CGAL users discussion list

["gre6" <>]

hi all!
I want to mesh a torus surface and the equation is (x^2+y^2+z^2+10^2-5^2)^2=4*10^2*(x^2+y^2), which is the equation (y-10)^2+z^2=5^2&&x=0 spin around the z axis. I revised the example code /examples/Surface_mesher/mesh_an_implicit_function.cpp as below:

FT sphere_function (Point_3 p) {
  const FT x2=p.x()*p.x(), y2=p.y()*p.y(), z2=p.z()*p.z();
  FT a = x2+y2+z2+100.0-25.0;
  return a*a-400.0*(x2+y2);
}

 Surface_3 surface(sphere_function,             // pointer to function
                    Sphere_3(Point_3(0,10.0,0), 100.0)); // bounding sphere

CGAL::Surface_mesh_default_criteria_3<Tr> criteria(30.0,  // angular bound
                                                     0.8,  // radius bound
                                                     0.8); // distance bound


But when I run the program it abort with the below information:
CGAL error: assertion violation!
Expr: false
File: /usr/include/CGAL/Delaunay_triangulation_3.h
Line: 1068
terminate called after throwing an instance of 'std::logic_error'
  what():  basic_string::_S_construct NULL not valid
Aborted

I don't know how to handle it. Any suggestions is helpful. 
Thank you!

gre6

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