Visual presentation of an intermediate step of the first part of SCARF showing the key concepts on which the algorithm is based: the skeleton G (all points); chains c⁰, c¹, and c²; chain ends ${\mathbf{c}}_0^0$ and ${\mathbf{c}}_{-1}^0$; and nearest neighbour g (red dot). The chain c¹ only has one point, which is fairly common when sorting points. Grey points are part of the skeleton G but are yet to be sorted.