This component groups points depending on which sides of a set of planes they are positioned. This point-plane-relation is encoded using a textual string, whose characters are either A for above, B for below, or X for invalid.

For example consider a case where a point is compared to a collection of four planes. In this case the relation description will contain four characters, which might look like "AAXB", indicating that the point was coincident with or above the first two planes (the two leading A's), that the third plane was invalid (the X) and that the point was below the final plane (the trailing B).

Do note this component has two quite distinct ways of going about this, which makes it a somewhat more complicated story than per usual.

If the Pt input access is set to item, then the Pt output is simply a direct copy of the input points, and the Gr output contains the plane relation description for each point. In this mode, the order of the input points is retained, as are null values.

However if the Pt input access is set to 'twig', then both the Pt and the Gr outputs will contain trees of values. These trees consist of separate lists, each containing all the points from the input that share a similar plane relation description text. In this mode, any null values present in the input will disappear entirely, and the order of input points is not retained.