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/* Copyright (c) 1986 Regents of the University of California */ |
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|
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#ifndef lint |
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static char SCCSid[] = "$SunId$ LBL"; |
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#endif |
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|
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/* |
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* gensky.c - program to generate sky functions. |
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* Our zenith is along the Z-axis, the X-axis |
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* points east, and the Y-axis points north. |
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* Radiance is in watts/steradian/sq. meter. |
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* |
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* 3/26/86 |
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*/ |
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|
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#include <stdio.h> |
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|
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#include <math.h> |
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|
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#include "color.h" |
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|
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#ifndef atof |
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extern double atof(); |
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#endif |
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extern char *strcpy(), *strcat(), *malloc(); |
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extern double stadj(), sdec(), sazi(), salt(); |
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|
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#define PI 3.141592654 |
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|
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#define DOT(v1,v2) (v1[0]*v2[0]+v1[1]*v2[1]+v1[2]*v2[2]) |
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|
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double normsc(); |
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/* sun calculation constants */ |
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extern double s_latitude; |
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extern double s_longitude; |
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extern double s_meridian; |
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/* required values */ |
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int month, day; /* date */ |
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double hour; /* standard time */ |
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double altitude, azimuth; /* or solar angles */ |
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/* default values */ |
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int cloudy = 0; |
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int dosun = 1; |
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double zenithbr = -1.0; |
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double turbidity = 2.75; |
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double gprefl = 0.2; |
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/* computed values */ |
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double sundir[3]; |
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double groundbr; |
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double F2; |
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double solarbr; |
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|
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char *progname; |
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char errmsg[128]; |
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|
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|
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main(argc, argv) |
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int argc; |
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char *argv[]; |
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{ |
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extern double fabs(); |
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int i; |
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|
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progname = argv[0]; |
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if (argc == 2 && !strcmp(argv[1], "-defaults")) { |
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printdefaults(); |
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exit(0); |
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} |
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if (argc < 4) |
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userror("arg count"); |
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if (!strcmp(argv[1], "-ang")) { |
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altitude = atof(argv[2]) * (PI/180); |
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azimuth = atof(argv[3]) * (PI/180); |
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month = 0; |
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} else { |
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month = atoi(argv[1]); |
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day = atoi(argv[2]); |
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hour = atof(argv[3]); |
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} |
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for (i = 4; i < argc; i++) |
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if (argv[i][0] == '-' || argv[i][0] == '+') |
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switch (argv[i][1]) { |
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case 's': |
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cloudy = 0; |
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dosun = argv[i][0] == '+'; |
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break; |
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case 'c': |
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cloudy = 1; |
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dosun = 0; |
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break; |
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case 't': |
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turbidity = atof(argv[++i]); |
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break; |
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case 'b': |
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zenithbr = atof(argv[++i]); |
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break; |
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case 'g': |
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gprefl = atof(argv[++i]); |
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break; |
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case 'a': |
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s_latitude = atof(argv[++i]) * (PI/180); |
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break; |
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case 'o': |
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s_longitude = atof(argv[++i]) * (PI/180); |
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break; |
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case 'm': |
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s_meridian = atof(argv[++i]) * (PI/180); |
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break; |
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default: |
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sprintf(errmsg, "unknown option: %s", argv[i]); |
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userror(errmsg); |
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} |
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else |
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userror("bad option"); |
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|
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if (fabs(s_meridian-s_longitude) > 30*PI/180) |
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fprintf(stderr, |
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"%s: warning: %.1f hours btwn. standard meridian and longitude\n", |
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progname, (s_longitude-s_meridian)*12/PI); |
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|
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printhead(argc, argv); |
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|
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computesky(); |
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printsky(); |
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} |
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|
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|
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computesky() /* compute sky parameters */ |
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{ |
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/* compute solar direction */ |
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if (month) { /* from date and time */ |
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int jd; |
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double sd, st; |
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|
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jd = jdate(month, day); /* Julian date */ |
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sd = sdec(jd); /* solar declination */ |
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st = hour + stadj(jd); /* solar time */ |
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altitude = salt(sd, st); |
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azimuth = sazi(sd, st); |
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} |
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sundir[0] = -sin(azimuth)*cos(altitude); |
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sundir[1] = -cos(azimuth)*cos(altitude); |
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sundir[2] = sin(altitude); |
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|
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/* Compute zenith brightness */ |
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if (zenithbr <= 0.0) |
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if (cloudy) { |
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zenithbr = 8.6*sundir[2] + .123; |
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zenithbr *= 1000.0/SKYEFFICACY; |
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} else { |
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zenithbr = (1.376*turbidity-1.81)*tan(altitude)+0.38; |
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zenithbr *= 1000.0/SKYEFFICACY; |
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} |
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if (zenithbr < 0.0) |
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zenithbr = 0.0; |
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/* Compute horizontal radiance */ |
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if (cloudy) { |
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groundbr = zenithbr*0.777778; |
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printf("# Ground ambient level: %f\n", groundbr); |
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} else { |
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F2 = 0.274*(0.91 + 10.0*exp(-3.0*(PI/2.0-altitude)) + |
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0.45*sundir[2]*sundir[2]); |
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groundbr = zenithbr*normsc(PI/2.0-altitude)/F2/PI; |
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printf("# Ground ambient level: %f\n", groundbr); |
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if (sundir[2] > 0.0) { |
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if (sundir[2] > .16) |
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solarbr = (1.5e9/SUNEFFICACY) * |
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(1.147 - .147/sundir[2]); |
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else |
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solarbr = 1.5e9/SUNEFFICACY*(1.147-.147/.16); |
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groundbr += solarbr*6e-5*sundir[2]/PI; |
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} else |
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dosun = 0; |
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} |
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groundbr *= gprefl; |
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} |
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|
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|
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printsky() /* print out sky */ |
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{ |
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if (dosun) { |
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printf("\nvoid light solar\n"); |
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printf("0\n0\n"); |
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printf("3 %.2e %.2e %.2e\n", solarbr, solarbr, solarbr); |
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printf("\nsolar source sun\n"); |
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printf("0\n0\n"); |
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printf("4 %f %f %f 0.5\n", sundir[0], sundir[1], sundir[2]); |
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} |
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|
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printf("\nvoid brightfunc skyfunc\n"); |
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printf("2 skybright skybright.cal\n"); |
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printf("0\n"); |
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if (cloudy) |
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printf("3 1 %.2e %.2e\n", zenithbr, groundbr); |
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else |
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printf("7 -1 %.2e %.2e %.2e %f %f %f\n", zenithbr, groundbr, |
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F2, sundir[0], sundir[1], sundir[2]); |
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} |
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|
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|
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printdefaults() /* print default values */ |
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{ |
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if (cloudy) |
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printf("-c\t\t\t\t# Cloudy sky\n"); |
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else if (dosun) |
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printf("+s\t\t\t\t# Sunny sky with sun\n"); |
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else |
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printf("-s\t\t\t\t# Sunny sky without sun\n"); |
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printf("-g %f\t\t\t# Ground plane reflectance\n", gprefl); |
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if (zenithbr > 0.0) |
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printf("-b %f\t\t\t# Zenith radiance (watts/ster/m2\n", zenithbr); |
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else |
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printf("-t %f\t\t\t# Atmospheric turbidity\n", turbidity); |
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printf("-a %f\t\t\t# Site latitude (degrees)\n", s_latitude*(180/PI)); |
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printf("-o %f\t\t\t# Site longitude (degrees)\n", s_longitude*(180/PI)); |
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printf("-m %f\t\t\t# Standard meridian (degrees)\n", s_meridian*(180/PI)); |
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} |
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|
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|
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userror(msg) /* print usage error and quit */ |
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char *msg; |
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{ |
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if (msg != NULL) |
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fprintf(stderr, "%s: Use error - %s\n", progname, msg); |
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fprintf(stderr, "Usage: %s month day hour [options]\n", progname); |
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fprintf(stderr, " Or: %s -ang altitude azimuth [options]\n", progname); |
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fprintf(stderr, " Or: %s -defaults\n", progname); |
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exit(1); |
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} |
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|
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|
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double |
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normsc(theta) /* compute normalization factor (E0*F2/L0) */ |
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double theta; |
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{ |
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static double nf[5] = {2.766521, 0.547665, |
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-0.369832, 0.009237, 0.059229}; |
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double x, nsc; |
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register int i; |
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/* polynomial approximation */ |
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x = (theta - PI/4.0)/(PI/4.0); |
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nsc = nf[4]; |
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for (i = 3; i >= 0; i--) |
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nsc = nsc*x + nf[i]; |
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|
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return(nsc); |
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} |
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|
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|
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printhead(ac, av) /* print command header */ |
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register int ac; |
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register char **av; |
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{ |
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putchar('#'); |
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while (ac--) { |
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putchar(' '); |
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fputs(*av++, stdout); |
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} |
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putchar('\n'); |
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} |
