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Optimizations by Norman Vine.

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curt 1998-08-12 21:13:22 +00:00
parent d212b2d459
commit 3082eaf550
1 changed files with 43 additions and 6 deletions
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49
Time/sunpos.cxx
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@ -7,8 +7,6 @@
// with your calculator, third edition_, peter duffett-smith,
// cambridge university press, 1988.)
//
// RCS $Id$
//
// Copyright (C) 1989, 1990, 1993, 1994, 1995 Kirk Lauritz Johnson
//
// Parts of the source code (as marked) are:
@ -166,12 +164,15 @@ static void ecliptic_to_equatorial(double lambda, double beta,
/* 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(lambda)*cos_e - tan(beta)*sin_e, cos(lambda));
*delta = asin(sin(beta)*cos_e + cos(beta)*sin_e*sin(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);
}
@ -270,6 +271,38 @@ void fgSunPosition(time_t ssue, double *lon, double *lat) {
}
/* 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);
// 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;
@ -287,8 +320,9 @@ void fgUpdateSunPos( void ) {
printf(" Updating Sun position\n");
fgSunPosition(t->cur_time, &l->sun_lon, &sun_gd_lat);
fgSunPosition(t->cur_time, &l->sun_lon, &sun_gd_lat);
// (not sure why there was two)
// fgSunPosition(t->cur_time, &l->sun_lon, &sun_gd_lat);
fgSunPositionGST(t->gst, &l->sun_lon, &sun_gd_lat);
fgGeodToGeoc(sun_gd_lat, 0.0, &sl_radius, &l->sun_gc_lat);
@ -370,6 +404,9 @@ void fgUpdateSunPos( void ) {
// $Log$
// 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.