Draw and modify curves on surface - Rhino 7

In Rhino 7 is there a way in which I can move a line that has been projected onto a complex 3D surface (in this case an organic shape with a complex topography) and keep the line constrained to the surface?

When I try to move the control points of such a line, they do not stay on the surface and I have to use “pull” to bring them back onto the surface. For complex lines this can be very time consuming.

Similarly for InterpCrvOnSrf, if I try to alter the initial line, it usually ends up not being on the surface after being edited.

I wondered if anyone knows of a way to almost treat the surface of an object as a C-Plane so that any points or lines I create/move Rhino automatically stay on on a surface.

Otherwise any hints to make this easier would be much appreciated!

I found this link for Rhino 6 which looks like exactly what I want, but it doesn’t seem to work on Rhino 7:

Also if it helps - what I’m trying to do is design a shoe upper pattern on a last. I can import a sketch with my lines, trace the lines and project onto the last, but from there if I want to modify any of the lines it takes a lot of time and effort. If there is a setting to tell Rhino to constrain any edits made to lines to the surface it would be incredible!

Many thanks

maybe you can try using a surface instead of a curve, and get their intersection curve (which for sure lies on the second srf as long as they intersect) ?

Very helpful suggestion, thank you.

What I’ve done is:

  • In a side viewport, created the line that will form my design
  • Turn on History
  • Use Ribbon to make a surface from this line which is wide enough to intersect with the surface I want to design on
  • Due to history, when I change the original line, the surface (created by Ribbon) changes with it
  • When it looks good, I can use Intersect to generate the line I’m interested in
  • It’s not perfect but is much, much better than what I was trying to do before!

Thanks again

Project a curve with history on and then adjusting the input curve may also be an option.

Thank you. Seems similar to the use of ribbon above, though have I missed something?

CurveOnSurface V6 now works on V7. CurveOnSurface | Food4Rhino

CurveOnSurfacePtOn which only works with curves created by CurveOnSurface

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I had to admit I hadn’t tried - one of the comments on the download page asked when it was to be upgraded for R7 so assumed (always a dangerous thing) that it didn’t work.

Just downloaded and tried and it’s exactly what I was after.

Thank you, marked this comment as the solution.