[Gmsh] Removing a volume from an ambient volume

[David Colignon]

Hi Travis,

solution a) should have worked. Can you send us your .geo file to check ?
And can you try with with the Tetgen 3D meshing algorithm instead of netgen ?

Cheers,

Dave

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David Colignon, Ph.D.
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Travis Thompson wrote:
> Hello.  I have been working with Gmsh for a finite elements project at
> Texas A&M university in college station, tx.
> 
> I am new to Gmsh and have been stuck on a particular problem for a
> while now; I was hoping maybe someone could shed some light on it.
> The setup is fairly simple.  I have a 3 dimensional rectangle which
> completely contains another 3 dimensional object.
> 
> The object inside the box is completely closed; i will refer to this
> object as Object A.  If I attach a volume element to object A and mesh
> the box + object A everything works wonderfully.  I get a nice 2d mesh
> on the bounding box and a nice 3d mesh inside object A.
> 
> The problem is that I need a 3d mesh inside the bounding box and i
> want *no mesh* in the interior of object A (that is, I want to mesh
> the complement of Object A with respect to the bounding box).
> 
> What I have tried:
> a) I have tried attaching a volume element to the ambient bounding box
> and selecting Object A as 'a hole'
> b) I have tried attaching a volume element to the bounding box and a
> volume element to Object A with the intention of Deleting the volume
> element attached to object A *after* computing the mesh.
> 
> However both (a) and (b) lead to gmsh crashing (same error on both
> windows and Linux versions)
> The error is:
> 
> ----------------------------
> Assertion Failed!
> 
> Program: c:\program files\gmsh-2.2.4-Windows\gmsh.exe
> File: tetgen.cxx
> Line: 22506
> 
> Expression: matchflag == true
> ---------------------------
> 
> I would imagine that what I am trying to do is quite basic; ie:
> meshing the complement of an object inside an ambient object.  I have
> been through the documentation but due to my lack of familiarity with
> Gmsh I have failed to figure out a method.
> 
> If anyone can shed any light on this I would greatly appreciate it!
> 
> Thank you in advance!
> 
> -Travis Thompson
> Graduate Student
> Dept of Mathematics, Texas A&M University
> 
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