DXF Export & polyline widths / What brush does AutoCAD use to render polylines?

[simon]

We've written a dxf export package for our electrical CAD product, however it seems that polylines render badly. To be geometrically accurate the polylines are widened by the linewidth, which gives accurate results in our package

When the dxf is imported into autocad we see this ...

and another DXF viewer (can't recall which) renders it slightly differently. 

Why has the autocad render got an angled end on the left hand vertical side? (it's much more obvious with thicker lines).

One suggestion is we've drawn the polyline in our app with a circular brush. 

Does our dxf file not include sufficient information? In autocad, _PEDIT and set a line width of 0 gives an accurate polyline (albeit with minimal line thickness).

I have a dxf you can look at too 🙂

Thanks for looking

[wispoxy]

Some suggestions for you

A similar Issue that ended with a conclusion:

http://www.cadeverything.com/help/showthread.php/2151-Setting-polyline-width-in-a-DXF-file

codes:

http://www.autodesk.com/techpubs/autocad/acad2000/dxf/polyline_dxf_06.htm

You also need to set code 43 to 1 for a constant width LWPOLYLINE; I don't know if there's a similar code for a POLYLINE

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AutoCAD DXF (Drawing Interchange Format, or Drawing Exchange Format) is a CAD data file format developed by Autodesk[2] for enabling data interoperability between AutoCAD and other programs.

DXF was originally introduced in December 1982 as part of AutoCAD 1.0, and was intended to provide an exact representation of the data in the AutoCAD native file format, DWG (Drawing), for which Autodesk for many years did not publish specifications. Because of this, correct imports of DXF files have been difficult. Autodesk now publishes the DXF specifications as a PDF[1] on its website.

Versions of AutoCAD from Release 10 (October 1988) and up support both ASCII and binary forms of DXF. Earlier versions support only ASCII.

As AutoCAD has become more powerful, supporting more complex object types, DXF has become less useful. Certain object types, including ACIS solids and regions, are not documented. Other object types, including AutoCAD 2006's dynamic blocks, and all of the objects specific to the vertical market versions of AutoCAD, are partially documented, but not well enough to allow other developers to support them. For these reasons many CAD applications use the DWG format which can be licensed from AutoDesk or non-natively from the Open Design Alliance.

DXF coordinates are always without dimensions so that the reader or user needs to know the drawing unit or has to extract it from the textual comments in the sheets.