Re: gEDA-user: final modification

[Peter Clifton <pcjc2@xxxxxxxxx>]

On Thu, 2008-11-06 at 21:08 +0100, Bert Timmerman wrote:
> Hi Ethan and all,
> 
> On Thu, 2008-11-06 at 13:18 -0500, Ethan Swint wrote:
> > > Is this really related to gerber output?
> > > PCB program already has arbitrary shaped copper polygons.
> > > Your mentioned AND, OR, XOR operations will again generate copper
> > > polygons -- so it should be possible to handle negative stuff inside pcb
> > > program, without concerning gerbers.
> > 
> > Only a hypothesis - I'm not active on the PCB development side, so I'm 
> > not sure what obstacles there are to constructive geometry techniques. 
> > 
> 
> IMHO, I would place my bets on replacing the original polygon with a
> series [0, 1, 2, ..., N] of new polygons describing the results of the
> boolean operations mentioned above.

I might go for the idea of adding the ability to define polygon shapes
with holes in them though, however I did manage to make this work with
one polygon, and an "anti-polygon" (polygon with a flag specified). I
then used the same mechanism which clears holes in polygons around pads,
etc.. to clear a holes in the shape of the anti-polygon(s).

> Modifying the existing polygon would probably become too cumbersome if
> new vertices need be added and holes ("negative" copper) in polygons to
> be defined in ways currently not feasible within the current pcb file
> format.

Actually its pretty easy.

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)



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