Acceleration of massless particles randomly sampled around a point mass, as a function of distance. The left and right panels illustrate results using the CIC and TSC mass interpolation (and inverse interpolation) schemes, respectively. The top panels show cases where the point mass is positioned at the centre of a cell, while the bottom panels depict cases where it is placed at the edge of a cell. The red, yellow, and blue data points represent accelerations computed using the FFT solver (uncorrected for the mass-assignment scheme), the FFT_7pt solver, and the multigrid solver, respectively. Circles denote radial acceleration, while triangles indicate tangential acceleration. The black solid line represents the theoretical prediction F(r, h) from Eq. (D.1). For comparison, dotted lines correspond to F(r, r_s), where r_s = (6/π)^1/3 h is the radius of a sphere with the same volume as a cell of size 2h. Dashed lines illustrate the periodic case $\tilde{F}(r,h)$.