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