# [Gmsh] Need quick help in generating a 3D tetrahedral mesh of a cylinder (bug?)

Toshiro K. Ohsumi ohsumit at cs.rpi.edu
Wed Dec 4 08:07:27 CET 2002

Hello,

I am using the latest gmsh, but it seems not to be able to generate a 3D
mesh given the attached cyl.geo file.  I am creating the top and bottom
circles (line loops 40 and 41) and the 4 panels make up the sides (the rest of
the line loops), I turn them into ruled surfaces then physical surfaces, then
volume, then physical volume.  I do not see why this does not work.  (What am I
doing wrong?)  Gmsh just keeps printint out Info : Relaxation factor = ...
followed by some message about coplanar points (but shouldn't the surfaces
contain coplanar points?).  Is this a bug?

I am doing it this way since I need to be able to specify boundary conditions
on the ends of the cylinder as well as on the outer [curved] wall.

I need to generate this soon (within a day or so), so any help would be
greatly appreciated.  Many thanks,

- Toshiro K. Ohsumi

-----------------------------------------------------------------------------

lc = 0.25;
Point(1) = {0.0, 0.0, -1.0, lc};
Point(2) = {1.0, 0.0, -1.0, lc};
Point(3) = {0.0, 1.0, -1.0, lc};
Point(4) = {-1.0, 0.0, -1.0, lc};
Point(5) = {0.0, -1.0, -1.0, lc};

Point(6) = {0.0, 0.0, 1.0, lc};
Point(7) = {1.0, 0.0, 1.0, lc};
Point(8) = {0.0, 1.0, 1.0, lc};
Point(9) = {-1.0, 0.0, 1.0, lc};
Point(10) = {0.0, -1.0, 1.0, lc};

Circle(13) = {2,1,3};
Circle(14) = {3,1,4};
Circle(15) = {4,1,5};
Circle(16) = {5,1,2};

Circle(17) = {8,6,7};
Circle(18) = {9,6,8};
Circle(19) = {10,6,9};
Circle(20) = {7,6,10};

Line(30) = {2, 7};
Line(31) = {3, 8};
Line(32) = {4, 9};
Line(33) = {5, 10};

Line(34) = {7, 2};
Line(35) = {8, 3};
Line(36) = {9, 4};
Line(37) = {10, 5};

Line Loop(40) = {13,14,15,16};
Line Loop(41) = {17,18,19,20};
Line Loop(42) = {13,31,17,34};
Line Loop(43) = {14,32,18,35};
Line Loop(44) = {15,33,19,36};
Line Loop(45) = {16,30,20,37};

Ruled Surface(50) = {40};
Ruled Surface(51) = {41};
Ruled Surface(52) = {42};
Ruled Surface(53) = {43};
Ruled Surface(54) = {44};
Ruled Surface(55) = {45};

Physical Surface(60) = {50};
Physical Surface(61) = {51};
Physical Surface(62) = {52};
Physical Surface(63) = {53};
Physical Surface(64) = {54};
Physical Surface(65) = {55};

Surface Loop(70) = {50,51,52,53,54,55};

Volume(80) = {70};
Physical Volume(81) = {80};