[Gmsh] Creating a spherical hole inside a volume [Files attached for testing]

[Christophe Geuzaine]

Gmsh does not support intersecting STL (mesh-based) and CAD entities; at least not yet. So if you need intersecting a sphere with your STL, you'll need to use something external to intersect (a mesh of the sphere) with the STL first, before importing in Gmsh. The new OpenCASCADE stuff will not help.

Christophe

> On 18 Mar 2017, at 02:34, Prithivirajan V <prithivi.purdue at gmail.com> wrote:
> 
> Thanks Guillaume ! 
> 
> I tried using the OpenCascade factory but I am getting an error, Possible due to the way I am importing stl files. Is there a specific way of importing them when I use 
> OpenCascade ?
> 
> I am getting the following errors (GEO file is attached) : 
> 
> Info    : Done reading 'Grain_Feature_1.stl'
> Error   : Unknown OpenCASCADE face with tag 1
> Error   : Unknown OpenCASCADE surface loop with tag 1
> 
> Info    : Done reading 'Grain_Feature_2.stl'
> Error   : Unknown OpenCASCADE face with tag 2
> Error   : Unknown OpenCASCADE surface loop with tag 2
> Error   : Unknown OpenCASCADE entity of dimension 3 with tag 1
> 
> 
> Could you or anyone help me fix this ?? 
> 
> On Fri, Mar 17, 2017 at 6:13 AM, DILASSER Guillaume <Guillaume.DILASSER at cea.fr> wrote:
> Hello,
> 
>  
> 
> Unfortunately, Gmsh is fairly limited when it comes to operations like computing intersections. However, you might be able to do something using the OpenCascade factory included in the latest nigthly build. You can download it from gsmh.info, under the download paragraph, just under the “Development version” mention. For example, you might want to have a look at the Boolean.geo exemple here and there few examples on how to import geometry from files (they will only work with the nightly, ID & password = gmsh). Hoping that will be helpful,
> 
>  
> 
> Faithfully Yours,
> 
>  
> 
> Guillaume DILASSER
> 
> Doctorant SACM / LEAS
> 
> CEA - Centre de Saclay - Bât.123 - PC 319c
> 
> 91191 Gif sur Yvette Cedex - France -
> 
>  
> 
> guillaume.dilasser at cea.fr
> 
>  
> 
> De : gmsh [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] De la part de Prithivirajan V
> Envoyé : vendredi 17 mars 2017 03:23
> À : gmsh at geuz.org
> Objet : [Gmsh] Creating a spherical hole inside a volume [Files attached for testing]
> 
>  
> 
> Hello all,
> 
> My objective is to create the spherical hole inside a volume. I have 2 STL files(see attached) as inputs. The complication is that the spherical hole intersects the two other existing volumes and it is not contained entirely in either one of the volumes.
> 
> 
> 
> I tried two approaches both of them were a failure (geo files are attached for both) :
> 
> Approach 1 :
> 
>  
> 
> I used the merge command and then I created a spherical volume  and performed meshing. The issue is the sphere is getting meshed separately without any relation to the other 2 volumes.
> 
> 
> Approach 2 :
> 
> First , I created an STL file of the spherical void separately. Now I used merge command on all 3 STL files. Now i am getting intersections which I am unable to resolve.
> 
> 
> I have been stuck here for a while in this, your help would be greatly appreciated!!!!
> 
>  
> 
> Thanks,
> 
> Prithivi
> 
> 
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine

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