[Gmsh] Normal vector orientation?

Kaveh Ghayour kghayour at yahoo.com
Thu Jan 6 03:23:18 CET 2005


Hi,

I have a convex plane curve, defined by its vertices
in counter-clockwise order. I extrude this plane
surface (translate it along some given directon) and
obtain a volume.  When I try to surface mesh the
resulting volume, my normals on the original surface
point outwards, but on the lower surface and the side
surfaces point inwards.

I do not get any error or warning messages.  Is this a
bug or am I doing something wrong?  The corresponding
geo file is :
Point(      1) = {  0.0000000E+00 ,  0.1212500E+00 , 
0.4400000E+00 ,  0.1000000E+00 };
Point(      2) = {  0.7426148E-01 ,  0.1212500E+00 , 
0.4325082E+00 ,  0.1000000E+00 };
Point(      3) = {  0.1459941E+00 ,  0.1212500E+00 , 
0.4102878E+00 ,  0.1000000E+00 };
Point(      4) = {  0.2127550E+00 ,  0.1212500E+00 , 
0.3740955E+00 ,  0.1000000E+00 };
Point(      5) = {  0.2722709E+00 ,  0.1212500E+00 , 
0.3251639E+00 ,  0.1000000E+00 };
Point(      6) = {  0.3225148E+00 ,  0.1212500E+00 , 
0.2651592E+00 ,  0.1000000E+00 };
Point(      7) = {  0.3617759E+00 ,  0.1212500E+00 , 
0.1961249E+00 ,  0.1000000E+00 };
Point(      8) = {  0.3887172E+00 ,  0.1212500E+00 , 
0.1204117E+00 ,  0.1000000E+00 };
Point(      9) = {  0.4024212E+00 ,  0.1212500E+00 , 
0.4059808E-01 ,  0.1000000E+00 };
Point(     10) = {  0.4024212E+00 ,  0.1212500E+00 ,
-0.4059808E-01 ,  0.1000000E+00 };
Point(     11) = {  0.3887172E+00 ,  0.1212500E+00 ,
-0.1204117E+00 ,  0.1000000E+00 };
Point(     12) = {  0.3617759E+00 ,  0.1212500E+00 ,
-0.1961249E+00 ,  0.1000000E+00 };
Point(     13) = {  0.3225148E+00 ,  0.1212500E+00 ,
-0.2651592E+00 ,  0.1000000E+00 };
Point(     14) = {  0.2722709E+00 ,  0.1212500E+00 ,
-0.3251639E+00 ,  0.1000000E+00 };
Point(     15) = {  0.2127550E+00 ,  0.1212500E+00 ,
-0.3740955E+00 ,  0.1000000E+00 };
Point(     16) = {  0.1459941E+00 ,  0.1212500E+00 ,
-0.4102878E+00 ,  0.1000000E+00 };
Point(     17) = {  0.7426148E-01 ,  0.1212500E+00 ,
-0.4325082E+00 ,  0.1000000E+00 };
Point(     18) = {  0.4949188E-16 ,  0.1212500E+00 ,
-0.4400000E+00 ,  0.1000000E+00 };
Point(     19) = {  0.0000000E+00 ,  0.1212500E+00 ,
-0.3600000E+00 ,  0.1000000E+00 };
Point(     20) = {  0.0000000E+00 ,  0.1212500E+00 ,
-0.2800000E+00 ,  0.1000000E+00 };
Point(     21) = {  0.0000000E+00 ,  0.1212500E+00 ,
-0.2000000E+00 ,  0.1000000E+00 };
Point(     22) = {  0.0000000E+00 ,  0.1212500E+00 ,
-0.1200000E+00 ,  0.1000000E+00 };
Point(     23) = {  0.0000000E+00 ,  0.1212500E+00 ,
-0.4000000E-01 ,  0.1000000E+00 };
Point(     24) = {  0.0000000E+00 ,  0.1212500E+00 , 
0.4000000E-01 ,  0.1000000E+00 };
Point(     25) = {  0.0000000E+00 ,  0.1212500E+00 , 
0.1200000E+00 ,  0.1000000E+00 };
Point(     26) = {  0.0000000E+00 ,  0.1212500E+00 , 
0.2000000E+00 ,  0.1000000E+00 };
Point(     27) = {  0.0000000E+00 ,  0.1212500E+00 , 
0.2800000E+00 ,  0.1000000E+00 };
Point(     28) = {  0.0000000E+00 ,  0.1212500E+00 , 
0.3600000E+00 ,  0.1000000E+00 };
 Line(      1) = {      1 ,      2 };
 Line(      2) = {      2 ,      3 };
 Line(      3) = {      3 ,      4 };
 Line(      4) = {      4 ,      5 };
 Line(      5) = {      5 ,      6 };
 Line(      6) = {      6 ,      7 };
 Line(      7) = {      7 ,      8 };
 Line(      8) = {      8 ,      9 };
 Line(      9) = {      9 ,     10 };
 Line(     10) = {     10 ,     11 };
 Line(     11) = {     11 ,     12 };
 Line(     12) = {     12 ,     13 };
 Line(     13) = {     13 ,     14 };
 Line(     14) = {     14 ,     15 };
 Line(     15) = {     15 ,     16 };
 Line(     16) = {     16 ,     17 };
 Line(     17) = {     17 ,     18 };
 Line(     18) = {     18 ,     19 };
 Line(     19) = {     19 ,     20 };
 Line(     20) = {     20 ,     21 };
 Line(     21) = {     21 ,     22 };
 Line(     22) = {     22 ,     23 };
 Line(     23) = {     23 ,     24 };
 Line(     24) = {     24 ,     25 };
 Line(     25) = {     25 ,     26 };
 Line(     26) = {     26 ,     27 };
 Line(     27) = {     27 ,     28 };
 Line(     28) = {     28 ,      1 };
Line Loop (1) = {  1,  2,  3,  4,  5,  6,  7,  8,  9,
10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,
23, 24, 25, 26, 27, 28};
Plane Surface(1) = {1};

Extrude Surface {1,
{0.5*0.04907477288,-0.8660254037844*0.04907477288,0}};

Thanks,

Kaveh


		
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