[Gmsh] Problem with Ellipse

Max Rudolph maxwellr at gmail.com
Tue Sep 18 21:56:05 CEST 2012


I'm trying to make a simple mesh of the surface of an ellipsoid. I
keep encountering the message below, which I think is erroneous. I am
trying to get gmsh to generate an elliptical arc between points 10 and
11, neither of which is on an axis of the ellipse. Point 25 is on the
major axis. I can construct an arc from point 11 to 25 and from -25 to
10, but not from 10 to 11. Can anyone help solve this problem?

Thanks,
Max

Error   : Ellipse 30 is wrong
Error   : Circle or ellipse arc 30 greater than Pi (angle=6.28319)
Error   : (If you understand what this implies, you can disable this error
Error   : message by selecting `Enable expert mode' in the option dialog.
Error   : Otherwise, please subdivide the arc in smaller pieces.)
Error   : Ellipse -30 is wrong

Input file:

a=4.0;
b=2.0;
c=2.0;
l=0.1;
Point(1) = {0,0,0,l};
xx=a*b*c/Sqrt(b^2*c^2+a^2*(b^2+c^2));

Point(10) = {xx,-xx,xx,l};
Point(11) = {-xx,-xx,xx,l};
Point(12) = {xx,xx,xx,l};
Point(13) = {-xx,xx,xx,l};
Point(14) = {xx,-xx,-xx,l};
Point(15) = {-xx,-xx,-xx,l};
Point(16) = {xx,xx,-xx,l};
Point(17) = {-xx,xx,-xx,l};

Point(22) = {0,-b*c/Sqrt(b^2+c^2),b*c/Sqrt(b^2+c^2),l};//point 22 is
on Ellipses 20-32 between 10 and 11.
Point(23) = {0,0,c,l};
Point(24) = {0,0,-c,l};
Point(25) = {a,0,0,l};
Point(26) = {-a,0,0,l};
Point(27) = {0,b,0,l};
Point(28) = {0,-b,0,l};

Ellipse(30) = {10,1,25,11};
Ellipse(31) = {11,1,25,25};
Ellipse(32) = {10,1,26,26};