Moved from .../Src/Scenery/ to .../Src/Astro/

2009-09-15 18:31:19 +02:00
parent 0363628a55
commit 7b3b55f6ef
16 changed files with 699 additions and 235 deletions
@@ -0,0 +1,199 @@
+/**************************************************************************
+ * 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 <string.h>
+
+#include "orbits.h"
+
+#include "../Include/general.h"
+#include "../Time/fg_time.h"
+
+
+struct OrbElements pltOrbElements[9];
+
+
+double fgCalcActTime(struct fgTIME t)
+{
+   double
+         actTime, UT;
+   int year;
+
+   /* a hack. This one introduces the 2000 problem into the program */
+   year = t.gmt->tm_year + 1900;
+
+   /* calculate the actual time, rember to add 1 to tm_mon! */
+   actTime = 367 * year - 7 *
+	          (year + ((t.gmt->tm_mon+1) + 9) / 12) / 4 + 275 *
+	           (t.gmt->tm_mon+1) / 9 + t.gmt->tm_mday - 730530;
+
+    UT = t.gmt->tm_hour + ((double) t.gmt->tm_min / 60);
+    /*printf("UT = %f\n", UT); */
+    actTime += (UT / 24.0);
+    #define DEBUG 1
+    #ifdef DEBUG
+    /* printf("  Actual Time:\n"); */
+    /* printf("  current day = %f\t", actTime); */
+    /* printf("  GMT = %d, %d, %d, %d, %d, %d\n",
+	   year, t.gmt->tm_mon, t.gmt->tm_mday,
+	   t.gmt->tm_hour, t.gmt->tm_min, t.gmt->tm_sec); */
+    #endif
+    return actTime;
+}
+
+/* convert degrees to radians */
+double fgDegToRad(double angle)
+{
+	return (angle * PIOVER180);
+}
+
+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 = abs(E0 - E1);
+            E0 = E1;
+		}
+        while (diff > fgDegToRad(0.001));
+        return E0;
+	}
+    return eccAnom;
+}
+
+
+
+void fgReadOrbElements(struct OrbElements *dest, FILE *src)
+{
+	char line[256];
+    int i,j;
+    j = 0;
+    do
+    {
+    	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);
+}
+
+
+void fgSolarSystemInit(struct fgTIME t)
+{
+   struct fgGENERAL *g;
+   char path[80];
+   int i;
+   FILE *data;
+
+   printf("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 )
+   {
+	    printf("Cannot open data file: '%s'\n", path);
+	    return;
+   }
+   #ifdef DEBUG
+   printf("  reading datafile %s\n", path);
+   #endif
+
+   /* for all the objects... */
+   for (i = 0; i < 9; i ++)
+   {
+      /* ...read from the data file ... */
+      fgReadOrbElements(&pltOrbElements[i], data);
+      /* ...and calculate the actual values */
+      fgSolarSystemUpdate(&pltOrbElements[i], t);
+   }
+
+}
+
+
+void fgSolarSystemUpdate(struct OrbElements *planet, struct fgTIME t)
+{
+   double
+         actTime;
+
+   actTime = fgCalcActTime(t);
+
+   /* calculate the actual orbital elements */
+    planet->M = fgDegToRad(planet->MFirst + (planet->MSec * actTime));	// angle in radians
+    planet->w = fgDegToRad(planet->wFirst + (planet->wSec * actTime));	// angle in radians
+    planet->N = fgDegToRad(planet->NFirst + (planet->NSec * actTime));	// angle in radians
+    planet->i = fgDegToRad(planet->iFirst + (planet->iSec * actTime));  // angle in radians
+    planet->e = planet->eFirst + (planet->eSec * actTime);
+    planet->a = planet->aFirst + (planet->aSec * actTime);
+}
+
+
+/* $Log$
+/* 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.
+ *
+ */