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flightgear/Time/fg_time.c
curt 73ed3c180e C++ - ifiing the code a bit. 
Starting to reorginize some of the lighting calcs to use a table lookup.
1998-04-22 13:24:04 +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 <Debug/fg_debug.h>
#include <Flight/flight.h>
#include <Include/fg_constants.h>
#include "fg_time.h"
#define DEGHR(x) ((x)/15.)
#define RADHR(x) DEGHR(x*RAD_TO_DEG)
struct fgTIME cur_time_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 1.41 1998/04/22 13:24:05 curt
/* C++ - ifiing the code a bit.
/* Starting to reorginize some of the lighting calcs to use a table lookup.
/*
* Revision 1.40 1998/04/18 04:14:09 curt
* Moved fg_debug.c to it's own library.
*
* 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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