[Gmsh] help finding line-point connectivity for imported geometry

jeremy theler jeremy at seamplex.com
Wed Dec 5 01:28:18 CET 2018

Hello Terrence, here are some ideas:

1. RTM


2. Grep for "boundary" in the examples

3. Gmsh also provides and API call for the "boundary" instruction which is
very handy

4. Do not use IGES, prefer BREP and STEP in that order

5. If you need to refine around a line use attractor+threshold instead,
again RTM and grep the examples and tutorial.


On Tue, Dec 4, 2018, 18:40 Terrence Moran <tpm92 at cornell.edu> wrote:

> Hello all,
> I am new to gmsh and I am struggling to find what points make up a line
> from an imported .iges file. The goal is to import an .iges file then use a
> script to find which points are on the top layer and then find which lines
> make that surface so I can refine the mesh along that surfaces boundary. So
> far I can extract the point's x-y-z coordinates but I cannot find which
> points make up a line. I have tried this:
> ***********
> //+
> SetFactory("OpenCASCADE");
> ShapeFromFile("box.iges")
> //+
> coords[] = Point{7};
> *point_nums[] = Line{1} // this does not work*
> c = #a[];
> Printf("x coord = %g", coords[0]);
> Printf("y coord = %g", coords[1]);
> Printf("z coord = %g", coords[2]);
> **************
> The point_nums comment does not work.
> I was wondering if it was possible to output the label of the two points
> that define a line.  I plan to find out 1) which points define the 1-D
> boundary I care about 2) which lines are made with those points so I can
> refine along the line. Or maybe there is a better way to do this all
> together? I essentially need the mesh to be fine along the defined line and
> coarse everywhere else.
> The reason I am not doing this manually is because I have 1000+ .iges
> files to mesh due to the scope of my project.
> any help would be greatly appreciated!
> Thanks,
> Terrence
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jeremy theler
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