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Date:	Sun, 27 Sep 2015 09:56:57 +0200
From:	"Gabriel Paubert (paubert AT iram DOT es) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
To:	"Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Subject:	Re: [geda-user] Apollon the technical thread
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On Sat, Sep 26, 2015 at 11:49:15PM +0200, Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
> > > For display on the screen I would agree but for the layout data:
> > > -- There will gerber files, does it work for gerber files?
> > > -- Does it work for design rule check?
> > > -- Other electrical tests especially if made in copper?
> > > 
> > > I would say it would be stupid to choose a font solution that does not
> > > work with design rule check or electric calculations.
> > 
> > For the record: current implementation of text in pcb hardly provide these 
> > checks, in the first place. DRC just looks at the line width and 
> > connection check simply ignores text in copper.
> > 
> > 
> > > Even though the
> > > functionality might be missing right now it might be implemented in the
> > > future.
> 
> If the font should look the same on screen as in the gerbers geometry must be such that it work for gerber files. For DRC to figure out the line width there must be a reasonable method to determine line width. It would be useful to check if text short circuit any connections. If the font library output some kind of bitmadded graphics it might be rather hard to implement check of line width.


I wouldn't even remotely consider bitmaps for the internal
representation: it is much easier to go from vector based
primitives to bitmaps than the oher way around. 

Besides that the most important export formats for manufacturing
are vector based. For example Gerber primitives are straight line 
segments and circular arcs, which can either be stroked with (not 
even arbitrary apertures), or filled when forming a closed contour. 
While it is possible to be more flexible than Gerber, the primitives 
should include what Gerber can do (this includes contours with arc 
elements).

I don't know what the resolution of the photoplotters used by my 
PCB manufacturers is but it seems that the standard resolution is 
in the ballpark of 1µm these days. And even slightly better, to the
point that we migt have to produce Gerbers with 100nm resolution:

https://www.ucamco.com/files/product_series/file/5/Flyer_Calibr8tor_Nano2_20131126.pdf?9b4b697aa2819c1574a713e2194d75e2

    Gabriel

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