--- /dev/null
+// moonpos.cxx (basically, this is a slightly modified version of the 'sunpos.cxx' file, adapted from XEarth)
+
+// kirk johnson
+// july 1993
+//
+// code for calculating the position on the earth's surface for which
+// the moon is directly overhead (adapted from _practical astronomy
+// with your calculator, third edition_, peter duffett-smith,
+// cambridge university press, 1988.)
+//
+// Copyright (C) 1989, 1990, 1993, 1994, 1995 Kirk Lauritz Johnson
+//
+// Parts of the source code (as marked) are:
+// Copyright (C) 1989, 1990, 1991 by Jim Frost
+// Copyright (C) 1992 by Jamie Zawinski <jwz@lucid.com>
+//
+// Permission to use, copy, modify and freely distribute xearth for
+// non-commercial and not-for-profit purposes is hereby granted
+// without fee, provided that both the above copyright notice and this
+// permission notice appear in all copies and in supporting
+// documentation.
+//
+// The author makes no representations about the suitability of this
+// software for any purpose. It is provided "as is" without express or
+// implied warranty.
+//
+// THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+// INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
+// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, INDIRECT
+// OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+// NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+// $Id$
+// (Log is kept at end of this file)
+
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "Include/compiler.h"
+#ifdef FG_HAVE_STD_INCLUDES
+# include <cmath>
+# include <cstdio>
+# include <ctime>
+#else
+# include <math.h>
+# include <stdio.h>
+# include <time.h>
+#endif
+
+
+//#include <Astro/orbits.hxx>
+#include <Astro/solarsystem.hxx>
+#include <Debug/logstream.hxx>
+#include <Include/fg_constants.h>
+#include <Main/views.hxx>
+#include <Math/fg_geodesy.hxx>
+#include <Math/mat3.h>
+#include <Math/point3d.hxx>
+#include <Math/polar3d.hxx>
+#include <Math/vector.hxx>
+#include <Scenery/scenery.hxx>
+
+#include "fg_time.hxx"
+#include "moonpos.hxx"
+
+extern SolarSystem *solarSystem;
+
+#undef E
+
+
+/*
+ * the epoch upon which these astronomical calculations are based is
+ * 1990 january 0.0, 631065600 seconds since the beginning of the
+ * "unix epoch" (00:00:00 GMT, Jan. 1, 1970)
+ *
+ * given a number of seconds since the start of the unix epoch,
+ * DaysSinceEpoch() computes the number of days since the start of the
+ * astronomical epoch (1990 january 0.0)
+ */
+
+#define EpochStart (631065600)
+#define DaysSinceEpoch(secs) (((secs)-EpochStart)*(1.0/(24*3600)))
+
+/*
+ * assuming the apparent orbit of the moon about the earth is circular,
+ * the rate at which the orbit progresses is given by RadsPerDay --
+ * FG_2PI radians per orbit divided by 365.242191 days per year:
+ */
+
+#define RadsPerDay (FG_2PI/365.242191)
+
+/*
+ * details of moon's apparent orbit at epoch 1990.0 (after
+ * duffett-smith, table 6, section 46)
+ *
+ * Epsilon_g (ecliptic longitude at epoch 1990.0) 279.403303 degrees
+ * OmegaBar_g (ecliptic longitude of perigee) 282.768422 degrees
+ * Eccentricity (eccentricity of orbit) 0.016713
+ */
+
+#define Epsilon_g (279.403303*(FG_2PI/360))
+#define OmegaBar_g (282.768422*(FG_2PI/360))
+#define Eccentricity (0.016713)
+
+/*
+ * MeanObliquity gives the mean obliquity of the earth's axis at epoch
+ * 1990.0 (computed as 23.440592 degrees according to the method given
+ * in duffett-smith, section 27)
+ */
+#define MeanObliquity (23.440592*(FG_2PI/360))
+
+/* static double solve_keplers_equation(double); */
+/* static double moon_ecliptic_longitude(time_t); */
+static void ecliptic_to_equatorial(double, double, double *, double *);
+static double julian_date(int, int, int);
+static double GST(time_t);
+
+/*
+ * solve Kepler's equation via Newton's method
+ * (after duffett-smith, section 47)
+ */
+/*
+static double solve_keplers_equation(double M) {
+ double E;
+ double delta;
+
+ E = M;
+ while (1) {
+ delta = E - Eccentricity*sin(E) - M;
+ if (fabs(delta) <= 1e-10) break;
+ E -= delta / (1 - Eccentricity*cos(E));
+ }
+
+ return E;
+}
+*/
+
+
+/* compute ecliptic longitude of moon (in radians) (after
+ * duffett-smith, section 47) */
+/*
+static double moon_ecliptic_longitude(time_t ssue) {
+ // time_t ssue; // seconds since unix epoch
+ double D, N;
+ double M_moon, E;
+ double v;
+
+ D = DaysSinceEpoch(ssue);
+
+ N = RadsPerDay * D;
+ N = fmod(N, FG_2PI);
+ if (N < 0) N += FG_2PI;
+
+ M_moon = N + Epsilon_g - OmegaBar_g;
+ if (M_moon < 0) M_moon += FG_2PI;
+
+ E = solve_keplers_equation(M_moon);
+ v = 2 * atan(sqrt((1+Eccentricity)/(1-Eccentricity)) * tan(E/2));
+
+ return (v + OmegaBar_g);
+}
+*/
+
+
+/* convert from ecliptic to equatorial coordinates (after
+ * duffett-smith, section 27) */
+
+static void ecliptic_to_equatorial(double lambda, double beta,
+ double *alpha, double *delta) {
+ /* double lambda; ecliptic longitude */
+ /* double beta; ecliptic latitude */
+ /* double *alpha; (return) right ascension */
+ /* double *delta; (return) declination */
+
+ double sin_e, cos_e;
+ double sin_l, cos_l;
+
+ sin_e = sin(MeanObliquity);
+ cos_e = cos(MeanObliquity);
+ sin_l = sin(lambda);
+ cos_l = cos(lambda);
+
+ *alpha = atan2(sin_l*cos_e - tan(beta)*sin_e, cos_l);
+ *delta = asin(sin(beta)*cos_e + cos(beta)*sin_e*sin_l);
+}
+
+
+/* computing julian dates (assuming gregorian calendar, thus this is
+ * only valid for dates of 1582 oct 15 or later) (after duffett-smith,
+ * section 4) */
+
+static double julian_date(int y, int m, int d) {
+ /* int y; year (e.g. 19xx) */
+ /* int m; month (jan=1, feb=2, ...) */
+ /* int d; day of month */
+
+ int A, B, C, D;
+ double JD;
+
+ /* lazy test to ensure gregorian calendar */
+ if (y < 1583) {
+ FG_LOG( FG_EVENT, FG_ALERT,
+ "WHOOPS! Julian dates only valid for 1582 oct 15 or later" );
+ }
+
+ if ((m == 1) || (m == 2)) {
+ y -= 1;
+ m += 12;
+ }
+
+ A = y / 100;
+ B = 2 - A + (A / 4);
+ C = (int)(365.25 * y);
+ D = (int)(30.6001 * (m + 1));
+
+ JD = B + C + D + d + 1720994.5;
+
+ return JD;
+}
+
+
+/* compute greenwich mean sidereal time (GST) corresponding to a given
+ * number of seconds since the unix epoch (after duffett-smith,
+ * section 12) */
+static double GST(time_t ssue) {
+ /* time_t ssue; seconds since unix epoch */
+
+ double JD;
+ double T, T0;
+ double UT;
+ struct tm *tm;
+
+ tm = gmtime(&ssue);
+
+ JD = julian_date(tm->tm_year+1900, tm->tm_mon+1, tm->tm_mday);
+ T = (JD - 2451545) / 36525;
+
+ T0 = ((T + 2.5862e-5) * T + 2400.051336) * T + 6.697374558;
+
+ T0 = fmod(T0, 24.0);
+ if (T0 < 0) T0 += 24;
+
+ UT = tm->tm_hour + (tm->tm_min + tm->tm_sec / 60.0) / 60.0;
+
+ T0 += UT * 1.002737909;
+ T0 = fmod(T0, 24.0);
+ if (T0 < 0) T0 += 24;
+
+ return T0;
+}
+
+
+/* given a particular time (expressed in seconds since the unix
+ * epoch), compute position on the earth (lat, lon) such that moon is
+ * directly overhead. (lat, lon are reported in radians */
+
+void fgMoonPosition(time_t ssue, double *lon, double *lat) {
+ /* time_t ssue; seconds since unix epoch */
+ /* double *lat; (return) latitude */
+ /* double *lon; (return) longitude */
+
+ /* double lambda; */
+ double alpha, delta;
+ double tmp;
+
+ /* lambda = moon_ecliptic_longitude(ssue); */
+ /* ecliptic_to_equatorial(lambda, 0.0, &alpha, &delta); */
+ //ecliptic_to_equatorial (solarPosition.lonMoon, 0.0, &alpha, &delta);
+
+ /* **********************************************************************
+ * NOTE: in the next function, each time the moon's position is updated, the
+ * the moon's longitude is returned from solarSystem->moon. Note that the
+ * moon's position is updated at a much higher frequency than the rate at
+ * which the solar system's rebuilds occur. This is not a problem, however,
+ * because the fgMoonPosition we're talking about here concerns the changing
+ * position of the moon due to the daily rotation of the earth.
+ * The ecliptic longitude, however, represents the position of the moon with
+ * respect to the stars, and completes just one cycle over the course of a
+ * year. Its therefore pretty safe to update the moon's longitude only once
+ * every ten minutes. (Comment added by Durk Talsma).
+ ************************************************************************/
+
+ ecliptic_to_equatorial( SolarSystem::theSolarSystem->getMoon()->getLon(),
+ 0.0, &alpha, &delta );
+ tmp = alpha - (FG_2PI/24)*GST(ssue);
+ if (tmp < -FG_PI) {
+ do tmp += FG_2PI;
+ while (tmp < -FG_PI);
+ } else if (tmp > FG_PI) {
+ do tmp -= FG_2PI;
+ while (tmp < -FG_PI);
+ }
+
+ *lon = tmp;
+ *lat = delta;
+}
+
+
+/* given a particular time expressed in side real time at prime
+ * meridian (GST), compute position on the earth (lat, lon) such that
+ * moon is directly overhead. (lat, lon are reported in radians */
+
+static void fgMoonPositionGST(double gst, double *lon, double *lat) {
+ /* time_t ssue; seconds since unix epoch */
+ /* double *lat; (return) latitude */
+ /* double *lon; (return) longitude */
+
+ /* double lambda; */
+ double alpha, delta;
+ double tmp;
+
+ /* lambda = moon_ecliptic_longitude(ssue); */
+ /* ecliptic_to_equatorial(lambda, 0.0, &alpha, &delta); */
+ //ecliptic_to_equatorial (solarPosition.lonMoon, 0.0, &alpha, &delta);
+ ecliptic_to_equatorial( SolarSystem::theSolarSystem->getMoon()->getLon(),
+ SolarSystem::theSolarSystem->getMoon()->getLat(),
+ &alpha, &delta );
+
+// tmp = alpha - (FG_2PI/24)*GST(ssue);
+ tmp = alpha - (FG_2PI/24)*gst;
+ if (tmp < -FG_PI) {
+ do tmp += FG_2PI;
+ while (tmp < -FG_PI);
+ } else if (tmp > FG_PI) {
+ do tmp -= FG_2PI;
+ while (tmp < -FG_PI);
+ }
+
+ *lon = tmp;
+ *lat = delta;
+}
+
+
+// update the cur_time_params structure with the current moon position
+void fgUpdateMoonPos( void ) {
+ fgLIGHT *l;
+ fgTIME *t;
+ FGView *v;
+ MAT3vec nup, nmoon, v0, surface_to_moon;
+ Point3D p, rel_moonpos;
+ double dot, east_dot;
+ double moon_gd_lat, sl_radius;
+ double ntmp;
+
+ l = &cur_light_params;
+ t = &cur_time_params;
+ v = ¤t_view;
+
+ FG_LOG( FG_EVENT, FG_INFO, " Updating Moon position" );
+
+ // (not sure why there was two)
+ // fgMoonPosition(t->cur_time, &l->moon_lon, &moon_gd_lat);
+ fgMoonPositionGST(t->gst, &l->moon_lon, &moon_gd_lat);
+
+ fgGeodToGeoc(moon_gd_lat, 0.0, &sl_radius, &l->moon_gc_lat);
+
+ p = Point3D( l->moon_lon, l->moon_gc_lat, sl_radius );
+ l->fg_moonpos = fgPolarToCart3d(p);
+
+ FG_LOG( FG_EVENT, FG_INFO, " t->cur_time = " << t->cur_time );
+ FG_LOG( FG_EVENT, FG_INFO,
+ " Moon Geodetic lat = " << moon_gd_lat
+ << " Geocentric lat = " << l->moon_gc_lat );
+
+ // I think this will work better for generating the moon light vector
+ l->moon_vec[0] = l->fg_moonpos.x();
+ l->moon_vec[1] = l->fg_moonpos.y();
+ l->moon_vec[2] = l->fg_moonpos.z();
+ MAT3_NORMALIZE_VEC(l->moon_vec, ntmp);
+ MAT3_SCALE_VEC(l->moon_vec_inv, l->moon_vec, -1.0);
+
+ // make sure these are directional light sources only
+ l->moon_vec[3] = 0.0;
+ l->moon_vec_inv[3] = 0.0;
+
+ // printf(" l->moon_vec = %.2f %.2f %.2f\n", l->moon_vec[0], l->moon_vec[1],
+ // l->moon_vec[2]);
+
+ // calculate the moon's relative angle to local up
+ MAT3_COPY_VEC(nup, v->get_local_up());
+ nmoon[0] = l->fg_moonpos.x();
+ nmoon[1] = l->fg_moonpos.y();
+ nmoon[2] = l->fg_moonpos.z();
+ MAT3_NORMALIZE_VEC(nup, ntmp);
+ MAT3_NORMALIZE_VEC(nmoon, ntmp);
+
+ l->moon_angle = acos(MAT3_DOT_PRODUCT(nup, nmoon));
+ // printf(" MOON ANGLE relative to current location = %.3f rads.\n",
+ // l->moon_angle);
+
+ // calculate vector to moon's position on the earth's surface
+ rel_moonpos = l->fg_moonpos - (v->get_view_pos() + scenery.center);
+ v->set_to_moon( rel_moonpos.x(), rel_moonpos.y(), rel_moonpos.z() );
+ // printf( "Vector to moon = %.2f %.2f %.2f\n",
+ // v->to_moon[0], v->to_moon[1], v->to_moon[2]);
+
+ // make a vector to the current view position
+ Point3D view_pos = v->get_view_pos();
+ MAT3_SET_VEC(v0, view_pos.x(), view_pos.y(), view_pos.z());
+
+ // Given a vector from the view position to the point on the
+ // earth's surface the moon is directly over, map into onto the
+ // local plane representing "horizontal".
+ map_vec_onto_cur_surface_plane( v->get_local_up(), v0, v->get_to_moon(),
+ surface_to_moon );
+ MAT3_NORMALIZE_VEC(surface_to_moon, ntmp);
+ v->set_surface_to_moon( surface_to_moon[0], surface_to_moon[1],
+ surface_to_moon[2] );
+ // printf("Surface direction to moon is %.2f %.2f %.2f\n",
+ // v->surface_to_moon[0], v->surface_to_moon[1], v->surface_to_moon[2]);
+ // printf("Should be close to zero = %.2f\n",
+ // MAT3_DOT_PRODUCT(v->local_up, v->surface_to_moon));
+
+ // calculate the angle between v->surface_to_moon and
+ // v->surface_east. We do this so we can sort out the acos()
+ // ambiguity. I wish I could think of a more efficient way ... :-(
+ east_dot = MAT3_DOT_PRODUCT( surface_to_moon, v->get_surface_east() );
+ // printf(" East dot product = %.2f\n", east_dot);
+
+ // calculate the angle between v->surface_to_moon and
+ // v->surface_south. this is how much we have to rotate the sky
+ // for it to align with the moon
+ dot = MAT3_DOT_PRODUCT( surface_to_moon, v->get_surface_south() );
+ // printf(" Dot product = %.2f\n", dot);
+ if ( east_dot >= 0 ) {
+ l->moon_rotation = acos(dot);
+ } else {
+ l->moon_rotation = -acos(dot);
+ }
+ // printf(" Sky needs to rotate = %.3f rads = %.1f degrees.\n",
+ // angle, angle * RAD_TO_DEG); */
+}
+
+
+// $Log$
+// Revision 1.1 1999/03/22 12:08:57 curt
+// Initial revision.
+//
+// Revision 1.19 1999/01/07 20:25:37 curt
+// Portability changes and updates from Bernie Bright.
+//
+// Revision 1.18 1998/12/09 18:50:36 curt
+// Converted "class fgVIEW" to "class FGView" and updated to make data
+// members private and make required accessor functions.
+//
+// Revision 1.17 1998/11/09 23:41:53 curt
+// Log message clean ups.
+//
+// Revision 1.16 1998/11/07 19:07:14 curt
+// Enable release builds using the --without-logging option to the configure
+// script. Also a couple log message cleanups, plus some C to C++ comment
+// conversion.
+//
+// Revision 1.15 1998/10/18 01:17:24 curt
+// Point3D tweaks.
+//
+// Revision 1.14 1998/10/17 01:34:32 curt
+// C++ ifying ...
+//
+// Revision 1.13 1998/10/16 00:56:12 curt
+// Converted to Point3D class.
+//
+// Revision 1.12 1998/09/15 04:27:50 curt
+// Changes for new astro code.
+//
+// Revision 1.11 1998/08/12 21:13:22 curt
+// Optimizations by Norman Vine.
+//
+// Revision 1.10 1998/07/22 21:45:39 curt
+// fg_time.cxx: Removed call to ctime() in a printf() which should be harmless
+// but seems to be triggering a bug.
+// light.cxx: Added code to adjust fog color based on moonrise/moonset effects
+// and view orientation. This is an attempt to match the fog color to the
+// sky color in the center of the screen. You see discrepancies at the
+// edges, but what else can be done?
+// moonpos.cxx: Caculate local direction to moon here. (what compass direction
+// do we need to face to point directly at moon)
+//
+// Revision 1.9 1998/07/08 14:48:39 curt
+// polar3d.h renamed to polar3d.hxx
+//
+// Revision 1.8 1998/05/02 01:53:18 curt
+// Fine tuning mktime() support because of varying behavior on different
+// platforms.
+//
+// Revision 1.7 1998/04/30 12:36:05 curt
+// C++-ifying a couple source files.
+//
+// Revision 1.6 1998/04/28 01:22:18 curt
+// Type-ified fgTIME and fgVIEW.
+//
+// Revision 1.5 1998/04/26 05:10:05 curt
+// "struct fgLIGHT" -> "fgLIGHT" because fgLIGHT is typedef'd.
+//
+// Revision 1.4 1998/04/25 22:06:34 curt
+// Edited cvs log messages in source files ... bad bad bad!
+//
+// Revision 1.3 1998/04/25 20:24:03 curt
+// Cleaned up initialization sequence to eliminate interdependencies
+// between moon position, lighting, and view position. This creates a
+// valid single pass initialization path.
+//
+// Revision 1.2 1998/04/24 00:52:31 curt
+// Wrapped "#include <config.h>" in "#ifdef HAVE_CONFIG_H"
+// Fog color fixes.
+// Separated out lighting calcs into their own file.
+//
+// Revision 1.1 1998/04/22 13:24:07 curt
+// C++ - ifiing the code a bit.
+// Starting to reorginize some of the lighting calcs to use a table lookup.
+//
+// Revision 1.27 1998/04/03 22:12:57 curt
+// Converting to Gnu autoconf system.
+// Centralized time handling differences.
+//
+// Revision 1.26 1998/02/23 19:08:00 curt
+// Incorporated Durk's Astro/ tweaks. Includes unifying the moon position
+// calculation code between moon display, and other FG sections that use this
+// for things like lighting.
+//
+// Revision 1.25 1998/02/09 15:07:53 curt
+// Minor tweaks.
+//
+// Revision 1.24 1998/01/27 00:48:07 curt
+// Incorporated Paul Bleisch's <pbleisch@acm.org> new debug message
+// system and commandline/config file processing code.
+//
+// Revision 1.23 1998/01/19 19:27:21 curt
+// Merged in make system changes from Bob Kuehne <rpk@sgi.com>
+// This should simplify things tremendously.
+//
+// Revision 1.22 1998/01/19 18:40:40 curt
+// Tons of little changes to clean up the code and to remove fatal errors
+// when building with the c++ compiler.
+//
+// Revision 1.21 1997/12/30 23:10:19 curt
+// Calculate lighting parameters here.
+//
+// Revision 1.20 1997/12/30 22:22:43 curt
+// Further integration of event manager.
+//
+// Revision 1.19 1997/12/30 20:47:59 curt
+// Integrated new event manager with subsystem initializations.
+//
+// Revision 1.18 1997/12/23 04:58:40 curt
+// Tweaked the sky coloring a bit to build in structures to allow finer rgb
+// control.
+//
+// Revision 1.17 1997/12/15 23:55:08 curt
+// Add xgl wrappers for debugging.
+// Generate terrain normals on the fly.
+//
+// Revision 1.16 1997/12/11 04:43:57 curt
+// Fixed moon vector and lighting problems. I thing the moon is now lit
+// correctly.
+//
+// Revision 1.15 1997/12/10 22:37:55 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 1997/12/09 04:25:39 curt
+// Working on adding a global lighting params structure.
+//
+// Revision 1.13 1997/11/25 19:25:42 curt
+// Changes to integrate Durk's moon/moon code updates + clean up.
+//
+// Revision 1.12 1997/11/15 18:15:39 curt
+// Reverse direction of moon vector, so object normals can be more normal.
+//
+// Revision 1.11 1997/10/28 21:07:21 curt
+// Changed GLUT/ -> Main/
+//
+// Revision 1.10 1997/09/13 02:00:09 curt
+// Mostly working on stars and generating sidereal time for accurate star
+// placement.
+//
+// Revision 1.9 1997/09/05 14:17:31 curt
+// More tweaking with stars.
+//
+// Revision 1.8 1997/09/05 01:36:04 curt
+// Working on getting stars right.
+//
+// Revision 1.7 1997/09/04 02:17:40 curt
+// Shufflin' stuff.
+//
+// Revision 1.6 1997/08/27 03:30:37 curt
+// Changed naming scheme of basic shared structures.
+//
+// Revision 1.5 1997/08/22 21:34:41 curt
+// Doing a bit of reorganizing and house cleaning.
+//
+// Revision 1.4 1997/08/19 23:55:09 curt
+// Worked on better simulating real lighting.
+//
+// Revision 1.3 1997/08/13 20:23:49 curt
+// The interface to moonpos now updates a global structure rather than returning
+// current moon position.
+//
+// Revision 1.2 1997/08/06 00:24:32 curt
+// Working on correct real time moon lighting.
+//
+// Revision 1.1 1997/08/01 15:27:56 curt
+// Initial revision.
+//
projects / flightgear.git / commitdiff