Snap to surface isocurves


I often want to snap to the intersection of U and V isocurves on a surface. The Intersect Osnap doesn’t work in this case.

Is there a way to do this that I haven’t discovered?

I normally ‘ExtractIsocurves’ then snap to the intersect of those…but would be great to be able to just snap on the isos directly!


I’m with you.
This simple addition would improve a lot Yue new users experience.
Everything visible should work.

How would you like to tell Rhino which isocurves to use, given they could be at any u or v position, not just convenient ones like the halfway points, say?

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I think for a start, I’d like to be able to snap to the intersection of visible isocurves - like the intersection of the two yellow ones shown in my image. For example, if I want to draw a line tangent to one of them, then the tangent osnap should recognize the isos.

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+1 to this. A “Visible Iso” snap would be really neat

Hello- along surface edges, the Knot Osnap can help if the isocurve dernsity is 1. The middle iso on a single span surface is not a knot so that one fails too.


For now, that particular one can be done by centre snap.

Hi @pascal yes that’s helpful too.

I gave a bad example! Nornally it’s not the centre I’m looking for…

No, I understand. It’s not a bad example, just a simple one. A simple example starts a dialogue which can explore more complex criteria. That’s usually a better vehicle for requirements elicitation than starting from an example that is so complex that the complexity hides gaping holes in what’s needed.

Anyway, I just thought the centre thing was worth mentioning for people who did want to snap to the visible intersection within a quadrilateral.


Yes, that’s a good point. In any case here’s a slightly less simplistic example…

3.3dm (134.7 KB)

For now a dumb macro might be of some use

#_ExtractIsocurve _Pause _Direction _Both _ExtractAll _Enter


Thanks Pascal, that’s great