1 /**************************************************************************
2 * fg_time.c -- data structures and routines for managing time related stuff.
4 * Written by Curtis Olson, started August 1997.
6 * Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2 of the
11 * License, or (at your option) any later version.
13 * This program is distributed in the hope that it will be useful, but
14 * WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 * (Log is kept at end of this file)
24 **************************************************************************/
33 #include <sys/time.h> /* for gettimeofday() */
34 #include <unistd.h> /* for gettimeofday() */
38 #include "../Include/constants.h"
39 #include "../Flight/flight.h"
40 #include "../Time/fg_time.h"
43 #define DEGHR(x) ((x)/15.)
44 #define RADHR(x) DEGHR(x*RAD_TO_DEG)
47 struct fgTIME cur_time_params;
48 struct fgLIGHT cur_light_params;
51 /* Initialize the time dependent variables */
53 void fgTimeInit(struct fgTIME *t) {
54 t->gst_diff = -9999.0;
58 /* given a date in months, mn, days, dy, years, yr, return the
59 * modified Julian date (number of days elapsed since 1900 jan 0.5),
60 * mjd. Adapted from Xephem. */
62 double cal_mjd (int mn, double dy, int yr) {
63 static double last_mjd, last_dy;
65 static int last_mn, last_yr;
69 if (mn == last_mn && yr == last_yr && dy == last_dy) {
75 y = (yr < 0) ? yr + 1 : yr;
81 if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
90 c = (long)((365.25*y) - 0.75) - 694025L;
92 c = (long)(365.25*y) - 694025L;
97 mjd = b + c + d + dy - 0.5;
108 /* given an mjd, return greenwich mean siderial time, gst */
110 double utc_gst (double mjd) {
112 double day = floor(mjd-0.5)+0.5;
113 double hr = (mjd-day)*24.0;
116 T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
117 x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
119 gst = (1.0/SIDRATE)*hr + x;
121 printf("gst => %.4f\n", gst);
127 /* given Julian Date and Longitude (decimal degrees West) compute and
128 * return Local Sidereal Time, in decimal hours.
130 * Provided courtesy of ecdowney@noao.edu (Elwood Downey)
133 double sidereal_precise (double mjd, double lng) {
137 /* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
140 /* convert to required internal units */
143 /* compute LST and print */
145 lst = gst - RADHR (lng);
146 lst -= 24.0*floor(lst/24.0);
147 /* printf ("%7.4f\n", lst); */
154 /* return a courser but cheaper estimate of sidereal time */
155 double sidereal_course(struct tm *gmt, time_t now, double lng) {
156 time_t start, start_gmt;
159 double diff, part, days, hours, lst;
169 printf("COURSE: GMT = %d/%d/%2d %d:%02d:%02d\n",
170 gmt->tm_mon, gmt->tm_mday, gmt->tm_year,
171 gmt->tm_hour, gmt->tm_min, gmt->tm_sec);
175 mt.tm_year = gmt->tm_year;
183 daylight = mt.tm_isdst;
184 gettimeofday(&tv, &tz);
185 timezone = tz.tz_minuteswest * 60;
188 if ( daylight > 0 ) {
190 } else if ( daylight < 0 ) {
191 printf("OOOPS, big time problem in fg_time.c, no daylight savings info.\n");
194 offset = -(timezone / 3600 - daylight);
196 printf("Raw time zone offset = %ld\n", timezone);
197 printf("Daylight Savings = %d\n", daylight);
199 printf("Local hours from GMT = %ld\n", offset);
201 start_gmt = start - timezone + (daylight * 3600);
203 printf("March 21 noon (CST) = %ld\n", start);
204 printf("March 21 noon (GMT) = %ld\n", start_gmt);
206 diff = (now - start_gmt) / (3600.0 * 24.0);
208 printf("Time since 3/21/%2d GMT = %.2f\n", gmt->tm_year, diff);
210 part = fmod(diff, 1.0);
212 hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
214 lst = (days - lng)/15.0 + hours - 12;
216 while ( lst < 0.0 ) {
220 printf("days = %.1f hours = %.2f lon = %.2f lst = %.2f\n",
221 days, hours, lng, lst);
227 /* Update the time dependent variables */
229 void fgTimeUpdate(struct fgFLIGHT *f, struct fgTIME *t) {
230 double gst_precise, gst_course;
231 static long int warp = 0;
233 /* get current Unix calendar time (in seconds) */
236 t->cur_time = time(NULL) + (0) * 60 * 60;
238 printf("Current Unix calendar time = %ld warp = %ld\n", t->cur_time, warp);
240 /* get GMT break down for current time */
241 t->gmt = gmtime(&t->cur_time);
242 printf("Current GMT = %d/%d/%2d %d:%02d:%02d\n",
243 t->gmt->tm_mon+1, t->gmt->tm_mday, t->gmt->tm_year,
244 t->gmt->tm_hour, t->gmt->tm_min, t->gmt->tm_sec);
246 /* calculate modified Julian date */
247 t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
248 (int)(t->gmt->tm_year + 1900));
250 /* add in partial day */
251 t->mjd += (t->gmt->tm_hour / 24.0) + (t->gmt->tm_min / (24.0 * 60.0)) +
252 (t->gmt->tm_sec / (24.0 * 60.0 * 60.0));
254 /* convert "back" to Julian date + partial day (as a fraction of one) */
255 t->jd = t->mjd + MJD0;
256 printf("Current Julian Date = %.5f\n", t->jd);
258 printf("Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG);
260 /* Calculate local side real time */
261 if ( t->gst_diff < -100.0 ) {
262 /* first time through do the expensive calculation & cheap
263 calculation to get the difference. */
264 printf("First time, doing precise gst\n");
265 t->gst = gst_precise = sidereal_precise(t->mjd, 0.00);
266 gst_course = sidereal_course(t->gmt, t->cur_time, 0.00);
267 t->gst_diff = gst_precise - gst_course;
270 sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG))
273 /* course + difference should drift off very slowly */
275 sidereal_course(t->gmt, t->cur_time, 0.00) + t->gst_diff;
277 sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG))
280 /* printf("Current lon=0.00 Sidereal Time = %.3f\n", t->gst); */
281 /* printf("Current LOCAL Sidereal Time = %.3f (%.3f) (diff = %.3f)\n",
282 t->lst, sidereal_precise(t->mjd, -(FG_Longitude * RAD_TO_DEG)),
288 /* Revision 1.20 1997/12/15 23:55:06 curt
289 /* Add xgl wrappers for debugging.
290 /* Generate terrain normals on the fly.
292 * Revision 1.19 1997/12/15 20:59:10 curt
295 * Revision 1.18 1997/12/12 21:41:31 curt
296 * More light/material property tweaking ... still a ways off.
298 * Revision 1.17 1997/12/12 19:53:04 curt
299 * Working on lightling and material properties.
301 * Revision 1.16 1997/12/11 04:43:57 curt
302 * Fixed sun vector and lighting problems. I thing the moon is now lit
305 * Revision 1.15 1997/12/10 22:37:54 curt
306 * Prepended "fg" on the name of all global structures that didn't have it yet.
307 * i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
309 * Revision 1.14 1997/12/10 01:19:52 curt
310 * Tweaks for verion 0.15 release.
312 * Revision 1.13 1997/12/09 05:11:56 curt
313 * Working on tweaking lighting.
315 * Revision 1.12 1997/12/09 04:25:37 curt
316 * Working on adding a global lighting params structure.
318 * Revision 1.11 1997/11/25 19:25:40 curt
319 * Changes to integrate Durk's moon/sun code updates + clean up.
321 * Revision 1.10 1997/11/15 18:16:42 curt
324 * Revision 1.9 1997/11/14 00:26:50 curt
325 * Transform scenery coordinates earlier in pipeline when scenery is being
326 * created, not when it is being loaded. Precalculate normals for each node
327 * as average of the normals of each containing polygon so Garoude shading is
330 * Revision 1.8 1997/10/25 03:30:08 curt
333 * Revision 1.7 1997/09/23 00:29:50 curt
334 * Tweaks to get things to compile with gcc-win32.
336 * Revision 1.6 1997/09/20 03:34:34 curt
337 * Still trying to get those durned stars aligned properly.
339 * Revision 1.5 1997/09/16 22:14:52 curt
340 * Tweaked time of day lighting equations. Don't draw stars during the day.
342 * Revision 1.4 1997/09/16 15:50:31 curt
343 * Working on star alignment and time issues.
345 * Revision 1.3 1997/09/13 02:00:08 curt
346 * Mostly working on stars and generating sidereal time for accurate star
349 * Revision 1.2 1997/08/27 03:30:35 curt
350 * Changed naming scheme of basic shared structures.
352 * Revision 1.1 1997/08/13 21:55:59 curt