1 /**************************************************************************
3 * Written by Durk Talsma. Started October 1997, for the flight gear project.
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License as
7 * published by the Free Software Foundation; either version 2 of the
8 * License, or (at your option) any later version.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 * (Log is kept at end of this file)
21 **************************************************************************/
34 #include <Astro/orbits.h>
35 #include <Astro/moon.h>
37 #include <Aircraft/aircraft.h>
38 #include <Debug/fg_debug.h>
39 #include <Include/fg_constants.h>
40 #include <Include/general.h>
41 #include <Main/views.h>
42 #include <Time/fg_time.h>
44 struct CelestialCoord moonPos;
46 static float xMoon, yMoon, zMoon;
47 static GLint moon = 0;
51 /* --------------------------------------------------------------
52 This section contains the code that calculates the actual
53 position of the moon in the night sky.
54 ----------------------------------------------------------------*/
55 struct CelestialCoord fgCalculateMoon(struct OrbElements params,
56 struct OrbElements sunParams,
60 geocCoord, topocCoord;
63 eccAnom, ecl, lonecl, latecl, actTime,
64 xv, yv, v, r, xh, yh, zh, xg, yg, zg, xe, ye, ze,
65 Ls, Lm, D, F, mpar, gclat, rho, HA, g;
70 a = ¤t_aircraft;
73 /* calculate the angle between ecliptic and equatorial coordinate
74 * system, in Radians */
75 actTime = fgCalcActTime(t);
76 ecl = ((DEG_TO_RAD * 23.4393) - (DEG_TO_RAD * 3.563E-7) * actTime);
77 /*ecl = 0.409093 - 6.2186E-9 * actTime; */
79 /* calculate the eccentric anomaly */
80 eccAnom = fgCalcEccAnom(params.M, params.e);
82 /* calculate the moon's distance (r) and true anomaly (v) */
83 xv = params.a * ( cos(eccAnom) - params.e);
84 yv = params.a * ( sqrt(1.0 - params.e*params.e) * sin(eccAnom));
86 r = sqrt(xv*xv + yv*yv);
88 /* estimate the geocentric rectangular coordinates here */
89 xh = r * (cos (params.N) * cos (v + params.w) -
90 sin (params.N) * sin (v + params.w) * cos (params.i));
91 yh = r * (sin (params.N) * cos (v + params.w) +
92 cos (params.N) * sin (v + params.w) * cos (params.i));
93 zh = r * (sin(v + params.w) * sin(params.i));
95 /* calculate the ecliptic latitude and longitude here */
96 lonecl = atan2( yh, xh);
97 latecl = atan2( zh, sqrt( xh*xh + yh*yh));
99 /* calculate a number of perturbations, i.e. disturbances caused by
100 * the gravitational influence of the sun and the other mayor
101 * planets. The largest of these even have their own names */
102 Ls = sunParams.M + sunParams.w;
103 Lm = params.M + params.w + params.N;
107 lonecl += DEG_TO_RAD * (
108 - 1.274 * sin (params.M - 2*D) /* the Evection */
109 + 0.658 * sin (2 * D) /* the Variation */
110 - 0.186 * sin (sunParams.M) /* the yearly variation */
111 - 0.059 * sin (2*params.M - 2*D)
112 - 0.057 * sin (params.M - 2*D + sunParams.M)
113 + 0.053 * sin (params.M + 2*D)
114 + 0.046 * sin (2*D - sunParams.M)
115 + 0.041 * sin (params.M - sunParams.M)
116 - 0.035 * sin (D) /* the Parallactic Equation */
117 - 0.031 * sin (params.M + sunParams.M)
118 - 0.015 * sin (2*F - 2*D)
119 + 0.011 * sin (params.M - 4*D)
121 latecl += DEG_TO_RAD * (
122 - 0.173 * sin (F - 2*D)
123 - 0.055 * sin (params.M - F - 2*D)
124 - 0.046 * sin (params.M + F - 2*D)
125 + 0.033 * sin (F + 2*D)
126 + 0.017 * sin (2 * params.M + F)
130 - 0.58 * cos(params.M - 2*D)
134 xg = r * cos(lonecl) * cos(latecl);
135 yg = r * sin(lonecl) * cos(latecl);
136 zg = r * sin(latecl);
139 ye = yg * cos(ecl) - zg * sin(ecl);
140 ze = yg * sin(ecl) + zg * cos(ecl);
145 geocCoord.RightAscension = atan2(ye, xe);
146 geocCoord.Declination = atan2(ze, sqrt(xe*xe + ye*ye));
148 /* New since 25 december 1997 */
149 /* Calculate the moon's topocentric position instead of it's geocentric! */
151 /* calculate the moon's parrallax, i.e. the apparent size of the
152 * (equatorial) radius of the Earth, as seen from the moon */
154 gclat = FG_Latitude - 0.083358 * sin (2 * DEG_TO_RAD * FG_Latitude);
155 rho = 0.99883 + 0.00167 * cos(2 * DEG_TO_RAD * FG_Latitude);
157 if (geocCoord.RightAscension < 0)
158 geocCoord.RightAscension += (2*FG_PI);
160 HA = t.lst - (3.8197186 * geocCoord.RightAscension);
162 g = atan (tan(gclat) / cos( (HA / 3.8197186)));
166 topocCoord.RightAscension = geocCoord.RightAscension -
167 mpar * rho * cos (gclat) * sin (HA) / cos (geocCoord.Declination);
168 topocCoord.Declination = geocCoord.Declination -
169 mpar * rho * sin (gclat) * sin (g - geocCoord.Declination) / sin (g);
174 void fgMoonInit( void ) {
175 GLfloat moonColor[4] = {0.85, 0.75, 0.35, 1.0};
176 GLfloat black[4] = { 0.0, 0.0, 0.0, 1.0 };
178 fgPrintf( FG_ASTRO, FG_INFO, "Initializing the Moon\n");
179 fgSolarSystemUpdate(&(pltOrbElements[1]), cur_time_params);
180 moonPos = fgCalculateMoon(pltOrbElements[1], pltOrbElements[0],
182 fgPrintf( FG_ASTRO, FG_DEBUG,
183 "Moon found at %f (ra), %f (dec)\n", moonPos.RightAscension,
184 moonPos.Declination);
186 xMoon = 60000.0 * cos(moonPos.RightAscension) * cos(moonPos.Declination);
187 yMoon = 60000.0 * sin(moonPos.RightAscension) * cos(moonPos.Declination);
188 zMoon = 60000.0 * sin(moonPos.Declination);
191 xglDeleteLists (moon, 1);
194 moon = xglGenLists (1);
195 xglNewList (moon, GL_COMPILE);
197 xglMaterialfv (GL_FRONT, GL_AMBIENT, black);
198 xglMaterialfv (GL_FRONT, GL_DIFFUSE, moonColor);
200 xglTranslatef (xMoon, yMoon, zMoon);
201 xglScalef (1400, 1400, 1400);
203 glutSolidSphere (1.0, 10, 10);
210 void fgMoonRender( void ) {
216 /* Revision 1.9 1998/04/18 04:13:56 curt
217 /* Moved fg_debug.c to it's own library.
219 * Revision 1.8 1998/04/03 21:52:49 curt
220 * Converting to Gnu autoconf system.
222 * Revision 1.7 1998/02/23 19:07:54 curt
223 * Incorporated Durk's Astro/ tweaks. Includes unifying the sun position
224 * calculation code between sun display, and other FG sections that use this
225 * for things like lighting.
227 * Revision 1.6 1998/02/07 15:29:32 curt
228 * Incorporated HUD changes and struct/typedef changes from Charlie Hotchkiss
229 * <chotchkiss@namg.us.anritsu.com>
231 * Revision 1.5 1998/02/02 20:53:21 curt
234 * Revision 1.4 1998/01/27 00:47:46 curt
235 * Incorporated Paul Bleisch's <bleisch@chromatic.com> new debug message
236 * system and commandline/config file processing code.
238 * Revision 1.3 1998/01/19 19:26:57 curt
239 * Merged in make system changes from Bob Kuehne <rpk@sgi.com>
240 * This should simplify things tremendously.
242 * Revision 1.2 1998/01/19 18:40:16 curt
243 * Tons of little changes to clean up the code and to remove fatal errors
244 * when building with the c++ compiler.
246 * Revision 1.1 1998/01/07 03:16:16 curt
247 * Moved from .../Src/Scenery/ to .../Src/Astro/
249 * Revision 1.16 1998/01/06 01:20:24 curt
250 * Tweaks to help building with MSVC++
252 * Revision 1.15 1998/01/05 18:44:35 curt
253 * Add an option to advance/decrease time from keyboard.
255 * Revision 1.14 1997/12/30 20:47:50 curt
256 * Integrated new event manager with subsystem initializations.
258 * Revision 1.13 1997/12/30 16:41:00 curt
259 * Added log at end of file.