Simplify a curve preserving the curve symmetry


Dear community,

I have two questions dealing with 3D curves:

  1. I have an input curve with mirror symmetry with respect to a plane.Is there a way to simplify such a curve in 2D or 3D while preserving the curve’s mirror symmetry? I experimented with FitCurve and RebuildCurve, but these break the symmetry of the input curve…
  2. Is there a way to offset a closed, non-selfintersecting curve (preferably on a surface) in a way that the offset curve is also still closed and non-selfintersecting?. I was also hoping to achieve this by smoothing the input curve using the procedure in the previous point, with the problems I mentioned there…

Any suggestions would be appreciated.

Kind regards,


(David Cockey) #2

OffsetCrvOnSrf offsets a curve on the surface.

There is a fundamental geometric limitation though (not a Rhino limitation). The offset curve will form a kink and self-intersect if the offset distance is greater than the local radius of the base curve tangent to the surface and the offset is “inward”,

(Pascal Golay) #3

Hi Filip - use History with your Symmetry command for this. You’d simplify the original, not the mirrored copy.