Hi Tim

When designing an entity "Interpolate Spline" and export for DXF-R12, lack a subroutine in:
POLYLINE VERTEX 42, see the internal structure of the DXF.
ENTITIES
0
POLYLINE
8
name of layer
66
1
10 #.#
20 #.#
30 70
1
0
VERTEX
8
name of layer
10 #.#
20 #.#
30 #.#
42 #.###

The bulge is the tangent of 1/4 the included angle for an arc segment, made negative
if the arc goes clockwise from the start point to the endpoint;
a bulge of 0 indicates a straight segment, and a bulge of 1 is a semicircle.

For a subroutine equation is: bulge= tan(sweepangle/4)
See in http://www.afralisp.net/lisp/Bulges1.htm

Regards,
Armando

Hi Tim

Other versions of DXF are OK.
The CamBam open any version DXF.
In DXF-R12 the ViaCAD converts "Interpolate Spline" in polyline, lack "bulge".

See http://www.relief.hu/h_dxf12.html

Cheers
Armando