[Cad] Which CAD Kernel Should the FOSS and OSHW Communities Focus On?

[Jeremy Wright]

> I am eager to convince people to write a cadquery interface around the
pythonized version of verbnurbs

@Bryan - You could start a discussion about this on the CadQuery Google
Group <https://groups.google.com/forum/#!forum/cadquery>.
Dave (the creator of CadQuery) likes B-Rep pretty well and would like to
see CadQuery move to PythonOCC, but we could at least talk about it. I'd be
interested in creating an experimental fork of CadQuery if this group can
come to a consensus on what the best path forward is.

@Daniel
> This is one of the big questions I hope to be able to answer through this
reading group.

That would be great if this group could do that.

> CGAL's CSG code works on polygon meshes (more specifically Nef polyhedra),
which I understand as a B-rep.  Is there some F-Rep code in there also?

In the first Hangout, it was mentioned that CSG encompasses F-Rep, so I was
assuming that CGAL was (at least mostly) F-Rep. I'm pretty ignorant when it
comes to CGAL though, and am happy to be corrected.

> If the goal is software that can fill the role of Solidworks, CSG operations
on polygon meshes isn't enough, though it's probably a necessary part.

I'm not sure about other members of the group, but my personal interest is
two part. Feel free to skip the links in #1 if you're only interested in a
Solidworks alternative.

1. Have a solid open source kernel to build scripted CAD (CadQuery) on top
of. The goal would be to (among other things) help continue the work that's
being done by Mach 30 through MTK
<https://opendesignengine.net/projects/mtk/wiki> and projects like the Yavin
thruster <https://opendesignengine.net/projects/yavin-thruster/wiki>. This
video <https://www.youtube.com/watch?v=oQJY-_c7Fg8> from the Open Hardware
Summit gives a broad overview of what I'm talking about.

2. The second is to have the FOSS Solidworks alternative that you've
mentioned.

Although 1 and 2 could be part of the same interface, I don't believe that
you can force all FOSS users to do scripted CAD. You need a traditional
point-and-click CAD GUI as well for the majority of users. Even with one on
one training, I've had a hard time getting traditional CAD users to embrace
CadQuery. It's too much of a shift in thinking.

Jeremy

On Tue, Nov 10, 2015 at 7:52 AM, Daniel Bergey <bergey at alum.mit.edu> wrote:

> On 2015-11-09 at 22:59, Jeremy Wright <wrightjmf at gmail.com> wrote:
> > Is there a single methodology (F-Rep, B-Rep, NURBS) that the various
> > open source (and open hardware) communities could focus on developing,
> > or is it not a one-size-fits-all situation?
>
> This is one of the big questions I hope to be able to answer through
> this reading group.
>
> > From the research I've done, there are three main open source kernels
> with
> > very different methodologies.
> >
> > 1. OpenCASCADE (B-Rep)
> > 2. CGAL (F-Rep)
> > 3. OpenNURBS (NURBS)
>
> CGAL's CSG code works on polygon meshes (more specifically Nef
> polyhedra), which I understand as a B-rep.  Is there some F-Rep code in
> there also?
>
> I think of NURBs as also being a type of B-rep, a bit more expressive
> than only allowing triangles or polygons.
>
> If the goal is software that can fill the role of Solidworks, CSG
> operations on polygon meshes isn't enough, though it's probably a
> necessary part.
>
> cheers,
> bergey
>
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