[vtkusers] all my streamlines are in white :(

[Yifei Li]

The structured grid I have only contains vector data. I guess this may be
the reason why streamlines are not colored because no scalar data is
available for color mapping

I attached my source code. Can someone help me out? Thanks a lot

Yifei


On Wed, Nov 9, 2011 at 1:50 PM, Yifei Li <yifli82 at gmail.com> wrote:

> Marcelino,
>
> Thank you for your help, but my problem persists.
>
> Setting a lookup table failed (although, like you said, it's not necessary
> since vtkPolyDataMappe already has one).
>
> Then I tried vtkAssignAttribute, it does not work for me either. I guess aa.Assign("SCALARS",
> "VECTORS", "POINT_DATA")    means treat the point data (velocity vectors)
> in the grid as scalars, which makes sense to me.
>
> I took a look at another example
> Examples/VisualizationAlgorithms/Python/OfficeTube.py, the only thing
> that's relevant to streamline coloring is
>
> mapStreamTube.SetScalarRange(reader.GetOutput().GetPointData().GetScalars().GetRange()),
> where mapStreamTube is a PolyDataMapper
>
>
> What I have in my program is very similar to the above:
> streamMapper.SetScalarRange(0.0,
> grid.GetPointData().GetVectors().GetMaxNorm())
>
> I print out the the value of GetMaxNorm() and it is not zero.
>
>
>
> On Wed, Nov 9, 2011 at 11:47 AM, Marcelino Rodriguez Cancio <
> marcelinorc at uclv.edu.cu> wrote:
>
>>  Yifei,****
>>
>> ** **
>>
>> >> no lookup table is set for the streamMapper. Why?****
>>
>> Because vtkPolyDataMapper has a default vtkLookUpTable.****
>>
>>  ****
>>
>> If I'm correct vtkPolyDataMapper colors via the active scalars of the
>> dataset. A common trick is to color the vectors by their magnitude
>> (although this may not be want you want). You may achieve this using
>> vtkAssingAtributte with something like the following:****
>>
>> ** **
>>
>> aa = vtkAssignAttribute() ****
>>
>> aa. SetInput(grid)****
>>
>> #Not so sure how to do this in Python since I have only worked in C++ and
>> TCL****
>>
>> aa.Assign("SCALARS", "VECTORS", "POINT_DATA")****
>>
>> ** **
>>
>> streamer.SetInputConnection(aa.GetOutputPort())****
>>
>> ** **
>>
>> ** **
>>
>> Hope it helps****
>>
>> Marcelino****
>>
>> ** **
>>
>> ** **
>>
>> *De:* vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] *En
>> nombre de *Yifei Li
>>
>> *Enviado el:* miércoles, 09 de noviembre de 2011 10:07 a.m.
>> *Para:* vtkusers at vtk.org
>> *Asunto:* Re: [vtkusers] all my streamlines are in white :(****
>>
>>  ** **
>>
>> Marcelino, ****
>>
>> ** **
>>
>> Thank you. I'll try you suggestion.****
>>
>> ** **
>>
>> But at the same time, if you take a look at the example that comes with
>> VTK Examples/GUI/Python/StreamlinesWithLineWidget.py, no lookup table is
>> set for the streamMapper. Why?****
>>
>> Yifei****
>>
>> On Wed, Nov 9, 2011 at 8:16 AM, Marcelino Rodriguez Cancio <
>> marcelinorc at uclv.edu.cu> wrote:****
>>
>> Yifei:****
>>
>>  ****
>>
>> I think you need to add a vtkLookUpTable:****
>>
>>  ****
>>
>> lut = vtkLookupTable()****
>>
>> lut.SetHueRange(667, 0.0)****
>>
>> lut.Build()****
>>
>>  ****
>>
>> streamMapper.SetLookupTable(lut)****
>>
>>  ****
>>
>> Greetings****
>>
>> Marcelino****
>>
>>  ****
>>
>>  ****
>>
>> *De:* vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] *En
>> nombre de *Yifei Li
>> *Enviado el:* martes, 08 de noviembre de 2011 08:24 p.m.
>> *Para:* vtkusers at vtk.org
>> *Asunto:* [vtkusers] all my streamlines are in white :(****
>>
>>  ****
>>
>> Hi all, ****
>>
>>  ****
>>
>> I want streamlines to be colored according to scalar values, but they are
>> all white. Can someone help me figure out what's wrong with my code? Thanks
>>  -Yifei****
>>
>>  ****
>>
>> # vector field data****
>>
>> grid = vtkStructuredGrid()****
>>
>> grid.SetPoints(points)****
>>
>> grid.GetPointData().SetVectors(vectors)****
>>
>>  ****
>>
>> ....****
>>
>> streamer = vtkStreamTracer()****
>>
>> ...****
>>
>> # show streamlines using ribbon****
>>
>> rf = vtkRibbonFilter()****
>>
>> rf.SetInputConnection(streamer.GetOutputPort())****
>>
>>  ****
>>
>> streamMapper = vtkPolyDataMapper()****
>>
>> streamMapper.SetInputConnection(rf.GetOutputPort())****
>>
>>  ****
>>
>> # I thought the following lines should make it ****
>>
>> streamMapper.ScalarVisibilityOn()****
>>
>> streamMapper.SetScalarRange(0.0,
>> grid.GetPointData().GetVectors().GetMaxNorm())****
>>
>>  ****
>>   ------------------------------
>>
>> -Universidad Central "Marta Abreu" de Las Villas. http://www.uclv.edu.cu
>> -Participe en Universidad 2012, del 13 al 17 de febrero de 2012.
>> Habana.Cuba. http://www.congresouniversidad.cu
>> -Consulte la enciclopedia colaborativa cubana. http://www.ecured.cu/****
>>
>> ** **
>>  ------------------------------
>>
>> -Universidad Central "Marta Abreu" de Las Villas. http://www.uclv.edu.cu
>> -Participe en Universidad 2012, del 13 al 17 de febrero de 2012.
>> Habana.Cuba. http://www.congresouniversidad.cu
>> -Consulte la enciclopedia colaborativa cubana. http://www.ecured.cu/
>>
>> ****
>>
>> ** **
>>
>> ** **
>>  ------------------------------
>>
>> -Universidad Central "Marta Abreu" de Las Villas. http://www.uclv.edu.cu
>> -Participe en Universidad 2012, del 13 al 17 de febrero de 2012.
>> Habana.Cuba. http://www.congresouniversidad.cu
>> -Consulte la enciclopedia colaborativa cubana. http://www.ecured.cu/
>>
>> ****
>>
>> ------------------------------
>> -Universidad Central "Marta Abreu" de Las Villas. http://www.uclv.edu.cu
>> -Participe en Universidad 2012, del 13 al 17 de febrero de 2012.
>> Habana.Cuba. http://www.congresouniversidad.cu
>> -Consulte la enciclopedia colaborativa cubana. http://www.ecured.cu/
>>
>>
>>
>> _______________________________________________
>> 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:
>> http://www.vtk.org/mailman/listinfo/vtkusers
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20111109/e340871b/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: test.py
Type: application/octet-stream
Size: 3554 bytes
Desc: not available
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20111109/e340871b/attachment.obj>