/**************************************************************************
* orbits.c - calculates the orbital elements of the sun, moon and planets.
* For inclusion in flight gear
*
* Written 1997 by Durk Talsma, started October 19, 1997.
*
* 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 <math.h>
#include <string.h>
#include <Astro/orbits.h>
#include <Include/fg_constants.h>
#include <Include/general.h>
#include <Time/fg_time.h>
#include <Main/fg_debug.h>
struct OrbElements pltOrbElements[9];
double fgCalcActTime(struct fgTIME t)
{
return (t.mjd - 36523.5);
}
double fgCalcEccAnom(double M, double e)
{
double
eccAnom, E0, E1, diff;
eccAnom = M + e * sin(M) * (1.0 + e * cos(M));
/* iterate to achieve a greater precision for larger eccentricities */
if (e > 0.05)
{
E0 = eccAnom;
do
{
E1 = E0 - (E0 - e * sin(E0) - M) / (1 - e * cos(E0));
diff = fabs(E0 - E1);
E0 = E1;
}
while (diff > (DEG_TO_RAD * 0.001));
return E0;
}
return eccAnom;
}
/* This function assumes that if the FILE ptr is valid that the
contents will be valid. Should we check the file for validity? */
/* Sounds like a good idea to me. What type of checks are you thinking
of, other than feof(FILE*)? That's currently the only check I can
think of (Durk) */
int fgReadOrbElements(struct OrbElements *dest, FILE *src)
{
char line[256];
int i,j;
j = 0;
do
{
if (feof (src)) {
fgPrintf (FG_ASTRO, FG_ALERT,
"End of file found while reading planetary positions:\n");
return 0;
}
fgets(line, 256,src);
for (i = 0; i < 256; i++)
{
if (line[i] == '#')
line[i] = 0;
}
/*printf("Reading line %d\n", j++); */
}
while (!(strlen(line)));
sscanf(line, "%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf\n",
&dest->NFirst, &dest->NSec,
&dest->iFirst, &dest->iSec,
&dest->wFirst, &dest->wSec,
&dest->aFirst, &dest->aSec,
&dest->eFirst, &dest->eSec,
&dest->MFirst, &dest->MSec);
return(1);
}
int fgSolarSystemInit(struct fgTIME t)
{
struct fgGENERAL *g;
char path[80];
int i;
FILE *data;
int ret_val = 0;
fgPrintf( FG_ASTRO, FG_INFO, "Initializing solar system\n");
/* build the full path name to the orbital elements database file */
g = &general;
path[0] = '\0';
strcat(path, g->root_dir);
strcat(path, "/Scenery/");
strcat(path, "Planets.dat");
if ( (data = fopen(path, "r")) == NULL )
{
fgPrintf( FG_ASTRO, FG_ALERT,
"Cannot open data file: '%s'\n", path);
} else {
/* printf(" reading datafile %s\n", path); */
fgPrintf( FG_ASTRO, FG_INFO, " reading datafile %s\n", path);
/* for all the objects... */
for (i = 0; i < 9; i ++)
{
/* ...read from the data file ... */
if (!(fgReadOrbElements (&pltOrbElements[i], data))) {
ret_val = 0;
}
/* ...and calculate the actual values */
fgSolarSystemUpdate(&pltOrbElements[i], t);
}
ret_val = 1;
}
return ret_val;
}
void fgSolarSystemUpdate(struct OrbElements *planet, struct fgTIME t)
{
double
actTime;
actTime = fgCalcActTime(t);
/* calculate the actual orbital elements */
planet->M = DEG_TO_RAD * (planet->MFirst + (planet->MSec * actTime));
planet->w = DEG_TO_RAD * (planet->wFirst + (planet->wSec * actTime));
planet->N = DEG_TO_RAD * (planet->NFirst + (planet->NSec * actTime));
planet->i = DEG_TO_RAD * (planet->iFirst + (planet->iSec * actTime));
planet->e = planet->eFirst + (planet->eSec * actTime);
planet->a = planet->aFirst + (planet->aSec * actTime);
}
/* $Log$
/* Revision 1.8 1998/02/23 19:07:55 curt
/* Incorporated Durk's Astro/ tweaks. Includes unifying the sun position
/* calculation code between sun display, and other FG sections that use this
/* for things like lighting.
/*
* Revision 1.7 1998/02/12 21:59:33 curt
* Incorporated code changes contributed by Charlie Hotchkiss
* <chotchkiss@namg.us.anritsu.com>
*
* Revision 1.6 1998/02/03 23:20:11 curt
* Lots of little tweaks to fix various consistency problems discovered by
* Solaris' CC. Fixed a bug in fg_debug.c with how the fgPrintf() wrapper
* passed arguments along to the real printf(). Also incorporated HUD changes
* by Michele America.
*
* Revision 1.5 1998/02/02 20:53:22 curt
* To version 0.29
*
* Revision 1.4 1998/01/27 00:47:47 curt
* Incorporated Paul Bleisch's <bleisch@chromatic.com> new debug message
* system and commandline/config file processing code.
*
* Revision 1.3 1998/01/22 02:59:27 curt
* Changed #ifdef FILE_H to #ifdef _FILE_H
*
* Revision 1.2 1998/01/19 19:26:58 curt
* Merged in make system changes from Bob Kuehne <rpk@sgi.com>
* This should simplify things tremendously.
*
* Revision 1.1 1998/01/07 03:16:17 curt
* Moved from .../Src/Scenery/ to .../Src/Astro/
*
* Revision 1.6 1997/12/30 20:47:52 curt
* Integrated new event manager with subsystem initializations.
*
* Revision 1.5 1997/12/15 23:55:02 curt
* Add xgl wrappers for debugging.
* Generate terrain normals on the fly.
*
* Revision 1.4 1997/12/10 22:37:51 curt
* Prepended "fg" on the name of all global structures that didn't have it yet.
* i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
*
* Revision 1.3 1997/11/25 23:20:44 curt
* Changed planets.dat Planets.dat
*
* Revision 1.2 1997/11/25 19:25:36 curt
* Changes to integrate Durk's moon/sun code updates + clean up.
*
* Revision 1.1 1997/10/25 03:16:10 curt
* Initial revision of code contributed by Durk Talsma.
*
*/