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Malte Brill wrote:<br>
<br>
<blockquote type="cite">Hi List,<br>
<br>
<br>
this one goes out to the math experts.<br>
How does one compute the area ( I hope it is the correct Term for<br>
flaecheninhalt in german) of a polygon with n sides.<br>
<br>
(That would get me started.)<br>
<br>
I want to extract all lines of 2 polygons by analysing their points,<br>
evaluate the area of each of them with some magic formula I don´t know <img
src="cid:part1.02090802.02020604@rz-online.de" alt=";-)"
class="moz-txt-smily" height="19" width="19" align="middle"><br>
and to figure out the area of the smallest polygon surrounding both of
them.<br>
<br>
<br>
<br>
</blockquote>
Hallo Malte,<br>
wenn sich das Polygon nicht schneidet, geht es folgendermaßen: Es wird
in Dreiecke zerlegt (man nimmt ein Polygonpunkt und verbindet ihn mit
allen anderen); angenommen, die Koordinaten der 3 Eckpunkte sind
(ax,ay), (bx,by) und (cx,cy) dann gilt für den Flächeninhalt: F =
[ax*(by - cy) + bx*(cy - ay) + cx*(ay - by)]/2.<br>
Diese Berechnung muß nun für alle entstandenen Dreiecke durchgeführt
und die Ergebnisse addiert werden.<br>
In English:<br>
If the polygon does not cross itself, the following method helps: the
polygon has to be divided into triangulars (choose one point of the
polygon and connect it with all the others); supposed, the coordinates
of the three triangular points are (ax,ay), (bx,by) und (cx,cy), then
the area F will be calculated with [ax*(by - cy) + bx*(cy - ay) + cx*(ay
- by)]/2.<br>
This has to be done for all the triangulars and the areas have be added
and give the total area.<br>
( I know, bad English from "old Europe")<br>
<br>
Gruß<br>
Gernot
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