[vtkusers] Use of Tessellation Shader in VTK

David E DeMarle dave.demarle at kitware.com
Thu Jun 20 14:47:39 EDT 2019

I do not think that tesselation shaders are exposed anywhere yet in VTK.
See vtkShader, vtkShaderProgram and vtkOpenGLPolyData's support for Vertex,
Geometry and Fragment shaders in comparison.

Note, you should re-ask on discourse.vtk.org. The vtk mailing lists are
about to be shut down, and you might have more luck there.

David E DeMarle
Kitware, Inc.
Principal Engineer

On Wed, Jun 19, 2019 at 6:32 AM Tharun <tharun160190 at gmail.com> wrote:

> I have a triangular mesh(polygons as cells in vtkPolyData). Each point has
> different color field data. On using Point Color data as scalars, triangles
> have graded color. But, what I want is like in the image below
> <http://vtk.1045678.n5.nabble.com/file/t341373/test.png> .
> I know that subdividing the triangular mesh into triangles having  same
> color data vertices can give result like this by using Cell data as
> scalars.
> Now, our workflow is similar to  example
> <
> https://vtk.org/gitweb?p=VTK.git;a=blob;f=Examples/VisualizationAlgorithms/Cxx/FilledContours.cxx>
> and I have the desired output. Meshes we deal with have 10s of millions of
> triangles and the process is quite slow.
> I recenlty read about Tessellation Shaders at  here
> <http://ogldev.atspace.co.uk/www/tutorial30/tutorial30.html>  , and they
> mentioned about "Primitive Generator" part of Tessellation where we can
> just
> mention the tessellation levels of each triangle by gl_TessLevelOuter and
> gl_TessLevelInner. I believe, specifying gl_TessLevelOuter for every
> triangle of original mesh based on Vertices Color Data for each edge of
> triangles solves my problem with performance.
> Can anybody please let me know how to do this in VTK?
> --
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