Mesh.CharacteristicLengthFromPoints = 1;
Mesh.Tetrahedra = 0;
Mesh.Voronoi = 1;

fac = 5e3;
Point(1) = {-1 * fac, -1 * fac ,-1 * fac};
Point(2) = {-1 * fac, 1 * fac, -1 * fac};
Point(3) = {1 * fac ,1 * fac ,-1 * fac};
Point(4) = {1 * fac ,-1 * fac, -1 * fac};
Line(1) = {1,2};
Line(2) = {2,3};
Line(3) = {3,4};
Line(4) = {4,1};
Line Loop(5) = {1,2,3,4};
Plane Surface(2) = {5};
Extrude{ 0 * fac, 0 * fac, 2 * fac }{ Surface{ 2 }; }
Surface Loop( 2 ) = { 2, 14, 18, 22, 26, 27 };

//Merge "s.stl";
Merge "m.stl";
Surface Loop( 1 ) = { 1 };
Volume( 2 ) = { 2, 1 };

Mesh 3;
