Offset - determining offset location

I am trying to offset multiple curves in a grasshopper script. On occasion, I am receiving errors as above.

I can see that the outside offset works (red line), but the inside offset gives strange results on small details (green line). Testing the offset command within Rhino it seems to be a product of where the offset is taken from, but I can’t figure out the rule so that I can control this en masse in GH.

Hi -

You didn’t supply any file so I drew a polyline that appears to be pretty much like what you have in the image and used Offset in Rhino. I couldn’t get “where the offset is taken from” to make any difference here. With the information that is provided, I can only suggest to look into how that curve was constructed.


Thanks for your quick reply. Please see the attached file.

An internal offset from around the cyan point results in a triangle. The same offset from around the pink point it results what I would expect.

Also, changing the offset from 500mm to 501mm (just beyond the size of the detail) seems to solve the issue. But this is not a sufficient work around for my workflow.

offset test.3dm (31.4 KB)

just for GH: it looks like flipping the curve sort of solves the issue

Thanks Inno, looks like it is a good work around, but I’m not sure if it will quite solve the issue always. I’m still struggling to understand the root of the problem

Hi Justin -

Thanks for that file. I see that a few different cases where offset failed were fixed in Rhino 8 in the last few days. I tested (8.0.21295.305, 2021-10-22) with your file and that works correctly now.


great news, I look forward to it