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Date: Mon, 7 Apr 2014 15:19:59 +0200
From: Gabriel Paubert <paubert AT iram DOT es>
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Subject: Re: [geda-user] Cooper arcs in footprint
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On Mon, Apr 07, 2014 at 04:53:53PM +0400, Алексей Харьковский wrote:
> >
> > http://pcb.geda-project.org/pcb-cvs/pcb.html#Arc-syntax
> >
> > Arc [X Y Width Height Thickness Clearance StartAngle DeltaAngle SFlags]
> >
> > If Width != Height we have a stretched arc -- and we additional may
> > rotate that one by freerotatebuffer(). I am not sure about the exact
> > shape.
> >
> 
> In theory - YES. It is.
> However arc angle edit works right.
> Can not be said about editing the length and width of Arcs.
> I attach example of manually edited arcs.
> 
> The Pcb read only Width value and make part of circle.
> That's why I said that we need an example.
> 
> Eveт if pcb will be supported eliptic arc, I do not see problems with
> mathematic analyses of this simple figures :)
> 
> 
> The Gerber RX-274 format is supported ellipse figure.

Sorry, your example does not prove anything.
Elliptical arcs are not a supported primitive of Gerber,
the official documentation only speaks of linear and
circular interpolation.

You can of course draw whatever you want with a large enough
number of small segments, or create almost ellipical apertures
with an outline (arbitrary polygon) aperture primitive with 
enough vertices.

And yes, there is a deprecated parameter (SF) of Gerber files
that allowed different scaling for X and Y axes, but it could
only be set globally for a file, so all you ellipses would have
the same excentricity and the same major axis direction (along
one of the main axes).

	Gabriel