ikarus/benchmarks.larceny/src/pnpoly.c

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/* PNPOLY - Test if a point is contained in a 2D polygon. */
#include <stdio.h>
/*
The code below is from Wm. Randolph Franklin <wrf@ecse.rpi.edu>
with some minor modifications for speed and style.
comp.graphics.algorithms FAQ
References:
[Gems IV] pp. 24-46
[O'Rourke] pp. 233-238
[Glassner:RayTracing]
*/
static int pnpoly(int npol, double *xp, double *yp, double x, double y)
{
int i, j, c = 0;
for (i = 0, j = npol-1; i < npol; j = i++)
{
if ((((yp[i]<=y) && (y<yp[j])) ||
((yp[j]<=y) && (y<yp[i]))) &&
(x < (xp[j] - xp[i]) * (y - yp[i]) / (yp[j] - yp[i]) + xp[i]))
c = !c;
}
return c;
}
static double xp[20] = {0.0,1.0,1.0,0.0,0.0,1.0,-.5,-1.0,-1.0,-2.0,
-2.5,-2.0,-1.5,-.5,1.0,1.0,0.0,-.5,-1.0,-.5};
static double yp[20] = {0.0,0.0,1.0,1.0,2.0,3.0,2.0,3.0,0.0,-.5,
-1.0,-1.5,-2.0,-2.0,-1.5,-1.0,-.5,-1.0,-1.0,-.5};
static int run ()
{
int npol=20, count=0;
if (pnpoly(npol,xp,yp,0.5,0.5)) count++;
if (pnpoly(npol,xp,yp,0.5,1.5)) count++;
if (pnpoly(npol,xp,yp,-.5,1.5)) count++;
if (pnpoly(npol,xp,yp,0.75,2.25)) count++;
if (pnpoly(npol,xp,yp,0,2.01)) count++;
if (pnpoly(npol,xp,yp,-.5,2.5)) count++;
if (pnpoly(npol,xp,yp,-1.0,-.5)) count++;
if (pnpoly(npol,xp,yp,-1.5,.5)) count++;
if (pnpoly(npol,xp,yp,-2.25,-1.0)) count++;
if (pnpoly(npol,xp,yp,0.5,-.25)) count++;
if (pnpoly(npol,xp,yp,0.5,-1.25)) count++;
if (pnpoly(npol,xp,yp,-.5,-2.5)) count++;
return count;
}
int main (int argc, char *argv[])
{
int i;
int result;
for (i=0; i<100000; i++)
result = run ();
if (result != 6)
printf ("*** wrong result ***\n");
return 0;
}