Top row: Ratio between the non-softened gravitational potential and the Plummer-, Ruffert-, and spline-softened gravitational potentials, as a function of the softening radius and of the distance to the core. Bottom row: Same as the top row but for the gravitational torque density associated with one of the two binary components. The white full lines indicates $\Vert r-r_i\Vert =ϵ$ and the dashed white line $\Vert r-r_i\Vert =h=14ϵ/5$.