src/common/clip.c

#ifndef lint
static const char       RCSid[] = "$Id$";
#endif
/*
 *  clip.c - routine to clip 3D line segments to a box.
 */

/* ====================================================================
 * The Radiance Software License, Version 1.0
 *
 * Copyright (c) 1990 - 2002 The Regents of the University of California,
 * through Lawrence Berkeley National Laboratory.   All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *         notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in
 *       the documentation and/or other materials provided with the
 *       distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *           if any, must include the following acknowledgment:
 *             "This product includes Radiance software
 *                 (http://radsite.lbl.gov/)
 *                 developed by the Lawrence Berkeley National Laboratory
 *               (http://www.lbl.gov/)."
 *       Alternately, this acknowledgment may appear in the software itself,
 *       if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
 *       and "The Regents of the University of California" must
 *       not be used to endorse or promote products derived from this
 *       software without prior written permission. For written
 *       permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Radiance",
 *       nor may "Radiance" appear in their name, without prior written
 *       permission of Lawrence Berkeley National Laboratory.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.   IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Lawrence Berkeley National Laboratory.   For more
 * information on Lawrence Berkeley National Laboratory, please see
 * <http://www.lbl.gov/>.
 */

#include  "fvect.h"

#include  "plocate.h"

#define MAXITER         6       /* maximum possible number of iterations */


int
clip(ep1, ep2, min, max)        /* clip a line segment to a box */
FLOAT  *ep1, *ep2;
FVECT  min, max;
{
        int  itlim = MAXITER;
        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 (itlim-- <= 0)       /* past theoretical limit? */
                        return(0);      /* quit fooling around */

                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);
}
Revision:	2.3
Committed:	Sat Feb 22 02:07:21 2003 UTC (21 years, 2 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.2:	+58 -5 lines
Log Message:	Changes and check-in for 3.5 release Includes new source files and modifications not recorded for many years See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.3	static const char RCSid[] = "$Id$";
3	greg	1.1	#endif
4			/*
5			* clip.c - routine to clip 3D line segments to a box.
6	greg	2.3	*/
7
8			/* ====================================================================
9			* The Radiance Software License, Version 1.0
10			*
11			* Copyright (c) 1990 - 2002 The Regents of the University of California,
12			* through Lawrence Berkeley National Laboratory. All rights reserved.
13			*
14			* Redistribution and use in source and binary forms, with or without
15			* modification, are permitted provided that the following conditions
16			* are met:
17			*
18			* 1. Redistributions of source code must retain the above copyright
19			* notice, this list of conditions and the following disclaimer.
20			*
21			* 2. Redistributions in binary form must reproduce the above copyright
22			* notice, this list of conditions and the following disclaimer in
23			* the documentation and/or other materials provided with the
24			* distribution.
25			*
26			* 3. The end-user documentation included with the redistribution,
27			* if any, must include the following acknowledgment:
28			* "This product includes Radiance software
29			* (http://radsite.lbl.gov/)
30			* developed by the Lawrence Berkeley National Laboratory
31			* (http://www.lbl.gov/)."
32			* Alternately, this acknowledgment may appear in the software itself,
33			* if and wherever such third-party acknowledgments normally appear.
34			*
35			* 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
36			* and "The Regents of the University of California" must
37			* not be used to endorse or promote products derived from this
38			* software without prior written permission. For written
39			* permission, please contact [email protected].
40			*
41			* 5. Products derived from this software may not be called "Radiance",
42			* nor may "Radiance" appear in their name, without prior written
43			* permission of Lawrence Berkeley National Laboratory.
44			*
45			* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
46			* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
47			* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
48			* DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
49			* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
50			* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
51			* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
52			* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
53			* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
54			* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
55			* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
56			* SUCH DAMAGE.
57			* ====================================================================
58	greg	1.1	*
59	greg	2.3	* This software consists of voluntary contributions made by many
60			* individuals on behalf of Lawrence Berkeley National Laboratory. For more
61			* information on Lawrence Berkeley National Laboratory, please see
62			* <http://www.lbl.gov/>.
63	greg	1.1	*/
64
65	greg	1.2	#include "fvect.h"
66
67	greg	1.1	#include "plocate.h"
68
69	greg	2.2	#define MAXITER 6 /* maximum possible number of iterations */
70	greg	1.1
71	greg	2.2
72	greg	2.3	int
73	greg	1.1	clip(ep1, ep2, min, max) /* clip a line segment to a box */
74	greg	1.2	FLOAT ep1, ep2;
75			FVECT min, max;
76	greg	1.1	{
77	greg	2.2	int itlim = MAXITER;
78	greg	1.1	int loc1, loc2;
79			int accept;
80	greg	1.2	FLOAT *dp;
81	greg	1.1	double d;
82			register int i, j;
83
84			/*
85			* The Cohen-Sutherland algorithm is used to determine
86			* what part (if any) of the given line segment is contained
87			* in the box specified by the min and max vectors.
88			* The routine returns non-zero if any segment is left.
89			*/
90
91			loc1 = plocate(ep1, min, max);
92			loc2 = plocate(ep2, min, max);
93
94			/* check for trivial accept and reject */
95			/* trivial accept is both points inside */
96			/* trivial reject is both points to one side */
97
98			while (!((accept = !(loc1 \| loc2)) \|\| (loc1 & loc2))) {
99
100	greg	2.2	if (itlim-- <= 0) /* past theoretical limit? */
101			return(0); /* quit fooling around */
102
103	greg	1.1	if (!loc1) { /* make sure first point is outside */
104			dp = ep1; ep1 = ep2; ep2 = dp;
105			i = loc1; loc1 = loc2; loc2 = i;
106			}
107
108			for (i = 0; i < 3; i++) { /* chop segment */
109
110			if (loc1 & position(i) & BELOW) {
111			d = (min[i] - ep1[i])/(ep2[i] - ep1[i]);
112			ep1[i] = min[i];
113			} else if (loc1 & position(i) & ABOVE) {
114			d = (max[i] - ep1[i])/(ep2[i] - ep1[i]);
115			ep1[i] = max[i];
116			} else
117			continue;
118
119			for (j = 0; j < 3; j++)
120			if (j != i)
121			ep1[j] += (ep2[j] - ep1[j])*d;
122			break;
123			}
124			loc1 = plocate(ep1, min, max);
125			}
126			return(accept);
127			}