# [Gmsh] Interior a sphere

Durufle marc marc_durufle at yahoo.fr
Tue Sep 21 14:17:36 CEST 2004

```Hello,
I used the following file "sphere.geo" :

lc=0.3;
r1=1.0;
//Sphere
Point(1) = {0,0,0,lc};
Point(2) = {0,0,-r1,lc};
Point(3) = {0,-r1,0,lc};
Point(4) = {0,0,r1,lc};

Line(1) = {1,2};
Circle(2) = {2,1,3};
Circle(3) = {3,1,4};
Line(4) = {4,1};

Line Loop(4) = {3,4,1,2};
Plane Surface(5) = {4};
Extrude Surface {5, {0.0,0.0,1.0}, {0.0,0.0,0.0},
2*Pi/3};
Extrude Surface {19, {0.0,0.0,1.0}, {0.0,0.0,0.0},
2*Pi/3};
Extrude Surface {33, {0.0,0.0,1.0}, {0.0,0.0,0.0},
2*Pi/3};

Surface Loop(47) = {13,18,27,32,41,46};

Physical Surface(1) = {13};
Physical Surface(2) = {18};
Physical Surface(3) = {27};
Physical Surface(4) = {32};
Physical Surface(5) = {41};
Physical Surface(6) = {46};

Volume(48) = {47};

Physical Volume(1) = {48};

When i compiled, all is ok, and i obtain a wonderful
surfacic mesh, but i want in truth a volumic mesh with
tetrahedra ! So, i would want to know what i did not
do correctly in this file. What are the modifications
I have to bring to my file. My second question is
When i call extrude command, how i can get the numbers
of the surfaces created during this operation ? At
present, i run gmsh, and i look at numbers, that are
displayed on the screen. I display then each surface,
to see what surface matches what number. And then i
construct my volume...
There is a better way to do that ?

Best regards

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```