src/gen/gensky.c

#ifndef lint
static const char       RCSid[] = "$Id: gensky.c,v 2.26 2014/07/30 17:30:27 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  <stdio.h>
#include  <stdlib.h>
#include  <string.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);
void printhead(int  ac, char  **av);


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);

        printhead(argc, argv);

        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 /= 6e-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 %.2e %.2e %.2e\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 %.2e %.2e\n", skytype, zenithbr, groundbr);
        else
                printf("7 %d %.2e %.2e %.2e %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);
}


void
printhead(              /* print command header */
        int  ac,
        char  **av
)
{
        putchar('#');
        while (ac--) {
                putchar(' ');
                fputs(*av++, stdout);
        }
        putchar('\n');
}
Revision:	2.27
Committed:	Thu Nov 7 23:15:07 2019 UTC (4 years, 5 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.26:	+22 -9 lines
Log Message:	Added more accurate Michalsky solar position calculation and made correction to old IES handbook formula (thanks to Axel Jacobs)
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.27	static const char RCSid[] = "$Id: gensky.c,v 2.26 2014/07/30 17:30:27 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			#include <stdio.h>
14	greg	2.20	#include <stdlib.h>
15			#include <string.h>
16	greg	1.1	#include <math.h>
17	greg	2.17	#include <ctype.h>
18	greg	2.26	#include "sun.h"
19	greg	1.6	#include "color.h"
20	greg	1.1
21	greg	2.17	#ifndef PI
22			#define PI 3.14159265358979323846
23			#endif
24	greg	1.1
25			#define DOT(v1,v2) (v1[0]v2[0]+v1[1]v2[1]+v1[2]*v2[2])
26
27	greg	2.13	#define S_CLEAR 1
28			#define S_OVER 2
29			#define S_UNIF 3
30			#define S_INTER 4
31
32	schorsch	2.21	#define overcast ((skytype==S_OVER)\|(skytype==S_UNIF))
33	greg	2.13
34	greg	1.1	double normsc();
35	greg	2.17
36			#undef toupper
37			#define toupper(c) ((c) & ~0x20) /* ASCII trick to convert case */
38
39			/* European and North American zones */
40			struct {
41			char zname[8]; /* time zone name (all caps) */
42			float zmer; /* standard meridian */
43			} tzone[] = {
44	schorsch	2.22	{"YST", 135}, {"YDT", 120},
45			{"PST", 120}, {"PDT", 105},
46			{"MST", 105}, {"MDT", 90},
47			{"CST", 90}, {"CDT", 75},
48			{"EST", 75}, {"EDT", 60},
49			{"AST", 60}, {"ADT", 45},
50			{"NST", 52.5}, {"NDT", 37.5},
51			{"GMT", 0}, {"BST", -15},
52			{"CET", -15}, {"CEST", -30},
53			{"EET", -30}, {"EEST", -45},
54			{"AST", -45}, {"ADT", -60},
55			{"GST", -60}, {"GDT", -75},
56			{"IST", -82.5}, {"IDT", -97.5},
57			{"JST", -135}, {"NDT", -150},
58			{"NZST", -180}, {"NZDT", -195},
59			{"", 0}
60	greg	2.17	};
61	greg	1.1	/* required values */
62	greg	2.27	int year = 0; /* year (optional) */
63	greg	2.3	int month, day; /* date */
64	greg	2.5	double hour; /* time */
65			int tsolar; /* 0=standard, 1=solar */
66	greg	2.3	double altitude, azimuth; /* or solar angles */
67	greg	1.1	/* default values */
68	greg	2.13	int skytype = S_CLEAR; /* sky type */
69	greg	1.1	int dosun = 1;
70	greg	2.12	double zenithbr = 0.0;
71			int u_zenith = 0; /* -1=irradiance, 1=radiance */
72	greg	2.24	double turbidity = 2.45;
73	greg	1.1	double gprefl = 0.2;
74			/* computed values */
75			double sundir[3];
76			double groundbr;
77			double F2;
78	greg	2.12	double solarbr = 0.0;
79			int u_solar = 0; /* -1=irradiance, 1=radiance */
80	greg	1.1
81			char *progname;
82			char errmsg[128];
83
84	schorsch	2.22	void computesky(void);
85			void printsky(void);
86			void printdefaults(void);
87			void userror(char *msg);
88			double normsc(void);
89	greg	2.23	int cvthour(char *hs);
90	greg	2.26	void printhead(int ac, char **av);
91	schorsch	2.22
92	greg	1.1
93	schorsch	2.22	int
94	greg	2.26	main(
95			int argc,
96			char *argv[]
97			)
98	greg	1.1	{
99	greg	2.23	int got_meridian = 0;
100	greg	1.1	int i;
101
102			progname = argv[0];
103			if (argc == 2 && !strcmp(argv[1], "-defaults")) {
104			printdefaults();
105			exit(0);
106			}
107			if (argc < 4)
108			userror("arg count");
109	greg	2.3	if (!strcmp(argv[1], "-ang")) {
110			altitude = atof(argv[2]) * (PI/180);
111			azimuth = atof(argv[3]) * (PI/180);
112			month = 0;
113			} else {
114			month = atoi(argv[1]);
115	greg	2.6	if (month < 1 \|\| month > 12)
116			userror("bad month");
117	greg	2.3	day = atoi(argv[2]);
118	greg	2.6	if (day < 1 \|\| day > 31)
119			userror("bad day");
120	greg	2.23	got_meridian = cvthour(argv[3]);
121	greg	2.3	}
122	greg	1.1	for (i = 4; i < argc; i++)
123			if (argv[i][0] == '-' \|\| argv[i][0] == '+')
124			switch (argv[i][1]) {
125			case 's':
126	greg	2.13	skytype = S_CLEAR;
127	greg	1.1	dosun = argv[i][0] == '+';
128			break;
129	greg	2.27	case 'y':
130			year = atoi(argv[++i]);
131			break;
132	greg	2.8	case 'r':
133	greg	2.12	case 'R':
134			u_solar = argv[i][1]=='R' ? -1 : 1;
135	greg	2.8	solarbr = atof(argv[++i]);
136			break;
137	greg	1.1	case 'c':
138	greg	2.13	skytype = S_OVER;
139	greg	1.1	break;
140	greg	2.13	case 'u':
141			skytype = S_UNIF;
142			break;
143			case 'i':
144			skytype = S_INTER;
145			dosun = argv[i][0] == '+';
146			break;
147	greg	1.1	case 't':
148			turbidity = atof(argv[++i]);
149			break;
150			case 'b':
151	greg	2.12	case 'B':
152			u_zenith = argv[i][1]=='B' ? -1 : 1;
153	greg	1.1	zenithbr = atof(argv[++i]);
154			break;
155			case 'g':
156			gprefl = atof(argv[++i]);
157			break;
158			case 'a':
159			s_latitude = atof(argv[++i]) * (PI/180);
160			break;
161			case 'o':
162			s_longitude = atof(argv[++i]) * (PI/180);
163			break;
164			case 'm':
165	greg	2.23	if (got_meridian) {
166			++i;
167			break; /* time overrides */
168			}
169	greg	1.1	s_meridian = atof(argv[++i]) * (PI/180);
170			break;
171			default:
172			sprintf(errmsg, "unknown option: %s", argv[i]);
173			userror(errmsg);
174			}
175			else
176			userror("bad option");
177	greg	1.5
178	greg	2.27	if (year && (year < 1950) \| (year > 2050))
179			fprintf(stderr,
180			"%s: warning - year should be in range 1950-2050\n",
181			progname);
182	greg	2.25	if (month && !tsolar && fabs(s_meridian-s_longitude) > 45*PI/180)
183	greg	1.5	fprintf(stderr,
184	greg	2.25	"%s: warning - %.1f hours btwn. standard meridian and longitude\n",
185	greg	1.5	progname, (s_longitude-s_meridian)*12/PI);
186	greg	1.1
187			printhead(argc, argv);
188
189			computesky();
190			printsky();
191	greg	2.15
192			exit(0);
193	greg	1.1	}
194
195
196	schorsch	2.22	void
197			computesky(void) /* compute sky parameters */
198	greg	1.1	{
199	greg	2.12	double normfactor;
200	greg	1.1	/* compute solar direction */
201	greg	2.3	if (month) { /* from date and time */
202	greg	2.27	double sd, st = hour;
203	greg	2.3
204	greg	2.27	if (year) { /* Michalsky algorithm? */
205			double mjd = mjdate(year, month, day, hour);
206			if (tsolar)
207			sd = msdec(mjd, NULL);
208			else
209			sd = msdec(mjd, &st);
210			} else {
211			int jd = jdate(month, day); /* Julian date */
212			sd = sdec(jd); /* solar declination */
213			if (!tsolar) /* get solar time? */
214			st = hour + stadj(jd);
215			}
216	greg	2.3	altitude = salt(sd, st);
217			azimuth = sazi(sd, st);
218	greg	2.17	printf("# Local solar time: %.2f\n", st);
219	greg	2.13	printf("# Solar altitude and azimuth: %.1f %.1f\n",
220	greg	2.11	180./PIaltitude, 180./PIazimuth);
221	greg	2.9	}
222	greg	2.13	if (!overcast && altitude > 87.*PI/180.) {
223	greg	2.9	fprintf(stderr,
224			"%s: warning - sun too close to zenith, reducing altitude to 87 degrees\n",
225			progname);
226			printf(
227			"# warning - sun too close to zenith, reducing altitude to 87 degrees\n");
228			altitude = 87.*PI/180.;
229	greg	2.3	}
230	greg	1.1	sundir[0] = -sin(azimuth)*cos(altitude);
231			sundir[1] = -cos(azimuth)*cos(altitude);
232			sundir[2] = sin(altitude);
233
234	greg	2.12	/* Compute normalization factor */
235	greg	2.13	switch (skytype) {
236			case S_UNIF:
237	greg	2.12	normfactor = 1.0;
238	greg	2.13	break;
239			case S_OVER:
240	greg	2.12	normfactor = 0.777778;
241	greg	2.13	break;
242			case S_CLEAR:
243	greg	2.12	F2 = 0.274(0.91 + 10.0exp(-3.0*(PI/2.0-altitude)) +
244			0.45sundir[2]sundir[2]);
245	greg	2.13	normfactor = normsc()/F2/PI;
246			break;
247			case S_INTER:
248			F2 = (2.739 + .9891sin(.3119+2.6altitude)) *
249			exp(-(PI/2.0-altitude)(.4441+1.48altitude));
250			normfactor = normsc()/F2/PI;
251			break;
252	greg	2.12	}
253	greg	1.1	/* Compute zenith brightness */
254	greg	2.12	if (u_zenith == -1)
255			zenithbr /= normfactor*PI;
256			else if (u_zenith == 0) {
257	greg	2.13	if (overcast)
258	greg	1.1	zenithbr = 8.6*sundir[2] + .123;
259	greg	2.12	else
260	greg	1.1	zenithbr = (1.376turbidity-1.81)tan(altitude)+0.38;
261	greg	2.13	if (skytype == S_INTER)
262			zenithbr = (zenithbr + 8.6*sundir[2] + .123)/2.0;
263	greg	2.12	if (zenithbr < 0.0)
264			zenithbr = 0.0;
265			else
266	greg	1.6	zenithbr *= 1000.0/SKYEFFICACY;
267	greg	2.12	}
268	greg	1.1	/* Compute horizontal radiance */
269	greg	2.12	groundbr = zenithbr*normfactor;
270	greg	2.13	printf("# Ground ambient level: %.1f\n", groundbr);
271	greg	2.14	if (!overcast && sundir[2] > 0.0 && (!u_solar \|\| solarbr > 0.0)) {
272	greg	2.12	if (u_solar == -1)
273			solarbr /= 6e-5*sundir[2];
274	greg	2.13	else if (u_solar == 0) {
275	greg	2.12	solarbr = 1.5e9/SUNEFFICACY *
276			(1.147 - .147/(sundir[2]>.16?sundir[2]:.16));
277	greg	2.13	if (skytype == S_INTER)
278			solarbr = 0.15; / fudge factor! */
279			}
280	greg	2.12	groundbr += 6e-5/PIsolarbrsundir[2];
281			} else
282			dosun = 0;
283	greg	1.1	groundbr *= gprefl;
284			}
285
286
287	schorsch	2.22	void
288			printsky(void) /* print out sky */
289	greg	1.1	{
290			if (dosun) {
291			printf("\nvoid light solar\n");
292			printf("0\n0\n");
293	greg	1.6	printf("3 %.2e %.2e %.2e\n", solarbr, solarbr, solarbr);
294	greg	1.1	printf("\nsolar source sun\n");
295			printf("0\n0\n");
296			printf("4 %f %f %f 0.5\n", sundir[0], sundir[1], sundir[2]);
297			}
298
299			printf("\nvoid brightfunc skyfunc\n");
300	greg	2.13	printf("2 skybr skybright.cal\n");
301	greg	1.1	printf("0\n");
302	greg	2.13	if (overcast)
303			printf("3 %d %.2e %.2e\n", skytype, zenithbr, groundbr);
304	greg	1.1	else
305	greg	2.13	printf("7 %d %.2e %.2e %.2e %f %f %f\n",
306			skytype, zenithbr, groundbr, F2,
307			sundir[0], sundir[1], sundir[2]);
308	greg	1.1	}
309
310
311	schorsch	2.22	void
312			printdefaults(void) /* print default values */
313	greg	1.1	{
314	greg	2.13	switch (skytype) {
315			case S_OVER:
316	greg	1.1	printf("-c\t\t\t\t# Cloudy sky\n");
317	greg	2.13	break;
318			case S_UNIF:
319			printf("-u\t\t\t\t# Uniform cloudy sky\n");
320			break;
321			case S_INTER:
322			if (dosun)
323			printf("+i\t\t\t\t# Intermediate sky with sun\n");
324			else
325			printf("-i\t\t\t\t# Intermediate sky without sun\n");
326			break;
327			case S_CLEAR:
328			if (dosun)
329			printf("+s\t\t\t\t# Sunny sky with sun\n");
330			else
331			printf("-s\t\t\t\t# Sunny sky without sun\n");
332			break;
333			}
334	greg	1.1	printf("-g %f\t\t\t# Ground plane reflectance\n", gprefl);
335			if (zenithbr > 0.0)
336			printf("-b %f\t\t\t# Zenith radiance (watts/ster/m2\n", zenithbr);
337			else
338			printf("-t %f\t\t\t# Atmospheric turbidity\n", turbidity);
339			printf("-a %f\t\t\t# Site latitude (degrees)\n", s_latitude*(180/PI));
340			printf("-o %f\t\t\t# Site longitude (degrees)\n", s_longitude*(180/PI));
341			printf("-m %f\t\t\t# Standard meridian (degrees)\n", s_meridian*(180/PI));
342			}
343
344
345	schorsch	2.22	void
346			userror( /* print usage error and quit */
347			char *msg
348			)
349	greg	1.1	{
350			if (msg != NULL)
351			fprintf(stderr, "%s: Use error - %s\n", progname, msg);
352			fprintf(stderr, "Usage: %s month day hour [options]\n", progname);
353	greg	2.3	fprintf(stderr, " Or: %s -ang altitude azimuth [options]\n", progname);
354	greg	1.1	fprintf(stderr, " Or: %s -defaults\n", progname);
355			exit(1);
356			}
357
358
359			double
360	schorsch	2.22	normsc(void) /* compute normalization factor (E0F2/L0) /
361	greg	1.1	{
362	greg	2.13	static double nfc[2][5] = {
363			/* clear sky approx. */
364			{2.766521, 0.547665, -0.369832, 0.009237, 0.059229},
365			/* intermediate sky approx. */
366			{3.5556, -2.7152, -1.3081, 1.0660, 0.60227},
367			};
368	greg	2.26	double *nf;
369	greg	1.1	double x, nsc;
370	greg	2.26	int i;
371	greg	1.1	/* polynomial approximation */
372	greg	2.13	nf = nfc[skytype==S_INTER];
373			x = (altitude - PI/4.0)/(PI/4.0);
374			nsc = nf[i=4];
375			while (i--)
376	greg	1.1	nsc = nsc*x + nf[i];
377
378			return(nsc);
379	greg	2.16	}
380
381
382	greg	2.23	int
383	schorsch	2.22	cvthour( /* convert hour string */
384			char *hs
385			)
386	greg	2.16	{
387	greg	2.26	char *cp = hs;
388			int i, j;
389	greg	2.16
390	schorsch	2.21	if ( (tsolar = cp == '+') ) cp++; / solar time? */
391	greg	2.17	while (isdigit(*cp)) cp++;
392			if (*cp == ':')
393			hour = atoi(hs) + atoi(++cp)/60.0;
394			else {
395	greg	2.16	hour = atof(hs);
396	greg	2.17	if (*cp == '.') cp++;
397			}
398			while (isdigit(*cp)) cp++;
399			if (!*cp)
400	greg	2.23	return(0);
401	greg	2.17	if (tsolar \|\| !isalpha(*cp)) {
402			fprintf(stderr, "%s: bad time format: %s\n", progname, hs);
403			exit(1);
404			}
405			i = 0;
406			do {
407			for (j = 0; cp[j]; j++)
408			if (toupper(cp[j]) != tzone[i].zname[j])
409			break;
410			if (!cp[j] && !tzone[i].zname[j]) {
411			s_meridian = tzone[i].zmer * (PI/180);
412	greg	2.23	return(1);
413	greg	2.17	}
414			} while (tzone[i++].zname[0]);
415
416			fprintf(stderr, "%s: unknown time zone: %s\n", progname, cp);
417			fprintf(stderr, "Known time zones:\n\t%s", tzone[0].zname);
418			for (i = 1; tzone[i].zname[0]; i++)
419			fprintf(stderr, " %s", tzone[i].zname);
420			putc('\n', stderr);
421			exit(1);
422	greg	1.1	}
423
424
425	schorsch	2.22	void
426			printhead( /* print command header */
427	greg	2.26	int ac,
428			char **av
429	schorsch	2.22	)
430	greg	1.1	{
431			putchar('#');
432			while (ac--) {
433			putchar(' ');
434			fputs(*av++, stdout);
435			}
436			putchar('\n');
437			}