[Gmsh] Bug: Extrusion with rotation by PI creates flat surface

[Daniel Huebner]

Dear List,

I am trying to extrude a rectangle with a rotation by PI. However this 
results in a flat surface instead of half of an cylinder. Please find a 
minimal .geo example below.

My Gmsh version is 3.0.5 and I am running on openSUSE Leap 42.2.

I have tested older Gmsh versions as well: The example is working with 
Gmsh version 2.8.5, but not with version 2.15.0.

Best regards
Daniel




Point(1) = {.5, 0, 0, 1.};
Point(2) = {1., 0, 0, 1.};
Point(3) = {1., 1., 0, 1.};
Point(4) = {.5, 1., 0, 1.};

Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 4};
Line(4) = {4, 1};

Line Loop(1) = {1, 2, 3, 4};

Plane Surface(1) = {1};
new_surf[] = Translate {0, 1.5, 0} { Duplicata{ Surface{1}; } };

// Correct
Extrude { {0,1,0}, {0,0,0}, Pi*.99999 } { Surface{1}; }
// False
Extrude { {0,1,0}, {0,0,0}, Pi } { Surface{new_surf[0]}; }