AutoCAD exporting scheme

I need to convert my Rhino file into CAD file which is then opened in Draft Sight.
DS is reading Rhino arcs as polylines and being limited software has problems editing them (eg. trimming). It recognizes Rhino arcs as splines.
Has anyone any idea on how to configure the export scheme to get rid of this problem, so DS reads arc as arcs?

Perhaps these export settings will help… --Mitch

Nope. It doesn’t work.
Draft Sight still sees them as splines. I am sending my exported files to the other guy and he says that I have managed once to do it right but I don’t remember what I have done. It have been hundred of files during last couple of months.
Oh! In my first post I should have written SPLINES not POLYLINES, and I mean splines when I say DS can’t edit them. Sorry for the mistake.

Hi Piotr - do these curves show up in Rhino as arcs? (What command)


Are you sure the arcs you are exporting from Rhino really arcs? Select one and check properties for sure. If it’s not a true arc, it will export as a spline. You can try checking the last checkbox “Simplify lines and arcs” and see if that helps, or run SimplifyCrv on all your entities inside Rhino before exporting. That will try and re-convert entities which are near true arcs/circles back into true arcs and circles.


NURBS arc - that’s what detail panel shows, and it returns the radius so I assume they are arcs.

I did this step too (simplifying) whit no success on the other side.

Hi Piottr - try SimplifyCrv on these - does that do anything? (Do they become plain arcs?)


No, it should just say “Arc” --Mitch

Strange. Half of the curves shows arc, Rest of them shows nurbs arc.
I have managed to solve the problem by ticking the ‘simplify arcs’ at the export panel. It did the trick.
Thanks for your help.

The export dialog has a looser simplify tolerance than SimplifyCrv has by default - 0.05 units in the dialog versus whatever your file tolerances are for SimplifyCrv - so maybe the dialog was successful. You can change the default in both.


What then is the difference between NURBS arc and simple arc?

Hi Piotr - a simple arc can be defined simply - by say a plane, and a radius and and angle, even though it will show control points and so on if asked - whereas a NURBS arc has control points, knots etc in its definition.


OK, thanks.