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/timeb.h> /* for ftime() and struct timeb */
35 # include <unistd.h> /* for gettimeofday() */
36 # include <sys/time.h> /* for get/setitimer, gettimeofday, struct timeval */
37 #endif /* USE_FTIME */
39 #include <Time/fg_time.h>
40 #include <Include/constants.h>
41 #include <Flight/flight.h>
44 #define DEGHR(x) ((x)/15.)
45 #define RADHR(x) DEGHR(x*RAD_TO_DEG)
48 struct fgTIME cur_time_params;
49 struct fgLIGHT cur_light_params;
52 /* Initialize the time dependent variables */
54 void fgTimeInit(struct fgTIME *t) {
55 printf("Initializing Time\n");
57 t->gst_diff = -9999.0;
63 /* given a date in months, mn, days, dy, years, yr, return the
64 * modified Julian date (number of days elapsed since 1900 jan 0.5),
65 * mjd. Adapted from Xephem. */
67 double cal_mjd (int mn, double dy, int yr) {
68 static double last_mjd, last_dy;
70 static int last_mn, last_yr;
74 if (mn == last_mn && yr == last_yr && dy == last_dy) {
80 y = (yr < 0) ? yr + 1 : yr;
86 if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
95 c = (long)((365.25*y) - 0.75) - 694025L;
97 c = (long)(365.25*y) - 694025L;
102 mjd = b + c + d + dy - 0.5;
113 /* given an mjd, return greenwich mean siderial time, gst */
115 double utc_gst (double mjd) {
117 double day = floor(mjd-0.5)+0.5;
118 double hr = (mjd-day)*24.0;
121 T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
122 x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
124 gst = (1.0/SIDRATE)*hr + x;
126 printf(" gst => %.4f\n", gst);
132 /* given Julian Date and Longitude (decimal degrees West) compute and
133 * return Local Sidereal Time, in decimal hours.
135 * Provided courtesy of ecdowney@noao.edu (Elwood Downey)
138 double sidereal_precise (double mjd, double lng) {
142 /* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
145 /* convert to required internal units */
148 /* compute LST and print */
150 lst = gst - RADHR (lng);
151 lst -= 24.0*floor(lst/24.0);
152 /* printf ("%7.4f\n", lst); */
159 /* return a courser but cheaper estimate of sidereal time */
160 double sidereal_course(struct tm *gmt, time_t now, double lng) {
161 time_t start, start_gmt;
164 double diff, part, days, hours, lst;
167 struct timeb current;
168 #endif /* USE_FTIME */
176 printf(" COURSE: GMT = %d/%d/%2d %d:%02d:%02d\n",
177 gmt->tm_mon, gmt->tm_mday, gmt->tm_year,
178 gmt->tm_hour, gmt->tm_min, gmt->tm_sec);
183 mt.tm_year = gmt->tm_year;
187 mt.tm_isdst = -1; /* let the system determine the proper time zone */
191 /* printf("start1 = %ld\n", start);
192 printf("start2 = %s", ctime(&start));
193 printf("start3 = %ld\n", start); */
195 daylight = mt.tm_isdst;
199 timezone = current.timezone * 60;
200 #endif /* USE_FTIME */
202 if ( daylight > 0 ) {
204 } else if ( daylight < 0 ) {
205 printf("OOOPS, big time problem in fg_time.c, no daylight savings info.\n");
208 offset = -(timezone / 3600 - daylight);
210 /* printf(" Raw time zone offset = %ld\n", timezone); */
211 /* printf(" Daylight Savings = %d\n", daylight); */
213 /* printf(" Local hours from GMT = %ld\n", offset); */
215 start_gmt = start - timezone + (daylight * 3600);
217 /* printf(" March 21 noon (CST) = %ld\n", start); */
218 /* printf(" March 21 noon (GMT) = %ld\n", start_gmt); */
220 diff = (now - start_gmt) / (3600.0 * 24.0);
222 /* printf(" Time since 3/21/%2d GMT = %.2f\n", gmt->tm_year, diff); */
224 part = fmod(diff, 1.0);
226 hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
228 lst = (days - lng)/15.0 + hours - 12;
230 while ( lst < 0.0 ) {
234 /* printf(" days = %.1f hours = %.2f lon = %.2f lst = %.2f\n",
235 days, hours, lng, lst); */
241 /* Update the time dependent variables */
243 void fgTimeUpdate(struct fgFLIGHT *f, struct fgTIME *t) {
244 double gst_precise, gst_course;
246 printf("Updating time\n");
248 /* get current Unix calendar time (in seconds) */
249 t->warp += t->warp_delta;
250 t->cur_time = time(NULL) + t->warp;
251 printf(" Current Unix calendar time = %ld warp = %ld delta = %ld\n",
252 t->cur_time, t->warp, t->warp_delta);
254 /* get GMT break down for current time */
255 t->gmt = gmtime(&t->cur_time);
256 printf(" Current GMT = %d/%d/%2d %d:%02d:%02d\n",
257 t->gmt->tm_mon+1, t->gmt->tm_mday, t->gmt->tm_year,
258 t->gmt->tm_hour, t->gmt->tm_min, t->gmt->tm_sec);
260 /* calculate modified Julian date */
261 t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
262 (int)(t->gmt->tm_year + 1900));
264 /* add in partial day */
265 t->mjd += (t->gmt->tm_hour / 24.0) + (t->gmt->tm_min / (24.0 * 60.0)) +
266 (t->gmt->tm_sec / (24.0 * 60.0 * 60.0));
268 /* convert "back" to Julian date + partial day (as a fraction of one) */
269 t->jd = t->mjd + MJD0;
270 printf(" Current Julian Date = %.5f\n", t->jd);
272 /* printf(" Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG); */
274 /* Calculate local side real time */
275 if ( t->gst_diff < -100.0 ) {
276 /* first time through do the expensive calculation & cheap
277 calculation to get the difference. */
278 printf(" First time, doing precise gst\n");
279 t->gst = gst_precise = sidereal_precise(t->mjd, 0.00);
280 gst_course = sidereal_course(t->gmt, t->cur_time, 0.00);
281 t->gst_diff = gst_precise - gst_course;
284 sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG))
287 /* course + difference should drift off very slowly */
289 sidereal_course(t->gmt, t->cur_time, 0.00) + t->gst_diff;
291 sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG))
294 /* printf(" Current lon=0.00 Sidereal Time = %.3f\n", t->gst); */
295 /* printf(" Current LOCAL Sidereal Time = %.3f (%.3f) (diff = %.3f)\n",
296 t->lst, sidereal_precise(t->mjd, -(FG_Longitude * RAD_TO_DEG)),
302 /* Revision 1.30 1998/01/21 21:11:35 curt
305 * Revision 1.29 1998/01/19 19:27:20 curt
306 * Merged in make system changes from Bob Kuehne <rpk@sgi.com>
307 * This should simplify things tremendously.
309 * Revision 1.28 1998/01/19 18:35:49 curt
310 * Minor tweaks and fixes for cygwin32.
312 * Revision 1.27 1998/01/13 00:23:13 curt
313 * Initial changes to support loading and management of scenery tiles. Note,
314 * there's still a fair amount of work left to be done.
316 * Revision 1.26 1998/01/05 18:44:36 curt
317 * Add an option to advance/decrease time from keyboard.
319 * Revision 1.25 1997/12/31 17:46:50 curt
320 * Tweaked fg_time.c to be able to use ftime() instead of gettimeofday()
322 * Revision 1.24 1997/12/30 22:22:42 curt
323 * Further integration of event manager.
325 * Revision 1.23 1997/12/30 20:47:58 curt
326 * Integrated new event manager with subsystem initializations.
328 * Revision 1.22 1997/12/30 01:38:47 curt
329 * Switched back to per vertex normals and smooth shading for terrain.
331 * Revision 1.21 1997/12/23 04:58:39 curt
332 * Tweaked the sky coloring a bit to build in structures to allow finer rgb
335 * Revision 1.20 1997/12/15 23:55:06 curt
336 * Add xgl wrappers for debugging.
337 * Generate terrain normals on the fly.
339 * Revision 1.19 1997/12/15 20:59:10 curt
342 * Revision 1.18 1997/12/12 21:41:31 curt
343 * More light/material property tweaking ... still a ways off.
345 * Revision 1.17 1997/12/12 19:53:04 curt
346 * Working on lightling and material properties.
348 * Revision 1.16 1997/12/11 04:43:57 curt
349 * Fixed sun vector and lighting problems. I thing the moon is now lit
352 * Revision 1.15 1997/12/10 22:37:54 curt
353 * Prepended "fg" on the name of all global structures that didn't have it yet.
354 * i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
356 * Revision 1.14 1997/12/10 01:19:52 curt
357 * Tweaks for verion 0.15 release.
359 * Revision 1.13 1997/12/09 05:11:56 curt
360 * Working on tweaking lighting.
362 * Revision 1.12 1997/12/09 04:25:37 curt
363 * Working on adding a global lighting params structure.
365 * Revision 1.11 1997/11/25 19:25:40 curt
366 * Changes to integrate Durk's moon/sun code updates + clean up.
368 * Revision 1.10 1997/11/15 18:16:42 curt
371 * Revision 1.9 1997/11/14 00:26:50 curt
372 * Transform scenery coordinates earlier in pipeline when scenery is being
373 * created, not when it is being loaded. Precalculate normals for each node
374 * as average of the normals of each containing polygon so Garoude shading is
377 * Revision 1.8 1997/10/25 03:30:08 curt
380 * Revision 1.7 1997/09/23 00:29:50 curt
381 * Tweaks to get things to compile with gcc-win32.
383 * Revision 1.6 1997/09/20 03:34:34 curt
384 * Still trying to get those durned stars aligned properly.
386 * Revision 1.5 1997/09/16 22:14:52 curt
387 * Tweaked time of day lighting equations. Don't draw stars during the day.
389 * Revision 1.4 1997/09/16 15:50:31 curt
390 * Working on star alignment and time issues.
392 * Revision 1.3 1997/09/13 02:00:08 curt
393 * Mostly working on stars and generating sidereal time for accurate star
396 * Revision 1.2 1997/08/27 03:30:35 curt
397 * Changed naming scheme of basic shared structures.
399 * Revision 1.1 1997/08/13 21:55:59 curt