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Date:	Wed, 23 Dec 2015 11:51:58 +0000
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Subject:	Re: [geda-user] Proposing a New Hierarchical Data Structure?
From:	"Peter Clifton (petercjclifton AT googlemail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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The rest of the world (aside from the 3D printing folks for some
reason), use STEP for 3D model interchange, and whilst STEP is not a
"simple" data-model, you only have to write the code once... ;) (And I
already did, mostly.).


FreeCAD STEP export is (I think still), based on OpenCascade.
OpenCascade is stuck at LGPL2, so is starting to look (again) like a
dead-end, this time because of license churn forced upon us (mostly by
virtue of linking against FSF stuff "somewhere" in the stack). Unless
that is rectified, I have limited inclination to work on fixing /
improving OpenCascade. Personally - I'm fine with (perhaps even
prefer), the V2 GPL / LGPL, but I also recognise it is not
future-proof in the context of a larger project that might need to
link against other libraries where stewards have set a minimum of the
V3 license version.

If anyone was to use FreeCAD for STEP export, you would likely want to
do some work on OpenCascade, to improve its STEP emission (primitives
it uses, whilst valid - can be less than optimal) and to add (if not
already present), code to set more entity names etc.. (which helps
when mating up different revisions of boards in a CAD package which
can import, and use the entity names when constructing mechanical
mates.


On 23 December 2015 at 07:15, Kai-Martin Knaak
<knaak AT iqo DOT uni-hannover DOT de> wrote:
> Peter Clifton wrote:
>
>> To this day, I don't (for example), know how to recreate (from the
>> standard) the minimum graph of entity information contained in the
>> StepCODE example "minimum AP203 file".. This example is supposed to ONLY
>> contain the minimum set of data entities required to create a valid
>> product.
>
> This is my clue to reiterate my proposal to not touch STEP at all but
> communicate the 3D geometry to freecad. Freecad supports python commands
> as a 3D geometry description. This essentially a scripted geometry
> definition.
>
> The freecad developers have managed to successfully export STEP data of
> their models since a number of years. The application is able to run GUI-
> less and can do whatever you please via python scripting. If pcb can
> export to freecad, the road to valid STEP data is free (pun intended :-)
>
> ---<)kaimartin(>---
> --
> Kai-Martin Knaak                                  tel: +49-511-762-2895
> Universität Hannover, Inst. für Quantenoptik      fax: +49-511-762-2211
> Welfengarten 1, 30167 Hannover           http://www.iqo.uni-hannover.de
> GPG key:    http://pgp.mit.edu:11371/pks/lookup?search=Knaak+kmk&op=get
>
>
>

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