Cannot change orientation of surface mesh with physical surface
The documentation specifies that the orientation of a surface mesh can be changed by giving a negative identification number in the creation of a physical surface. This does not seem to work. See this simple .geo script:
Point(1) = {0, 0, 0, 0};
Point(2) = {1, 0, 0, 0};
Point(3) = {0, 1, 0, 0};
Point(4) = {-1, 0, 0, 0};
Line(1) = {1, 2};
Line(2) = {1, 3};
Circle(3) = {2, 1, 3};
Line Loop(1) = {1, 3, -2};
Plane Surface(1) = {1};
Line(4) = {1, 4};
Circle(5) = {4, 1, 3};
Line Loop(2) = {4, 5, -2};
Plane Surface(2) = {2};
// The two surfaces have opposite orientation, create physical surface to impose same
// orientation to the mesh.
Physical Surface(1) = {1, -2};
Mesh 2;
Edited by Amaury Johnen