[vtkusers] vtkUniformGrid blanking

[Favre Jean]

From: vtkusers-bounces at vtk.org [vtkusers-bounces at vtk.org] on behalf of Alexandre Boucher [afboucher at gmail.com]
Sent: Tuesday, April 05, 2011 10:24 PM
To: vtkusers at vtk.org
Subject: [vtkusers] vtkUniformGrid blanking

Hello,

For some reason I am unable to use the blanking capability of the vtkUniformGrid class.  I am interested in blanking cells (do not work on point either).  For example the following (pyhton) code does not blank anything.  What am I doing wrong.

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Your grid construction is actually correct, but your choice of which mapper to use is not. Your default mapper does not support blanking. You should choose a filter which works on cells (for example vtkCellCenters) and see if it does the subsetting correctly. I have done this with a modified version of your code. My conclusion is that "yes, the blanking you have set in you grid is correct".

import vtk

uGrid = vtk.vtkUniformGrid()

uGrid.SetExtent(0,35, 0,35, 0,35)
uGrid.SetOrigin(0, 0,0)
uGrid.SetSpacing(1,1,1)
uGrid.SetScalarTypeToFloat ()
nCells = uGrid.GetNumberOfCells()

# Set the data vector
data = vtk.vtkFloatArray()
data.SetNumberOfValues(nCells)
data.SetNumberOfComponents(1)

# Set the blanking vector
dataBlank = vtk.vtkUnsignedCharArray()
dataBlank.SetNumberOfValues(nCells)
dataBlank.SetNumberOfComponents(1)

# first set all to 0 blanking
for i in range(nCells):
  data.SetValue(i, float(i)/nCells)
  dataBlank.SetValue(i, 0)

# then set a sub-set to 1 blanking
for i in range(nCells/2, nCells-1):
  dataBlank.SetValue(i, 1)

uGrid.GetCellData().SetScalars(data)
uGrid.SetCellVisibilityArray(dataBlank)

#use cell centers which should only operate on the subset
cc = vtk.vtkCellCenters()
cc.VertexCellsOn()
cc.SetInput(uGrid)
m0 = vtk.vtkDataSetMapper()
m0.SetInput(cc.GetOutput())
actor0 = vtk.vtkActor()
actor0.SetMapper(m0)

# use an outline instead of an opaque box
out = vtk.vtkOutlineFilter()
out.SetInput(uGrid)
mapper = vtk.vtkDataSetMapper()
mapper.SetInput(out.GetOutput())
actor = vtk.vtkActor()
actor.SetMapper(mapper)

ren = vtk.vtkRenderer()
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(ren)
renWin.SetSize(500, 500)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)

ren.AddActor(actor)
ren.AddActor(actor0)
iren.Initialize()
renWin.Render()
iren.Start()

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Jean M. Favre
Scientific Computing Research
Swiss National Supercomputing Center
CH-6928 Manno
Switzerland