[Gmsh] issue concerning the boolean difference of two volumes?

[Bertrand Thierry]

Hello Nicu,

The same problem on my computer. I guess it comes from a tolerance 
problem with the boolean operators.
Adding this to your code :
     Geometry.ToleranceBoolean = 0.001;
makes it work again.

(however, I'm not sure if it's the right way to deal with it, maybe 
someone else will confirm (/ou pas/) ?)

Bert

On 05/30/2018 12:08 PM, Nicolae Cindea wrote:
>
> Dear all,
>
> I think there is an issue concerning the difference (or the 
> intersection) of two volumes. The following code:
>
> // here starts the code
> SetFactory("OpenCASCADE");
>
> L = 0.5;   // cylinder length [0, L]
> l = 1.00;  // triangle edge
> r = 0.050; // radius of the sphere
>
> h = l * Sqrt(3) / 2;
>
> Sphere(2) = { 0, 0, 0, r };
>
> Point(101) = {      h / 3, 0, -l / 2 };
> Point(102) = {      h / 3, 0,  l / 2 };
> Point(103) = { -2 * h / 3, 0,  0     };
>
> Line(201) = { 102, 103 };
> Line(202) = { 103, 101 };
> Line(203) = { 101, 102 };
>
> Line Loop(204) = {201, 202, 203};
>
> Surface(3) = { 204 };
>
> Translate { -0.108320, 0, -0.062538 } { Surface{3};}
> out[] = Extrude { 0, L, 0 }{ Surface{3}; };
>
>
> BooleanDifference(8) = { Volume{3}; Delete; }{ Volume{2}; Delete; };
> // here ends the code
>
>
> gives the following error "Error   : Intersection operation cannot be 
> performed". Nevertheless, replacing the line
> Translate { -0.108320, 0, -0.062538 } { Surface{3};}
> by
> Translate { -0.108320, 0, -0.062537 } { Surface{3};}
> the error message disappears and everything work as supposed.
>
> Can somebody reproduce this comportment? Since the above .geo file is 
> generated from another language I'm searching a workaround to avoid 
> the problematic situations.
>
> Thank you.
>
> Regards,
> Nicolae.
>
> PS: my gmsh -info
>
> Version          : 3.0.6
> License          : GNU General Public License
> Build OS         : Linux64
> Build date       : 20171105
> Build host       : gmsh.info
> Build options    : 64Bit Ann Bamg Bfgs Blas(Generic) Blossom C++11 
> Chaco DIntegration Dlopen Fltk Gmm Jpeg(Fltk) Kbipack Lapack(Generic) 
> LinuxJoystick MathEx Med Mesh Metis Mmg3d Mpeg Netgen ONELAB 
> ONELABMetamodel OpenCASCADE OpenGL OptHom PETSc Parser Plugins 
> Png(Fltk) Post SLEPc Solver Taucs TetGen/BR Tetgen1.5 Voro3D Zlib
> FLTK version     : 1.3.4
> PETSc version    : 3.7.5 (complex arithmtic)
> OCC version      : 7.1.0
> MED version      : 3.2.0
> Packaged by      : gitlab-runner
> Web site         : http://gmsh.info
> Mailing list     : gmsh at onelab.info
>
> _______________________________________________
> gmsh mailing list
> gmsh at onelab.info
> http://onelab.info/mailman/listinfo/gmsh

-- 
Bertrand THIERRY
CNRS researcher (Chargé de Recherche)
Laboratoire Jacques-Louis Lions
Sorbonne Université
Office 310, Corridor 15/25
Tel: +33 (0)1 44 27 72 01
https://www.ljll.math.upmc.fr/bthierry

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://onelab.info/pipermail/gmsh/attachments/20180530/cffaa5e2/attachment.html>