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Point in a poly II
By Cornelis Wessels | Published Jul 16 1999 11:58 AM in Math and Physics
| If you find this article contains errors or problems rendering it unreadable (missing images or files, mangled code, improper text formatting, etc) please contact the editor so corrections can be made. Thank you for helping us improve this resource |
From pdxgate!usenet.ee.pdx.edu!reed!henson!news.u.washington.edu!usenet.coe.montana.edu!caen!uunet!mcsun!sun4nl!bsoatr!bskewe!kewe Tue Mar 2 15:21:37 PST 1993
In article douglasg@gr.hp.com writes:
>
> I'm looking for an algorithm which determines if a point
> falls within an arbitrary (convex or concave) polygon.
>
> Thanks,
>
> Douglas Gennetten
> Hewlett-Packard
>
>
>
Cornelis Wessels
kewe@bskewe.atr.bso.nl
Krommenoord 14
3079 ZT ROTTERDAM
The Netherlands
+31 - 10 - 4826394
In article douglasg@gr.hp.com writes:
>
> I'm looking for an algorithm which determines if a point
> falls within an arbitrary (convex or concave) polygon.
>
> Thanks,
>
> Douglas Gennetten
> Hewlett-Packard
>
>
>
BOOLEAN PointInsideOfPolygon ( POLYGOON *P, VECTOR2D *p )
{
VECTOR2D o, v, w;
INDEX ncross, N, n;
ncros = 0;
N = PolygonLength(P); /* Number of vertices */
GivePolygonVertex ( P, N, &o );
for ( n=1; n<=N; n++ )
{
GivePolygonVertex ( P, n, &v );
if ( o.x >= p->x && v.x < p->x ||
o.x < p->x && v.x >= p->x )
{
w.x = p->x;
LinearInterpolation ( &o, &v, &w );
if ( w.x == p->x && w.y == p->y )
return(TRUE);
else if ( w.y > p->y )
ncross++;
}
CopyVector2d ( &v, &o );
}
if ( ncross%2 == 0 )
return(FALSE);
else
return(TRUE);
}Cornelis Wessels
kewe@bskewe.atr.bso.nl
Krommenoord 14
3079 ZT ROTTERDAM
The Netherlands
+31 - 10 - 4826394
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