src/gen/gensky.c

#ifndef lint
static const char       RCSid[] = "$Id: gensky.c,v 2.29 2023/03/30 20:19:05 greg Exp $";
#endif
/*
 *  gensky.c - program to generate sky functions.
 *              Our zenith is along the Z-axis, the X-axis
 *              points east, and the Y-axis points north.
 *              Radiance is in watts/steradian/sq. meter.
 *
 *     3/26/86
 */

#include  "rtio.h"
#include  <stdlib.h>
#include  <math.h>
#include  <ctype.h>
#include  "sun.h"
#include  "color.h"

#ifndef  PI
#define  PI             3.14159265358979323846
#endif

#define  DOT(v1,v2)     (v1[0]*v2[0]+v1[1]*v2[1]+v1[2]*v2[2])

#define  S_CLEAR        1
#define  S_OVER         2
#define  S_UNIF         3
#define  S_INTER        4

#define  overcast       ((skytype==S_OVER)|(skytype==S_UNIF))

double  normsc();

#undef  toupper
#define  toupper(c)     ((c) & ~0x20)   /* ASCII trick to convert case */

                                        /* European and North American zones */
struct {
        char    zname[8];       /* time zone name (all caps) */
        float   zmer;           /* standard meridian */
} tzone[] = {
        {"YST", 135}, {"YDT", 120},
        {"PST", 120}, {"PDT", 105},
        {"MST", 105}, {"MDT", 90},
        {"CST", 90}, {"CDT", 75},
        {"EST", 75}, {"EDT", 60},
        {"AST", 60}, {"ADT", 45},
        {"NST", 52.5}, {"NDT", 37.5},
        {"GMT", 0}, {"BST", -15},
        {"CET", -15}, {"CEST", -30},
        {"EET", -30}, {"EEST", -45},
        {"AST", -45}, {"ADT", -60},
        {"GST", -60}, {"GDT", -75},
        {"IST", -82.5}, {"IDT", -97.5},
        {"JST", -135}, {"NDT", -150},
        {"NZST", -180}, {"NZDT", -195},
        {"", 0}
};
                                        /* required values */
int  year = 0;                                  /* year (optional) */
int  month, day;                                /* date */
double  hour;                                   /* time */
int  tsolar;                                    /* 0=standard, 1=solar */
double  altitude, azimuth;                      /* or solar angles */
                                        /* default values */
int  skytype = S_CLEAR;                         /* sky type */
int  dosun = 1;
double  zenithbr = 0.0;
int     u_zenith = 0;                           /* -1=irradiance, 1=radiance */
double  turbidity = 2.45;
double  gprefl = 0.2;
                                        /* computed values */
double  sundir[3];
double  groundbr;
double  F2;
double  solarbr = 0.0;
int     u_solar = 0;                            /* -1=irradiance, 1=radiance */

char  *progname;
char  errmsg[128];

void computesky(void);
void printsky(void);
void printdefaults(void);
void userror(char  *msg);
double normsc(void);
int cvthour(char  *hs);


int
main(
        int  argc,
        char  *argv[]
)
{
        int  got_meridian = 0;
        int  i;

        progname = argv[0];
        if (argc == 2 && !strcmp(argv[1], "-defaults")) {
                printdefaults();
                exit(0);
        }
        if (argc < 4)
                userror("arg count");
        if (!strcmp(argv[1], "-ang")) {
                altitude = atof(argv[2]) * (PI/180);
                azimuth = atof(argv[3]) * (PI/180);
                month = 0;
        } else {
                month = atoi(argv[1]);
                if (month < 1 || month > 12)
                        userror("bad month");
                day = atoi(argv[2]);
                if (day < 1 || day > 31)
                        userror("bad day");
                got_meridian = cvthour(argv[3]);
        }
        for (i = 4; i < argc; i++)
                if (argv[i][0] == '-' || argv[i][0] == '+')
                        switch (argv[i][1]) {
                        case 's':
                                skytype = S_CLEAR;
                                dosun = argv[i][0] == '+';
                                break;
                        case 'y':
                                year = atoi(argv[++i]);
                                break;
                        case 'r':
                        case 'R':
                                u_solar = argv[i][1]=='R' ? -1 : 1;
                                solarbr = atof(argv[++i]);
                                break;
                        case 'c':
                                skytype = S_OVER;
                                break;
                        case 'u':
                                skytype = S_UNIF;
                                break;
                        case 'i':
                                skytype = S_INTER;
                                dosun = argv[i][0] == '+';
                                break;
                        case 't':
                                turbidity = atof(argv[++i]);
                                break;
                        case 'b':
                        case 'B':
                                u_zenith = argv[i][1]=='B' ? -1 : 1;
                                zenithbr = atof(argv[++i]);
                                break;
                        case 'g':
                                gprefl = atof(argv[++i]);
                                break;
                        case 'a':
                                s_latitude = atof(argv[++i]) * (PI/180);
                                break;
                        case 'o':
                                s_longitude = atof(argv[++i]) * (PI/180);
                                break;
                        case 'm':
                                if (got_meridian) {
                                        ++i;
                                        break;          /* time overrides */
                                }
                                s_meridian = atof(argv[++i]) * (PI/180);
                                break;
                        default:
                                sprintf(errmsg, "unknown option: %s", argv[i]);
                                userror(errmsg);
                        }
                else
                        userror("bad option");

        if (year && (year < 1950) | (year > 2050))
                fprintf(stderr,
                        "%s: warning - year should be in range 1950-2050\n",
                        progname);
        if (month && !tsolar && fabs(s_meridian-s_longitude) > 45*PI/180)
                fprintf(stderr,
        "%s: warning - %.1f hours btwn. standard meridian and longitude\n",
                        progname, (s_longitude-s_meridian)*12/PI);

        fputs("# ", stdout);
        printargs(argc, argv, stdout);

        computesky();
        printsky();

        exit(0);
}


void
computesky(void)                        /* compute sky parameters */
{
        double  normfactor;
                                        /* compute solar direction */
        if (month) {                    /* from date and time */
                double  sd, st = hour;

                if (year) {                     /* Michalsky algorithm? */
                        double  mjd = mjdate(year, month, day, hour);
                        if (tsolar)
                                sd = msdec(mjd, NULL);
                        else
                                sd = msdec(mjd, &st);
                } else {
                        int  jd = jdate(month, day);    /* Julian date */
                        sd = sdec(jd);                  /* solar declination */
                        if (!tsolar)                    /* get solar time? */
                                st = hour + stadj(jd);
                }
                altitude = salt(sd, st);
                azimuth = sazi(sd, st);
                printf("# Local solar time: %.2f\n", st);
                printf("# Solar altitude and azimuth: %.1f %.1f\n",
                                180./PI*altitude, 180./PI*azimuth);
        }
        if (!overcast && altitude > 87.*PI/180.) {
                fprintf(stderr,
"%s: warning - sun too close to zenith, reducing altitude to 87 degrees\n",
                                progname);
                printf(
"# warning - sun too close to zenith, reducing altitude to 87 degrees\n");
                altitude = 87.*PI/180.;
        }
        sundir[0] = -sin(azimuth)*cos(altitude);
        sundir[1] = -cos(azimuth)*cos(altitude);
        sundir[2] = sin(altitude);

                                        /* Compute normalization factor */
        switch (skytype) {
        case S_UNIF:
                normfactor = 1.0;
                break;
        case S_OVER:
                normfactor = 0.777778;
                break;
        case S_CLEAR:
                F2 = 0.274*(0.91 + 10.0*exp(-3.0*(PI/2.0-altitude)) +
                                0.45*sundir[2]*sundir[2]);
                normfactor = normsc()/F2/PI;
                break;
        case S_INTER:
                F2 = (2.739 + .9891*sin(.3119+2.6*altitude)) *
                        exp(-(PI/2.0-altitude)*(.4441+1.48*altitude));
                normfactor = normsc()/F2/PI;
                break;
        }
                                        /* Compute zenith brightness */
        if (u_zenith == -1)
                zenithbr /= normfactor*PI;
        else if (u_zenith == 0) {
                if (overcast)
                        zenithbr = 8.6*sundir[2] + .123;
                else
                        zenithbr = (1.376*turbidity-1.81)*tan(altitude)+0.38;
                if (skytype == S_INTER)
                        zenithbr = (zenithbr + 8.6*sundir[2] + .123)/2.0;
                if (zenithbr < 0.0)
                        zenithbr = 0.0;
                else
                        zenithbr *= 1000.0/SKYEFFICACY;
        }
                                        /* Compute horizontal radiance */
        groundbr = zenithbr*normfactor;
        printf("# Ground ambient level: %.1f\n", groundbr);
        if (!overcast && sundir[2] > 0.0 && (!u_solar || solarbr > 0.0)) {
                if (u_solar == -1)
                        solarbr /= 5.98e-5*sundir[2];
                else if (u_solar == 0) {
                        solarbr = 1.5e9/SUNEFFICACY *
                        (1.147 - .147/(sundir[2]>.16?sundir[2]:.16));
                        if (skytype == S_INTER)
                                solarbr *= 0.15;        /* fudge factor! */
                }
                groundbr += 6e-5/PI*solarbr*sundir[2];
        } else
                dosun = 0;
        groundbr *= gprefl;
}


void
printsky(void)                  /* print out sky */
{
        if (dosun) {
                printf("\nvoid light solar\n");
                printf("0\n0\n");
                printf("3 %.3e %.3e %.3e\n", solarbr, solarbr, solarbr);
                printf("\nsolar source sun\n");
                printf("0\n0\n");
                printf("4 %f %f %f 0.5\n", sundir[0], sundir[1], sundir[2]);
        }
        
        printf("\nvoid brightfunc skyfunc\n");
        printf("2 skybr skybright.cal\n");
        printf("0\n");
        if (overcast)
                printf("3 %d %.3e %.3e\n", skytype, zenithbr, groundbr);
        else
                printf("7 %d %.3e %.3e %.3e %f %f %f\n",
                                skytype, zenithbr, groundbr, F2,
                                sundir[0], sundir[1], sundir[2]);
}


void
printdefaults(void)                     /* print default values */
{
        switch (skytype) {
        case S_OVER:
                printf("-c\t\t\t\t# Cloudy sky\n");
                break;
        case S_UNIF:
                printf("-u\t\t\t\t# Uniform cloudy sky\n");
                break;
        case S_INTER:
                if (dosun)
                        printf("+i\t\t\t\t# Intermediate sky with sun\n");
                else
                        printf("-i\t\t\t\t# Intermediate sky without sun\n");
                break;
        case S_CLEAR:
                if (dosun)
                        printf("+s\t\t\t\t# Sunny sky with sun\n");
                else
                        printf("-s\t\t\t\t# Sunny sky without sun\n");
                break;
        }
        printf("-g %f\t\t\t# Ground plane reflectance\n", gprefl);
        if (zenithbr > 0.0)
                printf("-b %f\t\t\t# Zenith radiance (watts/ster/m2\n", zenithbr);
        else
                printf("-t %f\t\t\t# Atmospheric turbidity\n", turbidity);
        printf("-a %f\t\t\t# Site latitude (degrees)\n", s_latitude*(180/PI));
        printf("-o %f\t\t\t# Site longitude (degrees)\n", s_longitude*(180/PI));
        printf("-m %f\t\t\t# Standard meridian (degrees)\n", s_meridian*(180/PI));
}


void
userror(                        /* print usage error and quit */
        char  *msg
)
{
        if (msg != NULL)
                fprintf(stderr, "%s: Use error - %s\n", progname, msg);
        fprintf(stderr, "Usage: %s month day hour [options]\n", progname);
        fprintf(stderr, "   Or: %s -ang altitude azimuth [options]\n", progname);
        fprintf(stderr, "   Or: %s -defaults\n", progname);
        exit(1);
}


double
normsc(void)                    /* compute normalization factor (E0*F2/L0) */
{
        static double  nfc[2][5] = {
                                /* clear sky approx. */
                {2.766521, 0.547665, -0.369832, 0.009237, 0.059229},
                                /* intermediate sky approx. */
                {3.5556, -2.7152, -1.3081, 1.0660, 0.60227},
        };
        double  *nf;
        double  x, nsc;
        int  i;
                                        /* polynomial approximation */
        nf = nfc[skytype==S_INTER];
        x = (altitude - PI/4.0)/(PI/4.0);
        nsc = nf[i=4];
        while (i--)
                nsc = nsc*x + nf[i];

        return(nsc);
}


int
cvthour(                        /* convert hour string */
        char  *hs
)
{
        char  *cp = hs;
        int     i, j;

        if ( (tsolar = *cp == '+') ) cp++;              /* solar time? */
        while (isdigit(*cp)) cp++;
        if (*cp == ':')
                hour = atoi(hs) + atoi(++cp)/60.0;
        else {
                hour = atof(hs);
                if (*cp == '.') cp++;
        }
        while (isdigit(*cp)) cp++;
        if (!*cp)
                return(0);
        if (tsolar || !isalpha(*cp)) {
                fprintf(stderr, "%s: bad time format: %s\n", progname, hs);
                exit(1);
        }
        i = 0;
        do {
                for (j = 0; cp[j]; j++)
                        if (toupper(cp[j]) != tzone[i].zname[j])
                                break;
                if (!cp[j] && !tzone[i].zname[j]) {
                        s_meridian = tzone[i].zmer * (PI/180);
                        return(1);
                }
        } while (tzone[i++].zname[0]);

        fprintf(stderr, "%s: unknown time zone: %s\n", progname, cp);
        fprintf(stderr, "Known time zones:\n\t%s", tzone[0].zname);
        for (i = 1; tzone[i].zname[0]; i++)
                fprintf(stderr, " %s", tzone[i].zname);
        putc('\n', stderr);
        exit(1);
}
Revision:	2.30
Committed:	Fri May 9 12:52:48 2025 UTC (4 days, 3 hours ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	HEAD
Changes since 2.29:	+2 -2 lines
Log Message:	fix(gensky): Improved accuracy of solar direct, which was off by 1/3%
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.30	static const char RCSid[] = "$Id: gensky.c,v 2.29 2023/03/30 20:19:05 greg Exp $";
3	greg	1.1	#endif
4			/*
5			* gensky.c - program to generate sky functions.
6			* Our zenith is along the Z-axis, the X-axis
7			* points east, and the Y-axis points north.
8			* Radiance is in watts/steradian/sq. meter.
9			*
10			* 3/26/86
11			*/
12
13	greg	2.28	#include "rtio.h"
14	greg	2.20	#include <stdlib.h>
15	greg	1.1	#include <math.h>
16	greg	2.17	#include <ctype.h>
17	greg	2.26	#include "sun.h"
18	greg	1.6	#include "color.h"
19	greg	1.1
20	greg	2.17	#ifndef PI
21			#define PI 3.14159265358979323846
22			#endif
23	greg	1.1
24			#define DOT(v1,v2) (v1[0]v2[0]+v1[1]v2[1]+v1[2]*v2[2])
25
26	greg	2.13	#define S_CLEAR 1
27			#define S_OVER 2
28			#define S_UNIF 3
29			#define S_INTER 4
30
31	schorsch	2.21	#define overcast ((skytype==S_OVER)\|(skytype==S_UNIF))
32	greg	2.13
33	greg	1.1	double normsc();
34	greg	2.17
35			#undef toupper
36			#define toupper(c) ((c) & ~0x20) /* ASCII trick to convert case */
37
38			/* European and North American zones */
39			struct {
40			char zname[8]; /* time zone name (all caps) */
41			float zmer; /* standard meridian */
42			} tzone[] = {
43	schorsch	2.22	{"YST", 135}, {"YDT", 120},
44			{"PST", 120}, {"PDT", 105},
45			{"MST", 105}, {"MDT", 90},
46			{"CST", 90}, {"CDT", 75},
47			{"EST", 75}, {"EDT", 60},
48			{"AST", 60}, {"ADT", 45},
49			{"NST", 52.5}, {"NDT", 37.5},
50			{"GMT", 0}, {"BST", -15},
51			{"CET", -15}, {"CEST", -30},
52			{"EET", -30}, {"EEST", -45},
53			{"AST", -45}, {"ADT", -60},
54			{"GST", -60}, {"GDT", -75},
55			{"IST", -82.5}, {"IDT", -97.5},
56			{"JST", -135}, {"NDT", -150},
57			{"NZST", -180}, {"NZDT", -195},
58			{"", 0}
59	greg	2.17	};
60	greg	1.1	/* required values */
61	greg	2.27	int year = 0; /* year (optional) */
62	greg	2.3	int month, day; /* date */
63	greg	2.5	double hour; /* time */
64			int tsolar; /* 0=standard, 1=solar */
65	greg	2.3	double altitude, azimuth; /* or solar angles */
66	greg	1.1	/* default values */
67	greg	2.13	int skytype = S_CLEAR; /* sky type */
68	greg	1.1	int dosun = 1;
69	greg	2.12	double zenithbr = 0.0;
70			int u_zenith = 0; /* -1=irradiance, 1=radiance */
71	greg	2.24	double turbidity = 2.45;
72	greg	1.1	double gprefl = 0.2;
73			/* computed values */
74			double sundir[3];
75			double groundbr;
76			double F2;
77	greg	2.12	double solarbr = 0.0;
78			int u_solar = 0; /* -1=irradiance, 1=radiance */
79	greg	1.1
80			char *progname;
81			char errmsg[128];
82
83	schorsch	2.22	void computesky(void);
84			void printsky(void);
85			void printdefaults(void);
86			void userror(char *msg);
87			double normsc(void);
88	greg	2.23	int cvthour(char *hs);
89	schorsch	2.22
90	greg	1.1
91	schorsch	2.22	int
92	greg	2.26	main(
93			int argc,
94			char *argv[]
95			)
96	greg	1.1	{
97	greg	2.23	int got_meridian = 0;
98	greg	1.1	int i;
99
100			progname = argv[0];
101			if (argc == 2 && !strcmp(argv[1], "-defaults")) {
102			printdefaults();
103			exit(0);
104			}
105			if (argc < 4)
106			userror("arg count");
107	greg	2.3	if (!strcmp(argv[1], "-ang")) {
108			altitude = atof(argv[2]) * (PI/180);
109			azimuth = atof(argv[3]) * (PI/180);
110			month = 0;
111			} else {
112			month = atoi(argv[1]);
113	greg	2.6	if (month < 1 \|\| month > 12)
114			userror("bad month");
115	greg	2.3	day = atoi(argv[2]);
116	greg	2.6	if (day < 1 \|\| day > 31)
117			userror("bad day");
118	greg	2.23	got_meridian = cvthour(argv[3]);
119	greg	2.3	}
120	greg	1.1	for (i = 4; i < argc; i++)
121			if (argv[i][0] == '-' \|\| argv[i][0] == '+')
122			switch (argv[i][1]) {
123			case 's':
124	greg	2.13	skytype = S_CLEAR;
125	greg	1.1	dosun = argv[i][0] == '+';
126			break;
127	greg	2.27	case 'y':
128			year = atoi(argv[++i]);
129			break;
130	greg	2.8	case 'r':
131	greg	2.12	case 'R':
132			u_solar = argv[i][1]=='R' ? -1 : 1;
133	greg	2.8	solarbr = atof(argv[++i]);
134			break;
135	greg	1.1	case 'c':
136	greg	2.13	skytype = S_OVER;
137	greg	1.1	break;
138	greg	2.13	case 'u':
139			skytype = S_UNIF;
140			break;
141			case 'i':
142			skytype = S_INTER;
143			dosun = argv[i][0] == '+';
144			break;
145	greg	1.1	case 't':
146			turbidity = atof(argv[++i]);
147			break;
148			case 'b':
149	greg	2.12	case 'B':
150			u_zenith = argv[i][1]=='B' ? -1 : 1;
151	greg	1.1	zenithbr = atof(argv[++i]);
152			break;
153			case 'g':
154			gprefl = atof(argv[++i]);
155			break;
156			case 'a':
157			s_latitude = atof(argv[++i]) * (PI/180);
158			break;
159			case 'o':
160			s_longitude = atof(argv[++i]) * (PI/180);
161			break;
162			case 'm':
163	greg	2.23	if (got_meridian) {
164			++i;
165			break; /* time overrides */
166			}
167	greg	1.1	s_meridian = atof(argv[++i]) * (PI/180);
168			break;
169			default:
170			sprintf(errmsg, "unknown option: %s", argv[i]);
171			userror(errmsg);
172			}
173			else
174			userror("bad option");
175	greg	1.5
176	greg	2.27	if (year && (year < 1950) \| (year > 2050))
177			fprintf(stderr,
178			"%s: warning - year should be in range 1950-2050\n",
179			progname);
180	greg	2.25	if (month && !tsolar && fabs(s_meridian-s_longitude) > 45*PI/180)
181	greg	1.5	fprintf(stderr,
182	greg	2.25	"%s: warning - %.1f hours btwn. standard meridian and longitude\n",
183	greg	1.5	progname, (s_longitude-s_meridian)*12/PI);
184	greg	1.1
185	greg	2.28	fputs("# ", stdout);
186			printargs(argc, argv, stdout);
187	greg	1.1
188			computesky();
189			printsky();
190	greg	2.15
191			exit(0);
192	greg	1.1	}
193
194
195	schorsch	2.22	void
196			computesky(void) /* compute sky parameters */
197	greg	1.1	{
198	greg	2.12	double normfactor;
199	greg	1.1	/* compute solar direction */
200	greg	2.3	if (month) { /* from date and time */
201	greg	2.27	double sd, st = hour;
202	greg	2.3
203	greg	2.27	if (year) { /* Michalsky algorithm? */
204			double mjd = mjdate(year, month, day, hour);
205			if (tsolar)
206			sd = msdec(mjd, NULL);
207			else
208			sd = msdec(mjd, &st);
209			} else {
210			int jd = jdate(month, day); /* Julian date */
211			sd = sdec(jd); /* solar declination */
212			if (!tsolar) /* get solar time? */
213			st = hour + stadj(jd);
214			}
215	greg	2.3	altitude = salt(sd, st);
216			azimuth = sazi(sd, st);
217	greg	2.17	printf("# Local solar time: %.2f\n", st);
218	greg	2.13	printf("# Solar altitude and azimuth: %.1f %.1f\n",
219	greg	2.11	180./PIaltitude, 180./PIazimuth);
220	greg	2.9	}
221	greg	2.13	if (!overcast && altitude > 87.*PI/180.) {
222	greg	2.9	fprintf(stderr,
223			"%s: warning - sun too close to zenith, reducing altitude to 87 degrees\n",
224			progname);
225			printf(
226			"# warning - sun too close to zenith, reducing altitude to 87 degrees\n");
227			altitude = 87.*PI/180.;
228	greg	2.3	}
229	greg	1.1	sundir[0] = -sin(azimuth)*cos(altitude);
230			sundir[1] = -cos(azimuth)*cos(altitude);
231			sundir[2] = sin(altitude);
232
233	greg	2.12	/* Compute normalization factor */
234	greg	2.13	switch (skytype) {
235			case S_UNIF:
236	greg	2.12	normfactor = 1.0;
237	greg	2.13	break;
238			case S_OVER:
239	greg	2.12	normfactor = 0.777778;
240	greg	2.13	break;
241			case S_CLEAR:
242	greg	2.12	F2 = 0.274(0.91 + 10.0exp(-3.0*(PI/2.0-altitude)) +
243			0.45sundir[2]sundir[2]);
244	greg	2.13	normfactor = normsc()/F2/PI;
245			break;
246			case S_INTER:
247			F2 = (2.739 + .9891sin(.3119+2.6altitude)) *
248			exp(-(PI/2.0-altitude)(.4441+1.48altitude));
249			normfactor = normsc()/F2/PI;
250			break;
251	greg	2.12	}
252	greg	1.1	/* Compute zenith brightness */
253	greg	2.12	if (u_zenith == -1)
254			zenithbr /= normfactor*PI;
255			else if (u_zenith == 0) {
256	greg	2.13	if (overcast)
257	greg	1.1	zenithbr = 8.6*sundir[2] + .123;
258	greg	2.12	else
259	greg	1.1	zenithbr = (1.376turbidity-1.81)tan(altitude)+0.38;
260	greg	2.13	if (skytype == S_INTER)
261			zenithbr = (zenithbr + 8.6*sundir[2] + .123)/2.0;
262	greg	2.12	if (zenithbr < 0.0)
263			zenithbr = 0.0;
264			else
265	greg	1.6	zenithbr *= 1000.0/SKYEFFICACY;
266	greg	2.12	}
267	greg	1.1	/* Compute horizontal radiance */
268	greg	2.12	groundbr = zenithbr*normfactor;
269	greg	2.13	printf("# Ground ambient level: %.1f\n", groundbr);
270	greg	2.14	if (!overcast && sundir[2] > 0.0 && (!u_solar \|\| solarbr > 0.0)) {
271	greg	2.12	if (u_solar == -1)
272	greg	2.30	solarbr /= 5.98e-5*sundir[2];
273	greg	2.13	else if (u_solar == 0) {
274	greg	2.12	solarbr = 1.5e9/SUNEFFICACY *
275			(1.147 - .147/(sundir[2]>.16?sundir[2]:.16));
276	greg	2.13	if (skytype == S_INTER)
277			solarbr = 0.15; / fudge factor! */
278			}
279	greg	2.12	groundbr += 6e-5/PIsolarbrsundir[2];
280			} else
281			dosun = 0;
282	greg	1.1	groundbr *= gprefl;
283			}
284
285
286	schorsch	2.22	void
287			printsky(void) /* print out sky */
288	greg	1.1	{
289			if (dosun) {
290			printf("\nvoid light solar\n");
291			printf("0\n0\n");
292	greg	2.29	printf("3 %.3e %.3e %.3e\n", solarbr, solarbr, solarbr);
293	greg	1.1	printf("\nsolar source sun\n");
294			printf("0\n0\n");
295			printf("4 %f %f %f 0.5\n", sundir[0], sundir[1], sundir[2]);
296			}
297
298			printf("\nvoid brightfunc skyfunc\n");
299	greg	2.13	printf("2 skybr skybright.cal\n");
300	greg	1.1	printf("0\n");
301	greg	2.13	if (overcast)
302	greg	2.29	printf("3 %d %.3e %.3e\n", skytype, zenithbr, groundbr);
303	greg	1.1	else
304	greg	2.29	printf("7 %d %.3e %.3e %.3e %f %f %f\n",
305	greg	2.13	skytype, zenithbr, groundbr, F2,
306			sundir[0], sundir[1], sundir[2]);
307	greg	1.1	}
308
309
310	schorsch	2.22	void
311			printdefaults(void) /* print default values */
312	greg	1.1	{
313	greg	2.13	switch (skytype) {
314			case S_OVER:
315	greg	1.1	printf("-c\t\t\t\t# Cloudy sky\n");
316	greg	2.13	break;
317			case S_UNIF:
318			printf("-u\t\t\t\t# Uniform cloudy sky\n");
319			break;
320			case S_INTER:
321			if (dosun)
322			printf("+i\t\t\t\t# Intermediate sky with sun\n");
323			else
324			printf("-i\t\t\t\t# Intermediate sky without sun\n");
325			break;
326			case S_CLEAR:
327			if (dosun)
328			printf("+s\t\t\t\t# Sunny sky with sun\n");
329			else
330			printf("-s\t\t\t\t# Sunny sky without sun\n");
331			break;
332			}
333	greg	1.1	printf("-g %f\t\t\t# Ground plane reflectance\n", gprefl);
334			if (zenithbr > 0.0)
335			printf("-b %f\t\t\t# Zenith radiance (watts/ster/m2\n", zenithbr);
336			else
337			printf("-t %f\t\t\t# Atmospheric turbidity\n", turbidity);
338			printf("-a %f\t\t\t# Site latitude (degrees)\n", s_latitude*(180/PI));
339			printf("-o %f\t\t\t# Site longitude (degrees)\n", s_longitude*(180/PI));
340			printf("-m %f\t\t\t# Standard meridian (degrees)\n", s_meridian*(180/PI));
341			}
342
343
344	schorsch	2.22	void
345			userror( /* print usage error and quit */
346			char *msg
347			)
348	greg	1.1	{
349			if (msg != NULL)
350			fprintf(stderr, "%s: Use error - %s\n", progname, msg);
351			fprintf(stderr, "Usage: %s month day hour [options]\n", progname);
352	greg	2.3	fprintf(stderr, " Or: %s -ang altitude azimuth [options]\n", progname);
353	greg	1.1	fprintf(stderr, " Or: %s -defaults\n", progname);
354			exit(1);
355			}
356
357
358			double
359	schorsch	2.22	normsc(void) /* compute normalization factor (E0F2/L0) /
360	greg	1.1	{
361	greg	2.13	static double nfc[2][5] = {
362			/* clear sky approx. */
363			{2.766521, 0.547665, -0.369832, 0.009237, 0.059229},
364			/* intermediate sky approx. */
365			{3.5556, -2.7152, -1.3081, 1.0660, 0.60227},
366			};
367	greg	2.26	double *nf;
368	greg	1.1	double x, nsc;
369	greg	2.26	int i;
370	greg	1.1	/* polynomial approximation */
371	greg	2.13	nf = nfc[skytype==S_INTER];
372			x = (altitude - PI/4.0)/(PI/4.0);
373			nsc = nf[i=4];
374			while (i--)
375	greg	1.1	nsc = nsc*x + nf[i];
376
377			return(nsc);
378	greg	2.16	}
379
380
381	greg	2.23	int
382	schorsch	2.22	cvthour( /* convert hour string */
383			char *hs
384			)
385	greg	2.16	{
386	greg	2.26	char *cp = hs;
387			int i, j;
388	greg	2.16
389	schorsch	2.21	if ( (tsolar = cp == '+') ) cp++; / solar time? */
390	greg	2.17	while (isdigit(*cp)) cp++;
391			if (*cp == ':')
392			hour = atoi(hs) + atoi(++cp)/60.0;
393			else {
394	greg	2.16	hour = atof(hs);
395	greg	2.17	if (*cp == '.') cp++;
396			}
397			while (isdigit(*cp)) cp++;
398			if (!*cp)
399	greg	2.23	return(0);
400	greg	2.17	if (tsolar \|\| !isalpha(*cp)) {
401			fprintf(stderr, "%s: bad time format: %s\n", progname, hs);
402			exit(1);
403			}
404			i = 0;
405			do {
406			for (j = 0; cp[j]; j++)
407			if (toupper(cp[j]) != tzone[i].zname[j])
408			break;
409			if (!cp[j] && !tzone[i].zname[j]) {
410			s_meridian = tzone[i].zmer * (PI/180);
411	greg	2.23	return(1);
412	greg	2.17	}
413			} while (tzone[i++].zname[0]);
414
415			fprintf(stderr, "%s: unknown time zone: %s\n", progname, cp);
416			fprintf(stderr, "Known time zones:\n\t%s", tzone[0].zname);
417			for (i = 1; tzone[i].zname[0]; i++)
418			fprintf(stderr, " %s", tzone[i].zname);
419			putc('\n', stderr);
420			exit(1);
421	greg	1.1	}