In the attached, I have a horizontal spline. Then I have a sequence of points. The uppermost point I created by intersecting a place through the curve.

So now I draw a curve through the point on the other curve. I can do line, polyline, interpretcrv, curvethroughpts, anything—

When I intersect the two curves, Rhino says they do not intersect.

Tolerance is 1/32". Visually, the two curves appear to intersect.

I can do the same at other points on the curve and they intersect.

I thought I would share this oddity.

Problem Intersect.3dm (3.0 MB)