src/gen/gensky.c

/* Copyright (c) 1992 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#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  <math.h>

#include  "color.h"

#ifndef atof
extern double  atof();
#endif
extern char  *strcpy(), *strcat(), *malloc();
extern double  stadj(), sdec(), sazi(), salt();

#define  PI             3.141592654

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

double  normsc();
                                        /* sun calculation constants */
extern double  s_latitude;
extern double  s_longitude;
extern double  s_meridian;
                                        /* required values */
int  month, day;                                /* date */
double  hour;                                   /* time */
int  tsolar;                                    /* 0=standard, 1=solar */
double  altitude, azimuth;                      /* or solar angles */
                                        /* default values */
int  cloudy = 0;                                /* 1=standard, 2=uniform */
int  dosun = 1;
double  zenithbr = -1.0;
double  turbidity = 2.75;
double  gprefl = 0.2;
                                        /* computed values */
double  sundir[3];
double  groundbr;
double  F2;
double  solarbr = -1.0;

char  *progname;
char  errmsg[128];


main(argc, argv)
int  argc;
char  *argv[];
{
        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");
                hour = atof(argv[3]);
                if (hour < 0 || hour >= 24)
                        userror("bad hour");
                tsolar = argv[3][0] == '+';
        }
        for (i = 4; i < argc; i++)
                if (argv[i][0] == '-' || argv[i][0] == '+')
                        switch (argv[i][1]) {
                        case 's':
                                cloudy = 0;
                                dosun = argv[i][0] == '+';
                                break;
                        case 'r':
                                solarbr = atof(argv[++i]);
                                break;
                        case 'c':
                                cloudy = argv[i][0] == '+' ? 2 : 1;
                                dosun = 0;
                                break;
                        case 't':
                                turbidity = atof(argv[++i]);
                                break;
                        case 'b':
                                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':
                                s_meridian = atof(argv[++i]) * (PI/180);
                                break;
                        default:
                                sprintf(errmsg, "unknown option: %s", argv[i]);
                                userror(errmsg);
                        }
                else
                        userror("bad option");

        if (fabs(s_meridian-s_longitude) > 30*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();
}


computesky()                    /* compute sky parameters */
{
                                        /* compute solar direction */
        if (month) {                    /* from date and time */
                int  jd;
                double  sd, st;

                jd = jdate(month, day);         /* Julian date */
                sd = sdec(jd);                  /* solar declination */
                if (tsolar)                     /* solar time */
                        st = hour;
                else
                        st = hour + stadj(jd);
                altitude = salt(sd, st);
                azimuth = sazi(sd, st);
        }
        if (!cloudy && 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 zenith brightness */
        if (zenithbr <= 0.0)
                if (cloudy) {
                        zenithbr = 8.6*sundir[2] + .123;
                        zenithbr *= 1000.0/WHTEFFICACY;
                } else {
                        zenithbr = (1.376*turbidity-1.81)*tan(altitude)+0.38;
                        zenithbr *= 1000.0/SKYEFFICACY;
                }
        if (zenithbr < 0.0)
                zenithbr = 0.0;
                                        /* Compute horizontal radiance */
        if (cloudy) {
                if (cloudy == 2)
                        groundbr = zenithbr;
                else
                        groundbr = zenithbr*0.777778;
                printf("# Ground ambient level: %f\n", groundbr);
        } else {
                F2 = 0.274*(0.91 + 10.0*exp(-3.0*(PI/2.0-altitude)) +
                                0.45*sundir[2]*sundir[2]);
                groundbr = zenithbr*normsc(altitude)/F2/PI;
                printf("# Ground ambient level: %f\n", groundbr);
                if (sundir[2] > 0.0 && solarbr != 0.0) {
                        if (solarbr < 0.0)
                                solarbr = 1.5e9/SUNEFFICACY *
                                (1.147 - .147/(sundir[2]>.16?sundir[2]:.16));
                        groundbr += solarbr*6e-5*sundir[2]/PI;
                } else
                        dosun = 0;
        }
        groundbr *= gprefl;
}


printsky()                      /* 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 skybright skybright.cal\n");
        printf("0\n");
        if (cloudy)
                printf("3 %d %.2e %.2e\n", cloudy, zenithbr, groundbr);
        else
                printf("7 -1 %.2e %.2e %.2e %f %f %f\n", zenithbr, groundbr,
                                F2, sundir[0], sundir[1], sundir[2]);
}


printdefaults()                 /* print default values */
{
        if (cloudy == 1)
                printf("-c\t\t\t\t# Cloudy sky\n");
        else if (cloudy == 2)
                printf("+c\t\t\t\t# Uniform cloudy sky\n");
        else 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");
        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));
}


userror(msg)                    /* 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(theta)                   /* compute normalization factor (E0*F2/L0) */
double  theta;
{
        static double  nf[5] = {2.766521, 0.547665,
                                -0.369832, 0.009237, 0.059229};
        double  x, nsc;
        register int  i;
                                        /* polynomial approximation */
        x = (theta - PI/4.0)/(PI/4.0);
        nsc = nf[4];
        for (i = 3; i >= 0; i--)
                nsc = nsc*x + nf[i];

        return(nsc);
}


printhead(ac, av)               /* print command header */
register int  ac;
register char  **av;
{
        putchar('#');
        while (ac--) {
                putchar(' ');
                fputs(*av++, stdout);
        }
        putchar('\n');
}
Revision:	2.9
Committed:	Wed Dec 9 08:32:52 1992 UTC (31 years, 4 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.8:	+9 -1 lines
Log Message:	Added protection against sun too close to zenith
#	User	Rev	Content
1	greg	2.9	/* Copyright (c) 1992 Regents of the University of California */
2	greg	1.1
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* gensky.c - program to generate sky functions.
9			* Our zenith is along the Z-axis, the X-axis
10			* points east, and the Y-axis points north.
11			* Radiance is in watts/steradian/sq. meter.
12			*
13			* 3/26/86
14			*/
15
16			#include <stdio.h>
17
18			#include <math.h>
19
20	greg	1.6	#include "color.h"
21	greg	1.1
22	greg	2.2	#ifndef atof
23			extern double atof();
24			#endif
25	greg	1.1	extern char strcpy(), strcat(), *malloc();
26			extern double stadj(), sdec(), sazi(), salt();
27
28			#define PI 3.141592654
29
30			#define DOT(v1,v2) (v1[0]v2[0]+v1[1]v2[1]+v1[2]*v2[2])
31
32			double normsc();
33			/* sun calculation constants */
34			extern double s_latitude;
35			extern double s_longitude;
36			extern double s_meridian;
37			/* required values */
38	greg	2.3	int month, day; /* date */
39	greg	2.5	double hour; /* time */
40			int tsolar; /* 0=standard, 1=solar */
41	greg	2.3	double altitude, azimuth; /* or solar angles */
42	greg	1.1	/* default values */
43	greg	2.4	int cloudy = 0; /* 1=standard, 2=uniform */
44	greg	1.1	int dosun = 1;
45			double zenithbr = -1.0;
46			double turbidity = 2.75;
47			double gprefl = 0.2;
48			/* computed values */
49			double sundir[3];
50			double groundbr;
51			double F2;
52	greg	2.8	double solarbr = -1.0;
53	greg	1.1
54			char *progname;
55			char errmsg[128];
56
57
58			main(argc, argv)
59			int argc;
60			char *argv[];
61			{
62			int i;
63
64			progname = argv[0];
65			if (argc == 2 && !strcmp(argv[1], "-defaults")) {
66			printdefaults();
67			exit(0);
68			}
69			if (argc < 4)
70			userror("arg count");
71	greg	2.3	if (!strcmp(argv[1], "-ang")) {
72			altitude = atof(argv[2]) * (PI/180);
73			azimuth = atof(argv[3]) * (PI/180);
74			month = 0;
75			} else {
76			month = atoi(argv[1]);
77	greg	2.6	if (month < 1 \|\| month > 12)
78			userror("bad month");
79	greg	2.3	day = atoi(argv[2]);
80	greg	2.6	if (day < 1 \|\| day > 31)
81			userror("bad day");
82	greg	2.3	hour = atof(argv[3]);
83	greg	2.6	if (hour < 0 \|\| hour >= 24)
84			userror("bad hour");
85	greg	2.5	tsolar = argv[3][0] == '+';
86	greg	2.3	}
87	greg	1.1	for (i = 4; i < argc; i++)
88			if (argv[i][0] == '-' \|\| argv[i][0] == '+')
89			switch (argv[i][1]) {
90			case 's':
91			cloudy = 0;
92			dosun = argv[i][0] == '+';
93			break;
94	greg	2.8	case 'r':
95			solarbr = atof(argv[++i]);
96			break;
97	greg	1.1	case 'c':
98	greg	2.4	cloudy = argv[i][0] == '+' ? 2 : 1;
99	greg	1.1	dosun = 0;
100			break;
101			case 't':
102			turbidity = atof(argv[++i]);
103			break;
104			case 'b':
105			zenithbr = atof(argv[++i]);
106			break;
107			case 'g':
108			gprefl = atof(argv[++i]);
109			break;
110			case 'a':
111			s_latitude = atof(argv[++i]) * (PI/180);
112			break;
113			case 'o':
114			s_longitude = atof(argv[++i]) * (PI/180);
115			break;
116			case 'm':
117			s_meridian = atof(argv[++i]) * (PI/180);
118			break;
119			default:
120			sprintf(errmsg, "unknown option: %s", argv[i]);
121			userror(errmsg);
122			}
123			else
124			userror("bad option");
125	greg	1.5
126			if (fabs(s_meridian-s_longitude) > 30*PI/180)
127			fprintf(stderr,
128			"%s: warning: %.1f hours btwn. standard meridian and longitude\n",
129			progname, (s_longitude-s_meridian)*12/PI);
130	greg	1.1
131			printhead(argc, argv);
132
133			computesky();
134			printsky();
135			}
136
137
138			computesky() /* compute sky parameters */
139			{
140			/* compute solar direction */
141	greg	2.3	if (month) { /* from date and time */
142			int jd;
143			double sd, st;
144
145			jd = jdate(month, day); /* Julian date */
146			sd = sdec(jd); /* solar declination */
147	greg	2.5	if (tsolar) /* solar time */
148			st = hour;
149			else
150			st = hour + stadj(jd);
151	greg	2.3	altitude = salt(sd, st);
152			azimuth = sazi(sd, st);
153	greg	2.9	}
154			if (!cloudy && altitude > 87.*PI/180.) {
155			fprintf(stderr,
156			"%s: warning - sun too close to zenith, reducing altitude to 87 degrees\n",
157			progname);
158			printf(
159			"# warning - sun too close to zenith, reducing altitude to 87 degrees\n");
160			altitude = 87.*PI/180.;
161	greg	2.3	}
162	greg	1.1	sundir[0] = -sin(azimuth)*cos(altitude);
163			sundir[1] = -cos(azimuth)*cos(altitude);
164			sundir[2] = sin(altitude);
165
166			/* Compute zenith brightness */
167			if (zenithbr <= 0.0)
168			if (cloudy) {
169			zenithbr = 8.6*sundir[2] + .123;
170	greg	2.6	zenithbr *= 1000.0/WHTEFFICACY;
171	greg	1.1	} else {
172			zenithbr = (1.376turbidity-1.81)tan(altitude)+0.38;
173	greg	1.6	zenithbr *= 1000.0/SKYEFFICACY;
174	greg	1.1	}
175	greg	1.2	if (zenithbr < 0.0)
176			zenithbr = 0.0;
177	greg	1.1	/* Compute horizontal radiance */
178			if (cloudy) {
179	greg	2.4	if (cloudy == 2)
180			groundbr = zenithbr;
181			else
182			groundbr = zenithbr*0.777778;
183	greg	1.1	printf("# Ground ambient level: %f\n", groundbr);
184			} else {
185			F2 = 0.274(0.91 + 10.0exp(-3.0*(PI/2.0-altitude)) +
186			0.45sundir[2]sundir[2]);
187	greg	2.6	groundbr = zenithbr*normsc(altitude)/F2/PI;
188	greg	1.1	printf("# Ground ambient level: %f\n", groundbr);
189	greg	2.8	if (sundir[2] > 0.0 && solarbr != 0.0) {
190			if (solarbr < 0.0)
191			solarbr = 1.5e9/SUNEFFICACY *
192			(1.147 - .147/(sundir[2]>.16?sundir[2]:.16));
193	greg	1.1	groundbr += solarbr6e-5sundir[2]/PI;
194			} else
195			dosun = 0;
196			}
197			groundbr *= gprefl;
198			}
199
200
201			printsky() /* print out sky */
202			{
203			if (dosun) {
204			printf("\nvoid light solar\n");
205			printf("0\n0\n");
206	greg	1.6	printf("3 %.2e %.2e %.2e\n", solarbr, solarbr, solarbr);
207	greg	1.1	printf("\nsolar source sun\n");
208			printf("0\n0\n");
209			printf("4 %f %f %f 0.5\n", sundir[0], sundir[1], sundir[2]);
210			}
211
212			printf("\nvoid brightfunc skyfunc\n");
213			printf("2 skybright skybright.cal\n");
214			printf("0\n");
215			if (cloudy)
216	greg	2.4	printf("3 %d %.2e %.2e\n", cloudy, zenithbr, groundbr);
217	greg	1.1	else
218	greg	1.6	printf("7 -1 %.2e %.2e %.2e %f %f %f\n", zenithbr, groundbr,
219			F2, sundir[0], sundir[1], sundir[2]);
220	greg	1.1	}
221
222
223			printdefaults() /* print default values */
224			{
225	greg	2.4	if (cloudy == 1)
226	greg	1.1	printf("-c\t\t\t\t# Cloudy sky\n");
227	greg	2.4	else if (cloudy == 2)
228			printf("+c\t\t\t\t# Uniform cloudy sky\n");
229	greg	1.1	else if (dosun)
230			printf("+s\t\t\t\t# Sunny sky with sun\n");
231			else
232			printf("-s\t\t\t\t# Sunny sky without sun\n");
233			printf("-g %f\t\t\t# Ground plane reflectance\n", gprefl);
234			if (zenithbr > 0.0)
235			printf("-b %f\t\t\t# Zenith radiance (watts/ster/m2\n", zenithbr);
236			else
237			printf("-t %f\t\t\t# Atmospheric turbidity\n", turbidity);
238			printf("-a %f\t\t\t# Site latitude (degrees)\n", s_latitude*(180/PI));
239			printf("-o %f\t\t\t# Site longitude (degrees)\n", s_longitude*(180/PI));
240			printf("-m %f\t\t\t# Standard meridian (degrees)\n", s_meridian*(180/PI));
241			}
242
243
244			userror(msg) /* print usage error and quit */
245			char *msg;
246			{
247			if (msg != NULL)
248			fprintf(stderr, "%s: Use error - %s\n", progname, msg);
249			fprintf(stderr, "Usage: %s month day hour [options]\n", progname);
250	greg	2.3	fprintf(stderr, " Or: %s -ang altitude azimuth [options]\n", progname);
251	greg	1.1	fprintf(stderr, " Or: %s -defaults\n", progname);
252			exit(1);
253			}
254
255
256			double
257			normsc(theta) /* compute normalization factor (E0F2/L0) /
258			double theta;
259			{
260			static double nf[5] = {2.766521, 0.547665,
261			-0.369832, 0.009237, 0.059229};
262			double x, nsc;
263			register int i;
264			/* polynomial approximation */
265			x = (theta - PI/4.0)/(PI/4.0);
266			nsc = nf[4];
267			for (i = 3; i >= 0; i--)
268			nsc = nsc*x + nf[i];
269
270			return(nsc);
271			}
272
273
274			printhead(ac, av) /* print command header */
275			register int ac;
276			register char **av;
277			{
278			putchar('#');
279			while (ac--) {
280			putchar(' ');
281			fputs(*av++, stdout);
282			}
283			putchar('\n');
284			}