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 printf("Initializing Time\n");
56 t->gst_diff = -9999.0;
60 /* given a date in months, mn, days, dy, years, yr, return the
61 * modified Julian date (number of days elapsed since 1900 jan 0.5),
62 * mjd. Adapted from Xephem. */
64 double cal_mjd (int mn, double dy, int yr) {
65 static double last_mjd, last_dy;
67 static int last_mn, last_yr;
71 if (mn == last_mn && yr == last_yr && dy == last_dy) {
77 y = (yr < 0) ? yr + 1 : yr;
83 if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
92 c = (long)((365.25*y) - 0.75) - 694025L;
94 c = (long)(365.25*y) - 694025L;
99 mjd = b + c + d + dy - 0.5;
110 /* given an mjd, return greenwich mean siderial time, gst */
112 double utc_gst (double mjd) {
114 double day = floor(mjd-0.5)+0.5;
115 double hr = (mjd-day)*24.0;
118 T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
119 x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
121 gst = (1.0/SIDRATE)*hr + x;
123 printf(" gst => %.4f\n", gst);
129 /* given Julian Date and Longitude (decimal degrees West) compute and
130 * return Local Sidereal Time, in decimal hours.
132 * Provided courtesy of ecdowney@noao.edu (Elwood Downey)
135 double sidereal_precise (double mjd, double lng) {
139 /* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
142 /* convert to required internal units */
145 /* compute LST and print */
147 lst = gst - RADHR (lng);
148 lst -= 24.0*floor(lst/24.0);
149 /* printf ("%7.4f\n", lst); */
156 /* return a courser but cheaper estimate of sidereal time */
157 double sidereal_course(struct tm *gmt, time_t now, double lng) {
158 time_t start, start_gmt;
161 double diff, part, days, hours, lst;
172 printf(" COURSE: GMT = %d/%d/%2d %d:%02d:%02d\n",
173 gmt->tm_mon, gmt->tm_mday, gmt->tm_year,
174 gmt->tm_hour, gmt->tm_min, gmt->tm_sec);
179 mt.tm_year = gmt->tm_year;
187 daylight = mt.tm_isdst;
188 gettimeofday(&tv, &tz);
189 timezone = tz.tz_minuteswest * 60;
192 if ( daylight > 0 ) {
194 } else if ( daylight < 0 ) {
195 printf("OOOPS, big time problem in fg_time.c, no daylight savings info.\n");
198 offset = -(timezone / 3600 - daylight);
200 /* printf(" Raw time zone offset = %ld\n", timezone); */
201 /* printf(" Daylight Savings = %d\n", daylight); */
203 /* printf(" Local hours from GMT = %ld\n", offset); */
205 start_gmt = start - timezone + (daylight * 3600);
207 /* printf(" March 21 noon (CST) = %ld\n", start); */
208 /* printf(" March 21 noon (GMT) = %ld\n", start_gmt); */
210 diff = (now - start_gmt) / (3600.0 * 24.0);
212 /* printf(" Time since 3/21/%2d GMT = %.2f\n", gmt->tm_year, diff); */
214 part = fmod(diff, 1.0);
216 hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
218 lst = (days - lng)/15.0 + hours - 12;
220 while ( lst < 0.0 ) {
224 /* printf(" days = %.1f hours = %.2f lon = %.2f lst = %.2f\n",
225 days, hours, lng, lst); */
231 /* Update the time dependent variables */
233 void fgTimeUpdate(struct fgFLIGHT *f, struct fgTIME *t) {
234 double gst_precise, gst_course;
235 static long int warp = 0;
237 printf("Updating time\n");
239 /* get current Unix calendar time (in seconds) */
242 t->cur_time = time(NULL) + (0) * 60 * 60;
244 printf(" Current Unix calendar time = %ld warp = %ld\n",
247 /* get GMT break down for current time */
248 t->gmt = gmtime(&t->cur_time);
249 printf(" Current GMT = %d/%d/%2d %d:%02d:%02d\n",
250 t->gmt->tm_mon+1, t->gmt->tm_mday, t->gmt->tm_year,
251 t->gmt->tm_hour, t->gmt->tm_min, t->gmt->tm_sec);
253 /* calculate modified Julian date */
254 t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
255 (int)(t->gmt->tm_year + 1900));
257 /* add in partial day */
258 t->mjd += (t->gmt->tm_hour / 24.0) + (t->gmt->tm_min / (24.0 * 60.0)) +
259 (t->gmt->tm_sec / (24.0 * 60.0 * 60.0));
261 /* convert "back" to Julian date + partial day (as a fraction of one) */
262 t->jd = t->mjd + MJD0;
263 printf(" Current Julian Date = %.5f\n", t->jd);
265 /* printf(" Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG); */
267 /* Calculate local side real time */
268 if ( t->gst_diff < -100.0 ) {
269 /* first time through do the expensive calculation & cheap
270 calculation to get the difference. */
271 printf(" First time, doing precise gst\n");
272 t->gst = gst_precise = sidereal_precise(t->mjd, 0.00);
273 gst_course = sidereal_course(t->gmt, t->cur_time, 0.00);
274 t->gst_diff = gst_precise - gst_course;
277 sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG))
280 /* course + difference should drift off very slowly */
282 sidereal_course(t->gmt, t->cur_time, 0.00) + t->gst_diff;
284 sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG))
287 /* printf(" Current lon=0.00 Sidereal Time = %.3f\n", t->gst); */
288 /* printf(" Current LOCAL Sidereal Time = %.3f (%.3f) (diff = %.3f)\n",
289 t->lst, sidereal_precise(t->mjd, -(FG_Longitude * RAD_TO_DEG)),
295 /* Revision 1.24 1997/12/30 22:22:42 curt
296 /* Further integration of event manager.
298 * Revision 1.23 1997/12/30 20:47:58 curt
299 * Integrated new event manager with subsystem initializations.
301 * Revision 1.22 1997/12/30 01:38:47 curt
302 * Switched back to per vertex normals and smooth shading for terrain.
304 * Revision 1.21 1997/12/23 04:58:39 curt
305 * Tweaked the sky coloring a bit to build in structures to allow finer rgb
308 * Revision 1.20 1997/12/15 23:55:06 curt
309 * Add xgl wrappers for debugging.
310 * Generate terrain normals on the fly.
312 * Revision 1.19 1997/12/15 20:59:10 curt
315 * Revision 1.18 1997/12/12 21:41:31 curt
316 * More light/material property tweaking ... still a ways off.
318 * Revision 1.17 1997/12/12 19:53:04 curt
319 * Working on lightling and material properties.
321 * Revision 1.16 1997/12/11 04:43:57 curt
322 * Fixed sun vector and lighting problems. I thing the moon is now lit
325 * Revision 1.15 1997/12/10 22:37:54 curt
326 * Prepended "fg" on the name of all global structures that didn't have it yet.
327 * i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
329 * Revision 1.14 1997/12/10 01:19:52 curt
330 * Tweaks for verion 0.15 release.
332 * Revision 1.13 1997/12/09 05:11:56 curt
333 * Working on tweaking lighting.
335 * Revision 1.12 1997/12/09 04:25:37 curt
336 * Working on adding a global lighting params structure.
338 * Revision 1.11 1997/11/25 19:25:40 curt
339 * Changes to integrate Durk's moon/sun code updates + clean up.
341 * Revision 1.10 1997/11/15 18:16:42 curt
344 * Revision 1.9 1997/11/14 00:26:50 curt
345 * Transform scenery coordinates earlier in pipeline when scenery is being
346 * created, not when it is being loaded. Precalculate normals for each node
347 * as average of the normals of each containing polygon so Garoude shading is
350 * Revision 1.8 1997/10/25 03:30:08 curt
353 * Revision 1.7 1997/09/23 00:29:50 curt
354 * Tweaks to get things to compile with gcc-win32.
356 * Revision 1.6 1997/09/20 03:34:34 curt
357 * Still trying to get those durned stars aligned properly.
359 * Revision 1.5 1997/09/16 22:14:52 curt
360 * Tweaked time of day lighting equations. Don't draw stars during the day.
362 * Revision 1.4 1997/09/16 15:50:31 curt
363 * Working on star alignment and time issues.
365 * Revision 1.3 1997/09/13 02:00:08 curt
366 * Mostly working on stars and generating sidereal time for accurate star
369 * Revision 1.2 1997/08/27 03:30:35 curt
370 * Changed naming scheme of basic shared structures.
372 * Revision 1.1 1997/08/13 21:55:59 curt