Mesh non manifold shape - opencascade brep

mgmskumara · April 29, 2020, 5:46am

I recently started to use Netgen for meshing. Thank you very much for making such a programme.

I want to made a non manifold shape. I have a blade shape with coating in .brep file format. Do any one have an experience to deal with non manifold shape. If Netgen is not support such type, can anyone tell me an other way to resolve this.
Here I have attached the shape and error that i’m getting.

Thank you,
Mahesh

Attachment: brepFile.zip

Attachment: brepFile_2020-04-29.zip

christopher · April 29, 2020, 6:47am

Hi Mahesh,
Netgen expects every surface to be framed by a directed curve. Your geometry seems to define edges multiple times. But the brep attachment is missing.
Best

mgmskumara · April 29, 2020, 7:17am

Hi Christopher,
Thank you very much for your quick reply.
I m sorry. I attached the brep file now.

Anyway the mentioned error comes because of a bug inside Netgen. I fixed that issue. Its related to open cascade. I have some experience with occ, so i fixed that issue.

Good news is Netgen has capability to mesh non manifold shapes.
I can submit my fix to the Github.

peter_heppel · August 19, 2020, 2:44pm

Hi Mahesh
It will be incredibly useful for structural analysis to be able to mesh non-manifold shapes. Where would I go to download a patch including your mod?
Thanks a lot
Peter

mgmskumara · August 20, 2020, 5:40am

I tried to submit, but i couldnt do that because i dont have much knowledge on github
please check these two

fix is in this file

github.com

mgmskumara/netgen/blob/master/occgenmesh.cpp

#ifdef OCCGEOMETRY

#include <mystdlib.h>
#include <occgeom.hpp>
#include <meshing.hpp>


namespace netgen
{

#include "occmeshsurf.hpp"

#define TCL_OK 0
#define TCL_ERROR 1

#define DIVIDEEDGESECTIONS 1000
#define IGNORECURVELENGTH 1e-4
#define VSMALL 1e-10

This file has been truncated. show original

If you cant get resolve, please comment here

sxmeng · August 24, 2020, 8:40am

Hi Christopher,

I’ve a less related question but related to mesh… If I have a very complicated surface given by an implicit function, I guess I have to manually generate the mesh? or there is a simple function call that I may try.

Thank you,
Shixu