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Subject: Re: [geda-user] Cooper arcs in footprint
From: Stefan Salewski <mail AT ssalewski DOT de>
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Date: Sun, 06 Apr 2014 15:19:19 +0200
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On Sun, 2014-04-06 at 16:44 +0400, Алексей Харьковский wrote:
> > I think gerber formats supports arcs.
> >
> 
> Right.
> 
> One problem with arcs is: If we have stretched arcs, DRC may be much
> > more difficult -- I have to admit that I have no idea how to test
> > stretched arcs for intersection with other elements (fast).
> 
> 
> I do not see the problem...
> 
> What the stretched arcs? Parts of ellipse?
> How I place ellipse part in pcb?
> 
> 

In PCB Editor you can currently only insert 90 degree arcs, a quarter of
of a full circle. You may rotate it later by freerotatebuffer() command.
PCB input file allows more parameters (which we currently only can
change with an text editor, by scripts or other tools)

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.

> > Another
> > problem can be autorouting when we have arcs on the board -- for
> > geometrical and topological routers there should be some difficulties.
> >
> 
> Why autorouting with arc in footprint more difficult then with arc added on
> cooper layer manually?
> Hole pad is circle - example of complete arc.

Stretched rotated arcs are not simple geometric objects -- same problems
in footprints or PCB file.

On Sun, 2014-04-06 at 13:23 +0200, Gabriel Paubert wrote:
I think gerber formats supports arcs.
> 
> Indeed, but it does not support ellipses:

That is interesting (and surprising for me). If that is true, maybe we
should restrict support to circular arcs only -- which is much simpler.