[vtk-developers] Fwd: vtkUnstructuredGridVolumeRayCastMapper (05B22CB8): Can't use the ray cast mapper without scalars!

[Ali Habib]

thanks alot for your great efforts,

Please I have another question it's not a perfect traingle ,I want to create
a mesh to be used in FEM any advice please


best regards

On Wed, Oct 7, 2009 at 9:59 PM, David Feng <dfeng at cs.unc.edu> wrote:

> I haven't used the vtkUnstructuredGridVolumeRayCastMapper before, nor do I
> know anything about meshing.   I'm guessing that
> vtkUnstructuredGridVolumeRayCastMapper is trying to composite all of the
> scalars on the geometry points, and fails when there aren't any.
> It looks like you're trying to set the scalars with this code:
> unstructuredReader->GetOutput()->GetPointData()->AddArray(arr);
>
> unstructuredReader->GetOutput()->GetPointData()->SetActiveScalars("myarray");
>
> I'd be careful with that.  Modifications to the output of a filter often
> get wiped out when the filter updates.  Better to make a copy of the output,
> if you have space:
>
> copy = vtkUnstructuredGrid::New()
> copy->DeepCopy(unstructuredReader->GetOutput());
> copy->GetPointData()->SetScalars(arr);
>
> But it seems like you really don't care about scalars defined at points,
> since you're just filling the scalar array with 1.0 everywhere.  If all you
> want is to see a surface, then render it using one of the standard geometry
> mappers.  The code would look something like this, in python:
>
> -----------
> sphereSource = vtk.vtkSphereSource()
> delaunay = vtk.vtkDelaunay3D()
> delaunay.SetInputConnection(sphereSource.GetOutputPort())
>
> mapper = vtk.vtkDataSetMapper()
> mapper.SetInputConnection(delaunay.GetOutputPort())
>
> actor = vtk.vtkActor()
> actor.SetMapper(mapper)
>
> ren = vtk.vtkRenderer()
> rwin = vtk.vtkRenderWindow()
> iren = vtk.vtkRenderWindowInteractor()
>
> ren.AddActor(actor)
> rwin.AddRenderer(ren)
> rwin.SetInteractor(iren)
> iren.Start()
> -------------
>
> I tested this out and it rendered a sphere.  It looks the same as the
> normal output from vtkSphereSource.  Again, I'm not familiar with what
> you're trying to do, but hopefully this was helpful.
>
> David
>
> Ali Habib wrote:
>
>> Dear All
>>  I know it's for developing just , but I sent 6 times to vtk user forum ,
>> with no reply helped me , so I am not sure is this bug or not
>>  best regards
>>
>> ---------- Forwarded message ----------
>> From: *Ali Habib* <ali.mahmoud.habib at gmail.com <mailto:
>> ali.mahmoud.habib at gmail.com>>
>> Date: Tue, Sep 29, 2009 at 9:47 PM
>> Subject: vtkUnstructuredGridVolumeRayCastMapper (05B22CB8): Can't use the
>> ray cast mapper without scalars!
>> To: vtkusers at vtk.org <mailto:vtkusers at vtk.org>
>>
>>
>> I wrote a code to make tetrahedral mesh on sphere , but it no give result
>> except :
>>  ERROR: In
>> m:\dev\cur\vtkdotnet\branch\50\VolumeRendering\vtkUnstructuredGridVolumeRayCastMapper.cxx,
>> line 274
>> vtkUnstructuredGridVolumeRayCastMapper (05B22CB8): Can't use the ray cast
>> mapper without scalars!
>>  every time I  run the code
>>  attached is the c++ code , your fast reply is highly appretiated
>>   best regards
>>
>> ------------------------------------------------------------------------
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