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root/radiance/ray/src/gen/sun.c
Revision: 2.2
Committed: Fri Oct 2 16:12:29 1992 UTC (31 years, 6 months ago) by greg
Content type: text/plain
Branch: MAIN
Changes since 2.1: +2 -8 lines
Log Message:
Removed problematic math function declarations

File Contents

# Content
1 /* Copyright (c) 1989 Regents of the University of California */
2
3 #ifndef lint
4 static char SCCSid[] = "$SunId$ LBL";
5 #endif
6
7 /*
8 * SOLAR CALCULATIONS
9 *
10 * 3/31/87
11 *
12 */
13
14 #include <math.h>
15
16 #define PI 3.141592654
17
18 double s_latitude = 0.66; /* site latitude (radians) */
19 double s_longitude = 2.13; /* site longitude (radians) */
20 double s_meridian = 2.0944; /* standard meridian (radians) */
21
22
23 int
24 jdate(month, day) /* Julian date (days into year) */
25 int month, day;
26 {
27 static short mo_da[12] = {0,31,59,90,120,151,181,212,243,273,304,334};
28
29 return(mo_da[month-1] + day);
30 }
31
32
33 double
34 stadj(jd) /* solar time adjustment from Julian date */
35 int jd;
36 {
37 return( 0.170 * sin( (4*PI/373) * (jd - 80) ) -
38 0.129 * sin( (2*PI/355) * (jd - 8) ) +
39 12 * (s_meridian - s_longitude) / PI );
40 }
41
42
43 double
44 sdec(jd) /* solar declination angle from Julian date */
45 int jd;
46 {
47 return( 0.4093 * sin( (2*PI/368) * (jd - 81) ) );
48 }
49
50
51 double
52 salt(sd, st) /* solar altitude from solar declination and solar time */
53 double sd, st;
54 {
55 return( asin( sin(s_latitude) * sin(sd) -
56 cos(s_latitude) * cos(sd) * cos(st*(PI/12)) ) );
57 }
58
59
60 double
61 sazi(sd, st) /* solar azimuth from solar declination and solar time */
62 double sd, st;
63 {
64 return( -atan2( cos(sd)*sin(st*(PI/12)),
65 -cos(s_latitude)*sin(sd) -
66 sin(s_latitude)*cos(sd)*cos(st*(PI/12)) ) );
67 }