I am attempting to create a simple algorithm to identify concentricity in a group of curves, in order to then create simple curvature for a 3d surface. There are several obvious uses for sorting such trees… However, here it seems to do a couple problematic things. First, after giving an object a 2 for outside, it replaces that with -1 for null, and then will not tag each -1 either as item in a list, member in a set, or as a null object. Is there any precedent? Why won’t it identify them? Then as a side note, any idea why I had to reverse the list in order to get the planar surface component to work properly?cull outliner dragon.gh (25.9 KB)Cull Outliner Dragon.3dm (108.6 KB)