Circle is not circle in DXF


in the attached, the circle is a circle in the object properties details.
Exported to DXF, Standard scheme, it is becomes a spline with several same points like:


What is wrong with this circle in Rhino?


CP_NoCircle.3dm (37.9 KB)

Dunno… Here exporting with “Default” scheme and re-importing, it is a circle… Are you sure your export scheme “Standard” hasn’t been modified? (Default can’t be modified, so it must be some other scheme?)


Hi Mitch,

Rhino itself seems to have some optimization when reading DXF.

I read the file with other software, and the circle fails to import.
When I inspect the DXF file, then I see the circle is not written as circle.

Strange is, when I create another circle at the same center in Rhino with the _Circle function, it comes out as circle in DXF.

But in Rhino, I can’t see a difference between the circles.
There must be a difference.
BTW, _Simplify doesn’t help.


OK, I don’t have any other software to test here… except Illustrator, and there, yes, it definitely is NOT a circle…


Charles, does either of the circles in the attached look correct to you?
TwoCircles.dxf (152.8 KB)


Hi Pascal,

yes, this comes in as 2 circles.
In the DXF, they are CIRCLE, so no wonder…

Again, what’s wrong with the circle in CP_NoCircle.3dm?


That is what I am trying to determine- no luck yet.


If they were drawn in Rhino as “Deformable” circles, then theyw on’t go out as circles.
Make sure in your named DWG/DXF export scheme, that the “Simplify objects” is selected with an appropriately loosened tolerance.

They were created as circles…
…and the object properties say they are circles.
Not elliptical arcs or other curves.

Do the object properties hide something?
If, how can I find out in Rhino what the object really is?


Hi Charles, all- What shows that it is a circle because it is a circular curve, but the more geeky ‘List’ command shows that it is not a circle object in Rhino but a NURBS curve that is an exact circle. SimplifyCrv should make a true circle object from this curve it seems to me, but it does not - as far as I can see that is a bug. I don’t know, but I’ll ask, if Export should at least offer the option to simplify these. I don’t know if there is any advantage to leavng these as NURBS curves at all, even within Rhino.


Hi Pascal,[quote=“pascal, post:10, topic:8534”]
SimplifyCrv should make a true circle object from this curve it seems to me, but it does not - as far as I can see that is a bug.

SimplyfyCrv does not often do what it should.

Try the attached.
Explode all.
SimplyfyCrv a few times.

The several results are different.
Same in V4, but different with other counts.

If this behaviour is considered as bug, then it should be repaired.


Hi Charles,
I always had the same problem when exporting for CNC. The CNC guys would complain about arcs and cirkles are either splines or polylines with lots of segments. The solution is simple: just set the AutoCAD version in the export options to Release 14 and make sure “Simplify lines & arcs” is checked.

hth, Tobias

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Hi Tobias,

I knows this issues very well.
DXF R14 doesn’t help, as I want to export splines as well.

All is fine with the standard scheme, except with those bogus circles.


Hi Charles- I am not seeing an attachment - can you send me that example directly?



Grr, forgotten.

CP_SimplyFail.3dm (199.7 KB)

Yeah- this is a combination of ‘true’ arcs (as reported by List) and arc-shaped NURBS curves. The developer agrees with me that these should simplify into true arcs, and that it is a bug that they do not…


(These are not visible to the public yet)

So there is hope…



This bug (RH-27259) is fixed in Rhino WIP 6.0.16306.09301 - released just now.

Hi Tobias. I can only say that I signed up for this page to thank you. This information has been very useful. I badly needed this solution after trying many permutations. Few people in Turkey know about Rhinoceros and I am trying to explain to everyone that this program is much better than Autocad. This problem was my biggest obstacle. Glad I got over this. Best regards.

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