Figure 3.

A needle in the bevel-left direction with orientation θ is tracing the solid action circle with radius r (a). A direction change would result in tracing the dotted circle. The action circle is divided into N_c = 40 discrete arcs of length δ (b). The action circle points are rounded to the nearest point on the Δ-density grid, and transitions for insertion of distance δ are defined by the vectors between rounded action circle points (c).