#463 keep dxf terminal
Re a recent discussion on the mailing list, i've done a little testing with the output of the dxf terminal (5.0pl6), and it looks quite OK to me in Autodesk Inventor 2015 and LibreCAD 2.1.3 (where dxf is the native format). In FEMM (v. 4.2), text is not imported of course, but everything else looks fine, too.
LibreCAD lands the axes in layer 0, together with the first subplot, and ticlabels in layer 2, together with subplot three. Also there is some dashing displayed, but not quite the way as intended. Looks like that's gnuplot's fault (see also "help dxf"), because Inventor and LibreCAD do the same. Same for the colouring.
Other that that, I'm very happy with the dxf terminal. Or really, I'm just very happy, because none of the above is really relevant, today. Getting accurately positioned points and connecting lines into your respective third-party software is the important feature, not directly getting a nice-looking sketch to print.
One useful addon might be if the coordinate system of the plot would not be lost in the dxf file. At the moment (as documented), all coordinates are relative to the position on the canvas (0,0 in lower left corner, canvas size as set). That made sense back in the times when people had actual plotters.
Now really awesome would be a terminal using the LibreDWG library, supporting 3d plots. :-)
Use of LibreDWG is not going to happen, since FSF refuses to license it usably (quite ironic for a project whose purpose for existence was to make the format available under a non-restrictive license). The project itself seems to have died because of this. The code repository for an older, possibly usable, version is currently empty.
However I see that there is a formal DXF spec from 2012 in the form of a downloadable PDF file from AutoCAD.
http://images.autodesk.com/adsk/files/autocad_2012_pdf_dxf-reference_enu.pdf
Some motivated person could probably update gnuplot's dxf support using this as a reference.
The wikipedia article https://en.wikipedia.org/wiki/.dwg points to a "re-"fork http://libdwg.sourceforge.net/en/index.html, no idea if that would be useable license-wise. At least it seems to have died only recently. UPDATE: And it is only for reading .dwg. Not useful here.
I skimmed through that spec file, does dxf today support 3D? That'd be interesting.
I tested a bit more, and rectangles/polygons come out broken in LibreCAD. They look OK in Inventor, though. I'll try to diagnose that and report back. (UPDATE: Was just the dashing that made it look strange.) Ellipses/circles seem to work.
Last edit: Karl Ratzsch 2017-05-23
Update: The dxf terminal is still included by default. The documentation includes a request
"someone please update this terminal to the 2012 DXF standard!"