Member component fails

why does the member component only find 10 points out of the 18 that it should find? (94.5 KB)

Member Index requires exact equality. The points coming out of those MidPt components are sometimes slightly different. I’m not 100% sure what causes this, or whether it’s a bug or just an artefact of the way Rhino deals with brep (I suspect the latter, see below).

You should use Closest Point instead of Member Index since that one understands it’s dealing with point data and can thus take distances into account. Alternatively, you can try and round your data to -say- six decimal places prior to comparing them for equality, but that is cumbersome with points and anyway is not as a good a solution as using Closest Point.

below: Edges in Breps should be coincident within tolerance of all faces that meet up at that edge. In practice this means an edge between two faces is a compromise between what face A wants it to be and what face B wants it to be. When you explode a brep, each edge only has a single face to worry about so it may well be slightly different.

i see and will try.
thanks a lot for the detailed and understandable information!