[Gmsh] Compound lines in STL

Bart Vermeulen bart.vermeulen at wur.nl
Wed Sep 3 12:17:27 CEST 2014

Dear all,

I am trying to create a mesh starting with a STL model. This model 
consists of 6 different surfaces. I use the file included below (quite 
similar to one of the tutorials). When I load this into gmsh I can see 
the geometry with the different surfaces. At the corners of each of the 
surfaces there is a point (4 points for each surface). The Compound 
lines connect these points directly instead of following the geometry 
(see attached screenshot). Obviously the meshing fails.

Any idea how to properly define the compound lines? (The surfaces ar OK)

Thanks in advance,
Bart Vermeulen

Merge "mmbendo.stl";

// We can now define a compound line (resp. surface) for each discrete
// line (resp. surface) in the model
ll[] = Line "*";
For j In {0 : #ll[]-1}
   Compound Line(newl) = ll[j];
ss[] = Surface "*";
s = news;
For i In {0 : #ss[]-1}
   Compound Surface(s+i) = ss[i];

// And we can create the volume based on the new compound entities
Surface Loop(1) = {s : s + #ss[]-1};
Volume(1) = {1};

Physical Surface(1) = {s : s + #ss[]-1};
Physical Volume(1) = 1;

uniform = 1;
   // uniform mesh size...
   Mesh.CharacteristicLengthMin = 15;
   Mesh.CharacteristicLengthMax = 15;
   // ... or apply a funny mesh size field, just because we can :-)
   Field[1] = MathEval;
   Field[1].F = "2*Sin((x+y)/5) + 3";
   Background Field = 1;

Mesh.RemeshAlgorithm = 0; // (0) no split (1) automatic (2) automatic 
only with metis
Mesh.RemeshParametrization = 7; // (0) harmonic (1) conformal spectral 
(7) conformal finite element
Geometry.HideCompounds = 0; // don't hide the compound entities
Mesh.Algorithm = 6; // Frontal

Bart Vermeulen
Wageningen University, Department of Environmental Sciences
Hydrology and Quantitative Water Management Group
Postal address: Postbus 47, 6700AA Wageningen,The Netherlands
Visiting address: Room 0.C027, Droevendaalsesteeg 3,6708PB Wageningen, The Netherlands
Tel. +31-317-482765 Fax +31-317-419000
email: bart.vermeulen at wur.nl

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