#include

#include #include "sunpos.hxx" // extern SolarSystem *solarSystem; extern FGEphemeris *ephem; #undef E #define MeanObliquity (23.440592*(FG_2PI/360)) static void ecliptic_to_equatorial(double, double, double *, double *); static double julian_date(int, int, int); static double GST(time_t); 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 sun is * directly overhead. (lat, lon are reported in radians */ void fgSunPosition(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 = sun_ecliptic_longitude(ssue); */ /* ecliptic_to_equatorial(lambda, 0.0, &alpha, &delta); */ //ecliptic_to_equatorial (solarPosition.lonSun, 0.0, &alpha, &delta); /* ********************************************************************** * NOTE: in the next function, each time the sun's position is updated, the * the sun's longitude is returned from solarSystem->sun. Note that the * sun'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 fgSunPosition we're talking about here concerns the changing * position of the sun due to the daily rotation of the earth. * The ecliptic longitude, however, represents the position of the sun with * respect to the stars, and completes just one cycle over the course of a * year. Its therefore pretty safe to update the sun's longitude only once * every ten minutes. (Comment added by Durk Talsma). ************************************************************************/ ecliptic_to_equatorial( ephem->get_sun()->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 * sun is directly overhead. (lat, lon are reported in radians */ static void fgSunPositionGST(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 = sun_ecliptic_longitude(ssue); */ /* ecliptic_to_equatorial(lambda, 0.0, &alpha, &delta); */ //ecliptic_to_equatorial (solarPosition.lonSun, 0.0, &alpha, &delta); ecliptic_to_equatorial( ephem->get_sun()->getLon(), ephem->get_sun()->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 sun position void fgUpdateSunPos( void ) { fgLIGHT *l; FGView *v; sgVec3 nup, nsun, v0, surface_to_sun; Point3D p, rel_sunpos; double dot, east_dot; double sun_gd_lat, sl_radius; l = &cur_light_params; SGTime *t = globals->get_time_params(); v = ¤t_view; FG_LOG( FG_EVENT, FG_INFO, " Updating Sun position" ); FG_LOG( FG_EVENT, FG_INFO, " Gst = " << t->getGst() ); fgSunPositionGST(t->getGst(), &l->sun_lon, &sun_gd_lat); fgGeodToGeoc(sun_gd_lat, 0.0, &sl_radius, &l->sun_gc_lat); p = Point3D( l->sun_lon, l->sun_gc_lat, sl_radius ); l->fg_sunpos = fgPolarToCart3d(p); FG_LOG( FG_EVENT, FG_INFO, " t->cur_time = " << t->get_cur_time() ); FG_LOG( FG_EVENT, FG_INFO, " Sun Geodetic lat = " << sun_gd_lat << " Geocentric lat = " << l->sun_gc_lat ); // update the sun light vector sgSetVec4( l->sun_vec, l->fg_sunpos.x(), l->fg_sunpos.y(), l->fg_sunpos.z(), 0.0 ); sgNormalizeVec4( l->sun_vec ); sgCopyVec4( l->sun_vec_inv, l->sun_vec ); sgNegateVec4( l->sun_vec_inv ); // make sure these are directional light sources only l->sun_vec[3] = l->sun_vec_inv[3] = 0.0; // cout << " l->sun_vec = " << l->sun_vec[0] << "," << l->sun_vec[1] // << ","<< l->sun_vec[2] << endl; // calculate the sun's relative angle to local up sgCopyVec3( nup, v->get_local_up() ); sgSetVec3( nsun, l->fg_sunpos.x(), l->fg_sunpos.y(), l->fg_sunpos.z() ); sgNormalizeVec3(nup); sgNormalizeVec3(nsun); // cout << "nup = " << nup[0] << "," << nup[1] << "," // << nup[2] << endl; // cout << "nsun = " << nsun[0] << "," << nsun[1] << "," // << nsun[2] << endl; l->sun_angle = acos( sgScalarProductVec3 ( nup, nsun ) ); cout << "sun angle relative to current location = " << l->sun_angle << endl; // calculate vector to sun's position on the earth's surface rel_sunpos = l->fg_sunpos - (v->get_view_pos() + scenery.center); v->set_to_sun( rel_sunpos.x(), rel_sunpos.y(), rel_sunpos.z() ); // printf( "Vector to sun = %.2f %.2f %.2f\n", // v->to_sun[0], v->to_sun[1], v->to_sun[2]); // make a vector to the current view position Point3D view_pos = v->get_view_pos(); sgSetVec3( 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 sun is directly over, map into onto the // local plane representing "horizontal". sgmap_vec_onto_cur_surface_plane( v->get_local_up(), v0, v->get_to_sun(), surface_to_sun ); sgNormalizeVec3(surface_to_sun); v->set_surface_to_sun( surface_to_sun[0], surface_to_sun[1], surface_to_sun[2] ); // cout << "(sg) Surface direction to sun is " // << surface_to_sun[0] << "," // << surface_to_sun[1] << "," // << surface_to_sun[2] << endl; // cout << "Should be close to zero = " // << sgScalarProductVec3(nup, surface_to_sun) << endl; // calculate the angle between v->surface_to_sun 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 = sgScalarProductVec3( surface_to_sun, v->get_surface_east() ); // cout << " East dot product = " << east_dot << endl; // calculate the angle between v->surface_to_sun and // v->surface_south. this is how much we have to rotate the sky // for it to align with the sun dot = sgScalarProductVec3( surface_to_sun, v->get_surface_south() ); // cout << " Dot product = " << dot << endl; if ( east_dot >= 0 ) { l->sun_rotation = acos(dot); } else { l->sun_rotation = -acos(dot); } // cout << " Sky needs to rotate = " << angle << " rads = " // << angle * RAD_TO_DEG << " degrees." << endl; }