[vtkusers] Re: problem viewing merged PolyData sets using

[Denis Saussus]

Thanks for the replies Goodwin.  You say that vtkGlyph3D needs both 
geometry and topology to work -- is that really true?  How come the 
code fragment I posted works just fine as long as the input to 
vtkGlyph3D is the original vtkPolyData object (made manually with just 
points) and NOT the output of vtkAppendPolyData().GetOutput() ?

Anyway, here is the how I created the vtkPolyData objects.

import RandomArray

points = vtk.vtkPoints()
for n in range(1000):
   x,y,z = [ RandomArray.normal(0, 1) for i in range(3) ]
   points.InsertPoint(n, x, y, z)
a = vtk.vtkPolyData()
a.SetPoints(points)

... and so on for b = vtk.vtkPolyData()

Let me clarify the problem what is at the heart of the problem (I think 
;)

This works:
...
a = vtk.vtkPolyData()
a.GetNumberOfPoints()
...

This does not work:  Why?
...
a = vtk.vtkPolyData()
apd  = vtk.vtkAppendPolyData()
apd.AddInput(a)
apd.GetOutput().GetNumberOfPoints()



Can you post the code where you've added points to the vtkPolyData 
objects?


"Denis Saussus" <dsaussus at fugro-jason.com> wrote in message
news:F42290EAAE100A4A99A3A9BE2059504FBDB121 at MAIL.fugro-jason.local...
How can I get the following to print the total
number of points in the appended set?

a = vtk.vtkPolyData()
b = vtk.vtkPolyData()

apd  = vtk.vtkAppendPolyData()
apd.AddInput(a)
apd.AddInput(b)

print apd.GetOutput().GetNumberOfPoints()

==> this prints '0' instead of a+b ?

I tried doing apd.Update() before but it didn't help.

What am I missing?


i Denis,

At a guess, I would say your vtkPolyData's have points (geometry) but no
vertices (topology). vtkGlyph3D needs both to work, although in theory 
it
should only need the points.

Here's a trick to get it to work:

...
...
apd = vtk.vtkAppendPolyData()
apd.AddInput(somePolyData)
apd.AddInput(someMorePolyData)

verts = vtk.vtkMaskPoints()
verts.SetInput(apd.GetOutput())
verts.GenerateVerticesOn()
verts.SetOnRatio(1)

aSphere = vtk.vtkSphereSource()
aSphere.SetRadius(1.0)

spheres = vtk.vtkGlyph3D()
spheres.SetInput(verts.GetOutput())
spheres.SetSource(aSphere.GetOutput())

...
...


hth

Goodwin
"Denis Saussus" <dsaussus at fugro-jason.com> wrote in message
news:F42290EAAE100A4A99A3A9BE2059504FBDB11C at MAIL.fugro-jason.local...
I am plotting a vtkPolyData set containing 3d points so that
they display as spheres.  I can get this to work very easily.

Now I have two vtkPolyData sets, each containing 3d points.
I want to plot them using a single mapper/actor.  I am doing this
simply by using vtkAppendPolyData to merge the two sets into
one.  My problem is that now nothing shows up.

Below is the script I am using.  Help greatly aprpeciated...




##########################
# Why does this not work?
##########################

somePolyData = vtk.vtkPolyData()
# assume this contains some valid 3d points

apd = vtk.vtkAppendPolyData()
apd.AddInput(somePolyData)
apd.AddInput(someMorePolyData)

aSphere = vtk.vtkSphereSource()
aSphere.SetRadius(1.0)

spheres = vtk.vtkGlyph3D()
spheres.SetInput(apd.GetOutput())
spheres.SetSource(aSphere.GetOutput())

mapSpheres = vtk.vtkPolyDataMapper()
mapSpheres.SetInput(spheres.GetOutput())

spheresActor = vtk.vtkActor()
spheresActor.SetMapper(mapSpheres)

ren = vtk.vtkRenderer()
ren.AddActor(spheresActor)
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(ren)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)
iren.Initialize()
renWin.Render()
iren.Start()
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