/* 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 #include #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); } 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'); }