Pressure on surface of rigid sphere for different incoming plane wave directions

[orchidas]

I followed along the rigid sphere scattering examples in Tutorials 1 and 2. I am explicitly trying to derive a scattering matrix based on spherical harmonic decomposition (eqs 7-10 in this paper).

For this, I need the pressure at discrete points on the surface of the sphere. This pressure is dependent on the incoming plane wave direction. In the tutorials, incoming plane waves are defined on a grid of points and the scattered field is calculated at those points. How can I evaluate the pressure on the sphere surface (at desired points) for a specific incoming plane wave direction?