virtual void interpolate(type &val, VMesh::ElemInterpolate &interp, type defval = (static_cast<type>(0))) const; \
virtual void minterpolate(std::vector<type> &val, VMesh::MultiElemInterpolate &interp, type defval = (static_cast<type>(0))) const; \
virtual void gradient(StackVector<type,3> &val, VMesh::ElemGradient &interp, type defval = (static_cast<type>(0))) const; \
virtual void mgradient(std::vector<StackVector<type,3> > &val, VMesh::MultiElemGradient &interp, type defval = (static_cast<type>(0))) const; \