Converting Rhino LW (lines, polylines and arcs) into AutoCAD 2020-22 LW


If I am trying to import Rhino linework (lines, polylines and arcs), into AutoCAD 2020-22 linework (lines/arcs/polylines), they turn into ‘splines’ the moment I try to join them to form ‘closed polylines’.
It seems like an easy conversion, however, can’t find any answers. Is there a way to achieve this without changing any geometry.

Thanks in advance for this.

Curve Test.3dm (270.7 KB)
Curve Test.dxf (11.9 KB)

Hi Cyrus - I am not sure I follow - these curves should form , and do here, polycurves, in Rhino when joined. I need more about what is not right, here…


Hi Pascal,
Thanks for looking into this. There is no issue in Rhino, however, when I export these to AutoCAD these turn into splines.

I see - here, your dxf is separate lines and arcs as Rhino sees it. The dxf export schemes offer various options for how curves and surfaces are exported -


Hi Pascal
I think I tried every combination in those export settings to avoid splines. But somehow it ends up in Splines. What settings would you use though?

Hi Cyrus - Rhino sees ‘proper’ lines and arcs in the dxf you posted -

does that same file read into the target application as splines?


It sees it as arc. Like below:

However, the moment I try to create a close boundary they become splines.

Hi Cyrus - I see - I am not going to be of much use then , I guess - that behavior seems to be in that application and not dependent on Rhino…?


Pascal, it is not a Rhino issue for sure. However, thank you so much.
Just now I may have figured it out. This might be a stroke of luck. But it seems that it has to do with the Curve Normals to be “+Z”. (image below).

So now when I try joining them in AutoCAD it forms polylines, and not splines.
Thanks again Pascal!