Reply To: Mass Flux Computation Issue
Specifying the origin and direction is one possibility of parametrizing the hyperplane used by the plane integral functors. You can see other possibilities that are overloaded by constructors of SuperLatticeIntegralFluxMass2D in e.g. Doxygen. So yes, the flux is computed through the plane that is orthogonal to the direction vector and intersects the origin.
As for the output vector: SuperPlaneIntegralFluxMass2D scales the integral obtained by SuperPlaneIntegral2D by the given factors. The other documented components are returned unchanged.
You do not need to wrap the mass flux functor in an interpolation functor as the integral functors return their result independent of the input coordinates (they are only accepted to satisfy the overall functor interface).