Using levelset to integrate a fespace variable in a subregion of the mesh

General Discussion
2

Hello,
according to the FreeFem documentation, when you write
int3d(Th3D,levelset=phi) the integral is performed where phi<0.
Thus you must change your definition of flevelset
Otherwise you can do also as in Vectorial PDE, conditions, stiffness matrix - #4 by fb77