Use of Tessellation Shader in VTK

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Use of Tessellation Shader in VTK

Tharun
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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Re: Use of Tessellation Shader in VTK

David E DeMarle
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 <[hidden email]> 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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Re: Use of Tessellation Shader in VTK

Tharun
Thank you for the response. I have asked on the discourse and my issue is
resolved now.



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