[vtkusers] Reducing the number of points in a vtkpolydata structure

[Jens Thomas]

Hello!

I'm trying to experiment with flow lines, and so am trying to overlay 
arrows onto streamlines.

I can get this to work by creating streamlines with vtkStreamline, then 
create a series of points with vtkStreampoints, and place arrows on the 
points with vtkGlyph3d.

This all works fine, but there are often far too many streampoints 
produced and I'd like a quick and easy way of decreasing the number of 
arrows - I'd prefer something simple as I'd like to include this 
functionality in a GUI. I can of course recompute the streampoints 
changing the IntegrationStepLength and TimeIncrement, but this seems 
rather heavyweight as I've got all the data I need and just want to 
sample a portion of it.

Ideally, I'd just like to decrease the number of points in the 
vtkPolyData produced by vtkStreamPoints.

I've tried using vtkMaskPolyData, but this just changes the number of 
cells and leaves the points unchanged.

Is there any way I can change the number of points?

Any suggestions would be greatly appreciated.

Best wishes,

Jens

-- 
===================================================================
Jens Thomas,                email:  j.m.h.thomas at dl.ac.uk
STFC Daresbury Lab,         tel:    +44-1925-603849
Warrington,                 fax:    +44-1925-603634
WA4 4AD,  UK.               http:   http://www.cse.scitech.ac.uk
===================================================================