X-Authentication-Warning:	delorie.com: mail set sender to geda-user-bounces using -f
X-Recipient:	geda-user AT delorie DOT com
Message-ID:	<f939dc32b1872b74667a44388d598707.squirrel@ssl-webmail-vh.nl.clara.net>
Date:	Sun, 27 Nov 2011 22:36:03 +0100
Subject:	[geda-user] Mathematics of the arc element in pcb.
From:	myken AT iae DOT nl
To:	geda-user AT delorie DOT com
User-Agent:	SquirrelMail/1.4.21
MIME-Version:	1.0
X-Priority:	3 (Normal)
Importance:	Normal
Reply-To:	geda-user AT delorie DOT com

Hello all,

I'm working on some functionality in pcb and I have a question.

The question is about the start angle and the delta of an Arc element in pcb.
If I draw an Arc in pcb then I will get the following entry in my pcb file:
Arc [X Y Width Height Thickness Clearance StartAngle DeltaAngle SFlags]
(no not literally but I hope you know what I mean ;-).

If the Width and the Height are the same the start angle (45 degrees) and
the delta (90 degrees) work as expected,
Arc[200000 150000 20000 20000 100 200 45 90 "clearline"]

But if the Width and the Height are not the same, it looks like the start
angle and the delta are totally ignored.
Arc[200000 150000 30000 20000 100 200 45 90 "clearline"]

Can anyone explain to me the mathematics behind the Arc element or point
me to the source code that does the mathematics?
Thank, Robert.

- Raw text -