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/* Copyright (c) 1992 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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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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#define S_CLEAR 1 |
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#define S_OVER 2 |
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#define S_UNIF 3 |
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#define S_INTER 4 |
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|
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#define overcast (skytype==S_OVER|skytype==S_UNIF) |
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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; /* time */ |
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int tsolar; /* 0=standard, 1=solar */ |
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double altitude, azimuth; /* or solar angles */ |
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/* default values */ |
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int skytype = S_CLEAR; /* sky type */ |
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int dosun = 1; |
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double zenithbr = 0.0; |
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int u_zenith = 0; /* -1=irradiance, 1=radiance */ |
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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 = 0.0; |
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int u_solar = 0; /* -1=irradiance, 1=radiance */ |
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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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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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if (month < 1 || month > 12) |
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userror("bad month"); |
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day = atoi(argv[2]); |
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if (day < 1 || day > 31) |
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userror("bad day"); |
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cvthour(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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skytype = S_CLEAR; |
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dosun = argv[i][0] == '+'; |
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break; |
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case 'r': |
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case 'R': |
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u_solar = argv[i][1]=='R' ? -1 : 1; |
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solarbr = atof(argv[++i]); |
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break; |
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case 'c': |
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skytype = S_OVER; |
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break; |
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case 'u': |
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skytype = S_UNIF; |
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break; |
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case 'i': |
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skytype = S_INTER; |
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dosun = argv[i][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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case 'B': |
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u_zenith = argv[i][1]=='B' ? -1 : 1; |
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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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exit(0); |
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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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double normfactor; |
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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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if (tsolar) /* solar time */ |
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st = hour; |
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else |
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st = hour + stadj(jd); |
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altitude = salt(sd, st); |
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azimuth = sazi(sd, st); |
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printf("# Solar altitude and azimuth: %.1f %.1f\n", |
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180./PI*altitude, 180./PI*azimuth); |
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} |
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if (!overcast && altitude > 87.*PI/180.) { |
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fprintf(stderr, |
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"%s: warning - sun too close to zenith, reducing altitude to 87 degrees\n", |
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progname); |
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printf( |
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"# warning - sun too close to zenith, reducing altitude to 87 degrees\n"); |
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altitude = 87.*PI/180.; |
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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 normalization factor */ |
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switch (skytype) { |
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case S_UNIF: |
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normfactor = 1.0; |
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break; |
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case S_OVER: |
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normfactor = 0.777778; |
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break; |
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case S_CLEAR: |
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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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normfactor = normsc()/F2/PI; |
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break; |
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case S_INTER: |
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F2 = (2.739 + .9891*sin(.3119+2.6*altitude)) * |
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exp(-(PI/2.0-altitude)*(.4441+1.48*altitude)); |
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normfactor = normsc()/F2/PI; |
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break; |
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} |
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/* Compute zenith brightness */ |
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if (u_zenith == -1) |
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zenithbr /= normfactor*PI; |
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else if (u_zenith == 0) { |
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if (overcast) |
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zenithbr = 8.6*sundir[2] + .123; |
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else |
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zenithbr = (1.376*turbidity-1.81)*tan(altitude)+0.38; |
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if (skytype == S_INTER) |
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zenithbr = (zenithbr + 8.6*sundir[2] + .123)/2.0; |
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if (zenithbr < 0.0) |
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zenithbr = 0.0; |
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else |
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zenithbr *= 1000.0/SKYEFFICACY; |
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} |
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/* Compute horizontal radiance */ |
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groundbr = zenithbr*normfactor; |
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printf("# Ground ambient level: %.1f\n", groundbr); |
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if (!overcast && sundir[2] > 0.0 && (!u_solar || solarbr > 0.0)) { |
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if (u_solar == -1) |
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solarbr /= 6e-5*sundir[2]; |
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else if (u_solar == 0) { |
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solarbr = 1.5e9/SUNEFFICACY * |
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(1.147 - .147/(sundir[2]>.16?sundir[2]:.16)); |
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if (skytype == S_INTER) |
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solarbr *= 0.15; /* fudge factor! */ |
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} |
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groundbr += 6e-5/PI*solarbr*sundir[2]; |
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} else |
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dosun = 0; |
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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 skybr skybright.cal\n"); |
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printf("0\n"); |
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if (overcast) |
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printf("3 %d %.2e %.2e\n", skytype, zenithbr, groundbr); |
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else |
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printf("7 %d %.2e %.2e %.2e %f %f %f\n", |
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skytype, zenithbr, groundbr, F2, |
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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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switch (skytype) { |
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case S_OVER: |
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printf("-c\t\t\t\t# Cloudy sky\n"); |
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break; |
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case S_UNIF: |
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printf("-u\t\t\t\t# Uniform cloudy sky\n"); |
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break; |
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case S_INTER: |
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if (dosun) |
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printf("+i\t\t\t\t# Intermediate sky with sun\n"); |
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else |
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printf("-i\t\t\t\t# Intermediate sky without sun\n"); |
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break; |
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case S_CLEAR: |
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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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break; |
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} |
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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() /* compute normalization factor (E0*F2/L0) */ |
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{ |
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static double nfc[2][5] = { |
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/* clear sky approx. */ |
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{2.766521, 0.547665, -0.369832, 0.009237, 0.059229}, |
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/* intermediate sky approx. */ |
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{3.5556, -2.7152, -1.3081, 1.0660, 0.60227}, |
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}; |
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register double *nf; |
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double x, nsc; |
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register int i; |
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/* polynomial approximation */ |
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nf = nfc[skytype==S_INTER]; |
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x = (altitude - PI/4.0)/(PI/4.0); |
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nsc = nf[i=4]; |
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while (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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cvthour(hs) /* convert hour string */ |
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char *hs; |
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{ |
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register char *cp = hs; |
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|
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while (*cp && *cp++ != ':') |
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; |
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if (*cp) |
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hour = atoi(hs) + atoi(cp)/60.0; |
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else |
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hour = atof(hs); |
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tsolar = *hs == '+'; |
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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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} |
