| 1 |
/* Copyright (c) 1986 Regents of the University of California */ |
| 2 |
|
| 3 |
#ifndef lint |
| 4 |
static char SCCSid[] = "$SunId$ LBL"; |
| 5 |
#endif |
| 6 |
|
| 7 |
/* |
| 8 |
* clip.c - routine to clip 3D line segments to a box. |
| 9 |
* |
| 10 |
* 8/28/85 |
| 11 |
*/ |
| 12 |
|
| 13 |
#include "plocate.h" |
| 14 |
|
| 15 |
|
| 16 |
clip(ep1, ep2, min, max) /* clip a line segment to a box */ |
| 17 |
double *ep1, *ep2; |
| 18 |
double min[3], max[3]; |
| 19 |
{ |
| 20 |
int loc1, loc2; |
| 21 |
int accept; |
| 22 |
double *dp; |
| 23 |
double d; |
| 24 |
register int i, j; |
| 25 |
|
| 26 |
/* |
| 27 |
* The Cohen-Sutherland algorithm is used to determine |
| 28 |
* what part (if any) of the given line segment is contained |
| 29 |
* in the box specified by the min and max vectors. |
| 30 |
* The routine returns non-zero if any segment is left. |
| 31 |
*/ |
| 32 |
|
| 33 |
loc1 = plocate(ep1, min, max); |
| 34 |
loc2 = plocate(ep2, min, max); |
| 35 |
|
| 36 |
/* check for trivial accept and reject */ |
| 37 |
/* trivial accept is both points inside */ |
| 38 |
/* trivial reject is both points to one side */ |
| 39 |
|
| 40 |
while (!((accept = !(loc1 | loc2)) || (loc1 & loc2))) { |
| 41 |
|
| 42 |
if (!loc1) { /* make sure first point is outside */ |
| 43 |
dp = ep1; ep1 = ep2; ep2 = dp; |
| 44 |
i = loc1; loc1 = loc2; loc2 = i; |
| 45 |
} |
| 46 |
|
| 47 |
for (i = 0; i < 3; i++) { /* chop segment */ |
| 48 |
|
| 49 |
if (loc1 & position(i) & BELOW) { |
| 50 |
d = (min[i] - ep1[i])/(ep2[i] - ep1[i]); |
| 51 |
ep1[i] = min[i]; |
| 52 |
} else if (loc1 & position(i) & ABOVE) { |
| 53 |
d = (max[i] - ep1[i])/(ep2[i] - ep1[i]); |
| 54 |
ep1[i] = max[i]; |
| 55 |
} else |
| 56 |
continue; |
| 57 |
|
| 58 |
for (j = 0; j < 3; j++) |
| 59 |
if (j != i) |
| 60 |
ep1[j] += (ep2[j] - ep1[j])*d; |
| 61 |
break; |
| 62 |
} |
| 63 |
loc1 = plocate(ep1, min, max); |
| 64 |
} |
| 65 |
return(accept); |
| 66 |
} |
