Possible Incorrect numbering

  • Nobody/Anonymous


    I am using OpenCascade geometry and created mesh with NetGen. It took a full one day to note that ".vol" format increment
    the surfNr() by one. What could be the reason to start face description by 2 ( neither make fortran  nor C/C++ fans happy with
    this starting number) ?


    • Philippose Rajan

      Hello there,

      A Good Evening to you :-)!

      Soo... I must say, thats an interesting find :-)! I am not 100% sure yet, but it looks like some kind of oversight in the code as far as I can see.....

      The issue is, that the code (still) uses a mix of 0-based and 1-based array addressing modes, and I think there has been a mix up here....

      I shall confirm this and let you know again... and shall see if I can remove the increment. However, this apparent "error" does not effect the mesh within Netgen (because in the Load function, the surfnr is decremented by 1)

      Thanks for the feedback...!

      Have a nice day!


    • Philippose Rajan

      Hi again,

      As I had mentioned in my previous post, the increment of the surface number in the Netgen Vol file is a part of the legacy code present in Netgen regarding the mixed 0-based and 1-based array addressing...

      To maintain compatibility with .vol files created using current and older versions of Netgen, this modification will not be made, since the reading and writing of vol files within the Netgen framework functions fine.

      My suggestion would be that you explicitly account for this (now known) offset in the surface numbering in the external software you are using to post-process the .vol files.

      Have a nice day!



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