# [Gmsh] [GMSH] Surface mesh for 3D solids

Anderson Gabriel Santiago agasantiago.usp at gmail.com
Wed May 16 00:28:54 CEST 2018

```Dear all,

I am using GMSH to create a 3D surface mesh. For some unknown reason, some
normal vectors points inwards, not outwards, as I would expect, since I
defined a solid limited by plane surfaces.

Here is the GEO file I created using the GMSH GUI.

// Gmsh project created on Tue May 15 19:19:43 2018
//+
Point(1) = {0, 0, 0, 1.0};
//+
Point(2) = {1, 0, 0, 1.0};
//+
Point(3) = {1, 1, 0, 1.0};
//+
Point(4) = {0, 1, 0, 1.0};
//+
Point(5) = {0, 0, 1, 1.0};
//+
Point(6) = {1, 0, 1, 1.0};
//+
Point(7) = {1, 1, 1, 1.0};
//+
Point(8) = {0, 1, 1, 1.0};
//+
Line(1) = {1, 2};
//+
Line(2) = {2, 6};
//+
Line(3) = {6, 5};
//+
Line(4) = {5, 1};
//+
Line(5) = {5, 8};
//+
Line(6) = {8, 4};
//+
Line(7) = {4, 1};
//+
Line(8) = {8, 7};
//+
Line(9) = {7, 3};
//+
Line(10) = {3, 4};
//+
Line(11) = {6, 7};
//+
Line(12) = {3, 2};
//+
Line Loop(1) = {4, -7, -6, -5};
//+
Plane Surface(1) = {1};
//+
Line Loop(2) = {2, 11, 9, 12};
//+
Plane Surface(2) = {2};
//+
Line Loop(3) = {3, 5, 8, -11};
//+
Plane Surface(3) = {3};
//+
Line Loop(4) = {10, 7, 1, -12};
//+
Plane Surface(4) = {4};
//+
Line Loop(5) = {9, 10, -6, 8};
//+
Plane Surface(5) = {5};
//+
Line Loop(6) = {3, 4, 1, 2};
//+
Plane Surface(6) = {6};
//+
Surface Loop(1) = {4, 5, 2, 6, 3, 1};
//+
Volume(1) = {1};
//+
Physical Surface(1) = {6};
//+
Physical Surface(2) = {4, 2, 3, 1};
//+
Physical Surface(3) = {5};
//+
Physical Volume(4) = {1};

Any help is appreciated.

--
Anderson Gabriel Santiago

~"If you are depressed,
you are living in the past.
If you are anxious,
you are living in the future.
If you are at peace,
you are living in the present."~   - Lao Tzu
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