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flightgear/Time/fg_time.c
curt 575d57249c We had unified some of the platform disparate time handling code, and 
there was a bug in timesum() which calculated a new time stamp based on
the current time stamp + offset.  This hosed the periodic event processing
logic because you'd never arrive at the time the event was scheduled for.
Sky updates and lighting changes are handled via this event mechanism so
they never changed ... it is fixed now.
1998-04-09 18:40:13 +00:00

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/**************************************************************************
* fg_time.c -- data structures and routines for managing time related stuff.
*
* Written by Curtis Olson, started August 1997.
*
* Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id$
* (Log is kept at end of this file)
**************************************************************************/
#include <config.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#ifdef HAVE_SYS_TIMEB_H
# include <sys/timeb.h> /* for ftime() and struct timeb */
#endif
#ifdef HAVE_UNISTD_H
# include <unistd.h> /* for gettimeofday() */
#endif
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h> /* for get/setitimer, gettimeofday, struct timeval */
#endif
#include <Time/fg_time.h>
#include <Include/fg_constants.h>
#include <Flight/flight.h>
#define DEGHR(x) ((x)/15.)
#define RADHR(x) DEGHR(x*RAD_TO_DEG)
#include <Main/fg_debug.h>
struct fgTIME cur_time_params;
struct fgLIGHT cur_light_params;
/* Initialize the time dependent variables */
void fgTimeInit(struct fgTIME *t) {
fgPrintf( FG_EVENT, FG_INFO, "Initializing Time\n");
t->gst_diff = -9999.0;
t->warp = (0) * 3600;
t->warp_delta = 0;
}
/* Portability wrap to get current time. */
void timestamp(fg_timestamp *timestamp) {
#if defined( HAVE_GETTIMEOFDAY )
struct timeval current;
struct timezone tz;
fg_timestamp currtime;
gettimeofday(&current, &tz);
timestamp->seconds = current.tv_sec;
timestamp->millis = current.tv_usec / 1000;
#elif defined( HAVE_GETLOCALTIME )
SYSTEMTIME current;
GetLocalTime(&current);
timestamp->seconds = current.wSecond;
timestamp->millis = current.wMilliseconds;
#elif defined( HAVE_FTIME )
struct timeb current;
ftime(&current);
timestamp->seconds = current.time;
timestamp->millis = current.millitm;
#else
# error Port me
#endif
}
/* Return duration in millis from first to last */
long timediff(fg_timestamp *first, fg_timestamp *last) {
return 1000 * (last->seconds - first->seconds) +
(last->millis - first->millis);
}
/* Return new timestamp given a time stamp and an interval to add in */
void timesum(fg_timestamp *res, fg_timestamp *start, long millis) {
res->seconds = start->seconds +
( start->millis + millis ) / 1000;
res->millis = ( start->millis + millis ) % 1000;
}
/* given a date in months, mn, days, dy, years, yr, return the
* modified Julian date (number of days elapsed since 1900 jan 0.5),
* mjd. Adapted from Xephem. */
double cal_mjd (int mn, double dy, int yr) {
static double last_mjd, last_dy;
double mjd;
static int last_mn, last_yr;
int b, d, m, y;
long c;
if (mn == last_mn && yr == last_yr && dy == last_dy) {
mjd = last_mjd;
return(mjd);
}
m = mn;
y = (yr < 0) ? yr + 1 : yr;
if (mn < 3) {
m += 12;
y -= 1;
}
if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
b = 0;
} else {
int a;
a = y/100;
b = 2 - a + a/4;
}
if (y < 0) {
c = (long)((365.25*y) - 0.75) - 694025L;
} else {
c = (long)(365.25*y) - 694025L;
}
d = (int)(30.6001*(m+1));
mjd = b + c + d + dy - 0.5;
last_mn = mn;
last_dy = dy;
last_yr = yr;
last_mjd = mjd;
return(mjd);
}
/* given an mjd, return greenwich mean siderial time, gst */
double utc_gst (double mjd) {
double gst;
double day = floor(mjd-0.5)+0.5;
double hr = (mjd-day)*24.0;
double T, x;
T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
x /= 3600.0;
gst = (1.0/SIDRATE)*hr + x;
fgPrintf( FG_EVENT, FG_DEBUG, " gst => %.4f\n", gst);
return(gst);
}
/* given Julian Date and Longitude (decimal degrees West) compute and
* return Local Sidereal Time, in decimal hours.
*
* Provided courtesy of ecdowney@noao.edu (Elwood Downey)
*/
double sidereal_precise (double mjd, double lng) {
double gst;
double lst;
/* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
mjd + MJD0, lng); */
/* convert to required internal units */
lng *= DEG_TO_RAD;
/* compute LST and print */
gst = utc_gst (mjd);
lst = gst - RADHR (lng);
lst -= 24.0*floor(lst/24.0);
/* printf ("%7.4f\n", lst); */
/* that's all */
return (lst);
}
/* return a courser but cheaper estimate of sidereal time */
double sidereal_course(struct tm *gmt, time_t now, double lng) {
time_t start, start_gmt;
struct tm mt;
long int offset;
double diff, part, days, hours, lst;
// ftime() needs a little extra help finding the current timezone
#if defined( HAVE_GETTIMEOFDAY )
#elif defined( HAVE_GETLOCALTIME )
#elif defined( HAVE_FTIME )
struct timeb current;
#else
# error Port me
#endif
#ifdef __CYGWIN32__
int daylight;
long int timezone;
#endif /* WIN32 */
/*
printf(" COURSE: GMT = %d/%d/%2d %d:%02d:%02d\n",
gmt->tm_mon, gmt->tm_mday, gmt->tm_year,
gmt->tm_hour, gmt->tm_min, gmt->tm_sec);
*/
mt.tm_mon = 2;
mt.tm_mday = 21;
mt.tm_year = gmt->tm_year;
mt.tm_hour = 12;
mt.tm_min = 0;
mt.tm_sec = 0;
mt.tm_isdst = -1; /* let the system determine the proper time zone */
start = mktime(&mt);
/* printf("start1 = %ld\n", start);
fgPrintf( FG_EVENT, FG_DEBUG, "start2 = %s", ctime(&start));
fgPrintf( FG_EVENT, FG_DEBUG, "start3 = %ld\n", start); */
#ifndef __CYGWIN32__
daylight = mt.tm_isdst;
#else
/* Yargs ... I'm just hardcoding this arbitrarily so it doesn't
* jump around */
daylight = 0;
fgPrintf( FG_EVENT, FG_WARN,
"no daylight savings info ... being hardcoded to %d\n", daylight);
#endif
// ftime() needs a little extra help finding the current timezone
#if defined( HAVE_GETTIMEOFDAY )
#elif defined( HAVE_GETLOCALTIME )
#elif defined( HAVE_FTIME )
ftime(&current);
timezone = current.timezone * 60;
#else
# error Port me
#endif
if ( daylight > 0 ) {
daylight = 1;
} else if ( daylight < 0 ) {
fgPrintf( FG_EVENT, FG_WARN,
"OOOPS, big time problem in fg_time.c, no daylight savings info.\n");
}
offset = -(timezone / 3600 - daylight);
/* printf(" Raw time zone offset = %ld\n", timezone); */
/* printf(" Daylight Savings = %d\n", daylight); */
/* printf(" Local hours from GMT = %ld\n", offset); */
start_gmt = start - timezone + (daylight * 3600);
/* printf(" March 21 noon (CST) = %ld\n", start); */
/* printf(" March 21 noon (GMT) = %ld\n", start_gmt); */
diff = (now - start_gmt) / (3600.0 * 24.0);
/* printf(" Time since 3/21/%2d GMT = %.2f\n", gmt->tm_year, diff); */
part = fmod(diff, 1.0);
days = diff - part;
hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
lst = (days - lng)/15.0 + hours - 12;
while ( lst < 0.0 ) {
lst += 24.0;
}
/* printf(" days = %.1f hours = %.2f lon = %.2f lst = %.2f\n",
days, hours, lng, lst); */
return(lst);
}
/* Update the time dependent variables */
void fgTimeUpdate(fgFLIGHT *f, struct fgTIME *t) {
double gst_precise, gst_course;
fgPrintf( FG_EVENT, FG_BULK, "Updating time\n");
/* get current Unix calendar time (in seconds) */
t->warp += t->warp_delta;
t->cur_time = time(NULL) + t->warp;
fgPrintf( FG_EVENT, FG_BULK,
" Current Unix calendar time = %ld warp = %ld delta = %ld\n",
t->cur_time, t->warp, t->warp_delta);
/* get GMT break down for current time */
t->gmt = gmtime(&t->cur_time);
fgPrintf( FG_EVENT, FG_BULK,
" Current GMT = %d/%d/%2d %d:%02d:%02d\n",
t->gmt->tm_mon+1, t->gmt->tm_mday, t->gmt->tm_year,
t->gmt->tm_hour, t->gmt->tm_min, t->gmt->tm_sec);
/* calculate modified Julian date */
t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
(int)(t->gmt->tm_year + 1900));
/* add in partial day */
t->mjd += (t->gmt->tm_hour / 24.0) + (t->gmt->tm_min / (24.0 * 60.0)) +
(t->gmt->tm_sec / (24.0 * 60.0 * 60.0));
/* convert "back" to Julian date + partial day (as a fraction of one) */
t->jd = t->mjd + MJD0;
fgPrintf( FG_EVENT, FG_BULK, " Current Julian Date = %.5f\n", t->jd);
/* printf(" Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG); */
/* Calculate local side real time */
if ( t->gst_diff < -100.0 ) {
/* first time through do the expensive calculation & cheap
calculation to get the difference. */
fgPrintf( FG_EVENT, FG_INFO, " First time, doing precise gst\n");
t->gst = gst_precise = sidereal_precise(t->mjd, 0.00);
gst_course = sidereal_course(t->gmt, t->cur_time, 0.00);
t->gst_diff = gst_precise - gst_course;
t->lst =
sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG))
+ t->gst_diff;
} else {
/* course + difference should drift off very slowly */
t->gst =
sidereal_course(t->gmt, t->cur_time, 0.00) + t->gst_diff;
t->lst =
sidereal_course(t->gmt, t->cur_time, -(FG_Longitude * RAD_TO_DEG))
+ t->gst_diff;
}
fgPrintf( FG_EVENT, FG_DEBUG,
" Current lon=0.00 Sidereal Time = %.3f\n", t->gst);
fgPrintf( FG_EVENT, FG_DEBUG,
" Current LOCAL Sidereal Time = %.3f (%.3f) (diff = %.3f)\n",
t->lst, sidereal_precise(t->mjd, -(FG_Longitude * RAD_TO_DEG)),
t->gst_diff);
}
/* $Log$
/* Revision 1.39 1998/04/09 18:40:14 curt
/* We had unified some of the platform disparate time handling code, and
/* there was a bug in timesum() which calculated a new time stamp based on
/* the current time stamp + offset. This hosed the periodic event processing
/* logic because you'd never arrive at the time the event was scheduled for.
/* Sky updates and lighting changes are handled via this event mechanism so
/* they never changed ... it is fixed now.
/*
* Revision 1.38 1998/04/08 23:35:40 curt
* Tweaks to Gnu automake/autoconf system.
*
* Revision 1.37 1998/04/03 22:12:55 curt
* Converting to Gnu autoconf system.
* Centralized time handling differences.
*
* Revision 1.36 1998/03/09 22:48:09 curt
* Debug message tweaks.
*
* Revision 1.35 1998/02/09 15:07:52 curt
* Minor tweaks.
*
* Revision 1.34 1998/02/07 15:29:47 curt
* Incorporated HUD changes and struct/typedef changes from Charlie Hotchkiss
* <chotchkiss@namg.us.anritsu.com>
*
* Revision 1.33 1998/02/02 20:54:04 curt
* Incorporated Durk's changes.
*
* Revision 1.32 1998/02/01 03:39:56 curt
* Minor tweaks.
*
* Revision 1.31 1998/01/27 00:48:06 curt
* Incorporated Paul Bleisch's <bleisch@chromatic.com> new debug message
* system and commandline/config file processing code.
*
* Revision 1.30 1998/01/21 21:11:35 curt
* Misc. tweaks.
*
* Revision 1.29 1998/01/19 19:27:20 curt
* Merged in make system changes from Bob Kuehne <rpk@sgi.com>
* This should simplify things tremendously.
*
* Revision 1.28 1998/01/19 18:35:49 curt
* Minor tweaks and fixes for cygwin32.
*
* Revision 1.27 1998/01/13 00:23:13 curt
* Initial changes to support loading and management of scenery tiles. Note,
* there's still a fair amount of work left to be done.
*
* Revision 1.26 1998/01/05 18:44:36 curt
* Add an option to advance/decrease time from keyboard.
*
* Revision 1.25 1997/12/31 17:46:50 curt
* Tweaked fg_time.c to be able to use ftime() instead of gettimeofday()
*
* Revision 1.24 1997/12/30 22:22:42 curt
* Further integration of event manager.
*
* Revision 1.23 1997/12/30 20:47:58 curt
* Integrated new event manager with subsystem initializations.
*
* Revision 1.22 1997/12/30 01:38:47 curt
* Switched back to per vertex normals and smooth shading for terrain.
*
* Revision 1.21 1997/12/23 04:58:39 curt
* Tweaked the sky coloring a bit to build in structures to allow finer rgb
* control.
*
* Revision 1.20 1997/12/15 23:55:06 curt
* Add xgl wrappers for debugging.
* Generate terrain normals on the fly.
*
* Revision 1.19 1997/12/15 20:59:10 curt
* Misc. tweaks.
*
* Revision 1.18 1997/12/12 21:41:31 curt
* More light/material property tweaking ... still a ways off.
*
* Revision 1.17 1997/12/12 19:53:04 curt
* Working on lightling and material properties.
*
* Revision 1.16 1997/12/11 04:43:57 curt
* Fixed sun vector and lighting problems. I thing the moon is now lit
* correctly.
*
* Revision 1.15 1997/12/10 22:37:54 curt
* Prepended "fg" on the name of all global structures that didn't have it yet.
* i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
*
* Revision 1.14 1997/12/10 01:19:52 curt
* Tweaks for verion 0.15 release.
*
* Revision 1.13 1997/12/09 05:11:56 curt
* Working on tweaking lighting.
*
* Revision 1.12 1997/12/09 04:25:37 curt
* Working on adding a global lighting params structure.
*
* Revision 1.11 1997/11/25 19:25:40 curt
* Changes to integrate Durk's moon/sun code updates + clean up.
*
* Revision 1.10 1997/11/15 18:16:42 curt
* minor tweaks.
*
* Revision 1.9 1997/11/14 00:26:50 curt
* Transform scenery coordinates earlier in pipeline when scenery is being
* created, not when it is being loaded. Precalculate normals for each node
* as average of the normals of each containing polygon so Garoude shading is
* now supportable.
*
* Revision 1.8 1997/10/25 03:30:08 curt
* Misc. tweaks.
*
* Revision 1.7 1997/09/23 00:29:50 curt
* Tweaks to get things to compile with gcc-win32.
*
* Revision 1.6 1997/09/20 03:34:34 curt
* Still trying to get those durned stars aligned properly.
*
* Revision 1.5 1997/09/16 22:14:52 curt
* Tweaked time of day lighting equations. Don't draw stars during the day.
*
* Revision 1.4 1997/09/16 15:50:31 curt
* Working on star alignment and time issues.
*
* Revision 1.3 1997/09/13 02:00:08 curt
* Mostly working on stars and generating sidereal time for accurate star
* placement.
*
* Revision 1.2 1997/08/27 03:30:35 curt
* Changed naming scheme of basic shared structures.
*
* Revision 1.1 1997/08/13 21:55:59 curt
* Initial revision.
*
*/
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