src/common/tcos.c

#ifndef lint
static const char       RCSid[] = "$Id$";
#endif
/*
 * Table-based cosine approximation.
 *
 * Use doubles in table even though we're not nearly that accurate just
 * to avoid conversion and guarantee that tsin(x)^2 + tcos(x)^2 == 1.
 *
 * No interpolation in this version.
 *
 * External symbols declared in standard.h
 */

/* ====================================================================
 * 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 <math.h>

#ifndef NCOSENTRY
#define NCOSENTRY       256
#endif

#ifdef M_PI
#define PI              ((double)M_PI)
#else
#define PI              3.14159265358979323846
#endif


double
tcos(x)                         /* approximate cosine */
register double x;
{
        static double   costab[NCOSENTRY+1];
        register int    i;

        if (costab[0] < 0.5)            /* initialize table */
                for (i = 0; i <= NCOSENTRY; i++)
                        costab[i] = cos((PI/2./NCOSENTRY)*i);
                                        /* normalize angle */
        if (x < 0.)
                x = -x;
        i = (NCOSENTRY*2./PI) * x  +  0.5;
        if (i >= 4*NCOSENTRY)
                i %= 4*NCOSENTRY;
        switch (i / NCOSENTRY) {
        case 0:
                return(costab[i]);
        case 1:
                return(-costab[(2*NCOSENTRY)-i]);
        case 2:
                return(-costab[i-(2*NCOSENTRY)]);
        case 3:
                return(costab[(4*NCOSENTRY)-i]);
        }
        return(0.);             /* should never be reached */
}
Revision:	3.2
Committed:	Sat Feb 22 02:07:22 2003 UTC (21 years, 2 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 3.1:	+60 -4 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	gwlarson	3.1	#ifndef lint
2	greg	3.2	static const char RCSid[] = "$Id$";
3	gwlarson	3.1	#endif
4			/*
5			* Table-based cosine approximation.
6			*
7			* Use doubles in table even though we're not nearly that accurate just
8			* to avoid conversion and guarantee that tsin(x)^2 + tcos(x)^2 == 1.
9			*
10			* No interpolation in this version.
11	greg	3.2	*
12			* External symbols declared in standard.h
13			*/
14
15			/* ====================================================================
16			* The Radiance Software License, Version 1.0
17			*
18			* Copyright (c) 1990 - 2002 The Regents of the University of California,
19			* through Lawrence Berkeley National Laboratory. All rights reserved.
20			*
21			* Redistribution and use in source and binary forms, with or without
22			* modification, are permitted provided that the following conditions
23			* are met:
24			*
25			* 1. Redistributions of source code must retain the above copyright
26			* notice, this list of conditions and the following disclaimer.
27			*
28			* 2. Redistributions in binary form must reproduce the above copyright
29			* notice, this list of conditions and the following disclaimer in
30			* the documentation and/or other materials provided with the
31			* distribution.
32			*
33			* 3. The end-user documentation included with the redistribution,
34			* if any, must include the following acknowledgment:
35			* "This product includes Radiance software
36			* (http://radsite.lbl.gov/)
37			* developed by the Lawrence Berkeley National Laboratory
38			* (http://www.lbl.gov/)."
39			* Alternately, this acknowledgment may appear in the software itself,
40			* if and wherever such third-party acknowledgments normally appear.
41			*
42			* 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
43			* and "The Regents of the University of California" must
44			* not be used to endorse or promote products derived from this
45			* software without prior written permission. For written
46			* permission, please contact [email protected].
47			*
48			* 5. Products derived from this software may not be called "Radiance",
49			* nor may "Radiance" appear in their name, without prior written
50			* permission of Lawrence Berkeley National Laboratory.
51			*
52			* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
53			* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
54			* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
55			* DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
56			* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
57			* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
58			* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
59			* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
60			* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
61			* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
62			* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
63			* SUCH DAMAGE.
64			* ====================================================================
65			*
66			* This software consists of voluntary contributions made by many
67			* individuals on behalf of Lawrence Berkeley National Laboratory. For more
68			* information on Lawrence Berkeley National Laboratory, please see
69			* <http://www.lbl.gov/>.
70	gwlarson	3.1	*/
71
72			#include <math.h>
73
74			#ifndef NCOSENTRY
75			#define NCOSENTRY 256
76			#endif
77
78			#ifdef M_PI
79			#define PI ((double)M_PI)
80			#else
81			#define PI 3.14159265358979323846
82			#endif
83
84
85			double
86			tcos(x) /* approximate cosine */
87			register double x;
88			{
89			static double costab[NCOSENTRY+1];
90			register int i;
91
92			if (costab[0] < 0.5) /* initialize table */
93			for (i = 0; i <= NCOSENTRY; i++)
94			costab[i] = cos((PI/2./NCOSENTRY)*i);
95			/* normalize angle */
96			if (x < 0.)
97			x = -x;
98			i = (NCOSENTRY2./PI) x + 0.5;
99			if (i >= 4*NCOSENTRY)
100			i %= 4*NCOSENTRY;
101			switch (i / NCOSENTRY) {
102			case 0:
103			return(costab[i]);
104			case 1:
105			return(-costab[(2*NCOSENTRY)-i]);
106			case 2:
107			return(-costab[i-(2*NCOSENTRY)]);
108			case 3:
109			return(costab[(4*NCOSENTRY)-i]);
110			}
111			return(0.); /* should never be reached */
112			}