We need to talk about Offset

Dear Rhino/Grasshopper developers thanks for Rhino 6, many useful improvements, render, Rhinocommon functions … but there is an old subject Polyline Offset see this thread :

Are there some news about Polyline offset ?
I know Clipper is a good solution for Grasshopper and Rhino.
Update : @pascal it is not a Grasshopper question more a Rhino core function. There is a reliability problem with offset Polyline. It doesn’t work on some the cells which are simple polygon (see the picture).
The same as in Grasshopper, I used Rhino 6 and offset multiple

And Clipper solution


offset fail.gh (6.9 KB)



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Thanks for bringing this up again here. It’s been bugging me quite regularly as well.


Any response from the mcneel team? Can Clipper be incorporated into Rhino?


Still a bug. Apparently, in closed curves, it randomly chooses the inside.
I have ran into this in two separate projects.

Clipper shout definitly incorporated to GH and rhino…


Read this old but good thingy (the general case is PolyCurve offset):

anoffsetalgorithm.pdf (723.4 KB)

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Dear @laurent_delrieu,

I am bringing this old thread.

Is there a good way to offset curves that contains line and arc segments?
The issue is that clipper offsets only polylines and arcs are represented as many points.
The CNC I am using does not like many points, and I would like to have arcs and lines as a tool-path.

Is there any way to offset this polycurve with a good line-arc curve?

The paper you reference, is there a code too? :slight_smile:


Any answer to that ? Same issue here…Trying to offset a bunch of open polycurves, @PeterFotiadis anything more that can help ? Thanks in advance


Well … since all my stuff is strictly internal (CNC routing and the likes) the only thing that I can do is to provide some indicative help in case that you want to try to write a C# that does that (Liu’s paper attached above should be your quide).

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You might have a better answer in the official Clipper forum:

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Ok, I am trying to make offsets in the curves that overlap in the border of the piece, on the undercuts. Any clue on this would be very nice. You already helped me in another post, but it was for a different situation of offsets, many thanks. No problem with C#, I am far for been an expert, but I wil try.


I will check that too, thanks !!