Fig. 3

An illustration for the acceleration of the non-singular calculations of the boundary-patch integrals, namely, the boundary-patch non-adjacent interactions presented in “FFT-based equivalent source acceleration of the non-singular surface and boundary-patch integrals”. The locations \(\varvec{x}_{ij, \ell }\) of the equivalent sources on the parallel faces of cells \(\mathcal C_{ij}\) are depicted by solid black circles. The true source points are shown as red diamonds. The virtual source points (with zero weights) are shown as green stars. The image also depicts the neighbourhood \(\mathcal N(\varvec{x} )\) for a target point \(\varvec{x}\)