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Subject: 3D data and support [WAS: Re: [geda-user] FOSDEM]
From: Peter Clifton <pcjc2 AT cam DOT ac DOT uk>
To: geda-user AT delorie DOT com
Date: Sun, 15 Feb 2015 02:16:26 +0000
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On Sat, 2015-02-14 at 18:53 -0500, Evan Foss wrote:
> I would want full 3D data since you can always reject data but adding
> it in later is hard. just look at how long this thread has gotten.
> 
> A simple hight does not help me when I have parts like this
> http://www.mouser.com/ProductDetail/Omron/2SMPP-02/?qs=3P%252bcriiv584EfFf%252bLos22A%3D%3D&kpid=492727993&gclid=CjwKEAiAgfymBRCEhpTR8NXpx1USJAAV0dQylSBgkXS3S-jSknPvwRo1CnbsiYWkc30-ns0GFfAO2xoC7Nbw_wcB
> 
> (pressure sensor with vertical port for a hose)

I'm working on 3D support, albeit slowly, and there are a lot of
use-cases. I'm enumerating some below to further my clever "your wrong"
argument to KMK regarding 3D support inside PCB.



Break-down of 3D features one might care about:


Modelling...

I don't actually envisage building any 3D modelling tools into PCB
(mechanical CAD, and component vendor models are better sources there),
but I believe we do need to capture enough information to correctly
model the board construction and stack-up.

2.5D regions (for keep-outs) might be feasible to model within PCB
though, if use-cases below demand them.



Board only 3D export....

I already use STEP export of my general shape (incl. fixing holes) of my
boards to feed into caseworks and overall product design.



Shape + Z 2.5D keep-outs...

Well - modelling any keep-outs would be a good start in PCB, but in the
absence of full component models (or to augment with further clearance
for whatever reason), modelling keep-outs with height enables more
information to be transferred on to mechanical designers when exporting
board information for caseworks design etc.


Adding components...

This can be useful for checking 3D clearances (with component models
populated). I currently do this in a commercial 3D cad package, using
the STEP export of my plain board model (complete with vias). I then
manually construct an assembly with models of components either
hand-created, or imported from vendor provided STEP models.

This would be lots easier if I could pre-associate the correct 3D models
with PCB footprints, and directly export an assembly containing the
board AND the models.

(Actually this is not so hard to achieve, given a little extra data with
each footprint).



3D Components within PCB...

One might like have 3D views with components inside PCB, which means
having a source of that 3D component model, and ways to import that into
PCB and align it with the relevant footprint.

This would enable less formalised 3D clearance checks, done using
eyeballs whilst designing the PCB. (Real numerical 3D clearance checks
would probably require importing a 3D cad kernel, which could bring
license issues).

I primarily care about components modelled in mechanical CAD formats
(not graphics rendering formats like VRML), so this is hard. STEP is the
interchange format we need to handle, yet it is not feasible to import
directly (it is too complex).

To do this I think we need to fork an external process to convert to a
simpler (faceted) model. I say external process due to potential
licensing issues of OpenCascade (Now LGPL2, but _not_ LGPL2+). This is
however, the most realistic for library which could handle processing
the conversion.



More complex export, including traces in 3D....

Modelling board construction and stack-up to enable a more realistic
view of the board construction in 3D, and give data to export to other
CAD / CAE work-flows.

People doing high layer-count boards care about visualising this
(including at design time), and those doing RF, controlled impedance, or
high-reliability may require exporting 3D data of the board construction
and traces to conduct simulations and analysis.

Imagine:

PCB->Full 3D trace geometry export->FEA Field solverThere are also
reasons o
                                  ->PCB Warpage analysis / DRC
                                  -> ....


Parts modelling....

I'm currently investigating AP210, and expect to be running some trial
conversions of KiCAD library parts and 3D models when I have some time,
and a few further details from the guys who have been developing this
standard.

This format should allow us to model all information we could possibly
desire about a part, in a way compatible with ECAD tools, and
(crucially) MCAD as well.

Having parts models in AP210 (and suitable code to handle them), I
should be able to directly export a full 3D board + parts model for
consumption by downstream tools. It will also be possible to embed
faceted geometry representations that are simple enough for us to parse
and render without heavy-weight CAD libraries. (Both faceted and BREP
models can co-exist in STEP files).


Kind regards,

Peter

-- 
Peter Clifton <peter DOT clifton AT clifton-electronics DOT co DOT uk>

Clifton Electronics