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CLIP.C
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C/C++ Source or Header
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1993-10-07
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2KB
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69 lines
/* Copyright (c) 1986 Regents of the University of California */
#ifndef lint
static char SCCSid[] = "@(#)clip.c 2.1 11/12/91 LBL";
#endif
/*
* clip.c - routine to clip 3D line segments to a box.
*
* 8/28/85
*/
#include "fvect.h"
#include "plocate.h"
clip(ep1, ep2, min, max) /* clip a line segment to a box */
FLOAT *ep1, *ep2;
FVECT min, max;
{
int loc1, loc2;
int accept;
FLOAT *dp;
double d;
register int i, j;
/*
* The Cohen-Sutherland algorithm is used to determine
* what part (if any) of the given line segment is contained
* in the box specified by the min and max vectors.
* The routine returns non-zero if any segment is left.
*/
loc1 = plocate(ep1, min, max);
loc2 = plocate(ep2, min, max);
/* check for trivial accept and reject */
/* trivial accept is both points inside */
/* trivial reject is both points to one side */
while (!((accept = !(loc1 | loc2)) || (loc1 & loc2))) {
if (!loc1) { /* make sure first point is outside */
dp = ep1; ep1 = ep2; ep2 = dp;
i = loc1; loc1 = loc2; loc2 = i;
}
for (i = 0; i < 3; i++) { /* chop segment */
if (loc1 & position(i) & BELOW) {
d = (min[i] - ep1[i])/(ep2[i] - ep1[i]);
ep1[i] = min[i];
} else if (loc1 & position(i) & ABOVE) {
d = (max[i] - ep1[i])/(ep2[i] - ep1[i]);
ep1[i] = max[i];
} else
continue;
for (j = 0; j < 3; j++)
if (j != i)
ep1[j] += (ep2[j] - ep1[j])*d;
break;
}
loc1 = plocate(ep1, min, max);
}
return(accept);
}