As I said, the original file contains valid DXF information which is still valid in newer DXF formats.
Thus it's not surprising, that upgrading the DXF version does not change the results.
You asked for details about my investigations. It is as simple as open the DXF file in a text editor and use an appropriate DXF reference to understand the content. It helps when doing this regularly, but it's not rocket science.
I opened the file in Autodesk TrueView for reference. It shows kind of your expected result.
I say kind of
, because it is also not what I'd expect from my DXF reference studies.
What I recommend is:
- explode the polylines
- separate the doubled contours, best is to move on new layers
- optionally make polylines from separated contours again
- create the spline from separated contours
To detail my recommendation, I did some more investigations.
- The DXF contains 4 POLYLINE entities, 2 curves and the 2 straight connection lines.
- The curves are doubled because they contain two kinds of VERTEX entities.
- Each curve has well over 20 VERTEX entities representing points on the spline-fit POLYLINE (what TrueView shows)
- Each curve has about 160 VERTEX entities representing control points, defining the spline frame
So the truth is somewhere in-between, both halves do not show the intended curve.
Depending on the required tolerance the ~160 vertex contours are already good approximations.
For the exact splines use Snap on Endpoints
only and select the curve to follow.
This makes it easier, to follow the selected curve points (blue).
To create the spline use Tool->Curve->Spline through points
and follow the ~20 vertex contour.
Or with Tool->Curve->Spline
you have to set Degree
to 2 and follow the ~160 vertex contour.
investing less than half an hour into Search function can save hours or days of waiting for a solution