[vtkusers] vtkUnstructuredGrid and Gouraud Shading

Ken Martin ken.martin at kitware.com
Tue Nov 29 09:33:31 EST 2016

You need normals for smooth shading. So yes, something like

vtkUnstructuredGrid -> vtkGeometryFilter (with merging on) ->

Do you have to convert to polydata? Technically no, you could volume render
the 3D cells using ProjectedTetrahedra but the most common approach is to
extract some sort of polygonal surface and render that.

On Tue, Nov 29, 2016 at 6:57 AM, Luca Pallozzi Lavorante <
lplavorante at gmail.com> wrote:

> Hi  vtkusers,
> how can I display a vtkUnstructuredGrid using Gouraud shading? I have seen
> two or three similar posts on the list but was unable to find any answer.
> I have an unstructured grid with ~50000 3D cells (Triquadratic Hexahedra).
> I need to extract its outer shape and visualize it with a smooth
> appearance. I verified that the method vtkActor::GetProperty()->SetInterpolationToGouraud()
> is of no avail on an actor built directly from the grid's vtkDataSetMapper.
> So I though I should convert the unstructured grid to a polygonal
> representation in order to compute normals on it using vtkPolyDataNormals.
> Here I have another doubt. I want to extract just the boundary faces from
> the unstructured grid (something I have successfully done using a
> vtkDataSetSurfaceFilter fed with a vtkStructuredGrid).
> Which is the proper pipeline I should follow?
> vtkUnstructuredGrid -> vtkDataSetSurfaceFilter -> vtkPolyDataNormals ?
> Is vtkDataSetSurfaceFilter able to extract only the boundary faces from an
> unstructured grid?
> Also, is the polygonal conversion strictly necessary? I ask this because
> this is probably computationally costly.
>  Thank you in advance for any help,
>           Luca
> _______________________________________________
> 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
> Search the list archives at: http://markmail.org/search/?q=vtkusers
> Follow this link to subscribe/unsubscribe:
> http://public.kitware.com/mailman/listinfo/vtkusers

Ken Martin PhD
Chairman & CFO
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065
518 371 3971

This communication, including all attachments, contains confidential and
legally privileged information, and it is intended only for the use of the
addressee.  Access to this email by anyone else is unauthorized. If you are
not the intended recipient, any disclosure, copying, distribution or any
action taken in reliance on it is prohibited and may be unlawful. If you
received this communication in error please notify us immediately and
destroy the original message.  Thank you.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://public.kitware.com/pipermail/vtkusers/attachments/20161129/04663f4a/attachment.html>

More information about the vtkusers mailing list