[vtkusers] write a specific point's normal of polyData

[Hila Hiler]

Dear David,
I appreciate your kind responses ...

1. Attached a clearer image represents two colored arrows:

first (white) from the .vtp file which visualized by 3dGlyphs and second
(pink) represents what I'm searching for: the orthogonal arrows - which
have been achieved by the filter in para-view: normal glyphs.

which arrow (white or pink) is achieved by this command?
m_normalGenerator->GetOutput()->GetPointData()->GetNormals()->GetTupleValue(idx,arr);

2. The cellData's normal is calculated due to an 'average surface' in an
area (cell)? any further details about this cell (how does it look like
etc)?


On Tue, Mar 13, 2012 at 2:07 PM, David Doria <daviddoria at gmail.com> wrote:

> > questions:
> > -------------
> > 1. why the following window of vtk appears with this massage ?
> >       "vtkFieldData::GetComponent was deprecated for vtk 5.2 and will be
> > removed "
>
> Why you are using GetComponent? You should probably use
>
>  double arr[3];
>
>  m_normalGenerator->GetOutput()->GetPointData()->GetNormals()->GetTupleValue(idx,
> arr);
>
> instead.
>
> > 2. what's the difference between calculating cell/point normals?
>
> If you compute point normals, a normal is produced at every point in
> the PointData. If you compute cell normals,  a normal is produced at
> every cell in the CellData.
>
> > 3. regarding the vtkXMLPolyDataWriter:
> >       - why the .vtp represents in 3d Glyphse arrows in the same
> direction
> > as the surface and not in the orthogonal plane as supposed to be? (image
> > attached)
>
> Your screenshot does not include the relevant portion of the window to
> show us your settings. My bet is that you did not set the glyphs to
> use the normals.
>
> David
>
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