asymmetric-point-neighbours x y z d1 d2 procedure

  Takes a set of points and returns an directed graph of those points which are near each other. This procedure works like point-neighbours with the following difference. Points within distance d1 are always symmetrically neighbours. Points outside distance d2 are never neighbours. Points between distance d1 and distance d2 are chosen as neighbours randomly with probability of 0.5.

The d1 parameter may be 0.0.

(asymmetric-point-neighbours x y z 0. 0.2)