# Why does this not intersect?

intersect.3dm (43.8 KB) I used Object intersect but to no avail. — Mark

Yeah, that looks buggy to me… No intersection in V6 either. Problem with degree 5 surfaces?

Thanks for checking Mitch.—- Mark

Problem is with the the parts of the surfaces that are tending to co-incidence. Demonstrated by cutting one surface with any longitudinal isocurve: whichever part contains the co-incident surface region cannot give an intersection, the rest does so.

This is not new: Rhino has always been unable to find these intersections (perhaps wherever the two surfaces are within tolerance of each other?). However, in my recollection it traditionally drew the part of the intersection that it could establish.

My feeling is that this inability is a limitation of our concept that an intersection is a curve. In a system limited by tolerance values, an intersection may be a surface in places. If one needs to have a curve, then any curve that lies within the boundaries of the intersection surface is valid, opening a way to complete the curve with an extension on the surface that tends to a convenient point (such as where the edges intersect, or in the same plane as the rest). Or Rhino could highlight the bounds of the coincident surface area and invite the user to complete the curve on that surface.

Regards
Jeremy

Thanks Jeremy for the detailed explanation. Although in the scenario I had , it is easy enough to get an intersection with an additional planar surface . I ran into this before, but an older mind tends to forget why it happened.— Mark