Re: GSoC 2017 - Implement boolean operations on polygons

[Richard Crozier]

On 04/03/17 23:13, Juan Pablo Carbajal wrote:
> On Sat, Mar 4, 2017 at 6:14 PM, PhilipNienhuis <address@hidden> wrote:
> > abhishek singla wrote
> > > My name is Abhishek Singla. I am interested in working on the idea
> > > " Implement boolean operations on polygons".
> > > I have knowledge of C++ and have also used octave as part of my curriculum
> > > in subject Numerical Mathematics.
> > > I want to contribute to the idea as I think I possess the required skill
> > > set for this. But I do not know how to start working on it.
> > > I would highly appreciate if you could give me a brief procedure on how to
> > > get started on this idea.
> >
> > The description of this project needs to be adapted.
> > Last year most of this has already been implemented (by Amr Keleg who did
> > good work), but not yet integrated into the geometry or mapping package. To
> > get that far several issues have to be solved:
> >
> > - Weeding out the Boost library dependency (comprising just include files).
> > In the eyes of the involved package maintainers (who weren't involved as
> > mentors) this is a ridiculously large library compared to the two or three
> > functions that use it.
> >
> > - Polishing the existing code (a.o., error catching, input validation, etc).
> >
> > - Making the code independent of just one Boost version (currently 1.60).
> >
> > More info in the patch tracker, see patch #9000.
> >
> > I doubt if the above three together would qualify for a GSOC project.
> >
> > Philip
> >
> >
> >
> > --
> > View this message in context: 
> > http://octave.1599824.n4.nabble.com/GSoC-2017-Implement-boolean-operations-on-polygons-tp4682161p4682164.html
> > Sent from the Octave - Maintainers mailing list archive at Nabble.com.
> Hi,
>
> Exactly as Phillip said, the interaciont with boost has to be more clever.
>
> If you want to move in another direction, binding to CGAL[1] would be
> another option. This will also allows us to have many other cool
> functions for geometry.
> Now this approach might be worth a new package maybe called CGAL.
> Just to have it in mind. Choose wisely (hint: the boost cleaning up is
> simpler).
>
> [1]: http://doc.cgal.org/latest/Boolean_set_operations_2/index.html

I'd be wary of CGAL, I tried to create a wrapper, see here:

https://github.com/crobarcro/mpolycsg

but I found their algorithms to have limitations that made them of no 
use to me, see:

http://cgal-discuss.949826.n4.nabble.com/CGAL-difference-on-Nef-polyhedron-produces-shape-with-duplicate-vertices-td4659760.html#a4659782

That was a couple of years ago now, so maybe they fixed the issues, but 
their code is very complex and difficult to use, and far inferior to, 
say, OpenCASCADE which would be far more useful.

There is a python interface to OpenCASCADE based on SWIG (see 
http://www.pythonocc.org/), there is also FreeCAD, which is a GUI 
program, but also a standalone python interface to OpenCASCADE geometry 
modelling routines and probably simpler to copy if anyone was interested.

Richard




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