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

#ifndef lint
static char SCCSid[] = "@(#)gensky.c 2.18 7/18/96 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  <ctype.h>

#include  "color.h"

extern char  *strcpy(), *strcat(), *malloc();
extern double  stadj(), sdec(), sazi(), salt(), tz2mer();

#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();
					/* sun calculation constants */
extern double  s_latitude;
extern double  s_longitude;
extern double  s_meridian;

#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,
	"WET", -15, "WETDST", -30,
	"MET", -30, "METDST", -45,
	"MEZ", -30, "MESZ", -45,
	"", 0
};
					/* required values */
int  position;				/* planet position, 0 to 359 */
double  hour;				/* time, using martian 24-hour clock */
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 = 2.75;
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];


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

	progname = argv[0];
	if (argc == 2 && !strcmp(argv[1], "-defaults")) {
		printdefaults();
		exit(0);
	}
	if (argc < 3)
		userror("arg count");
	if (!strcmp(argv[1], "-ang")) {
		altitude = atof(argv[2]) * (PI/180);
		azimuth = atof(argv[3]) * (PI/180);
		position = -1;
	} else {
		position = atoi(argv[1]);
		if (position < 0 || position > 359)
			userror("bad position, try 0 to 359");
		cvthour(argv[2]);
	}
	for (i = 3; 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 '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':
				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) > 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);
}


computesky()			/* compute sky parameters */
{
	double	normfactor;
					/* compute solar direction */
	if (position > -1) {		/* from date and time */
		int  pd;
		double  sd, st;

		pd = position;			/* Position date */
		sd = sdec(pd);			/* solar declination */
		if (tsolar)			/* solar time */
			s