Why are these surfaces getting multiple intersection curve results instead of just one curve each?

Try intersecting the black surface with the red (Rhino gave me 5 intersections) and the black with the blue (another 5 one time, 6 intersections another time). And the intersections do not even make a continuous line.

Is there a glitch or error with the surfaces?

Thanks,

Matt

WhyNIntersections.3dm (187.7 KB)

Seems like a bug.

Hi Matt - my guess of the moment is that it’s because the intersection falls right on an isocurve, well knot in this case, of one of the inputs - it looks like the surface may have been extended with Type=Line at some point, is that correct? There is a fully multiple knot (= kink if you move a control point there) as a consequence. If I split that surface back at the knot and extendSrf > Type=Smooth out again as you have it, the intersection is as expected.

WhyNIntersections_PG.3dm (158.6 KB)

-Pascal

Thanks all, for confirming that it’s a bug.

Pascal - yes, I used ExtendSrf and must have not have changed “Type=Line” to “Type=Smooth”. That forgetfulness would also explain minor geometric issues I had elsewhere when I was extending other surfs.

Matt