Mesh File Format

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2009-03-29
2013-05-27
  • Hello,

    Where can I find a detailed description of NetGen Mesh file format ? I am particularly interested in knowing which edges ( and face)
    lies on a geometry given by BRep ( OCCGeometry ).

    Thanks
    csv

    Poona, India

     
    • Hello there,

      A Good Evening to you!

      I am not sure I completely understood your question.... do you only want to know which face of the geometry has what number, and which edges belong to which face? Or do you want to know to which face a given surface mesh element belongs?

      If you only want to know which face has what number, and more information about the wires and edges constituting an OpenCascade geometry, you can use the "IGES/STEP Topology Explorer/Doctor" which can be found in the "Geometry" menu of the Netgen GUI.

      In the topology explorer, if you click on "Analyse Geometry", the window above it gives a tree listing of all the entities found in the geometry. Then, you can either double click on a face in the graphical window to highlight it in the list, or vice versa, etc...etc....

      If you wanted to know which surface a specific surface mesh element belongs to, then you should save the mesh in the native ".vol" format, and then you can open this .vol file using a text editor.

      You will see that the VOL file is actually sufficiently documented in itself...

      Hope this helps...!

      Have a nice day!

      Philippose

       
    • Hello Philippose,

      Thanks for the reply.

      The actual requirement is as follows.

      I want to use NetGen with initial triangulation then I want to handle Mesh and Geometry myself. So if someone gives me an
      edge (n1,n2) I want to know which curves from geometry it belongs to.  Similarly if there is one triangle ( n1,n2, n3) I want to
      know which geometric face, it belong to.

      I found that NeutralFormat quite easy compared to *.vol format. But I have one doubt in Neutral format. In the facedecriptor
      there are two element (1) surfNr (2) BCProperty .   which one of them belong to the geometry entitity ( It my guess that one of
      the  number indicated the geometric face) ?

      Similar to the faces, can be identify edges also ? but how ?

      Thanks.
      csv

      Poona, India

       
    • Hello,

      A Good evening to you!

      When you mean "handle mesh and geometry myself"... do you mean that you want to write your own algorithm for 3D meshing within Netgen?

      Anyway.... for the functionality you are looking for, you could take a look at the "topology.hpp" (and the corresponding topology.cpp) file..... Here you will find a Mesh Topology class, along with functions for accessing a large variety of "cross-relations" such as the surface elements of an edge, or the geometric face a surface element belongs to, etc...etc...etc....

      Downside is, that you will have to adapt the code yourself to fit your requirements...

      Hope this helps...

      Have a nice day!

      Philippose