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"

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;
double  hour;
                                        /* 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  atof(), fabs();
        int  i;

        progname = argv[0];
        if (argc == 2 && !strcmp(argv[1], "-defaults")) {
                printdefaults();
                exit(0);
        }
        if (argc < 4)
                userror("arg count");
        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 */
{
        int  jd;
        double  sd, st;
        double  altitude, azimuth;
                                        /* compute solar direction */
        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 -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:	2.1
Committed:	Tue Nov 12 17:05:02 1991 UTC (32 years, 5 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.6:	+0 -0 lines
Log Message:	updated revision number for release 2.0
#	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			extern char strcpy(), strcat(), *malloc();
23			extern double stadj(), sdec(), sazi(), salt();
24
25			#define PI 3.141592654
26
27			#define DOT(v1,v2) (v1[0]v2[0]+v1[1]v2[1]+v1[2]*v2[2])
28
29			double normsc();
30			/* sun calculation constants */
31			extern double s_latitude;
32			extern double s_longitude;
33			extern double s_meridian;
34			/* required values */
35			int month, day;
36			double hour;
37			/* default values */
38			int cloudy = 0;
39			int dosun = 1;
40			double zenithbr = -1.0;
41			double turbidity = 2.75;
42			double gprefl = 0.2;
43			/* computed values */
44			double sundir[3];
45			double groundbr;
46			double F2;
47			double solarbr;
48
49			char *progname;
50			char errmsg[128];
51
52
53			main(argc, argv)
54			int argc;
55			char *argv[];
56			{
57	greg	1.5	extern double atof(), fabs();
58	greg	1.1	int i;
59
60			progname = argv[0];
61			if (argc == 2 && !strcmp(argv[1], "-defaults")) {
62			printdefaults();
63			exit(0);
64			}
65			if (argc < 4)
66			userror("arg count");
67			month = atoi(argv[1]);
68			day = atoi(argv[2]);
69			hour = atof(argv[3]);
70			for (i = 4; i < argc; i++)
71			if (argv[i][0] == '-' \|\| argv[i][0] == '+')
72			switch (argv[i][1]) {
73			case 's':
74			cloudy = 0;
75			dosun = argv[i][0] == '+';
76			break;
77			case 'c':
78			cloudy = 1;
79			dosun = 0;
80			break;
81			case 't':
82			turbidity = atof(argv[++i]);
83			break;
84			case 'b':
85			zenithbr = atof(argv[++i]);
86			break;
87			case 'g':
88			gprefl = atof(argv[++i]);
89			break;
90			case 'a':
91			s_latitude = atof(argv[++i]) * (PI/180);
92			break;
93			case 'o':
94			s_longitude = atof(argv[++i]) * (PI/180);
95			break;
96			case 'm':
97			s_meridian = atof(argv[++i]) * (PI/180);
98			break;
99			default:
100			sprintf(errmsg, "unknown option: %s", argv[i]);
101			userror(errmsg);
102			}
103			else
104			userror("bad option");
105	greg	1.5
106			if (fabs(s_meridian-s_longitude) > 30*PI/180)
107			fprintf(stderr,
108			"%s: warning: %.1f hours btwn. standard meridian and longitude\n",
109			progname, (s_longitude-s_meridian)*12/PI);
110	greg	1.1
111			printhead(argc, argv);
112
113			computesky();
114			printsky();
115			}
116
117
118			computesky() /* compute sky parameters */
119			{
120			int jd;
121			double sd, st;
122			double altitude, azimuth;
123			/* compute solar direction */
124			jd = jdate(month, day); /* Julian date */
125			sd = sdec(jd); /* solar declination */
126			st = hour + stadj(jd); /* solar time */
127			altitude = salt(sd, st);
128			azimuth = sazi(sd, st);
129			sundir[0] = -sin(azimuth)*cos(altitude);
130			sundir[1] = -cos(azimuth)*cos(altitude);
131			sundir[2] = sin(altitude);
132
133			/* Compute zenith brightness */
134			if (zenithbr <= 0.0)
135			if (cloudy) {
136			zenithbr = 8.6*sundir[2] + .123;
137	greg	1.6	zenithbr *= 1000.0/SKYEFFICACY;
138	greg	1.1	} else {
139			zenithbr = (1.376turbidity-1.81)tan(altitude)+0.38;
140	greg	1.6	zenithbr *= 1000.0/SKYEFFICACY;
141	greg	1.1	}
142	greg	1.2	if (zenithbr < 0.0)
143			zenithbr = 0.0;
144	greg	1.1	/* Compute horizontal radiance */
145			if (cloudy) {
146			groundbr = zenithbr*0.777778;
147			printf("# Ground ambient level: %f\n", groundbr);
148			} else {
149			F2 = 0.274(0.91 + 10.0exp(-3.0*(PI/2.0-altitude)) +
150			0.45sundir[2]sundir[2]);
151			groundbr = zenithbr*normsc(PI/2.0-altitude)/F2/PI;
152			printf("# Ground ambient level: %f\n", groundbr);
153			if (sundir[2] > 0.0) {
154			if (sundir[2] > .16)
155	greg	1.6	solarbr = (1.5e9/SUNEFFICACY) *
156			(1.147 - .147/sundir[2]);
157	greg	1.1	else
158	greg	1.6	solarbr = 1.5e9/SUNEFFICACY*(1.147-.147/.16);
159	greg	1.1	groundbr += solarbr6e-5sundir[2]/PI;
160			} else
161			dosun = 0;
162			}
163			groundbr *= gprefl;
164			}
165
166
167			printsky() /* print out sky */
168			{
169			if (dosun) {
170			printf("\nvoid light solar\n");
171			printf("0\n0\n");
172	greg	1.6	printf("3 %.2e %.2e %.2e\n", solarbr, solarbr, solarbr);
173	greg	1.1	printf("\nsolar source sun\n");
174			printf("0\n0\n");
175			printf("4 %f %f %f 0.5\n", sundir[0], sundir[1], sundir[2]);
176			}
177
178			printf("\nvoid brightfunc skyfunc\n");
179			printf("2 skybright skybright.cal\n");
180			printf("0\n");
181			if (cloudy)
182	greg	1.6	printf("3 1 %.2e %.2e\n", zenithbr, groundbr);
183	greg	1.1	else
184	greg	1.6	printf("7 -1 %.2e %.2e %.2e %f %f %f\n", zenithbr, groundbr,
185			F2, sundir[0], sundir[1], sundir[2]);
186	greg	1.1	}
187
188
189			printdefaults() /* print default values */
190			{
191			if (cloudy)
192			printf("-c\t\t\t\t# Cloudy sky\n");
193			else if (dosun)
194			printf("+s\t\t\t\t# Sunny sky with sun\n");
195			else
196			printf("-s\t\t\t\t# Sunny sky without sun\n");
197			printf("-g %f\t\t\t# Ground plane reflectance\n", gprefl);
198			if (zenithbr > 0.0)
199			printf("-b %f\t\t\t# Zenith radiance (watts/ster/m2\n", zenithbr);
200			else
201			printf("-t %f\t\t\t# Atmospheric turbidity\n", turbidity);
202			printf("-a %f\t\t\t# Site latitude (degrees)\n", s_latitude*(180/PI));
203			printf("-o %f\t\t\t# Site longitude (degrees)\n", s_longitude*(180/PI));
204			printf("-m %f\t\t\t# Standard meridian (degrees)\n", s_meridian*(180/PI));
205			}
206
207
208			userror(msg) /* print usage error and quit */
209			char *msg;
210			{
211			if (msg != NULL)
212			fprintf(stderr, "%s: Use error - %s\n", progname, msg);
213			fprintf(stderr, "Usage: %s month day hour [options]\n", progname);
214			fprintf(stderr, " Or: %s -defaults\n", progname);
215			exit(1);
216			}
217
218
219			double
220			normsc(theta) /* compute normalization factor (E0F2/L0) /
221			double theta;
222			{
223			static double nf[5] = {2.766521, 0.547665,
224			-0.369832, 0.009237, 0.059229};
225			double x, nsc;
226			register int i;
227			/* polynomial approximation */
228			x = (theta - PI/4.0)/(PI/4.0);
229			nsc = nf[4];
230			for (i = 3; i >= 0; i--)
231			nsc = nsc*x + nf[i];
232
233			return(nsc);
234			}
235
236
237			printhead(ac, av) /* print command header */
238			register int ac;
239			register char **av;
240			{
241			putchar('#');
242			while (ac--) {
243			putchar(' ');
244			fputs(*av++, stdout);
245			}
246			putchar('\n');
247			}