Re: gEDA-user: GL pcb bugs and a question re the log/library window, gerber outline output

[Peter Clifton <pcjc2@xxxxxxxxx>]

On Tue, 2009-02-17 at 13:29 -0800, Ben Jackson wrote:
> On Tue, Feb 17, 2009 at 09:08:33PM +0000, Peter Clifton wrote:
> > > 
> > > I think the only straightforward way to fix the self-intersecting arc is
> > > to build it internally from two parts and union them.  Might be slow on
> > > teardrop'd boards.
> > 
> > Probably just need some simple geometry to work out if it would
> > self-intersect or not fn(radius, width, angle), and do something
> > different with those cases which do. Unfortunately, there is (of
> > course), a whole family of potential intersections, so its not quite as
> > simple as just specifying an outer circle poly, with a circular hole.
> 
> You just build it as two halves and use the polygon code to union it.
> The math to make the self-intersecting arc "by hand" is going to end up
> being a special case of exactly what the polygon code will do.  Your fn()
> shouldn't be too bad, I think it's just "find the coordinates of the arc
> endpoints and see if they're <thickness apart".

Plus some tolerance I'd guess, to account for potential errors in
whatever \_/ approximation gets used for the caps.

I agree we ought to use the polygon code rather than trying to special
case it directly, I just hoped we could avoid the cost of bisecting each
arc we cleared.

-- 
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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