# How to define a point mesh (grid) using ParaView Catalyst?

**URL:** https://discourse.paraview.org/t/how-to-define-a-point-mesh-grid-using-paraview-catalyst/291
**Category:** In Situ Support
**Created:** [July 9, 2018, 2:44pm UTC](https://discourse.paraview.org/t/how-to-define-a-point-mesh-grid-using-paraview-catalyst/291 "2018-07-09T14:44:19Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![jchou](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/j/58f4c7/32.png) [@jchou](https://discourse.paraview.org/u/jchou)
#### Post date: [July 9, 2018, 2:44pm UTC](https://discourse.paraview.org/t/how-to-define-a-point-mesh-grid-using-paraview-catalyst/291/1 "2018-07-09T14:44:19Z")

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Hi everyone,

Coming from VisIt libsim world, I wonder how it is possible to define a point mesh (grid) in ParaView catalyst. Actually in VisIt, a point mesh (grid) is a set of 2D or 3D points where the nodes also constitute the cells in the mesh. I have checked `vtkPointSet`, but it seems that this grid type cannot be used directly and the derived grid types should be used instead.

Any ideas? As an example, you can see the picture of a 3D point mesh, adopted from VisIt user manual below:

 ![21](https://discourse.paraview.org/uploads/default/original/1X/c8f16c8b4552682cb8587e7e10a5df9b95caa4ca.png)

Thanks  
Chou

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### Author: ![Dave\_DeMarle](https://discourse.paraview.org/user_avatar/discourse.paraview.org/dave_demarle/32/27_2.png) [@Dave\_DeMarle](https://discourse.paraview.org/u/Dave_DeMarle)
#### Post date: [July 10, 2018, 9:03pm UTC](https://discourse.paraview.org/t/how-to-define-a-point-mesh-grid-using-paraview-catalyst/291/2 "2018-07-10T21:03:37Z")

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vtkUnstructuredGrid and vtkPolyData (both subclasses of vtkPointSet) can work for this. The key idea is to populate the Points with the coordinates, and separately populate the cell array with VTK\_VERTEX cells. The vertex indices can simply increment (the n’th cell refers the the n’th point). (A single VTK\_POLYVERTEX cell that lists all the points is an alternative).

[https://gitlab.kitware.com/paraview/paraview/blob/master/Examples/Catalyst/CxxParticlePathExample/FEDataStructures.cxx](https://gitlab.kitware.com/paraview/paraview/blob/master/Examples/Catalyst/CxxParticlePathExample/FEDataStructures.cxx) is a reasonable starting point, change it to make VTK\_VERTEX instead of hexes.