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 */
40 #include "../Include/constants.h"
41 #include "../Flight/flight.h"
42 #include "../Time/fg_time.h"
45 #define DEGHR(x) ((x)/15.)
46 #define RADHR(x) DEGHR(x*RAD_TO_DEG)
49 struct fgTIME cur_time_params;
50 struct fgLIGHT cur_light_params;
53 /* Initialize the time dependent variables */
55 void fgTimeInit(struct fgTIME *t) {
56 printf("Initializing Time\n");
58 t->gst_diff = -9999.0;
65 /* given a date in months, mn, days, dy, years, yr, return the
66 * modified Julian date (number of days elapsed since 1900 jan 0.5),
67 * mjd. Adapted from Xephem. */
69 double cal_mjd (int mn, double dy, int yr) {
70 static double last_mjd, last_dy;
72 static int last_mn, last_yr;
76 if (mn == last_mn && yr == last_yr && dy == last_dy) {
82 y = (yr < 0) ? yr + 1 : yr;
88 if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
97 c = (long)((365.25*y) - 0.75) - 694025L;
99 c = (long)(365.25*y) - 694025L;
104 mjd = b + c + d + dy - 0.5;
115 /* given an mjd, return greenwich mean siderial time, gst */
117 double utc_gst (double mjd) {
119 double day = floor(mjd-0.5)+0.5;
120 double hr = (mjd-day)*24.0;
123 T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
124 x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
126 gst = (1.0/SIDRATE)*hr + x;
128 printf(" gst => %.4f\n", gst);
134 /* given Julian Date and Longitude (decimal degrees West) compute and
135 * return Local Sidereal Time, in decimal hours.
137 * Provided courtesy of ecdowney@noao.edu (Elwood Downey)
140 double sidereal_precise (double mjd, double lng) {
144 /* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
147 /* convert to required internal units */
150 /* compute LST and print */
152 lst = gst - RADHR (lng);
153 lst -= 24.0*floor(lst/24.0);
154 /* printf ("%7.4f\n", lst); */
161 /* return a courser but cheaper estimate of sidereal time */
162 double sidereal_course(struct tm *gmt, time_t now, double lng) {
163 time_t start, start_gmt;
166 double diff, part, days, hours, lst;
169 struct timeb current;
170 #endif /* USE_FTIME */
178 printf(" COURSE: GMT = %d/%d/%2d %d:%02d:%02d\n",
179 gmt->tm_mon, gmt->tm_mday, gmt->tm_year,
180 gmt->tm_hour, gmt->tm_min, gmt->tm_sec);
185 mt.tm_year = gmt->tm_year;
189 mt.tm_isdst = -1; /* let the system determine the proper time zone */
193 /* printf("start1 = %ld\n", start);
194 printf("start2 = %s", ctime(&start));
195 printf("start3 = %ld\n", start); */
197 daylight = mt.tm_isdst;
201 timezone = current.timezone * 60;
202 #endif /* USE_FTIME */
204 if ( daylight > 0 ) {
206 } else if ( daylight < 0 ) {
207 printf("OOOPS, big time problem in fg_time.c, no daylight savings info.\n");
210 offset = -(timezone / 3600 - daylight);
212 /* printf(" Raw time zone offset = %ld\n", timezone); */
213 /* printf(" Daylight Savings = %d\n", daylight); */
215 /* printf(" Local hours from GMT = %ld\n", offset); */
217 start_gmt = start - timezone + (daylight * 3600);
219 /* printf(" March 21 noon (CST) = %ld\n", start); */
220 /* printf(" March 21 noon (GMT) = %ld\n", start_gmt); */
222 diff = (now - start_gmt) / (3600.0 * 24.0);
224 /* printf(" Time since 3/21/%2d GMT = %.2f\n", gmt->tm_year, diff); */
226 part = fmod(diff, 1.0);
228 hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
230 lst = (days - lng)/15.0 + hours - 12;
232 while ( lst < 0.0 ) {
236 /* printf(" days = %.1f hours = %.2f lon = %.2f lst = %.2f\n",
237 days, hours, lng, lst); */
243 /* Update the time dependent variables */
245 void fgTimeUpdate(struct fgFLIGHT *f, struct fgTIME *t) {
246 double gst_precise, gst_course;
248 printf("Updating time\n");
250 /* get current Unix calendar time (in seconds) */
251 t->warp += t->warp_delta;
252 t->cur_time = time(NULL) + t->warp;
253 printf(" Current Unix calendar time = %ld warp = %ld delta = %ld\n",
254 t->cur_time, t->warp, t->warp_delta);
256 /* get GMT break down for current time */
257 t->gmt = gmtime(&t->cur_time);
258 printf(" Current GMT = %d/%d/%2d %d:%02d:%02d\n",
259 t->gmt->tm_mon+1, t->gmt->tm_mday, t->gmt->tm_year,
260 t->gmt->tm_hour, t->gmt->tm_min, t->gmt->tm_sec);
262 /* calculate modified Julian date */
263 t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
264 (int)(t->gmt->tm_year + 1900));
266 /* add in partial day */
267 t->mjd += (t->gmt->tm_hour / 24.0) + (t->gmt->tm_min / (24.0 * 60.0)) +
268 (t->gmt->tm_sec / (24.0 * 60.0 * 60.0));
270 /* convert "back" to Julian date + partial day (as a fraction of one) */
271 t->jd = t->mjd + MJD0;
272 printf(" Current Julian Date = %.5f\n", t->jd);
274 /* printf(" Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG); */
276 /* Calculate local side real time */
277 if ( t->gst_diff < -100.0 ) {
278 /* first time through do the expensive calculation & cheap
279 calculation to get the difference. */
280 printf(" First time, doing precise gst\n");
281 t->gst = gst_precise = sidereal_precise(t->mjd, 0.00);
282 gst_course = sidereal_course(t->gmt, t->cur_time, 0.00);
283 t->gst_diff = gst_precise - gst_course;
286 sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG))
289 /* course + difference should drift off very slowly */
291 sidereal_course(t->gmt, t->cur_time, 0.00) + t->gst_diff;
293 sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG))
296 /* printf(" Current lon=0.00 Sidereal Time = %.3f\n", t->gst); */
297 /* printf(" Current LOCAL Sidereal Time = %.3f (%.3f) (diff = %.3f)\n",
298 t->lst, sidereal_precise(t->mjd, -(FG_Longitude * RAD_TO_DEG)),
304 /* Revision 1.28 1998/01/19 18:35:49 curt
305 /* Minor tweaks and fixes for cygwin32.
307 * Revision 1.27 1998/01/13 00:23:13 curt
308 * Initial changes to support loading and management of scenery tiles. Note,
309 * there's still a fair amount of work left to be done.
311 * Revision 1.26 1998/01/05 18:44:36 curt
312 * Add an option to advance/decrease time from keyboard.
314 * Revision 1.25 1997/12/31 17:46:50 curt
315 * Tweaked fg_time.c to be able to use ftime() instead of gettimeofday()
317 * Revision 1.24 1997/12/30 22:22:42 curt
318 * Further integration of event manager.
320 * Revision 1.23 1997/12/30 20:47:58 curt
321 * Integrated new event manager with subsystem initializations.
323 * Revision 1.22 1997/12/30 01:38:47 curt
324 * Switched back to per vertex normals and smooth shading for terrain.
326 * Revision 1.21 1997/12/23 04:58:39 curt
327 * Tweaked the sky coloring a bit to build in structures to allow finer rgb
330 * Revision 1.20 1997/12/15 23:55:06 curt
331 * Add xgl wrappers for debugging.
332 * Generate terrain normals on the fly.
334 * Revision 1.19 1997/12/15 20:59:10 curt
337 * Revision 1.18 1997/12/12 21:41:31 curt
338 * More light/material property tweaking ... still a ways off.
340 * Revision 1.17 1997/12/12 19:53:04 curt
341 * Working on lightling and material properties.
343 * Revision 1.16 1997/12/11 04:43:57 curt
344 * Fixed sun vector and lighting problems. I thing the moon is now lit
347 * Revision 1.15 1997/12/10 22:37:54 curt
348 * Prepended "fg" on the name of all global structures that didn't have it yet.
349 * i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
351 * Revision 1.14 1997/12/10 01:19:52 curt
352 * Tweaks for verion 0.15 release.
354 * Revision 1.13 1997/12/09 05:11:56 curt
355 * Working on tweaking lighting.
357 * Revision 1.12 1997/12/09 04:25:37 curt
358 * Working on adding a global lighting params structure.
360 * Revision 1.11 1997/11/25 19:25:40 curt
361 * Changes to integrate Durk's moon/sun code updates + clean up.
363 * Revision 1.10 1997/11/15 18:16:42 curt
366 * Revision 1.9 1997/11/14 00:26:50 curt
367 * Transform scenery coordinates earlier in pipeline when scenery is being
368 * created, not when it is being loaded. Precalculate normals for each node
369 * as average of the normals of each containing polygon so Garoude shading is
372 * Revision 1.8 1997/10/25 03:30:08 curt
375 * Revision 1.7 1997/09/23 00:29:50 curt
376 * Tweaks to get things to compile with gcc-win32.
378 * Revision 1.6 1997/09/20 03:34:34 curt
379 * Still trying to get those durned stars aligned properly.
381 * Revision 1.5 1997/09/16 22:14:52 curt
382 * Tweaked time of day lighting equations. Don't draw stars during the day.
384 * Revision 1.4 1997/09/16 15:50:31 curt
385 * Working on star alignment and time issues.
387 * Revision 1.3 1997/09/13 02:00:08 curt
388 * Mostly working on stars and generating sidereal time for accurate star
391 * Revision 1.2 1997/08/27 03:30:35 curt
392 * Changed naming scheme of basic shared structures.
394 * Revision 1.1 1997/08/13 21:55:59 curt