Hi David,

that is interesting.

gives



As you can see, it converts the shape into triangles. If I take that manually apart the structure looks like this:

or 



That shows what happens, but not exactly why it happens. The imported file (apart from being three dimensional instead of two dimensional as the original), appears to use the first point {0,0,0} always as the starting point of the vertex, and then uses sequences of two consecutive vertices for the polygons.

I'll check whether some nice option fixes that.

M.

PS: Here's a related post:
http://forums.wolfram.com/mathgroup/archive/2011/Oct/msg00133.html

Thank you, Marco.

This is really part of a larger issue. I was trying to generate DXF files which could be read by another application -- Comsol Multiphysics -- into a 2D workplane. If I generate a simple polygon formed with a closed sequence of 2D lines, Comsol imports it fine. But if I export a file containing a Mathematica rectangle graphic, or a disk graphic, then the Comsol import attempt results in a error "The file contains no geometry objects of the requested type."

I don't have problems with this in general, so I got to wondering if Mathematica could even import what it itself had exported. -- It appears not.

I open the DXF file with Wordpad and it contains 3D faces. For Comsol, DXF is a 2D format. I don't know what Wolfram had in mind here, but it would be nice if 2D objects could be exported in a 2D format. Mathematica does not support any of the standard 3D exchange formats -- IGES, STEP, SAT, Parasolid.

Best,
David