[vtkusers] How to Recover vtkPolyData from vtkThreshold

[John Platt]

Hi Mathieu,

Real FE analyses can be tricky to handle. I extract all the surface
cells first and then get the corresponding result data to colour map.
This is for speed and memory - there seems no point in getting data for
a cell that will be filtered out later.

However, not all the surface cells have the required results. For
example, in models incorporating fluids and solids, there are no fluid
pressures in the solid. Cell faces with no results are removed using a
threshold. So I have

vtkUnstructuredGrid > vtkDataSetSurfaceFilter >
vtkMergeDataObjectFilterEx

			  > vtkThresholdPolyData > vtkPolyDataMapper >
...

It would be nice if some how you specify for a cell "Hey, I have no
scalar value, Mapper ignore me" but I don't know how to do that!

Well, that's where I'm coming from but it could be completely mad!

Your interest and support is very much appreciated.

Many thanks

John.


-----Original Message-----
From: Mathieu Malaterre [mailto:mathieu.malaterre at kitware.com] 
Sent: 17 June 2004 13:43
To: John Platt
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] How to Recover vtkPolyData from vtkThreshold

John,

	I am not sure I understand your pipeline, but since you are
using a 
vtkDataSetSurfaceFilter, why couldn't you just put the vtkThreshold just

before the vtkDataSetSurfaceFilter ?

HTH
Mathieu

John Platt wrote:
> Hi Shyam,
> 
> Thanks for your suggestion. The polydata has already been through
> vtkDataSetSurfaceFilter, and since speed is an issue, I wanted to
avoid
> doubling up. I have opted for a new filter vtkThresholdPolyData
instead.
> 
> Thanks again for your interest.
> 
> John.
> 
> -----Original Message-----
> From: vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] On
> Behalf Of R K Shyam Prakash
> Sent: 17 June 2004 10:11
> To: 'John Platt'; vtkusers at vtk.org
> Subject: RE: [vtkusers] How to Recover vtkPolyData from vtkThreshold
> 
> John,
> 
> 
>>>>I would like to render selective cells from vtkPolyData. I tried
>>>
>>> vtkPolyData > vtkThreshold > vtkPolyDataMapper
>>>
>>>>but this does not compile because the output of vtkThreshold is of
>>>
>>>type vtkUnstructuredGrid.
>>>
>>>>Is there anyway of recovering the output of vtkThreshold as
>>>
>>>vtkPolyData or an alternative filter?
> 
> 
> Use the following pipe line.
> vtkPolyData > vtkThreahold > vtkGeometryFilter > vtkPolyDataMapper
> 
> --Shyam
> 
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