Yours,
CWBoon
> Date: Mon, 7 Dec 2009 18:24:30 +0100
> From: bruno.chareyre@xxxxxxxxxxx
> To: yade-dev@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Yade-dev] Triangulation, Tesselation, and the rest
>
> Concerning the license of CGAL, I'm still waiting an answer from
> developpers of CGAL, but I'm a bit pessimistic after reading the text
> below.
> What I don't understand is that even CGAL seems to have license issues,
> based on the bolded paragraph, since CGAL code and examples are linked
> to GPL libraries (lapack, geomview, Qt, boost, taucs, ...)
>
> Bruno
>
> Q Public License (QPL), Version 1.0
> <http://doc.trolltech.com/3.0/license.html>
>
> This is a non-copyleft free software license which is incompatible
> with the GNU GPL. It also causes major practical inconvenience,
> because modified sources can only be distributed as patches.
>
> We recommend that you avoid using the QPL for anything that you
> write, and use QPL-covered software packages only when absolutely
> necessary. However, this avoidance no longer applies to Qt itself,
> since Qt is now also released under the GNU GPL.
>
> *_ Since the QPL is incompatible with the GNU GPL, you cannot take a
> GPL-covered program and QPL-covered program and link them together,
> no matter how._*
>
> However, if you have written a program that uses QPL-covered library
> (called FOO), and you want to release your program under the GNU
> GPL, you can easily do that. You can resolve the conflict /for your
> program/ by adding a notice like this to it:
>
> As a special exception, you have permission to link this program
> with the FOO library and distribute executables, as long as you
> follow the requirements of the GNU GPL in regard to all of the
> software in the executable aside from FOO.
>
>
> You can do this, legally, if you are the copyright holder for the
> program. Add it in the source files, after the notice that says the
> program is covered by the GNU GPL.
>
>
> (from free software foundation website :
> http://www.fsf.org/licensing/licenses/index_html/view?searchterm=qpl)
>
>
>
>
>
> Bruno Chareyre a écrit :
> > Hello
> >
> > I'm thinking to how MicroMacroAnalyzer (MMA) could be modified in
> > order to be used in a more versatile way (partly because Vaçlav told
> > me he could use that - still true?).
> >
> > Currently, if you put MicroMacro engine in your simulation,
> > MMA::action() will (in short) :
> > - scan bodies and build a regular(*) triangulation of the spheres
each
> > N iterations;
> > - compute the average strain in each tetrahedron and assign it to
> > grains (so that the "strain" of one grain is a sum over adjacent
> > tetrahedra), based on the dispacements of particules on the interval
> > [n,n+N].
> > - save the state of the sample in a text file (with a specific
> > convention), so that strains can be recomputed later (out of yade)
> > with different interval sizes (like [n,n+2N], [n,n+3N], etc.)
> > - write local strains, porosity, fabric tensor, and other
> > micromechanical quantities in txt files too.
> >
> > Problems :
> > - This engine is doing always the same thing, you can't change
what it
> > does if you don't modify the code and recompile. It is a pitty, since
> > many geometrical functions available in lib/Triangulation could be
> > usefull as well (e.g. computing the dual Voronoi graph).
> > - If you want to access to quantities like porosity at the scale of
> > tetrahedra, you have no way to do that in yade, because you need to
> > access the CGAL structure using the concepts of cell_iterators,
> > edge_iterators,... which are not defined in yade.
> >
> > So, I'm wondering how to improve that, and I hesitate between 2
> > approaches :
> >
> > a) enrich the interface of TesselationWrapper or MicroMacro, so that
> > instead of just "MM::action()", many members could be accessed via
> > python, and different things can be computed on demand, and returned
> > in a standard format. e.g. for the porosity in a cell of the
> > triangulation, there could something like :
> >
> > pair<int [4], Real porosity> MMAnalyzer::porosityInNextCell (void);//
> > usage : while (porosity!=-1) porosity = porosityInNextCell().second;
> >
> >
> > b) expose and make full usage of all typedefs defined in def_types.h.
> > In that case, no need for interface any more, the full lists of
edges,
> > cells, or facets can be visited, but the user need to learn how to
use
> > CGAL and/or my triangulation classes before doing anything. Example :
> >
> > for (finite_cell_iterator
cell=MMA->triangulation->finite_cells_begin;
> > cell != MMA->triangulation->finite_cells_end; cell++)
> > {
> > porosity = MMA::Porosity(cell);
> > if (cell->vertex(2)->id == x) do something;//etc.
> > }
> >
> > I created a draft wiki page about this :
> > https://yade-dem.org/index.php/Triangulation
> >
> > Bruno
> >
> >
> > (*) Regular is for weighted points (center + radius), while the usual
> > Delaunay is for points. It can make a big difference (and Delaunay
can
> > give stupid result) when radii are not all the same.
> >
>
>
> --
>
> _______________
> Chareyre Bruno
> Maître de Conférences
>
> Grenoble INP
> Laboratoire 3SR - bureau E145
> BP 53 - 38041, Grenoble cedex 9 - France
> Tél : 33 4 56 52 86 21
> Fax : 33 4 76 82 70 43
> ________________
>
>
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