From af6da1d3c1aff4dd28626c6dbfd83b3bfccec705 Mon Sep 17 00:00:00 2001
From: ehofman <ehofman>
Date: Mon, 9 Nov 2009 10:28:59 +0000
Subject: [PATCH] sun postition fixes

Was: allow sound effects in the configuration file to be added to the 'avionics' sample group by setting '<type>avionics</type>'.

but this change obviously snuck in with that.
---
 src/Time/tmp.cxx | 40 ++++++++++++++++++++++------------------
 1 file changed, 22 insertions(+), 18 deletions(-)

diff --git a/src/Time/tmp.cxx b/src/Time/tmp.cxx
index ab4ca22fc..0e04d5b24 100644
--- a/src/Time/tmp.cxx
+++ b/src/Time/tmp.cxx
@@ -76,25 +76,31 @@ void fgUpdateSunPos( void ) {
     SG_LOG( SG_EVENT, SG_DEBUG, "  Updating Sun position" );
     SG_LOG( SG_EVENT, SG_DEBUG, "  Gst = " << time_now->getGst() );
 
-    double sun_lon;
-    double sun_gd_lat;
-    fgSunPositionGST(time_now->getGst(), &sun_lon, &sun_gd_lat);
+    double sun_lon, sun_lat;
+    fgSunPositionGST(time_now->getGst(), &sun_lon, &sun_lat);
     light->set_sun_lon(sun_lon);
-    light->set_sun_lat(sun_gd_lat);
+    light->set_sun_lat(sun_lat);
 
     // update the sun light vector
-    // calculations are in the horizontal normal plane:
-    // x-north, y-east, z-down
+    // calculations are in the horizontal normal plane: x-north, y-east, z-down
+    static SGQuatd q = SGQuatd::fromLonLat(SGGeod::fromRad(0,0));
 
-    SGGeod geodViewPos = SGGeod::fromCart(viewer->getViewPosition());
-    SGGeod geodSunPos = SGGeod::fromRad(sun_lon, sun_gd_lat);
+    // sun orientation
+    SGGeod geodSunPos = SGGeod::fromRad(sun_lon, sun_lat);
+    SGQuatd sunOr = SGQuatd::fromLonLat(geodSunPos);
 
-    //static SGQuatd q = SGQuatd::fromLonLat(SGGeod::fromRad(0,0));
+    // scenery orientation
+    SGGeod geodViewPos = SGGeod::fromCart(viewer->getViewPosition());
     SGQuatd hlOr = SGQuatd::fromLonLat(geodViewPos);
-    SGQuatd sunOr = SGQuatd::fromLonLat(geodSunPos);
+    SGVec3d localAt = hlOr.backTransform(SGVec3d::e3());
+
+    // transpose the sun direction from (lat,lon) to (0,0)
+    SGVec3d transSunDir = (q*sunOr).transform(-localAt);
+    SGQuatd sunDirOr = SGQuatd::fromRealImag(0, transSunDir);
 
-    SGVec3d sunDirection = (hlOr*sunOr).transform(SGVec3d::e3());
-    light->set_sun_rotation( acos(sunDirection[1]) - SGD_PI_2 );
+    // transpose the calculated sun vector back to (lat,lon)
+    SGVec3d sunDirection = sunDirOr.transform(localAt);
+    light->set_sun_rotation( acos(sunDirection[1])-SGD_PI_2 );
     light->set_sun_angle( acos(-sunDirection[2]) );
 
     SGVec3d sunPos = SGVec3d::fromGeod(geodSunPos);
@@ -128,15 +134,14 @@ void fgUpdateSunPos( void ) {
     // calculate the sun's relative angle to local up
     SGVec3d viewPos = v->get_view_pos();
     SGQuatd hlOr = SGQuatd::fromLonLat(SGGeod::fromCart(viewPos));
-    SGVec3f nup(toVec3f(hlOr.backTransform(-SGVec3d::e3())));
-
-    SGVec3f nsun(toVec3f(normalize(sunpos)));
+    SGVec3f world_up = toVec3f(hlOr.backTransform(-SGVec3d::e3()));
+    SGVec3f nsun = toVec3f(normalize(sunpos));
     // cout << "nup = " << nup[0] << "," << nup[1] << ","
     //      << nup[2] << endl;
     // cout << "nsun = " << nsun[0] << "," << nsun[1] << ","
     //      << nsun[2] << endl;
 
-    l->set_sun_angle( acos( dot ( nup, nsun ) ) );
+    l->set_sun_angle( acos( dot ( world_up, nsun ) ) );
     SG_LOG( SG_EVENT, SG_DEBUG, "sun angle relative to current location = "
             << l->get_sun_angle() );
 
@@ -152,10 +157,9 @@ void fgUpdateSunPos( void ) {
     // earth's surface the sun is directly over, map into onto the
     // local plane representing "horizontal".
 
-    SGVec3f world_up = toVec3f(hlOr.backTransform(-SGVec3d::e3()));
-    SGVec3f view_pos = toVec3f(v->get_view_pos());
     // surface direction to go to head towards sun
     SGVec3f surface_to_sun;
+    SGVec3f view_pos = toVec3f(v->get_view_pos());
     sgmap_vec_onto_cur_surface_plane( world_up.data(), view_pos.data(),
                                       to_sun.data(), surface_to_sun.data() );
     surface_to_sun = normalize(surface_to_sun);
-- 
2.39.5