src/gen/gensky.c

/* Copyright (c) 1986 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;                                   /* standard time */
double  altitude, azimuth;                      /* or solar angles */
                                        /* default values */
int  cloudy = 0;
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;

char  *progname;
char  errmsg[128];


main(argc, argv)
int  argc;
char  *argv[];
{
        extern double  fabs();
        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]);
                day = atoi(argv[2]);
                hour = atof(argv[3]);
        }
        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 'c':
                                cloudy = 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 */
                st = hour + stadj(jd);          /* solar time */
                altitude = salt(sd, st);
                azimuth = sazi(sd, st);
        }
        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/SKYEFFICACY;
                } 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) {
                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(PI/2.0-altitude)/F2/PI;
                printf("# Ground ambient level: %f\n", groundbr);
                if (sundir[2] > 0.0) {
                        if (sundir[2] > .16)
                                solarbr = (1.5e9/SUNEFFICACY) *
                                        (1.147 - .147/sundir[2]);
                        else
                                solarbr = 1.5e9/SUNEFFICACY*(1.147-.147/.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 1 %.2e %.2e\n", 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)
                printf("-c\t\t\t\t# 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:	2.3
Committed:	Tue Mar 10 11:12:06 1992 UTC (33 years, 8 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.2:	+23 -13 lines
Log Message:	added -ang option for specifying solar angles explicitly
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1986 Regents of the University of California */
2
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			double hour; /* standard time */
40			double altitude, azimuth; /* or solar angles */
41	greg	1.1	/* default values */
42			int cloudy = 0;
43			int dosun = 1;
44			double zenithbr = -1.0;
45			double turbidity = 2.75;
46			double gprefl = 0.2;
47			/* computed values */
48			double sundir[3];
49			double groundbr;
50			double F2;
51			double solarbr;
52
53			char *progname;
54			char errmsg[128];
55
56
57			main(argc, argv)
58			int argc;
59			char *argv[];
60			{
61	greg	2.2	extern double fabs();
62	greg	1.1	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			day = atoi(argv[2]);
78			hour = atof(argv[3]);
79			}
80	greg	1.1	for (i = 4; i < argc; i++)
81			if (argv[i][0] == '-' \|\| argv[i][0] == '+')
82			switch (argv[i][1]) {
83			case 's':
84			cloudy = 0;
85			dosun = argv[i][0] == '+';
86			break;
87			case 'c':
88			cloudy = 1;
89			dosun = 0;
90			break;
91			case 't':
92			turbidity = atof(argv[++i]);
93			break;
94			case 'b':
95			zenithbr = atof(argv[++i]);
96			break;
97			case 'g':
98			gprefl = atof(argv[++i]);
99			break;
100			case 'a':
101			s_latitude = atof(argv[++i]) * (PI/180);
102			break;
103			case 'o':
104			s_longitude = atof(argv[++i]) * (PI/180);
105			break;
106			case 'm':
107			s_meridian = atof(argv[++i]) * (PI/180);
108			break;
109			default:
110			sprintf(errmsg, "unknown option: %s", argv[i]);
111			userror(errmsg);
112			}
113			else
114			userror("bad option");
115	greg	1.5
116			if (fabs(s_meridian-s_longitude) > 30*PI/180)
117			fprintf(stderr,
118			"%s: warning: %.1f hours btwn. standard meridian and longitude\n",
119			progname, (s_longitude-s_meridian)*12/PI);
120	greg	1.1
121			printhead(argc, argv);
122
123			computesky();
124			printsky();
125			}
126
127
128			computesky() /* compute sky parameters */
129			{
130			/* compute solar direction */
131	greg	2.3	if (month) { /* from date and time */
132			int jd;
133			double sd, st;
134
135			jd = jdate(month, day); /* Julian date */
136			sd = sdec(jd); /* solar declination */
137			st = hour + stadj(jd); /* solar time */
138			altitude = salt(sd, st);
139			azimuth = sazi(sd, st);
140			}
141	greg	1.1	sundir[0] = -sin(azimuth)*cos(altitude);
142			sundir[1] = -cos(azimuth)*cos(altitude);
143			sundir[2] = sin(altitude);
144
145			/* Compute zenith brightness */
146			if (zenithbr <= 0.0)
147			if (cloudy) {
148			zenithbr = 8.6*sundir[2] + .123;
149	greg	1.6	zenithbr *= 1000.0/SKYEFFICACY;
150	greg	1.1	} else {
151			zenithbr = (1.376turbidity-1.81)tan(altitude)+0.38;
152	greg	1.6	zenithbr *= 1000.0/SKYEFFICACY;
153	greg	1.1	}
154	greg	1.2	if (zenithbr < 0.0)
155			zenithbr = 0.0;
156	greg	1.1	/* Compute horizontal radiance */
157			if (cloudy) {
158			groundbr = zenithbr*0.777778;
159			printf("# Ground ambient level: %f\n", groundbr);
160			} else {
161			F2 = 0.274(0.91 + 10.0exp(-3.0*(PI/2.0-altitude)) +
162			0.45sundir[2]sundir[2]);
163			groundbr = zenithbr*normsc(PI/2.0-altitude)/F2/PI;
164			printf("# Ground ambient level: %f\n", groundbr);
165			if (sundir[2] > 0.0) {
166			if (sundir[2] > .16)
167	greg	1.6	solarbr = (1.5e9/SUNEFFICACY) *
168			(1.147 - .147/sundir[2]);
169	greg	1.1	else
170	greg	1.6	solarbr = 1.5e9/SUNEFFICACY*(1.147-.147/.16);
171	greg	1.1	groundbr += solarbr6e-5sundir[2]/PI;
172			} else
173			dosun = 0;
174			}
175			groundbr *= gprefl;
176			}
177
178
179			printsky() /* print out sky */
180			{
181			if (dosun) {
182			printf("\nvoid light solar\n");
183			printf("0\n0\n");
184	greg	1.6	printf("3 %.2e %.2e %.2e\n", solarbr, solarbr, solarbr);
185	greg	1.1	printf("\nsolar source sun\n");
186			printf("0\n0\n");
187			printf("4 %f %f %f 0.5\n", sundir[0], sundir[1], sundir[2]);
188			}
189
190			printf("\nvoid brightfunc skyfunc\n");
191			printf("2 skybright skybright.cal\n");
192			printf("0\n");
193			if (cloudy)
194	greg	1.6	printf("3 1 %.2e %.2e\n", zenithbr, groundbr);
195	greg	1.1	else
196	greg	1.6	printf("7 -1 %.2e %.2e %.2e %f %f %f\n", zenithbr, groundbr,
197			F2, sundir[0], sundir[1], sundir[2]);
198	greg	1.1	}
199
200
201			printdefaults() /* print default values */
202			{
203			if (cloudy)
204			printf("-c\t\t\t\t# Cloudy sky\n");
205			else if (dosun)
206			printf("+s\t\t\t\t# Sunny sky with sun\n");
207			else
208			printf("-s\t\t\t\t# Sunny sky without sun\n");
209			printf("-g %f\t\t\t# Ground plane reflectance\n", gprefl);
210			if (zenithbr > 0.0)
211			printf("-b %f\t\t\t# Zenith radiance (watts/ster/m2\n", zenithbr);
212			else
213			printf("-t %f\t\t\t# Atmospheric turbidity\n", turbidity);
214			printf("-a %f\t\t\t# Site latitude (degrees)\n", s_latitude*(180/PI));
215			printf("-o %f\t\t\t# Site longitude (degrees)\n", s_longitude*(180/PI));
216			printf("-m %f\t\t\t# Standard meridian (degrees)\n", s_meridian*(180/PI));
217			}
218
219
220			userror(msg) /* print usage error and quit */
221			char *msg;
222			{
223			if (msg != NULL)
224			fprintf(stderr, "%s: Use error - %s\n", progname, msg);
225			fprintf(stderr, "Usage: %s month day hour [options]\n", progname);
226	greg	2.3	fprintf(stderr, " Or: %s -ang altitude azimuth [options]\n", progname);
227	greg	1.1	fprintf(stderr, " Or: %s -defaults\n", progname);
228			exit(1);
229			}
230
231
232			double
233			normsc(theta) /* compute normalization factor (E0F2/L0) /
234			double theta;
235			{
236			static double nf[5] = {2.766521, 0.547665,
237			-0.369832, 0.009237, 0.059229};
238			double x, nsc;
239			register int i;
240			/* polynomial approximation */
241			x = (theta - PI/4.0)/(PI/4.0);
242			nsc = nf[4];
243			for (i = 3; i >= 0; i--)
244			nsc = nsc*x + nf[i];
245
246			return(nsc);
247			}
248
249
250			printhead(ac, av) /* print command header */
251			register int ac;
252			register char **av;
253			{
254			putchar('#');
255			while (ac--) {
256			putchar(' ');
257			fputs(*av++, stdout);
258			}
259			putchar('\n');
260			}