DWG export as splines not working


(Willem Derks) #1

Hi,

Is there anything that changed with the DWG/DXF exporter (recently)
I have a client that gets arcs imported when I explicitly export arcs as splines.
The export settings I use have always been working up until a couple of day ago when I exported for that client again.
The major problem here is that his laser cutter will “stall” on arc’s with a huge radius, so we need to make absolutely sure that no arcs with a radius larger than X are present in the exported file.

dwgARCasSpline.zip

It seems the exporter is failing to properly convert arcs to splines or at least we cannot see it is doing that.

We are working/hacking around it right now as time is running out, but some insight in the exporter and a confirmation on it’s proper working would be good to have for future projects.

Thanks
-Willem


(John Brock) #2

I can not repeat this.
I drew an arc, a degree 3 curve, and a rounded rectangle.
I set the DWG export options to make Splines.
I opened the resulting DWG files in AutoCAD 2013 and all three curves are Splines.V5_DWG_SplineTest.png


(Pascal Golay) #3

JB, try Willem’s file - I get almost all arcs if I reopen the dwg exported with his scheme from the original 3dm.

-Pascal


(John Brock) #4

Using my scheme I’m getting Splines. I just tired his scheme and I’m still getting Splines in AutoCAD.


#5

I get 192 “elliptical arcs” out of 196 curves imported here, SimplifyCrv turns them into arcs…
–Mitch


(Willem Derks) #6

John,
could that be the cause; simplyfy running after the conversion to splines, converting the splines back to arcs again?

-Willem


(Willem Derks) #7

Hi John,

There is apparently another issue with simplify in this thread i try to link to below
(If anyone can tell me how to properly link to another topic and post please let me know)
-hmmm seems the link worked better than expected

-Willem


#8

They’re not getting converted to splines, though - before the simplify, they’re “elliptical arcs” (partial ellipses)…
–Mitch


(Willem Derks) #9

Hi John,

Revisiting this issue. Please have a look at this packageALL_splines.zip(39.6 KB)

The curves in the Rhino File will export to DWG as arcs regardless of export settings!

The issue I have, is that my client’s laser cutter stalls on arcs with a radius that is too large. He is trying to resolve that issue on his side, but in the mean time we need a reliable way to get DWG files out of Rhino that does not contain arcs.

Thanks
-Willem


(John Brock) #10

When I open the Rhino 3DM file, the curves are indeed arcs.
Using your export ini file, then opening the fresulting DWG file in AutoCAD 2013, using the List command they show up as Splines:
SPLINE Layer: "SNIJDEN"
Space: Model space
Handle = 6b
Length: 747.7476
Order: 3
Properties: Planar, Rational, Non-Periodic
Parametric Range: Start 0.0000
End 747.7476
Number of control points: 3
Control Points: X = 2744.0331, Y = 3485.7222, Z = 0.0000
Weight 1.0000

                               X = 2370.5558, Y = 3467.1866, Z = 0.0000
                               Weight   0.9997

                               X = 1998.2911, Y = 3431.8607, Z = 0.0000
                               Weight   1.0000

I used the Rebuild command in Rhino and made them degree three curves with 4 control points (no longer arcs in Rhino), and exported those as DWG.
These List as:
SPLINE Layer: "SNIJDEN"
Space: Model space
Handle = 6b
Length: 747.7476
Order: 4
Properties: Planar, Non-Rational, Non-Periodic
Parametric Range: Start 0.0000
End 1.0000
Number of control points: 4
Control Points: X = 2744.0331, Y = 3485.7222, Z = 0.0000
X = 2495.0902, Y = 3473.3674, Z = 0.0000
X = 2246.4256, Y = 3455.4075, Z = 0.0000
X = 1998.2911, Y = 3431.8607, Z = 0.0000

As far as I can tell, Rhino is doing with it says it is. See if these rebuilt, single span, degree 3 curves perform better for your customer. My guess is the degree 2, 3-point “splines” are being interpreted as arcs.
ARCS_01_Deg3.dwg(20.0 KB)


(Willem Derks) #11

Hi John,
Thanks for the testing and the reply.

I opened my exported DWG back in Rhino, and there, those curves are reported to be arcs.
My client uses a different software that apparently handles the curves different from AutoCad and
translates them as arcs as well.

We try and dig some more to find a solution.
Thanks
-Willem