Lately I have seen more people asking about board shapes which are not easily described by a small number of line segments and circular arcs, and Jean-Pierre mentioned STEP Import for a board shape. I think the best mechanism for complex board shapes will remain the DXF format since STEP (or even IGES) can contain so much information and it is impossible to guess the design intent; however many MCADs will create a DXF outline which will make use of circular arcs, line segments, ellipses, Rational Polynomial Curves, NURBS, and occasionally even Bezier curves. I would suggest that rather than think of attempting to import a board outline + cutouts + drill holes from STEP/IGES we should add to the features of the DXF importer to support at least ellipses and rational polynomial curves (which is what SolidWorks uses even for circular arcs) and possibly 2D NURBS if anyone knows an MCAD that exports it in DXF.
The question of natively supporting RPCs and NURBS within KiCad is something to consider in order to preserve such information which is ultimately imported from MCADs, even if we never support native tools to edit these entities. Who knows, maybe in the future someone would like to use such features to describe a track shape rather than generating an inefficient line segment approximation (oh, the DRC nightmare). In the (far) future there is also the PRC file specification which I think would be very good to support. At the very least we can create previews of STEP and IGES files for quick display and this would also allow the eventual creation and decoding of 3D PDFs. The specification allows arbitrary metadata which in theory we can exploit to ensure that KiCad knows what parts are outlines, cutouts, drill holes (N/PTH) and we can have more unambiguous exchange of data; of course every MCAD would need an exporter which could provide the information in just the way KiCad wants, so this would not only be a huge project but we can safely guarantee that DXF will remain the best general solution. - Cirilo
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