MedCoupling Projection operators


I am a new user of MedCoupling, and I am playing with the remappers.

I am a FEM developer, and I use Lagrangian-type elements: quad4-quad8-quad9 and similar for other geometries.

Assuming I have two meshes (source and target) whose corresponding FEM spaces satisfy U_s ⊆ U_t, (hierarchical meshes like in geometric multigrid) is there a way to project the fields exactly? The entries of the projecting matrix would be phi_s(x_t), where phi_s are the lagrangian shape functions of the source mesh and x_t the coordinates of the target mesh.

I used remapper P1-P1 options on exactly the same mesh, and the only element that seems to work is the TRI3 type.