
modified. I just pushed a change to VTK master that fixes this. The
following python script shows how to change the lookup table and re-render
the view:

from vtk import *
import time

s = vtkRandomGraphSource()
view = vtkGraphLayoutView()
rep = view.SetRepresentationFromInputConnection(s.GetOutputPort())
rep.ColorVerticesByArrayOn()
lut = vtkLookupTable()
lut.Build()
theme = vtkViewTheme()
theme.SetPointLookupTable(lut)
view.ApplyViewTheme(theme)
view.ResetCamera()
view.Render()
time.sleep(2)

# Modify the lookup table
lut.SetHueRange(0.0, 0.0)
lut.Build()
view.Render()
time.sleep(2)

Jeff

On Tue, Feb 8, 2011 at 11:18 AM, Steffen Oeltze <
stoeltze at isg.cs.uni-magdeburg.de> wrote:

> Dear VTK-users
>
> I have written an application that displays a graph with colored edges. The
> application is interactive and I would like to change the edge coloring
> depending on some user interaction. The coloring is accomplished via a
> vtkLookupTable and a vtkViewTheme. I tried two different strategies so far.
> Unfortunately, only the second one works which I guess is slower and less
> effective than the first one. The first one only works if I manually enforce
> a new rendering of the graph by selecting, e.g., an edge. In my source code,
> I tried several update mechanisms, e.g., calling Modified() on the
> vtkViewTheme after reassigning the modified vtkLookupTable, but none of them
> worked. Any help on how I can imitate the update-mechanism which is
> initiated after edge selection is deeply appreciated.
>
> 1.) (works only after manual update)
> - generate the vtkLookupTable, a vtkViewTheme, and a vtkGraphLayoutView
> - assign the vtkLookupTable to the vtkViewTheme
> - assign the vtkViewTheme to the vtkGraphLayoutView
> - render the graph
> ...user interaction...
> - update the vtkLookupTable
> - render the graph again
>
> 2.) (works)
> - generate the vtkLookupTable, a vtkViewTheme, and a vtkGraphLayoutView
> - assign the vtkLookupTable to the vtkViewTheme
> - assign the vtkViewTheme to the vtkGraphLayoutView
> - delete the vtkViewTheme
> - render the graph
> ...user interaction...
> update the vtkLookupTable
> - generate a new vtkViewTheme
> - assign the modified vtkLookupTable to the new vtkViewTheme
> - assign the new vtkViewTheme to the vtkGraphLayoutView
> - delete the new vtkViewTheme
> - render the graph again
>
> Steffen
>
> --
> Dr.-Ing. Steffen Oeltze
> Department of Simulation and Graphics, School of Computer Science
> Otto-von-Guericke-University Magdeburg
>
> Universitätsplatz 2, 39106 Magdeburg
> GERMANY
>
> Phone:  (+49-391) 67-1 25 27
> Fax:    (+49 391) 67-1 11 64
> Email:  stoeltze at isg.cs.uni-magdeburg.de
> Web:    http://www.vismd.de/
>
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-- 
Jeff Baumes, Ph.D.
Technical Lead, Kitware Inc.
(518) 881-4932
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