Exporting polyline with arc segments to DXF

Rhino
,
1

I’m hoping to export some polycurves with arc segments to DXF. The polycurves may be open or closed. I’d prefer to have the result preserve the arcs rather than tessellate them.

  • If my export scheme converts Rhino arcs to polylines, the resulting entity is an LWPOLYLINE, preserving the polyline flag (which indicates whether the polycurve is open/closed), but tessellating all arcs.
  • If my export scheme converts Rhino arcs to DXF “polylines w/ bulge arcs”, the resulting entity is a POLYLINE, and the polyline flag is lost—I can no longer determine (by checking the flag, at least) whether the polycurve is closed.

Is there any way to export a polycurve to DXF that both preserves the arcs and the polyline flag? Or am I better off just checking whether the endpoints of the polycurve coincide?

(FYI, using Rhino for Mac).
@tim

2

Hi David,
There are many settings, so it is important that we see what you are getting and understand why you are not getting what you want.

Here are some settings that might help:
First see this page in on the Help that details DWF Export settings.

Scroll to the explanation on “simple entities.”
Specifically:

  • Circles, arcs, ellipses, and lines export as AutoCAD circle, arc, ellipse, and line entities.
  • 2-D curves are simplified. This means if the curve is just one line, arc, or circle, it is exported as an AutoCAD line, arc, or circle. If there are arcs in the curve with discontinuous curvature at the ends, it is exported as a bulge arc in a polyline.

Here is our simple test file:
test DXF.3dm (29.6 KB)
We exported and modified 2007 Natural, we are not sure what is the best for you.

We set “Polylines” as “Polylines”, and Simplify Lines and Arc (as discussed above.)
We also checked “Use LW Polylines when possible” and “Simplify Lines and Arcs.”

image
image964×673 48.9 KB

image
image658×719 22.3 KB

When I opened the file in AutoCAD, I had a joined LWPolyline that could be exploded into Arc and Lines.

image
image1135×581 38.9 KB

DXF 01.dxf (158.6 KB)

If this does not solve your issue, please attach the following:

  • A small 3DM that will show us the issue.
  • The DXF that you export.
  • And a screen capture the the DXF version and settings that you use.
  • And describe what you are getting and what you want.

Sincerely,
Mary Ann Fugier

3

Your best option is to use the Convert command in Rhino to replace higher degree NURBS curves with chains of arcs.

4

just to connect to another dxf-export issue…

maybe also consider to use iges or another file format.
Don t expect to much from .dxf.
If you really want to dig in check the reference

5

I design in NURBS and need to export for CNC to Acad. DWG or DXF. I struggled quite a long time until I found out my settings that work for complex and closed shapes. Use Convert in Rhino. Set arches, simplification, zero for max and min length. Rhino export without Convert would export nurbes without bulges. Use a style where you set exports to polylines and polylines with bulges but what is important PROJECT TO CPLANE! This helpes a lot! Without it, shapes get mixed results. Even if they work from time to time, the number of vortices is much higher.

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