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About MCAD integration


People keep asking about this... at the moment DXF is the only useful
way to export a board to a 3D mcad (then you estrude it 1,6mm, usually,
but you don't have component boundaries and stuff).

IDF3 *is* plausible to make, but does actually someone want it? In
SolidWorks AFAIK you have to buy a special purpose module to import it
(strange thing: while IDF3 is designed to go both ways, it seems that
only the ECAD->MCAD route is used). IDF4 exists but AFAIK nobody uses it
(like IPC356B!)

General consensus is that STEP is the desiderable format (too bad IGES
went out of popularity... it was freely documented and it's the
precursor of STEP). However it's huge, no, bigger than huge, it's
ISO-committee-designed. I have found this old message around, for more


The only STEP toolkit available for open source is the one in
OpenCASCADE. The zipped tar is more than 110MB (it's a whole geometry
engine for cad...), I feel it's a little big as a dependency :D It seems
that freecad uses it.

I tried to look inside a STEP file. It's quite readable actually, *if*
you have the schema to cross reference with. Too bad you have to pay,
a lot, for that. And extremely verbose; it's actually a dump of a graph
database (a good idea for a cad format IMHO). Too bad that for
describing a parallelepiped geometry the ST-Developer kit (commercial)
uses no less than 215 object (*two hundred fifteen* objects). And that
using the AP-203 (the entry level schema). I reordered and indented the
thing, it's quite obvious what is going on. I'll try to add a hole in
that box to see what infernal representation it spawns:D

However it seems feasible to reverse engineer the format for generating
at least something like the IDF3 representation: board shape and prisms
for component shapes. Not exactly like having the 'perfect' model, but
beats extruding the board profile from the dxf at least.

Any ideas on this? IIRC there were some people interested in this kind
of thing.

Lorenzo Marcantonio
Logos Srl

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