# [Gmsh] Mesh of a ball

**Marc Durufle**
marc.durufle at inria.fr

*Fri Jan 16 16:29:11 CET 2004*

Hello,
i find gmsh very cool. But i really don't understand how works the
extrusion. If i want to create a sphere, i can by example make an
extrusion by rotation of an angle of Pi/2, and by symetry i can have the
sphere. Then, i make a 3D mesh of the ball. But my question is when you
extrude a line, you get a surface, and where do you put the number of
this surface ??
the beginning of Boule.geo should begin like that :
lc=0.5;
// two points for an arc
Point(1) = {0,0,-2.0};
Point(2) = {0,-2.0,0.0};
//center of the ball
Point(4) = {0.0,0.0,0.0}
Circle(1) = {1,4,2}
// i want to extrude Circle 1 of an angle Pi/2 around the axis Oz
Extrude Line = {1,{0,0,1},{0,0,0},Pi/2};
// where is my surface, resulting of the extrusion ???
Well, if you have a file, which mesh a ball, i am interested.
(Une couronne sphérique aussi, pour les francophones ).
Thank you in advance.
--------------------------
Marc Durufle
Inria Rocquencourt
Tel : 01 39 63 56 27
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