[cad-linux] Re: the parametric project

Roland,

I really meat "brave". No sed needed. :-)
But why not start with existing software? OpenCascade might
come into mind. They have everything onboard, except=20
"application parametrics", aka constaint solving and they have
no database backend.=20

You could use OC for a start to integrate
a constraint solver and a database backend. This would give you a
better and much faster feedback. You would much sooner see
all the problems involved with constraint solving and databases.
This might prevent you from changing large amounts of self
developed code in order to later fit in constraints and databases.
Later on, you can still go on with a own modeller implementation,
based on the experiences made.

Bye,
Thomas

> --- Thomas Schmidt <thomas.schmidt@xxxxxxxxxx> wrote:
> > Roland,
> >
> > It seems you actually want to setup a new parametric modeller. The
> > brave =3D
> > ones rule the world.
> >
> :-) That really hits the nail on the head - I am glad you said the
>
> "brave ones" allthough I am sure you thought of 's/brave/crazy/' here.
>
> Anyway, such a modelling kernel would be some really interesting
> project, especially if it is backed up by a database as was discussed
> earlier.
>
> A CAD system that allows a user to specify dimensions by parameters is
> probably built upon some form of a constraint solver. I assume that the
> term "parametric" is used  because what the user actually notices and
> sees is, that an edge can have a length that can be changed at any time
> and the endpoints will automagically move. Parametric is a term that
> refers to the application of the solver not it's implementation.
>
> The first and most succesful system that implemented this feature was
> certainly Pro-E, they even named the company Parametric.
>
> Roland
>
> > I assume that you use the term "parametric"  not to refer to the
> > parametr=3D
> > ic functions of curves and surfaces,
> > but to a system, where objects interact by constraints. I have ever
> > wonde=3D
> > red why the term "parametric"
> > is used to describe a constaint solving system. Does anybody know?
> > Anyway, you might want to have a look here :
> > http://www.cs.washington.edu=3D
> > /research/constraints/
> > The constaint solver they describe, are mostly based on local
> > propagation=3D
> >  algorithms
> > and therefor not very well suited for (complex) 3D modelling, but you
> > get=3D
> >  a good introduction into the world of
> > constaints and their solving algorithms. There is even some code for
> > a fe=3D
> > w solver.
> > I also found many research papers about constaint solving algorithm
> > on ht=3D
> > tp://citeseer.nj.nec.com/cs.
> > Search for constaints or solver. Mostly academic papers, but
> > interesting =3D
> > anyway.
>
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