[vtkusers] Help with VtkDatasetsurface filter

Wed Apr 3 22:27:50 EDT 2013

Bhanu,

Could you post a small snippet showing how you are using VTK to render
your unstructured grid?

I suspect you are using a vtkDataSetMapper. The documentation for this
class says:

"The 2D faces of 3D cells are mapped only if they are used by only one
cell, i.e., on the boundary of the data set."

If you are in fact using a vtkDataSetMapper, I believe it is applying
a vtkDataSetSurfaceFilter underneath and rendering only the boundary
polygons. Hence you should see no difference in either image or
performance if you apply the vtkDataSetSurfaceFilter yourself before
sending it to a vtkDataSetMapper.

If you ever want to render the whole volume, you would need to use
something like a vtkUnstructuredGridVolumeMapper.

Hope that helps,
Cory

On Wed, Apr 3, 2013 at 9:59 PM, Alex Malyushytskyy <alexmalvtk at gmail.com> wrote:
> As far as I understand if all internal surfaces were eliminated (for example
> by vtkDataSetSurfaceFilter ) you would see only blue,
> but I do not think vtkDataSetSurfaceFilterdoes it.
>
> Below is only my assumption, since I did not look in the
> vtkDataSetSurfaceFilter internals and documentation does not answer the
> question, but I would expect that filter only combines small primitives
> which are in the same geometrical plane and are connected into large and
> eliminates duplicates when it works on the unstructured grid .
>
> It the array you colored original database is transferred you will see the
> same colors as with original database.
>
> Regards,
>       Alex
>
>
> On Wed, Apr 3, 2013 at 7:42 AM, Bhanu Hariharan <bhanu at petrotel.com> wrote:
>>
>> Thanks Alex.
>>
>> However the resulting picture (full sized model) is the same. I expected
>> different picture but it is not.
>>
>> I made outer cells all blue and in between cells all red. A transparent
>> image of this grid when all cells are rendered is purple (which is expected
>> blend of red and blue).
>>
>> But it remains the same image when I render just surface - I expect to see
>> only BLUE?
>> Is this a VTK bug perhaps??
>>
>> Thanks again.
>> Bhanu
>>
>>
>>
>> On Tue, Apr 2, 2013 at 6:14 PM, Alex Malyushytskyy <alexmalvtk at gmail.com>
>> wrote:
>>>
>>> I was not suggesting to use VTKActor, cause it means that your
>>> performance at least for large number of nodes
>>> will decrease. I only said it would make a difference ( possibly from
>>> very slow to slow or the same you currently have).
>>>
>>> As for opacity, I would expect picture be different, but I would not
>>> expect human eye to see the difference.
>>> Keep in mind that as far as I understand curse model only used during
>>> transition or rotation, resulted picture shown is full sized model,
>>>
>>> Regards,
>>>    Alex
>>>
>>>
>>> On Tue, Apr 2, 2013 at 3:14 PM, Bhanu Hariharan <bhanu at petrotel.com>
>>> wrote:
>>> > Alex,
>>> > I will try your suggestions - using VTKActor to see difference and
>>> > different
>>> > frame rates.
>>> >
>>> > I have one more question that's not related to rendering performance.
>>> > It
>>> > concerns opacity.
>>> >
>>> > I was alteast expecting to see different images when I specify opacity
>>> > < 1
>>> > for the grid.
>>> >
>>> > Shouldn't a transparent image look different when I render all cells
>>> > (all
>>> > layers) than when I render just surface cells?
>>> >
>>> >
>>> > Thanks again,
>>> > Bhanu
>>> >
>>> >
>>> >
>>> >
>>> > On Tue, Apr 2, 2013 at 4:49 PM, Alex Malyushytskyy
>>> > <alexmalvtk at gmail.com>
>>> > wrote:
>>> >>
>>> >> LOD (level of details)  technique consists of run time assessment of
>>> >> performance and building a special model which will be used in certain
>>> >> circumstances and on the one hand would look as close as possible to
>>> >> the original, but on another hand allows achieve desired or better
>>> >> performance.
>>> >> That what LOD actor does, crude models will be silently created and
>>> >> displayed during rotation or when actor is moved.
>>> >>
>>> >> Now assume there are 2 model - lets say 1st is your unstructured grid,
>>> >> another is result of dataSetSurfaceFilter.
>>> >> Since both are using LOD actors, the following might happen:
>>> >>
>>> >> 1st model is found to be too big to be displayed and as a result crude
>>> >> model with N1 number of nodes is created and displayed
>>> >> 2nd model is found to be too big to be displayed and as a result crude
>>> >> model with N2 number of nodes is created and displayed
>>> >> or it is small enough , so it is displayed as is (but lets say still
>>> >> have N2 nodes)
>>> >>
>>> >> Now N1 might be mostly the same as N2.
>>> >> And you see no difference in performance during transition or
>>> >> rotation.
>>> >> Basically this means that LOD actor does his job well enough.
>>> >> I bet if you were using regular actors you would see a huge
>>> >> performance increase.
>>> >>
>>> >> If you need further performance you may just specify different frame
>>> >> rate.
>>> >> From http://www.vtk.org/doc/release/4.0/html/classvtkLODActor.html:
>>> >>
>>> >> "To control the frame rate, you typically set the
>>> >> vtkRenderWindowInteractor DesiredUpdateRate and StillUpdateRate. This
>>> >> then will cause vtkLODActor to adjust its LOD to fulfill the requested
>>> >> update rate.
>>> >> For greater control on levels of detail, see also vtkLODProp3D. That
>>> >> class allows arbitrary definition of each LOD.
>>> >> "
>>> >>
>>> >> Hope this helps,
>>> >>
>>> >> Alex
>>> >>
>>> >>
>>> >>
>>> >>
>>> >> On Tue, Apr 2, 2013 at 2:18 PM, Bhanu Hariharan <bhanu at petrotel.com>
>>> >> wrote:
>>> >> > Alex,
>>> >> >
>>> >> > To be specific in one of my cases,  No. of surfaces rendered were
>>> >> > reduced
>>> >> > from 6163542 to 373626 assuming grid has hexahedrons each with 6
>>> >> > surfaces. I
>>> >> > got the number 373626 by doing
>>> >> >
>>> >> > dataSetSurfaceFilter->GetOutput()->GetNumberOfCells()
>>> >> >
>>> >> > Thats a significant reduction of number of surfaces. These are
>>> >> > rendered
>>> >> > using VTKLODActor.
>>> >> >
>>> >> > Can you please explain what you mean by "actually shown primitives
>>> >> > during
>>> >> > rotation". What are the shown primitives?
>>> >> >
>>> >> > I am just adding the output of the dataSetSurfaceFilter to a
>>> >> > vtkDataSetMapper and then to a vtkLODActor.
>>> >> >
>>> >> > All I know if no. of surfaces are reduced. Do I need to do/check
>>> >> > something
>>> >> > else?
>>> >> >
>>> >> > If you need something specific to answer more specifically, I can
>>> >> > provide
>>> >> > the details. It would be a great help.
>>> >> >
>>> >> > Thanks,
>>> >> > Bhanu
>>> >> >
>>> >> >
>>> >> > ---------- Forwarded message ----------
>>> >> > From: Alex Malyushytskyy <alexmalvtk at gmail.com>
>>> >> > Date: Tue, Apr 2, 2013 at 4:03 PM
>>> >> > Subject: Re: [vtkusers] Help with VtkDatasetsurface filter
>>> >> > To: "vtkusers at vtk.org" <vtkusers at vtk.org>
>>> >> >
>>> >> >
>>> >> > You may get only general advice asking general questions.
>>> >> > Compare  the number of nodes/cells you are you are getting from
>>> >> > vtkDataSetSurfaceFilter with
>>> >> > such in the unstructured grid,
>>> >> > Even though it may be significantly decreased in some cases, for
>>> >> > example if LOD actors are used,  they may decrease actually shown
>>> >> > primitives during rotation approximately to the same number and you
>>> >> > will not see any difference in the performance.
>>> >> >
>>> >> > Regards,
>>> >> >     Alex
>>> >> >
>>> >> >
>>> >> > On Tue, Apr 2, 2013 at 8:27 AM, Bhanu Hariharan <bhanu at petrotel.com>
>>> >> > wrote:
>>> >> >> Hi All,
>>> >> >> I was wondering if anyone would be kind enough to answer the
>>> >> >> following
>>> >> >> query
>>> >> >> for me.
>>> >> >>
>>> >> >> I had posted this a while back and still havent found the reason
>>> >> >> why
>>> >> >> vtkDataSetSurfaceFilter hasn't made rendering any faster. The
>>> >> >> interaction
>>> >> >> and rendering time to rotate zoom etc seem to be just the same as
>>> >> >> though I
>>> >> >> rendered all cells in the unstructured grid.
>>> >> >> The reason I chose to introduce rendering just surface cells in the
>>> >> >> first
>>> >> >> place was to make rendering faster. But I am surprised it doesnt
>>> >> >> make
>>> >> >> any
>>> >> >> difference at all :(.
>>> >> >> Any words or ideas?
>>> >> >>
>>> >> >> Thanks so much
>>> >> >> Bhanu
>>> >> >>
>>> >> >>
>>> >> >>
>>> >> >> On Mon, Mar 11, 2013 at 4:30 PM, Bhanu Hariharan
>>> >> >> <bhanu at petrotel.com>
>>> >> >> wrote:
>>> >> >>>
>>> >> >>> One related question though. I started using Surface Filter really
>>> >> >>> only
>>> >> >>> for performance reasons.
>>> >> >>>
>>> >> >>> I was thinking if I rendered just surface cells, the rendering and
>>> >> >>> rotation etc would be must faster.
>>> >> >>> However I do not find it any different than when I render all
>>> >> >>> cells.
>>> >> >>> What
>>> >> >>> am I missing?
>>> >> >>> Any reasons anyone can think of, please let me know.
>>> >> >>>
>>> >> >>>
>>> >> >>>
>>> >> >>> Thanks,
>>> >> >>> Bhanu
>>> >> >>>
>>> >> >>>
>>> >> >>>
>>> >> >>> On Mon, Mar 11, 2013 at 4:12 PM, Bhanu Hariharan
>>> >> >>> <bhanu at petrotel.com>
>>> >> >>> wrote:
>>> >> >>>>
>>> >> >>>> David,
>>> >> >>>> As you suggested, I got it to work using SetGlobalIds and then
>>> >> >>>> retrieving
>>> >> >>>> that using GetGlobalIds. Many thanks for your patience and help.
>>> >> >>>>
>>> >> >>>>
>>> >> >>>> -Bhanu
>>> >> >>>>
>>> >> >>>>
>>> >> >>>> On Wed, Mar 6, 2013 at 11:41 AM, Bhanu Hariharan
>>> >> >>>> <bhanu at petrotel.com>
>>> >> >>>> wrote:
>>> >> >>>>>
>>> >> >>>>> David,
>>> >> >>>>>
>>> >> >>>>> I am using vtk 5.2 - is it possible that this function was not
>>> >> >>>>> defined
>>> >> >>>>> in that version.
>>> >> >>>>>
>>> >> >>>>> I get the error that SetOriginalCellIdsName is not a member of
>>> >> >>>>> vtkDataSetSurfaceFilter   :(
>>> >> >>>>>
>>> >> >>>>> Bhanu
>>> >> >>>>>
>>> >> >>>>>
>>> >> >>>>>
>>> >> >>>>> On Wed, Mar 6, 2013 at 10:36 AM, David E DeMarle
>>> >> >>>>> <dave.demarle at kitware.com> wrote:
>>> >> >>>>>>
>>> >> >>>>>> Give DSF a name for the array.
>>> >> >>>>>> SetOriginalCellIdsName("idsintoDSForsomething")
>>> >> >>>>>> Then retrieve it from the output like
>>> >> >>>>>>
>>> >> >>>>>> DSF->GetOutput()->GetCellData()->GetArray("idsintoDSForsomething")
>>> >> >>>>>>
>>> >> >>>>>>
>>> >> >>>>>> David E DeMarle
>>> >> >>>>>> Kitware, Inc.
>>> >> >>>>>> R&D Engineer
>>> >> >>>>>> 21 Corporate Drive
>>> >> >>>>>> Clifton Park, NY 12065-8662
>>> >> >>>>>> Phone: 518-881-4909
>>> >> >>>>>>
>>> >> >>>>>>
>>> >> >>>>>> On Wed, Mar 6, 2013 at 11:29 AM, Bhanu Hariharan
>>> >> >>>>>> <bhanu at petrotel.com>
>>> >> >>>>>> wrote:
>>> >> >>>>>>>
>>> >> >>>>>>>
>>> >> >>>>>>> David,
>>> >> >>>>>>>
>>> >> >>>>>>> I had turned on PassThroughCell. But I do not know how to
>>> >> >>>>>>> access
>>> >> >>>>>>> the
>>> >> >>>>>>> new Ids array after the fact.
>>> >> >>>>>>> VTK Doc says something about a 'OrginalCellIds' but I am not
>>> >> >>>>>>> sure
>>> >> >>>>>>> how
>>> >> >>>>>>> to access this.
>>> >> >>>>>>> So I extracted the output of DSF to a vtkPolyData but still
>>> >> >>>>>>> cant
>>> >> >>>>>>> figure out how to get to that new Ids array.
>>> >> >>>>>>> Any help with that is really appreciated.
>>> >> >>>>>>>
>>> >> >>>>>>> I will try your other suggestion in the meantime.
>>> >> >>>>>>>
>>> >> >>>>>>> Thanks,
>>> >> >>>>>>> Bhanu
>>> >> >>>>>>>
>>> >> >>>>>>>
>>> >> >>>>>>> On Wed, Mar 6, 2013 at 9:25 AM, David E DeMarle
>>> >> >>>>>>> <dave.demarle at kitware.com> wrote:
>>> >> >>>>>>>>
>>> >> >>>>>>>> Sorry for the confusion, it has been a long time since I
>>> >> >>>>>>>> added
>>> >> >>>>>>>> that
>>> >> >>>>>>>> code the DataSetSurfaceFilter. Turning
>>> >> >>>>>>>> PassThroughCell/PointIds
>>> >> >>>>>>>> in
>>> >> >>>>>>>> fact
>>> >> >>>>>>>> generates a new Ids array, which you can retrieve after the
>>> >> >>>>>>>> fact
>>> >> >>>>>>>> to
>>> >> >>>>>>>> do the
>>> >> >>>>>>>> lookups into the data that is input to the DSF and extract
>>> >> >>>>>>>> particular
>>> >> >>>>>>>> cells/points by their offset (n'th cell in the cell array,
>>> >> >>>>>>>> n'th
>>> >> >>>>>>>> point in the
>>> >> >>>>>>>> point array)
>>> >> >>>>>>>>
>>> >> >>>>>>>> However I still recommend making your own ids array and using
>>> >> >>>>>>>> that
>>> >> >>>>>>>> instead of PassThrough. vtkIdFilter will generate them for
>>> >> >>>>>>>> you.
>>> >> >>>>>>>> The
>>> >> >>>>>>>> array
>>> >> >>>>>>>> marked as the active global ids array is treated specially by
>>> >> >>>>>>>> most
>>> >> >>>>>>>> filters
>>> >> >>>>>>>> in that they try to preserve it across operations (including
>>> >> >>>>>>>> threshold and
>>> >> >>>>>>>> DSF). We added this to VTK a few years ago specifically for
>>> >> >>>>>>>> this
>>> >> >>>>>>>> case of
>>> >> >>>>>>>> finding out where particular result values come from (and in
>>> >> >>>>>>>> particular for
>>> >> >>>>>>>> surface selection). So the Threshold and surface filter will
>>> >> >>>>>>>> push
>>> >> >>>>>>>> globalIDS
>>> >> >>>>>>>> forward just fine. Once you get a result, grab the active
>>> >> >>>>>>>> globaIDs
>>> >> >>>>>>>> array,
>>> >> >>>>>>>> look for the values in it, and look them up in the original
>>> >> >>>>>>>> data.
>>> >> >>>>>>>> The
>>> >> >>>>>>>> extract selections filter will do the job of looking them up
>>> >> >>>>>>>> in
>>> >> >>>>>>>> the
>>> >> >>>>>>>> original
>>> >> >>>>>>>> data and pulling them out as a new dataset.
>>> >> >>>>>>>>
>>> >> >>>>>>>>
>>> >> >>>>>>>> David E DeMarle
>>> >> >>>>>>>> Kitware, Inc.
>>> >> >>>>>>>> R&D Engineer
>>> >> >>>>>>>> 21 Corporate Drive
>>> >> >>>>>>>> Clifton Park, NY 12065-8662
>>> >> >>>>>>>> Phone: 518-881-4909
>>> >> >>>>>>>>
>>> >> >>>>>>>>
>>> >> >>>>>>>> On Wed, Mar 6, 2013 at 10:02 AM, Bhanu Hariharan
>>> >> >>>>>>>> <bhanu at petrotel.com>
>>> >> >>>>>>>> wrote:
>>> >> >>>>>>>>>
>>> >> >>>>>>>>> David,
>>> >> >>>>>>>>> Thanks for replying. However I have a doubt.
>>> >> >>>>>>>>> Are you suggesting the VTKUnstructuredgrid should have an
>>> >> >>>>>>>>> globalids
>>> >> >>>>>>>>> array? Is that what the member is called - globalIds? I
>>> >> >>>>>>>>> actually
>>> >> >>>>>>>>> pass
>>> >> >>>>>>>>> VTKUnstructuredgrid  to a VTKThreshold filter and then pass
>>> >> >>>>>>>>> that
>>> >> >>>>>>>>> filter to
>>> >> >>>>>>>>> VTKdatasetsurfacefilter.
>>> >> >>>>>>>>>
>>> >> >>>>>>>>> Perhaps you can post a couple lines of code. That would be
>>> >> >>>>>>>>> very
>>> >> >>>>>>>>> helpful.
>>> >> >>>>>>>>> Thanks,
>>> >> >>>>>>>>> Bhanu
>>> >> >>>>>>>>>
>>> >> >>>>>>>>>
>>> >> >>>>>>>>>
>>> >> >>>>>>>>> On Tue, Mar 5, 2013 at 6:55 PM, David E DeMarle
>>> >> >>>>>>>>> <dave.demarle at kitware.com> wrote:
>>> >> >>>>>>>>>>
>>> >> >>>>>>>>>> The input data should have a globalids array containing a
>>> >> >>>>>>>>>> unique
>>> >> >>>>>>>>>> value for each cell. If it does, extract will preserve it.
>>> >> >>>>>>>>>> After
>>> >> >>>>>>>>>> the
>>> >> >>>>>>>>>> extraction, use that array in the polydata to do the look
>>> >> >>>>>>>>>> up to
>>> >> >>>>>>>>>> the original
>>> >> >>>>>>>>>> cell in the unstructured grid.
>>> >> >>>>>>>>>>
>>> >> >>>>>>>>>> On Mar 5, 2013 6:00 PM, "Bhanu Hariharan"
>>> >> >>>>>>>>>> <bhanu at petrotel.com>
>>> >> >>>>>>>>>> wrote:
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> Hi All,
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> I need some help doing the following. Please could one of
>>> >> >>>>>>>>>>> you
>>> >> >>>>>>>>>>> guide me on how.
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> I use a vtkDataSetSurfaceFilter on VTKUnstructuredGrid to
>>> >> >>>>>>>>>>> render
>>> >> >>>>>>>>>>> skin of that grid. That works fine and I can see the
>>> >> >>>>>>>>>>> number of
>>> >> >>>>>>>>>>> surfaces
>>> >> >>>>>>>>>>> shown by grabbing the
>>> >> >>>>>>>>>>> dataSetSurfaceFilter->GetOutput()->GetNumberOfCells().
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> I need a way to map the surface back to the original cell
>>> >> >>>>>>>>>>> id.
>>> >> >>>>>>>>>>> That
>>> >> >>>>>>>>>>> is if I have 2 cells and I render just skin, number of
>>> >> >>>>>>>>>>> surfaces
>>> >> >>>>>>>>>>> rendered are
>>> >> >>>>>>>>>>> 10. I need to be able to pick on any of these 10 surfaces
>>> >> >>>>>>>>>>> and
>>> >> >>>>>>>>>>> map
>>> >> >>>>>>>>>>> them back
>>> >> >>>>>>>>>>> to either of the the 2 grid cells.
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> http://www.vtk.org/doc says :
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> If PassThroughCellIdsOn is 1, then the output polygonal
>>> >> >>>>>>>>>>> dataset
>>> >> >>>>>>>>>>> will have a celldata array that holds the cell index of
>>> >> >>>>>>>>>>> the
>>> >> >>>>>>>>>>> original 3D cell
>>> >> >>>>>>>>>>> that produced each output cell. This is useful for cell
>>> >> >>>>>>>>>>> picking.
>>> >> >>>>>>>>>>> I turned the PassThroughCellIds On and I have UseStrips
>>> >> >>>>>>>>>>> turned
>>> >> >>>>>>>>>>> off.
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> Then I did
>>> >> >>>>>>>>>>> vtkPolyData *surfacePolyData =
>>> >> >>>>>>>>>>> dataSetSurfaceFilter->GetOutput();
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> But I do not see how I can access that celldata array that
>>> >> >>>>>>>>>>> holds
>>> >> >>>>>>>>>>> the original 3D cells for the surfaces.
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> Please can anyone advise on how.
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> Thanks in advance.
>>> >> >>>>>>>>>>> Bhanu
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> _______________________________________________
>>> >> >>>>>>>>>>> Powered by www.kitware.com
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> Visit other Kitware open-source projects at
>>> >> >>>>>>>>>>> http://www.kitware.com/opensource/opensource.html
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> Please keep messages on-topic and check the VTK FAQ at:
>>> >> >>>>>>>>>>> http://www.vtk.org/Wiki/VTK_FAQ
>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>>> Follow this link to subscribe/unsubscribe:
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>>> >> >>>>>>>>>>>
>>> >> >>>>>>>>>
>>> >> >>>>>>>>
>>> >> >>>>>>>
>>> >> >>>>>>
>>> >> >>>>>
>>> >> >>>>
>>> >> >>>
>>> >> >>
>>> >> >>
>>> >> >> _______________________________________________
>>> >> >> Powered by www.kitware.com
>>> >> >>
>>> >> >> Visit other Kitware open-source projects at
>>> >> >> http://www.kitware.com/opensource/opensource.html
>>> >> >>
>>> >> >> Please keep messages on-topic and check the VTK FAQ at:
>>> >> >> http://www.vtk.org/Wiki/VTK_FAQ
>>> >> >>
>>> >> >> Follow this link to subscribe/unsubscribe:
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>>> >> >>
>>> >> > _______________________________________________
>>> >> > Powered by www.kitware.com
>>> >> >
>>> >> > Visit other Kitware open-source projects at
>>> >> > http://www.kitware.com/opensource/opensource.html
>>> >> >
>>> >> > Please keep messages on-topic and check the VTK FAQ at:
>>> >> > http://www.vtk.org/Wiki/VTK_FAQ
>>> >> >
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>>> >
>>> >
>>> _______________________________________________
>>> Powered by www.kitware.com
>>>
>>> Visit other Kitware open-source projects at
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>>>
>>> Please keep messages on-topic and check the VTK FAQ at:
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>>>
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>>
>>
>
>
> _______________________________________________
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>
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>
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>
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-- 
Cory Quammen
Research Associate
Department of Computer Science
The University of North Carolina at Chapel Hill