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root/radiance/ray/src/gen/gendaymtx.c
Revision: 2.36
Committed: Mon Apr 13 17:12:19 2020 UTC (3 years, 11 months ago) by greg
Content type: text/plain
Branch: MAIN
Changes since 2.35: +55 -21 lines
Log Message:
Updates to gendaymtx requested by Ladybug Tools

File Contents

# User Rev Content
1 greg 2.1 #ifndef lint
2 greg 2.36 static const char RCSid[] = "$Id: gendaymtx.c,v 2.35 2020/01/07 18:26:55 greg Exp $";
3 greg 2.1 #endif
4     /*
5     * gendaymtx.c
6     *
7     * Generate a daylight matrix based on Perez Sky Model.
8     *
9     * Most of this code is borrowed (see copyright below) from Ian Ashdown's
10     * excellent re-implementation of Jean-Jacques Delaunay's gendaylit.c
11     *
12     * Created by Greg Ward on 1/16/13.
13     */
14    
15     /*********************************************************************
16     *
17     * H32_gendaylit.CPP - Perez Sky Model Calculation
18     *
19     * Version: 1.00A
20     *
21     * History: 09/10/01 - Created.
22     * 11/10/08 - Modified for Unix compilation.
23     * 11/10/12 - Fixed conditional __max directive.
24     * 1/11/13 - Tweaks and optimizations (G.Ward)
25     *
26     * Compilers: Microsoft Visual C/C++ Professional V10.0
27     *
28     * Author: Ian Ashdown, P.Eng.
29     * byHeart Consultants Limited
30     * 620 Ballantree Road
31     * West Vancouver, B.C.
32     * Canada V7S 1W3
33     * e-mail: [email protected]
34     *
35     * References: Perez, R., P. Ineichen, R. Seals, J. Michalsky, and R.
36     * Stewart. 1990. ìModeling Daylight Availability and
37     * Irradiance Components from Direct and Global
38     * Irradiance,î Solar Energy 44(5):271-289.
39     *
40     * Perez, R., R. Seals, and J. Michalsky. 1993.
41     * ìAll-Weather Model for Sky Luminance Distribution -
42     * Preliminary Configuration and Validation,î Solar Energy
43     * 50(3):235-245.
44     *
45     * Perez, R., R. Seals, and J. Michalsky. 1993. "ERRATUM to
46     * All-Weather Model for Sky Luminance Distribution -
47     * Preliminary Configuration and Validation,î Solar Energy
48     * 51(5):423.
49     *
50     * NOTE: This program is a completely rewritten version of
51     * gendaylit.c written by Jean-Jacques Delaunay (1994).
52     *
53     * Copyright 2009-2012 byHeart Consultants Limited. All rights
54     * reserved.
55     *
56     * Redistribution and use in source and binary forms, with or without
57     * modification, are permitted for personal and commercial purposes
58     * provided that redistribution of source code must retain the above
59     * copyright notice, this list of conditions and the following
60     * disclaimer:
61     *
62     * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED
63     * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
64     * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
65     * DISCLAIMED. IN NO EVENT SHALL byHeart Consultants Limited OR
66     * ITS EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
67     * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
68     * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
69     * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
70     * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
71     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
72     * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
73     * POSSIBILITY OF SUCH DAMAGE.
74     *
75     *********************************************************************/
76    
77     /* Zenith is along the Z-axis */
78     /* X-axis points east */
79     /* Y-axis points north */
80     /* azimuth is measured as degrees or radians east of North */
81    
82     /* Include files */
83     #define _USE_MATH_DEFINES
84     #include <stdlib.h>
85     #include <ctype.h>
86 greg 2.30 #include "platform.h"
87 greg 2.1 #include "rtmath.h"
88 greg 2.23 #include "rtio.h"
89 greg 2.1 #include "color.h"
90 greg 2.30 #include "sun.h"
91 greg 2.1
92     char *progname; /* Program name */
93     char errmsg[128]; /* Error message buffer */
94     const double DC_SolarConstantE = 1367.0; /* Solar constant W/m^2 */
95     const double DC_SolarConstantL = 127.5; /* Solar constant klux */
96    
97     double altitude; /* Solar altitude (radians) */
98     double azimuth; /* Solar azimuth (radians) */
99     double apwc; /* Atmospheric precipitable water content */
100     double dew_point = 11.0; /* Surface dew point temperature (deg. C) */
101     double diff_illum; /* Diffuse illuminance */
102     double diff_irrad; /* Diffuse irradiance */
103     double dir_illum; /* Direct illuminance */
104     double dir_irrad; /* Direct irradiance */
105     int julian_date; /* Julian date */
106     double perez_param[5]; /* Perez sky model parameters */
107     double sky_brightness; /* Sky brightness */
108     double sky_clearness; /* Sky clearness */
109     double solar_rad; /* Solar radiance */
110     double sun_zenith; /* Sun zenith angle (radians) */
111     int input = 0; /* Input type */
112 greg 2.11 int output = 0; /* Output type */
113 greg 2.1
114     extern double dmax( double, double );
115     extern double CalcAirMass();
116     extern double CalcDiffuseIllumRatio( int );
117     extern double CalcDiffuseIrradiance();
118     extern double CalcDirectIllumRatio( int );
119     extern double CalcDirectIrradiance();
120     extern double CalcEccentricity();
121     extern double CalcPrecipWater( double );
122     extern double CalcRelHorzIllum( float *parr );
123     extern double CalcRelLuminance( double, double );
124     extern double CalcSkyBrightness();
125     extern double CalcSkyClearness();
126     extern int CalcSkyParamFromIllum();
127     extern int GetCategoryIndex();
128     extern void CalcPerezParam( double, double, double, int );
129     extern void CalcSkyPatchLumin( float *parr );
130     extern void ComputeSky( float *parr );
131    
132     /* Degrees into radians */
133     #define DegToRad(deg) ((deg)*(PI/180.))
134    
135     /* Radiuans into degrees */
136     #define RadToDeg(rad) ((rad)*(180./PI))
137    
138    
139     /* Perez sky model coefficients */
140    
141     /* Reference: Perez, R., R. Seals, and J. Michalsky, 1993. "All- */
142     /* Weather Model for Sky Luminance Distribution - */
143     /* Preliminary Configuration and Validation," Solar */
144     /* Energy 50(3):235-245, Table 1. */
145    
146     static const double PerezCoeff[8][20] =
147     {
148     /* Sky clearness (epsilon): 1.000 to 1.065 */
149     { 1.3525, -0.2576, -0.2690, -1.4366, -0.7670,
150     0.0007, 1.2734, -0.1233, 2.8000, 0.6004,
151     1.2375, 1.0000, 1.8734, 0.6297, 0.9738,
152     0.2809, 0.0356, -0.1246, -0.5718, 0.9938 },
153     /* Sky clearness (epsilon): 1.065 to 1.230 */
154     { -1.2219, -0.7730, 1.4148, 1.1016, -0.2054,
155     0.0367, -3.9128, 0.9156, 6.9750, 0.1774,
156     6.4477, -0.1239, -1.5798, -0.5081, -1.7812,
157     0.1080, 0.2624, 0.0672, -0.2190, -0.4285 },
158     /* Sky clearness (epsilon): 1.230 to 1.500 */
159     { -1.1000, -0.2515, 0.8952, 0.0156, 0.2782,
160     -0.1812, - 4.5000, 1.1766, 24.7219, -13.0812,
161     -37.7000, 34.8438, -5.0000, 1.5218, 3.9229,
162     -2.6204, -0.0156, 0.1597, 0.4199, -0.5562 },
163     /* Sky clearness (epsilon): 1.500 to 1.950 */
164     { -0.5484, -0.6654, -0.2672, 0.7117, 0.7234,
165     -0.6219, -5.6812, 2.6297, 33.3389, -18.3000,
166     -62.2500, 52.0781, -3.5000, 0.0016, 1.1477,
167     0.1062, 0.4659, -0.3296, -0.0876, -0.0329 },
168     /* Sky clearness (epsilon): 1.950 to 2.800 */
169     { -0.6000, -0.3566, -2.5000, 2.3250, 0.2937,
170     0.0496, -5.6812, 1.8415, 21.0000, -4.7656 ,
171     -21.5906, 7.2492, -3.5000, -0.1554, 1.4062,
172     0.3988, 0.0032, 0.0766, -0.0656, -0.1294 },
173     /* Sky clearness (epsilon): 2.800 to 4.500 */
174     { -1.0156, -0.3670, 1.0078, 1.4051, 0.2875,
175     -0.5328, -3.8500, 3.3750, 14.0000, -0.9999,
176     -7.1406, 7.5469, -3.4000, -0.1078, -1.0750,
177     1.5702, -0.0672, 0.4016, 0.3017, -0.4844 },
178     /* Sky clearness (epsilon): 4.500 to 6.200 */
179     { -1.0000, 0.0211, 0.5025, -0.5119, -0.3000,
180     0.1922, 0.7023, -1.6317, 19.0000, -5.0000,
181     1.2438, -1.9094, -4.0000, 0.0250, 0.3844,
182     0.2656, 1.0468, -0.3788, -2.4517, 1.4656 },
183     /* Sky clearness (epsilon): 6.200 to ... */
184     { -1.0500, 0.0289, 0.4260, 0.3590, -0.3250,
185     0.1156, 0.7781, 0.0025, 31.0625, -14.5000,
186     -46.1148, 55.3750, -7.2312, 0.4050, 13.3500,
187     0.6234, 1.5000, -0.6426, 1.8564, 0.5636 }
188     };
189    
190     /* Perez irradiance component model coefficients */
191    
192     /* Reference: Perez, R., P. Ineichen, R. Seals, J. Michalsky, and R. */
193     /* Stewart. 1990. ìModeling Daylight Availability and */
194     /* Irradiance Components from Direct and Global */
195     /* Irradiance,î Solar Energy 44(5):271-289. */
196    
197     typedef struct
198     {
199     double lower; /* Lower bound */
200     double upper; /* Upper bound */
201     } CategoryBounds;
202    
203     /* Perez sky clearness (epsilon) categories (Table 1) */
204     static const CategoryBounds SkyClearCat[8] =
205     {
206     { 1.000, 1.065 }, /* Overcast */
207     { 1.065, 1.230 },
208     { 1.230, 1.500 },
209     { 1.500, 1.950 },
210     { 1.950, 2.800 },
211     { 2.800, 4.500 },
212     { 4.500, 6.200 },
213 greg 2.12 { 6.200, 12.01 } /* Clear */
214 greg 2.1 };
215    
216     /* Luminous efficacy model coefficients */
217     typedef struct
218     {
219     double a;
220     double b;
221     double c;
222     double d;
223     } ModelCoeff;
224    
225     /* Diffuse luminous efficacy model coefficients (Table 4, Eqn. 7) */
226     static const ModelCoeff DiffuseLumEff[8] =
227     {
228     { 97.24, -0.46, 12.00, -8.91 },
229     { 107.22, 1.15, 0.59, -3.95 },
230     { 104.97, 2.96, -5.53, -8.77 },
231     { 102.39, 5.59, -13.95, -13.90 },
232     { 100.71, 5.94, -22.75, -23.74 },
233     { 106.42, 3.83, -36.15, -28.83 },
234     { 141.88, 1.90, -53.24, -14.03 },
235     { 152.23, 0.35, -45.27, -7.98 }
236     };
237    
238     /* Direct luminous efficacy model coefficients (Table 4, Eqn. 8) */
239     static const ModelCoeff DirectLumEff[8] =
240     {
241     { 57.20, -4.55, -2.98, 117.12 },
242     { 98.99, -3.46, -1.21, 12.38 },
243     { 109.83, -4.90, -1.71, -8.81 },
244     { 110.34, -5.84, -1.99, -4.56 },
245     { 106.36, -3.97, -1.75, -6.16 },
246     { 107.19, -1.25, -1.51, -26.73 },
247     { 105.75, 0.77, -1.26, -34.44 },
248     { 101.18, 1.58, -1.10, -8.29 }
249     };
250    
251 greg 2.3 #ifndef NSUNPATCH
252 greg 2.10 #define NSUNPATCH 4 /* max. # patches to spread sun into */
253 greg 2.3 #endif
254    
255 greg 2.35 #define SUN_ANG_DEG 0.533 /* sun full-angle in degrees */
256    
257 greg 2.10 int nsuns = NSUNPATCH; /* number of sun patches to use */
258     double fixed_sun_sa = -1; /* fixed solid angle per sun? */
259    
260 greg 2.1 int verbose = 0; /* progress reports to stderr? */
261    
262     int outfmt = 'a'; /* output format */
263    
264     int rhsubdiv = 1; /* Reinhart sky subdivisions */
265    
266 greg 2.4 COLOR skycolor = {.96, 1.004, 1.118}; /* sky coloration */
267     COLOR suncolor = {1., 1., 1.}; /* sun color */
268     COLOR grefl = {.2, .2, .2}; /* ground reflectance */
269 greg 2.1
270     int nskypatch; /* number of Reinhart patches */
271     float *rh_palt; /* sky patch altitudes (radians) */
272     float *rh_pazi; /* sky patch azimuths (radians) */
273     float *rh_dom; /* sky patch solid angle (sr) */
274    
275 greg 2.36 #define vector(v,alt,azi) ( (v)[1] = cos(alt), \
276     (v)[0] = (v)[1]*sin(azi), \
277     (v)[1] *= cos(azi), \
278     (v)[2] = sin(alt) )
279 greg 2.1
280     #define rh_vector(v,i) vector(v,rh_palt[i],rh_pazi[i])
281    
282     #define rh_cos(i) tsin(rh_palt[i])
283    
284 greg 2.36 #define solar_minute(jd,hr) ((24*60)*((jd)-1)+(int)((hr)*60.+.5))
285    
286 greg 2.1 extern int rh_init(void);
287     extern float * resize_dmatrix(float *mtx_data, int nsteps, int npatch);
288 greg 2.36 extern void OutputSun(int id, int goodsun, FILE *fp, FILE *mfp);
289 greg 2.1 extern void AddDirect(float *parr);
290    
291 greg 2.14
292     static const char *
293     getfmtname(int fmt)
294     {
295     switch (fmt) {
296     case 'a':
297     return("ascii");
298     case 'f':
299     return("float");
300     case 'd':
301     return("double");
302     }
303     return("unknown");
304     }
305    
306    
307 greg 2.1 int
308     main(int argc, char *argv[])
309     {
310     char buf[256];
311 greg 2.14 int doheader = 1; /* output header? */
312 greg 2.8 double rotation = 0; /* site rotation (degrees) */
313 greg 2.1 double elevation; /* site elevation (meters) */
314 greg 2.36 int leap_day = 0; /* add leap day? */
315 greg 2.1 int dir_is_horiz; /* direct is meas. on horizontal? */
316 greg 2.34 FILE *sunsfp = NULL; /* output file for individual suns */
317 greg 2.36 FILE *modsfp = NULL; /* modifier output file */
318 greg 2.1 float *mtx_data = NULL; /* our matrix data */
319 greg 2.28 int avgSky = 0; /* compute average sky r.t. matrix? */
320 greg 2.27 int ntsteps = 0; /* number of time steps */
321 greg 2.28 int tstorage = 0; /* number of allocated time steps */
322     int nstored = 0; /* number of time steps in matrix */
323 greg 2.1 int last_monthly = 0; /* month of last report */
324     int mo, da; /* month (1-12) and day (1-31) */
325     double hr; /* hour (local standard time) */
326     double dir, dif; /* direct and diffuse values */
327     int mtx_offset;
328     int i, j;
329    
330     progname = argv[0];
331     /* get options */
332     for (i = 1; i < argc && argv[i][0] == '-'; i++)
333     switch (argv[i][1]) {
334 greg 2.4 case 'g': /* ground reflectance */
335     grefl[0] = atof(argv[++i]);
336     grefl[1] = atof(argv[++i]);
337     grefl[2] = atof(argv[++i]);
338 greg 2.1 break;
339 greg 2.4 case 'v': /* verbose progress reports */
340 greg 2.1 verbose++;
341     break;
342 greg 2.14 case 'h': /* turn off header */
343     doheader = 0;
344     break;
345 greg 2.4 case 'o': /* output format */
346 greg 2.1 switch (argv[i][2]) {
347     case 'f':
348     case 'd':
349     case 'a':
350     outfmt = argv[i][2];
351     break;
352     default:
353     goto userr;
354     }
355     break;
356 greg 2.11 case 'O': /* output type */
357     switch (argv[i][2]) {
358     case '0':
359     output = 0;
360     break;
361     case '1':
362     output = 1;
363     break;
364     default:
365     goto userr;
366     }
367     if (argv[i][3])
368     goto userr;
369     break;
370 greg 2.4 case 'm': /* Reinhart subdivisions */
371 greg 2.1 rhsubdiv = atoi(argv[++i]);
372     break;
373 greg 2.4 case 'c': /* sky color */
374 greg 2.1 skycolor[0] = atof(argv[++i]);
375     skycolor[1] = atof(argv[++i]);
376     skycolor[2] = atof(argv[++i]);
377     break;
378 greg 2.36 case 'D': /* output suns to file */
379     if (strcmp(argv[++i], "-")) {
380     sunsfp = fopen(argv[i], "w");
381     if (sunsfp == NULL) {
382     fprintf(stderr,
383     "%s: cannot open '%s' for output\n",
384     progname, argv[i]);
385     exit(1);
386     }
387     break; /* still may output matrix */
388     }
389     sunsfp = stdout; /* sending to stdout, so... */
390     /* fall through */
391 greg 2.34 case 'n': /* no matrix output */
392     avgSky = -1;
393     rhsubdiv = 1;
394     /* fall through */
395 greg 2.4 case 'd': /* solar (direct) only */
396 greg 2.1 skycolor[0] = skycolor[1] = skycolor[2] = 0;
397 greg 2.33 grefl[0] = grefl[1] = grefl[2] = 0;
398 greg 2.1 break;
399 greg 2.36 case 'M': /* send sun modifiers to file */
400     if ((modsfp = fopen(argv[++i], "w")) == NULL) {
401 greg 2.34 fprintf(stderr, "%s: cannot open '%s' for output\n",
402 greg 2.35 progname, argv[i]);
403 greg 2.34 exit(1);
404     }
405     break;
406 greg 2.4 case 's': /* sky only (no direct) */
407     suncolor[0] = suncolor[1] = suncolor[2] = 0;
408 greg 2.1 break;
409 greg 2.8 case 'r': /* rotate distribution */
410     if (argv[i][2] && argv[i][2] != 'z')
411     goto userr;
412     rotation = atof(argv[++i]);
413     break;
414 greg 2.10 case '5': /* 5-phase calculation */
415     nsuns = 1;
416 greg 2.19 fixed_sun_sa = PI/360.*atof(argv[++i]);
417 greg 2.21 if (fixed_sun_sa <= 0) {
418     fprintf(stderr, "%s: missing solar disk size argument for '-5' option\n",
419 greg 2.35 progname);
420 greg 2.21 exit(1);
421     }
422 greg 2.19 fixed_sun_sa *= fixed_sun_sa*PI;
423 greg 2.10 break;
424 greg 2.27 case 'A': /* compute average sky */
425     avgSky = 1;
426     break;
427 greg 2.1 default:
428     goto userr;
429     }
430     if (i < argc-1)
431     goto userr;
432     if (i == argc-1 && freopen(argv[i], "r", stdin) == NULL) {
433     fprintf(stderr, "%s: cannot open '%s' for input\n",
434     progname, argv[i]);
435     exit(1);
436     }
437 greg 2.36 if ((modsfp != NULL) & (sunsfp == NULL))
438     fprintf(stderr, "%s: warning -M output will be empty without -D\n",
439     progname);
440 greg 2.1 if (verbose) {
441     if (i == argc-1)
442     fprintf(stderr, "%s: reading weather tape '%s'\n",
443     progname, argv[i]);
444     else
445     fprintf(stderr, "%s: reading weather tape from <stdin>\n",
446     progname);
447     }
448     /* read weather tape header */
449 greg 2.2 if (scanf("place %[^\r\n] ", buf) != 1)
450 greg 2.1 goto fmterr;
451     if (scanf("latitude %lf\n", &s_latitude) != 1)
452     goto fmterr;
453     if (scanf("longitude %lf\n", &s_longitude) != 1)
454     goto fmterr;
455     if (scanf("time_zone %lf\n", &s_meridian) != 1)
456     goto fmterr;
457     if (scanf("site_elevation %lf\n", &elevation) != 1)
458     goto fmterr;
459     if (scanf("weather_data_file_units %d\n", &input) != 1)
460     goto fmterr;
461     switch (input) { /* translate units */
462     case 1:
463     input = 1; /* radiometric quantities */
464     dir_is_horiz = 0; /* direct is perpendicular meas. */
465     break;
466     case 2:
467     input = 1; /* radiometric quantities */
468     dir_is_horiz = 1; /* solar measured horizontally */
469     break;
470     case 3:
471     input = 2; /* photometric quantities */
472     dir_is_horiz = 0; /* direct is perpendicular meas. */
473     break;
474     default:
475     goto fmterr;
476     }
477     rh_init(); /* initialize sky patches */
478     if (verbose) {
479     fprintf(stderr, "%s: location '%s'\n", progname, buf);
480     fprintf(stderr, "%s: (lat,long)=(%.1f,%.1f) degrees north, west\n",
481     progname, s_latitude, s_longitude);
482 greg 2.35 if (avgSky >= 0)
483     fprintf(stderr, "%s: %d sky patches\n",
484     progname, nskypatch);
485     if (sunsfp)
486     fprintf(stderr, "%s: outputting suns to file\n",
487     progname);
488 greg 2.8 if (rotation != 0)
489     fprintf(stderr, "%s: rotating output %.0f degrees\n",
490     progname, rotation);
491 greg 2.1 }
492 greg 2.2 /* convert quantities to radians */
493     s_latitude = DegToRad(s_latitude);
494     s_longitude = DegToRad(s_longitude);
495     s_meridian = DegToRad(s_meridian);
496 greg 2.27 /* initial allocation */
497 greg 2.28 mtx_data = resize_dmatrix(mtx_data, tstorage=2, nskypatch);
498 greg 2.1 /* process each time step in tape */
499     while (scanf("%d %d %lf %lf %lf\n", &mo, &da, &hr, &dir, &dif) == 5) {
500     double sda, sta;
501 greg 2.27
502 greg 2.28 mtx_offset = 3*nskypatch*nstored;
503     nstored += !avgSky | !nstored;
504 greg 2.27 /* make space for next row */
505 greg 2.28 if (nstored > tstorage) {
506     tstorage += (tstorage>>1) + nstored + 7;
507     mtx_data = resize_dmatrix(mtx_data, tstorage, nskypatch);
508 greg 2.15 }
509 greg 2.27 ntsteps++; /* keep count of time steps */
510 greg 2.1 /* compute solar position */
511 greg 2.36 if ((mo == 2) & (da == 29)) {
512     julian_date = 60;
513     leap_day = 1;
514     } else
515     julian_date = jdate(mo, da) + leap_day;
516 greg 2.1 sda = sdec(julian_date);
517     sta = stadj(julian_date);
518     altitude = salt(sda, hr+sta);
519 greg 2.8 azimuth = sazi(sda, hr+sta) + PI - DegToRad(rotation);
520 greg 2.36
521     if (dir+dif <= 1e-4) { /* effectively nighttime? */
522     if (!avgSky | !mtx_offset)
523     memset(mtx_data+mtx_offset, 0,
524     sizeof(float)*3*nskypatch);
525     if (sunsfp) /* output black sun */
526     OutputSun(solar_minute(julian_date,hr), 0,
527     sunsfp, modsfp);
528     continue;
529     }
530 greg 2.1 /* convert measured values */
531     if (dir_is_horiz && altitude > 0.)
532     dir /= sin(altitude);
533     if (input == 1) {
534     dir_irrad = dir;
535     diff_irrad = dif;
536     } else /* input == 2 */ {
537     dir_illum = dir;
538     diff_illum = dif;
539     }
540     /* compute sky patch values */
541     ComputeSky(mtx_data+mtx_offset);
542 greg 2.35
543 greg 2.36 if (sunsfp) /* output sun if requested */
544     OutputSun(solar_minute(julian_date,hr), 1,
545     sunsfp, modsfp);
546 greg 2.35
547 greg 2.34 if (avgSky < 0) /* no matrix? */
548     continue;
549    
550 greg 2.4 AddDirect(mtx_data+mtx_offset);
551 greg 2.27 /* update cumulative sky? */
552     for (i = 3*nskypatch*(avgSky&(ntsteps>1)); i--; )
553     mtx_data[i] += mtx_data[mtx_offset+i];
554 greg 2.34 /* monthly reporting */
555     if (verbose && mo != last_monthly)
556     fprintf(stderr, "%s: stepping through month %d...\n",
557     progname, last_monthly=mo);
558 greg 2.36 /* note whether leap-day was given */
559 greg 2.34 }
560     if (!ntsteps) {
561     fprintf(stderr, "%s: no valid time steps on input\n", progname);
562     exit(1);
563 greg 2.1 }
564     /* check for junk at end */
565     while ((i = fgetc(stdin)) != EOF)
566     if (!isspace(i)) {
567     fprintf(stderr, "%s: warning - unexpected data past EOT: ",
568     progname);
569     buf[0] = i; buf[1] = '\0';
570     fgets(buf+1, sizeof(buf)-1, stdin);
571     fputs(buf, stderr); fputc('\n', stderr);
572     break;
573     }
574 greg 2.34
575     if (avgSky < 0) /* no matrix output? */
576     goto alldone;
577    
578 greg 2.27 dif = 1./(double)ntsteps; /* average sky? */
579     for (i = 3*nskypatch*(avgSky&(ntsteps>1)); i--; )
580     mtx_data[i] *= dif;
581 greg 2.1 /* write out matrix */
582 greg 2.14 if (outfmt != 'a')
583     SET_FILE_BINARY(stdout);
584 greg 2.1 #ifdef getc_unlocked
585     flockfile(stdout);
586     #endif
587     if (verbose)
588     fprintf(stderr, "%s: writing %smatrix with %d time steps...\n",
589 greg 2.28 progname, outfmt=='a' ? "" : "binary ", nstored);
590 greg 2.14 if (doheader) {
591     newheader("RADIANCE", stdout);
592     printargs(argc, argv, stdout);
593     printf("LATLONG= %.8f %.8f\n", RadToDeg(s_latitude),
594     -RadToDeg(s_longitude));
595     printf("NROWS=%d\n", nskypatch);
596 greg 2.28 printf("NCOLS=%d\n", nstored);
597 greg 2.14 printf("NCOMP=3\n");
598 greg 2.29 if ((outfmt == 'f') | (outfmt == 'd'))
599     fputendian(stdout);
600 greg 2.18 fputformat((char *)getfmtname(outfmt), stdout);
601 greg 2.14 putchar('\n');
602     }
603 greg 2.1 /* patches are rows (outer sort) */
604     for (i = 0; i < nskypatch; i++) {
605     mtx_offset = 3*i;
606     switch (outfmt) {
607     case 'a':
608 greg 2.28 for (j = 0; j < nstored; j++) {
609 greg 2.3 printf("%.3g %.3g %.3g\n", mtx_data[mtx_offset],
610 greg 2.1 mtx_data[mtx_offset+1],
611     mtx_data[mtx_offset+2]);
612     mtx_offset += 3*nskypatch;
613     }
614 greg 2.28 if (nstored > 1)
615 greg 2.2 fputc('\n', stdout);
616 greg 2.1 break;
617     case 'f':
618 greg 2.28 for (j = 0; j < nstored; j++) {
619 greg 2.23 putbinary(mtx_data+mtx_offset, sizeof(float), 3,
620 greg 2.1 stdout);
621     mtx_offset += 3*nskypatch;
622     }
623     break;
624     case 'd':
625 greg 2.28 for (j = 0; j < nstored; j++) {
626 greg 2.1 double ment[3];
627     ment[0] = mtx_data[mtx_offset];
628     ment[1] = mtx_data[mtx_offset+1];
629     ment[2] = mtx_data[mtx_offset+2];
630 greg 2.23 putbinary(ment, sizeof(double), 3, stdout);
631 greg 2.1 mtx_offset += 3*nskypatch;
632     }
633     break;
634     }
635     if (ferror(stdout))
636     goto writerr;
637     }
638 greg 2.34 alldone:
639     if (fflush(NULL) == EOF)
640 greg 2.1 goto writerr;
641     if (verbose)
642     fprintf(stderr, "%s: done.\n", progname);
643     exit(0);
644     userr:
645 greg 2.34 fprintf(stderr, "Usage: %s [-v][-h][-A][-d|-s|-n][-D file][-r deg][-m N][-g r g b][-c r g b][-o{f|d}][-O{0|1}] [tape.wea]\n",
646 greg 2.1 progname);
647     exit(1);
648     fmterr:
649 greg 2.34 fprintf(stderr, "%s: weather tape format error in header\n", progname);
650 greg 2.1 exit(1);
651     writerr:
652     fprintf(stderr, "%s: write error on output\n", progname);
653     exit(1);
654     }
655    
656     /* Return maximum of two doubles */
657     double dmax( double a, double b )
658     { return (a > b) ? a : b; }
659    
660     /* Compute sky patch radiance values (modified by GW) */
661     void
662     ComputeSky(float *parr)
663     {
664     int index; /* Category index */
665     double norm_diff_illum; /* Normalized diffuse illuimnance */
666     int i;
667    
668     /* Calculate atmospheric precipitable water content */
669     apwc = CalcPrecipWater(dew_point);
670    
671 greg 2.6 /* Calculate sun zenith angle (don't let it dip below horizon) */
672     /* Also limit minimum angle to keep circumsolar off zenith */
673     if (altitude <= 0.0)
674     sun_zenith = DegToRad(90.0);
675     else if (altitude >= DegToRad(87.0))
676     sun_zenith = DegToRad(3.0);
677     else
678     sun_zenith = DegToRad(90.0) - altitude;
679 greg 2.1
680     /* Compute the inputs for the calculation of the sky distribution */
681    
682     if (input == 0) /* XXX never used */
683     {
684     /* Calculate irradiance */
685     diff_irrad = CalcDiffuseIrradiance();
686     dir_irrad = CalcDirectIrradiance();
687    
688     /* Calculate illuminance */
689     index = GetCategoryIndex();
690     diff_illum = diff_irrad * CalcDiffuseIllumRatio(index);
691     dir_illum = dir_irrad * CalcDirectIllumRatio(index);
692     }
693     else if (input == 1)
694     {
695     sky_brightness = CalcSkyBrightness();
696     sky_clearness = CalcSkyClearness();
697    
698 greg 2.9 /* Limit sky clearness */
699     if (sky_clearness > 11.9)
700     sky_clearness = 11.9;
701    
702     /* Limit sky brightness */
703     if (sky_brightness < 0.01)
704 greg 2.11 sky_brightness = 0.01;
705 greg 2.9
706 greg 2.1 /* Calculate illuminance */
707     index = GetCategoryIndex();
708     diff_illum = diff_irrad * CalcDiffuseIllumRatio(index);
709     dir_illum = dir_irrad * CalcDirectIllumRatio(index);
710     }
711     else if (input == 2)
712     {
713     /* Calculate sky brightness and clearness from illuminance values */
714     index = CalcSkyParamFromIllum();
715     }
716    
717 greg 2.11 if (output == 1) { /* hack for solar radiance */
718     diff_illum = diff_irrad * WHTEFFICACY;
719     dir_illum = dir_irrad * WHTEFFICACY;
720     }
721 greg 2.1 /* Compute ground radiance (include solar contribution if any) */
722 greg 2.3 parr[0] = diff_illum;
723 greg 2.1 if (altitude > 0)
724 greg 2.3 parr[0] += dir_illum * sin(altitude);
725 greg 2.4 parr[2] = parr[1] = parr[0] *= (1./PI/WHTEFFICACY);
726     multcolor(parr, grefl);
727 greg 2.1
728 greg 2.32 if (bright(skycolor) <= 1e-4) { /* 0 sky component? */
729     memset(parr+3, 0, sizeof(float)*3*(nskypatch-1));
730     return;
731     }
732 greg 2.1 /* Calculate Perez sky model parameters */
733     CalcPerezParam(sun_zenith, sky_clearness, sky_brightness, index);
734    
735     /* Calculate sky patch luminance values */
736     CalcSkyPatchLumin(parr);
737    
738     /* Calculate relative horizontal illuminance */
739     norm_diff_illum = CalcRelHorzIllum(parr);
740    
741 greg 2.13 /* Check for zero sky -- make uniform in that case */
742     if (norm_diff_illum <= FTINY) {
743     for (i = 1; i < nskypatch; i++)
744     setcolor(parr+3*i, 1., 1., 1.);
745     norm_diff_illum = PI;
746     }
747 greg 2.1 /* Normalization coefficient */
748     norm_diff_illum = diff_illum / norm_diff_illum;
749    
750     /* Apply to sky patches to get absolute radiance values */
751     for (i = 1; i < nskypatch; i++) {
752 greg 2.7 scalecolor(parr+3*i, norm_diff_illum*(1./WHTEFFICACY));
753 greg 2.1 multcolor(parr+3*i, skycolor);
754     }
755     }
756    
757     /* Add in solar direct to nearest sky patches (GW) */
758     void
759     AddDirect(float *parr)
760     {
761     FVECT svec;
762 greg 2.3 double near_dprod[NSUNPATCH];
763     int near_patch[NSUNPATCH];
764     double wta[NSUNPATCH], wtot;
765 greg 2.1 int i, j, p;
766    
767 greg 2.4 if (dir_illum <= 1e-4 || bright(suncolor) <= 1e-4)
768 greg 2.1 return;
769 greg 2.10 /* identify nsuns closest patches */
770     if (nsuns > NSUNPATCH)
771     nsuns = NSUNPATCH;
772     else if (nsuns <= 0)
773     nsuns = 1;
774     for (i = nsuns; i--; )
775 greg 2.1 near_dprod[i] = -1.;
776     vector(svec, altitude, azimuth);
777     for (p = 1; p < nskypatch; p++) {
778     FVECT pvec;
779     double dprod;
780     rh_vector(pvec, p);
781     dprod = DOT(pvec, svec);
782 greg 2.10 for (i = 0; i < nsuns; i++)
783 greg 2.1 if (dprod > near_dprod[i]) {
784 greg 2.10 for (j = nsuns; --j > i; ) {
785 greg 2.1 near_dprod[j] = near_dprod[j-1];
786     near_patch[j] = near_patch[j-1];
787     }
788     near_dprod[i] = dprod;
789     near_patch[i] = p;
790     break;
791     }
792     }
793     wtot = 0; /* weight by proximity */
794 greg 2.10 for (i = nsuns; i--; )
795 greg 2.1 wtot += wta[i] = 1./(1.002 - near_dprod[i]);
796     /* add to nearest patch radiances */
797 greg 2.10 for (i = nsuns; i--; ) {
798 greg 2.2 float *pdest = parr + 3*near_patch[i];
799 greg 2.10 float val_add = wta[i] * dir_illum / (WHTEFFICACY * wtot);
800    
801     val_add /= (fixed_sun_sa > 0) ? fixed_sun_sa
802     : rh_dom[near_patch[i]] ;
803 greg 2.4 *pdest++ += val_add*suncolor[0];
804     *pdest++ += val_add*suncolor[1];
805     *pdest++ += val_add*suncolor[2];
806 greg 2.2 }
807 greg 2.1 }
808    
809 greg 2.35 /* Output a sun to indicated file if appropriate for this time step */
810     void
811 greg 2.36 OutputSun(int id, int goodsun, FILE *fp, FILE *mfp)
812 greg 2.35 {
813     double srad;
814     FVECT sv;
815    
816 greg 2.36 srad = DegToRad(SUN_ANG_DEG/2.);
817    
818     if (altitude < -srad) /* well below horizon? */
819 greg 2.35 return;
820    
821 greg 2.36 srad = goodsun ? dir_illum/(WHTEFFICACY * PI*srad*srad) : 0;
822 greg 2.35 vector(sv, altitude, azimuth);
823     fprintf(fp, "\nvoid light solar%d\n0\n0\n", id);
824     fprintf(fp, "3 %.3e %.3e %.3e\n", srad*suncolor[0],
825     srad*suncolor[1], srad*suncolor[2]);
826     fprintf(fp, "\nsolar%d source sun%d\n0\n0\n", id, id);
827     fprintf(fp, "4 %.6f %.6f %.6f %.4f\n", sv[0], sv[1], sv[2], SUN_ANG_DEG);
828 greg 2.36
829     if (mfp != NULL) /* saving modifier IDs? */
830     fprintf(mfp, "solar%d\n", id);
831 greg 2.35 }
832    
833 greg 2.1 /* Initialize Reinhart sky patch positions (GW) */
834     int
835     rh_init(void)
836     {
837     #define NROW 7
838     static const int tnaz[NROW] = {30, 30, 24, 24, 18, 12, 6};
839     const double alpha = (PI/2.)/(NROW*rhsubdiv + .5);
840     int p, i, j;
841     /* allocate patch angle arrays */
842     nskypatch = 0;
843     for (p = 0; p < NROW; p++)
844     nskypatch += tnaz[p];
845     nskypatch *= rhsubdiv*rhsubdiv;
846     nskypatch += 2;
847     rh_palt = (float *)malloc(sizeof(float)*nskypatch);
848     rh_pazi = (float *)malloc(sizeof(float)*nskypatch);
849     rh_dom = (float *)malloc(sizeof(float)*nskypatch);
850     if ((rh_palt == NULL) | (rh_pazi == NULL) | (rh_dom == NULL)) {
851     fprintf(stderr, "%s: out of memory in rh_init()\n", progname);
852     exit(1);
853     }
854     rh_palt[0] = -PI/2.; /* ground & zenith patches */
855     rh_pazi[0] = 0.;
856     rh_dom[0] = 2.*PI;
857     rh_palt[nskypatch-1] = PI/2.;
858     rh_pazi[nskypatch-1] = 0.;
859     rh_dom[nskypatch-1] = 2.*PI*(1. - cos(alpha*.5));
860     p = 1; /* "normal" patches */
861     for (i = 0; i < NROW*rhsubdiv; i++) {
862     const float ralt = alpha*(i + .5);
863     const int ninrow = tnaz[i/rhsubdiv]*rhsubdiv;
864 greg 2.3 const float dom = 2.*PI*(sin(alpha*(i+1)) - sin(alpha*i)) /
865     (double)ninrow;
866 greg 2.1 for (j = 0; j < ninrow; j++) {
867     rh_palt[p] = ralt;
868     rh_pazi[p] = 2.*PI * j / (double)ninrow;
869     rh_dom[p++] = dom;
870     }
871     }
872     return nskypatch;
873     #undef NROW
874     }
875    
876     /* Resize daylight matrix (GW) */
877     float *
878     resize_dmatrix(float *mtx_data, int nsteps, int npatch)
879     {
880     if (mtx_data == NULL)
881     mtx_data = (float *)malloc(sizeof(float)*3*nsteps*npatch);
882     else
883     mtx_data = (float *)realloc(mtx_data,
884     sizeof(float)*3*nsteps*npatch);
885     if (mtx_data == NULL) {
886     fprintf(stderr, "%s: out of memory in resize_dmatrix(%d,%d)\n",
887     progname, nsteps, npatch);
888     exit(1);
889     }
890     return(mtx_data);
891     }
892    
893     /* Determine category index */
894     int GetCategoryIndex()
895     {
896     int index; /* Loop index */
897    
898     for (index = 0; index < 8; index++)
899     if ((sky_clearness >= SkyClearCat[index].lower) &&
900     (sky_clearness < SkyClearCat[index].upper))
901     break;
902    
903     return index;
904     }
905    
906     /* Calculate diffuse illuminance to diffuse irradiance ratio */
907    
908     /* Reference: Perez, R., P. Ineichen, R. Seals, J. Michalsky, and R. */
909     /* Stewart. 1990. ìModeling Daylight Availability and */
910     /* Irradiance Components from Direct and Global */
911     /* Irradiance,î Solar Energy 44(5):271-289, Eqn. 7. */
912    
913     double CalcDiffuseIllumRatio( int index )
914     {
915     ModelCoeff const *pnle; /* Category coefficient pointer */
916    
917     /* Get category coefficient pointer */
918     pnle = &(DiffuseLumEff[index]);
919    
920     return pnle->a + pnle->b * apwc + pnle->c * cos(sun_zenith) +
921     pnle->d * log(sky_brightness);
922     }
923    
924     /* Calculate direct illuminance to direct irradiance ratio */
925    
926     /* Reference: Perez, R., P. Ineichen, R. Seals, J. Michalsky, and R. */
927     /* Stewart. 1990. ìModeling Daylight Availability and */
928     /* Irradiance Components from Direct and Global */
929     /* Irradiance,î Solar Energy 44(5):271-289, Eqn. 8. */
930    
931     double CalcDirectIllumRatio( int index )
932     {
933     ModelCoeff const *pnle; /* Category coefficient pointer */
934    
935     /* Get category coefficient pointer */
936     pnle = &(DirectLumEff[index]);
937    
938     /* Calculate direct illuminance from direct irradiance */
939    
940     return dmax((pnle->a + pnle->b * apwc + pnle->c * exp(5.73 *
941     sun_zenith - 5.0) + pnle->d * sky_brightness),
942     0.0);
943     }
944    
945     /* Calculate sky brightness */
946    
947     /* Reference: Perez, R., P. Ineichen, R. Seals, J. Michalsky, and R. */
948     /* Stewart. 1990. ìModeling Daylight Availability and */
949     /* Irradiance Components from Direct and Global */
950     /* Irradiance,î Solar Energy 44(5):271-289, Eqn. 2. */
951    
952     double CalcSkyBrightness()
953     {
954     return diff_irrad * CalcAirMass() / (DC_SolarConstantE *
955     CalcEccentricity());
956     }
957    
958     /* Calculate sky clearness */
959    
960     /* Reference: Perez, R., P. Ineichen, R. Seals, J. Michalsky, and R. */
961     /* Stewart. 1990. ìModeling Daylight Availability and */
962     /* Irradiance Components from Direct and Global */
963     /* Irradiance,î Solar Energy 44(5):271-289, Eqn. 1. */
964    
965     double CalcSkyClearness()
966     {
967     double sz_cubed; /* Sun zenith angle cubed */
968    
969     /* Calculate sun zenith angle cubed */
970 greg 2.11 sz_cubed = sun_zenith*sun_zenith*sun_zenith;
971 greg 2.1
972     return ((diff_irrad + dir_irrad) / diff_irrad + 1.041 *
973     sz_cubed) / (1.0 + 1.041 * sz_cubed);
974     }
975    
976     /* Calculate diffuse horizontal irradiance from Perez sky brightness */
977    
978     /* Reference: Perez, R., P. Ineichen, R. Seals, J. Michalsky, and R. */
979     /* Stewart. 1990. ìModeling Daylight Availability and */
980     /* Irradiance Components from Direct and Global */
981     /* Irradiance,î Solar Energy 44(5):271-289, Eqn. 2 */
982     /* (inverse). */
983    
984     double CalcDiffuseIrradiance()
985     {
986     return sky_brightness * DC_SolarConstantE * CalcEccentricity() /
987     CalcAirMass();
988     }
989    
990     /* Calculate direct normal irradiance from Perez sky clearness */
991    
992     /* Reference: Perez, R., P. Ineichen, R. Seals, J. Michalsky, and R. */
993     /* Stewart. 1990. ìModeling Daylight Availability and */
994     /* Irradiance Components from Direct and Global */
995     /* Irradiance,î Solar Energy 44(5):271-289, Eqn. 1 */
996     /* (inverse). */
997    
998     double CalcDirectIrradiance()
999     {
1000     return CalcDiffuseIrradiance() * ((sky_clearness - 1.0) * (1 + 1.041
1001 greg 2.11 * sun_zenith*sun_zenith*sun_zenith));
1002 greg 2.1 }
1003    
1004     /* Calculate sky brightness and clearness from illuminance values */
1005     int CalcSkyParamFromIllum()
1006     {
1007     double test1 = 0.1;
1008     double test2 = 0.1;
1009     int counter = 0;
1010     int index = 0; /* Category index */
1011    
1012     /* Convert illuminance to irradiance */
1013     diff_irrad = diff_illum * DC_SolarConstantE /
1014     (DC_SolarConstantL * 1000.0);
1015     dir_irrad = dir_illum * DC_SolarConstantE /
1016     (DC_SolarConstantL * 1000.0);
1017    
1018     /* Calculate sky brightness and clearness */
1019     sky_brightness = CalcSkyBrightness();
1020     sky_clearness = CalcSkyClearness();
1021    
1022     /* Limit sky clearness */
1023     if (sky_clearness > 12.0)
1024     sky_clearness = 12.0;
1025    
1026     /* Limit sky brightness */
1027 greg 2.9 if (sky_brightness < 0.01)
1028 greg 2.1 sky_brightness = 0.01;
1029    
1030     while (((fabs(diff_irrad - test1) > 10.0) ||
1031     (fabs(dir_irrad - test2) > 10.0)) && !(counter == 5))
1032     {
1033     test1 = diff_irrad;
1034     test2 = dir_irrad;
1035     counter++;
1036    
1037     /* Convert illuminance to irradiance */
1038     index = GetCategoryIndex();
1039     diff_irrad = diff_illum / CalcDiffuseIllumRatio(index);
1040 greg 2.26 dir_irrad = CalcDirectIllumRatio(index);
1041     if (dir_irrad > 0.1)
1042     dir_irrad = dir_illum / dir_irrad;
1043 greg 2.1
1044     /* Calculate sky brightness and clearness */
1045     sky_brightness = CalcSkyBrightness();
1046     sky_clearness = CalcSkyClearness();
1047    
1048     /* Limit sky clearness */
1049     if (sky_clearness > 12.0)
1050     sky_clearness = 12.0;
1051    
1052     /* Limit sky brightness */
1053 greg 2.9 if (sky_brightness < 0.01)
1054 greg 2.1 sky_brightness = 0.01;
1055     }
1056    
1057     return GetCategoryIndex();
1058     }
1059    
1060     /* Calculate relative luminance */
1061    
1062     /* Reference: Perez, R., R. Seals, and J. Michalsky. 1993. */
1063     /* ìAll-Weather Model for Sky Luminance Distribution - */
1064     /* Preliminary Configuration and Validation,î Solar Energy */
1065     /* 50(3):235-245, Eqn. 1. */
1066    
1067     double CalcRelLuminance( double gamma, double zeta )
1068     {
1069     return (1.0 + perez_param[0] * exp(perez_param[1] / cos(zeta))) *
1070     (1.0 + perez_param[2] * exp(perez_param[3] * gamma) +
1071     perez_param[4] * cos(gamma) * cos(gamma));
1072     }
1073    
1074     /* Calculate Perez sky model parameters */
1075    
1076     /* Reference: Perez, R., R. Seals, and J. Michalsky. 1993. */
1077     /* ìAll-Weather Model for Sky Luminance Distribution - */
1078     /* Preliminary Configuration and Validation,î Solar Energy */
1079     /* 50(3):235-245, Eqns. 6 - 8. */
1080    
1081     void CalcPerezParam( double sz, double epsilon, double delta,
1082     int index )
1083     {
1084     double x[5][4]; /* Coefficents a, b, c, d, e */
1085     int i, j; /* Loop indices */
1086    
1087     /* Limit sky brightness */
1088     if (epsilon > 1.065 && epsilon < 2.8)
1089     {
1090     if (delta < 0.2)
1091     delta = 0.2;
1092     }
1093    
1094     /* Get Perez coefficients */
1095     for (i = 0; i < 5; i++)
1096     for (j = 0; j < 4; j++)
1097     x[i][j] = PerezCoeff[index][4 * i + j];
1098    
1099     if (index != 0)
1100     {
1101     /* Calculate parameter a, b, c, d and e (Eqn. 6) */
1102     for (i = 0; i < 5; i++)
1103     perez_param[i] = x[i][0] + x[i][1] * sz + delta * (x[i][2] +
1104     x[i][3] * sz);
1105     }
1106     else
1107     {
1108     /* Parameters a, b and e (Eqn. 6) */
1109     perez_param[0] = x[0][0] + x[0][1] * sz + delta * (x[0][2] +
1110     x[0][3] * sz);
1111     perez_param[1] = x[1][0] + x[1][1] * sz + delta * (x[1][2] +
1112     x[1][3] * sz);
1113     perez_param[4] = x[4][0] + x[4][1] * sz + delta * (x[4][2] +
1114     x[4][3] * sz);
1115    
1116     /* Parameter c (Eqn. 7) */
1117     perez_param[2] = exp(pow(delta * (x[2][0] + x[2][1] * sz),
1118     x[2][2])) - x[2][3];
1119    
1120     /* Parameter d (Eqn. 8) */
1121     perez_param[3] = -exp(delta * (x[3][0] + x[3][1] * sz)) +
1122     x[3][2] + delta * x[3][3];
1123     }
1124     }
1125    
1126     /* Calculate relative horizontal illuminance (modified by GW) */
1127    
1128     /* Reference: Perez, R., R. Seals, and J. Michalsky. 1993. */
1129     /* ìAll-Weather Model for Sky Luminance Distribution - */
1130     /* Preliminary Configuration and Validation,î Solar Energy */
1131     /* 50(3):235-245, Eqn. 3. */
1132    
1133     double CalcRelHorzIllum( float *parr )
1134     {
1135     int i;
1136     double rh_illum = 0.0; /* Relative horizontal illuminance */
1137    
1138     for (i = 1; i < nskypatch; i++)
1139 greg 2.7 rh_illum += parr[3*i+1] * rh_cos(i) * rh_dom[i];
1140 greg 2.1
1141 greg 2.7 return rh_illum;
1142 greg 2.1 }
1143    
1144     /* Calculate earth orbit eccentricity correction factor */
1145    
1146     /* Reference: Sen, Z. 2008. Solar Energy Fundamental and Modeling */
1147     /* Techniques. Springer, p. 72. */
1148    
1149     double CalcEccentricity()
1150     {
1151     double day_angle; /* Day angle (radians) */
1152     double E0; /* Eccentricity */
1153    
1154     /* Calculate day angle */
1155     day_angle = (julian_date - 1.0) * (2.0 * PI / 365.0);
1156    
1157     /* Calculate eccentricity */
1158     E0 = 1.00011 + 0.034221 * cos(day_angle) + 0.00128 * sin(day_angle)
1159     + 0.000719 * cos(2.0 * day_angle) + 0.000077 * sin(2.0 *
1160     day_angle);
1161    
1162     return E0;
1163     }
1164    
1165     /* Calculate atmospheric precipitable water content */
1166    
1167     /* Reference: Perez, R., P. Ineichen, R. Seals, J. Michalsky, and R. */
1168     /* Stewart. 1990. ìModeling Daylight Availability and */
1169     /* Irradiance Components from Direct and Global */
1170     /* Irradiance,î Solar Energy 44(5):271-289, Eqn. 3. */
1171    
1172     /* Note: The default surface dew point temperature is 11 deg. C */
1173     /* (52 deg. F). Typical values are: */
1174    
1175     /* Celsius Fahrenheit Human Perception */
1176     /* > 24 > 75 Extremely uncomfortable */
1177     /* 21 - 24 70 - 74 Very humid */
1178     /* 18 - 21 65 - 69 Somewhat uncomfortable */
1179     /* 16 - 18 60 - 64 OK for most people */
1180     /* 13 - 16 55 - 59 Comfortable */
1181     /* 10 - 12 50 - 54 Very comfortable */
1182     /* < 10 < 49 A bit dry for some */
1183    
1184     double CalcPrecipWater( double dpt )
1185     { return exp(0.07 * dpt - 0.075); }
1186    
1187     /* Calculate relative air mass */
1188    
1189     /* Reference: Kasten, F. 1966. "A New Table and Approximation Formula */
1190     /* for the Relative Optical Air Mass," Arch. Meteorol. */
1191     /* Geophys. Bioklimataol. Ser. B14, pp. 206-233. */
1192    
1193     /* Note: More sophisticated relative air mass models are */
1194     /* available, but they differ significantly only for */
1195     /* sun zenith angles greater than 80 degrees. */
1196    
1197     double CalcAirMass()
1198     {
1199     return (1.0 / (cos(sun_zenith) + 0.15 * pow(93.885 -
1200     RadToDeg(sun_zenith), -1.253)));
1201     }
1202    
1203     /* Calculate Perez All-Weather sky patch luminances (modified by GW) */
1204    
1205     /* NOTE: The sky patches centers are determined in accordance with the */
1206     /* BRE-IDMP sky luminance measurement procedures. (See for example */
1207     /* Mardaljevic, J. 2001. "The BRE-IDMP Dataset: A New Benchmark */
1208     /* for the Validation of Illuminance Prediction Techniques," */
1209     /* Lighting Research & Technology 33(2):117-136.) */
1210    
1211     void CalcSkyPatchLumin( float *parr )
1212     {
1213     int i;
1214     double aas; /* Sun-sky point azimuthal angle */
1215     double sspa; /* Sun-sky point angle */
1216     double zsa; /* Zenithal sun angle */
1217    
1218     for (i = 1; i < nskypatch; i++)
1219     {
1220     /* Calculate sun-sky point azimuthal angle */
1221     aas = fabs(rh_pazi[i] - azimuth);
1222    
1223     /* Calculate zenithal sun angle */
1224     zsa = PI * 0.5 - rh_palt[i];
1225    
1226     /* Calculate sun-sky point angle (Equation 8-20) */
1227     sspa = acos(cos(sun_zenith) * cos(zsa) + sin(sun_zenith) *
1228     sin(zsa) * cos(aas));
1229    
1230     /* Calculate patch luminance */
1231     parr[3*i] = CalcRelLuminance(sspa, zsa);
1232     if (parr[3*i] < 0) parr[3*i] = 0;
1233     parr[3*i+2] = parr[3*i+1] = parr[3*i];
1234     }
1235     }