Bug: Export DWG/DXF converts degree-1 to degree-2 NURBS curves

8.7.24138.15431, 2024-05-17

With an AutoCAD Export Scheme with Curves set to Splines and Simplify lines & arcs disabled, degree-1 NURBS curves are exported to degree-2. This also affects the output when Export surfaces as is set to Curves. When Export surfaces as is set to Solids, the degree-1 edges appear to be retained.

This can be tested by exporting Export_me_to_DWG_or_DXF.3dm (49.4 KB) using the Default scheme.

Possible workaround
Enable Simplify lines & arcs and set Simplify tolerance to 0. This converts single spans degree-1 to lines and multi-span degree-1 to polylines.

Hi Steven - thanks, I’ll investigate.

RH-82317 Export dwg degree change

On the other hand it looks maybe Acad considers splines to be degree > 1, since they seem only to refere to these as ‘smooth’.