Improove FGTileMgr::scenery_available for small ranges.

Use SGGeod in FGTileMgr, FGScenery apis.

Modified Files:
	src/AIModel/AIBallistic.cxx src/Main/main.cxx
	src/Scenery/scenery.cxx src/Scenery/scenery.hxx
	src/Scenery/tilemgr.cxx src/Scenery/tilemgr.hxx
	src/Scripting/NasalSys.cxx

src/AIModel/AIBallistic.cxx

@@ -433,8 +433,8 @@ void FGAIBallistic::setForcePath(const string& p) {
 
 bool FGAIBallistic::getHtAGL(){
 
-    if (globals->get_scenery()->get_elevation_m(pos.getLatitudeDeg(), pos.getLongitudeDeg(),
-        10000.0, _elevation_m, &_material)){
+    if (globals->get_scenery()->get_elevation_m(SGGeod::fromGeodM(pos, 10000),
+                                                _elevation_m, &_material)){
             _ht_agl_ft = pos.getElevationFt() - _elevation_m * SG_METER_TO_FEET;
             if (_material) {
                 const vector<string>& names = _material->get_names();

src/Main/main.cxx

@@ -137,7 +137,8 @@ void fgUpdateTimeDepCalcs() {
         // We require just to have 50 meter scenery availabe around
         // the aircraft.
         double range = 1000.0;
-        if (globals->get_scenery()->scenery_available(lat, lon, range)) {
+        SGGeod geod = SGGeod::fromDeg(lon, lat);
+        if (globals->get_scenery()->scenery_available(geod, range)) {
             //SG_LOG(SG_FLIGHT, SG_INFO, "Finally initializing fdm");
             cur_fdm_state->init();
             if ( cur_fdm_state->get_bound() ) {

src/Scenery/scenery.cxx

@@ -117,13 +117,6 @@ void FGScenery::bind() {
 void FGScenery::unbind() {
 }
 
-bool
-FGScenery::get_elevation_m(double lat, double lon, double max_alt,
-                           double& alt, const SGMaterial** material)
-{
-  return get_elevation_m(SGGeod::fromDegM(lon, lat, max_alt), alt, material);
-}
-
 bool
 FGScenery::get_cart_elevation_m(const SGVec3d& pos, double max_altoff,
                                 double& alt, const SGMaterial** material)
@@ -212,13 +205,13 @@ FGScenery::get_cart_ground_intersection(const SGVec3d& pos, const SGVec3d& dir,
   return hits;
 }
 
-bool FGScenery::scenery_available(double lat, double lon, double range_m)
+bool FGScenery::scenery_available(const SGGeod& position, double range_m)
 {
-  if(globals->get_tile_mgr()->scenery_available(lat, lon, range_m))
+  if(globals->get_tile_mgr()->scenery_available(position, range_m))
   {
     double elev;
-    get_elevation_m(lat, lon, SG_MAX_ELEVATION_M, elev, 0);
-    SGVec3f p = SGVec3f::fromGeod(SGGeod::fromDegM(lon,lat,elev));
+    get_elevation_m(SGGeod::fromGeodM(position, SG_MAX_ELEVATION_M), elev, 0);
+    SGVec3f p = SGVec3f::fromGeod(SGGeod::fromGeodM(position, elev));
     simgear::CheckSceneryVisitor csnv(getPagerSingleton(), p.osg(), range_m);
     // currently the PagedLODs will not be loaded by the DatabasePager
     // while the splashscreen is there, so CheckSceneryVisitor force-loads

src/Scenery/scenery.hxx

@@ -70,8 +70,6 @@ public:
     /// lat/lon pair. If there is no scenery for that point, the altitude
     /// value is undefined. 
     /// All values are meant to be in meters or degrees.
-    bool get_elevation_m(double lat, double lon, double max_alt,
-                         double& alt, const SGMaterial** material);
     bool get_elevation_m(const SGGeod& geod, double& alt,
                          const SGMaterial** material);
 
@@ -87,7 +85,7 @@ public:
     /// value is undefined.
     /// All values are meant to be in meters.
     bool get_cart_elevation_m(const SGVec3d& pos, double max_altoff,
-                              double& radius, const SGMaterial** material);
+                              double& elevation, const SGMaterial** material);
 
     /// Compute the nearest intersection point of the line starting from 
     /// start going in direction dir with the terrain.
@@ -105,7 +103,7 @@ public:
     /// Returns true if scenery is avaliable for the given lat, lon position
     /// within a range of range_m.
     /// lat and lon are expected to be in degrees.
-    bool scenery_available(double lat, double lon, double range_m);
+    bool scenery_available(const SGGeod& position, double range_m);
 
     // Static because access to the pager is needed before the rest of
     // the scenery is initialized.

src/Scenery/tilemgr.cxx

@@ -383,26 +383,26 @@ void FGTileMgr::prep_ssg_nodes(float vis) {
 }
 
 bool FGTileMgr::scenery_available(const SGGeod& position, double range_m)
-{
-    return scenery_available(position.getLatitudeDeg(),
-                             position.getLongitudeDeg(), range_m);
-}
-
-bool FGTileMgr::scenery_available(double lat, double lon, double range_m)
 {
   // sanity check (unfortunately needed!)
-  if ( lon <= -180.0 || lon >= 180.0 || lat <= -90.0 || lat >= 90.0 )
+  if (position.getLongitudeDeg() < -180 || position.getLongitudeDeg() > 180 ||
+      position.getLatitudeDeg() < -90 || position.getLatitudeDeg() > 90)
     return false;
   
-  SGBucket bucket(lon, lat);
+  SGBucket bucket(position);
   TileEntry *te = tile_cache.get_tile(bucket);
   if (!te || !te->is_loaded())
     return false;
 
+  SGVec3d cartPos = SGVec3d::fromGeod(position);
+
   // Traverse all tiles required to be there for the given visibility.
   // This uses exactly the same algorithm like the tile scheduler.
   double tile_width = bucket.get_width_m();
   double tile_height = bucket.get_height_m();
+  double tile_r = 0.5*sqrt(tile_width*tile_width + tile_height*tile_height);
+  double max_dist = tile_r + range_m;
+  double max_dist2 = max_dist*max_dist;
   
   int xrange = (int)fabs(range_m / tile_width) + 1;
   int yrange = (int)fabs(range_m / tile_height) + 1;
@@ -411,7 +411,11 @@ bool FGTileMgr::scenery_available(double lat, double lon, double range_m)
     for ( int y = -yrange; y <= yrange; ++y ) {
       // We have already checked for the center tile.
       if ( x != 0 || y != 0 ) {
-        SGBucket b = sgBucketOffset( lon, lat, x, y );
+        SGBucket b = sgBucketOffset( position.getLongitudeDeg(),
+                                     position.getLatitudeDeg(), x, y );
+        // Do not ask if it is just the next tile but way out of range.
+        if (max_dist2 < distSqr(cartPos, SGVec3d::fromGeod(b.get_center())))
+          continue;
         TileEntry *te = tile_cache.get_tile(b);
         if (!te || !te->is_loaded())
           return false;

src/Scenery/tilemgr.hxx

@@ -106,7 +106,6 @@ public:
     /// Returns true if scenery is avaliable for the given lat, lon position
     /// within a range of range_m.
     /// lat and lon are expected to be in degrees.
-    bool scenery_available(double lat, double lon, double range_m);
     bool scenery_available(const SGGeod& position, double range_m);
 
     // Load a model for a tile

src/Scripting/NasalSys.cxx

@@ -471,7 +471,8 @@ static naRef f_geodinfo(naContext c, naRef me, int argc, naRef* args)
     double lon = naNumValue(args[1]).num;
     double elev;
     const SGMaterial *mat;
-    if(!globals->get_scenery()->get_elevation_m(lat, lon, 10000.0, elev, &mat))
+    SGGeod geod = SGGeod::fromDegM(lon, lat, 10000);
+    if(!globals->get_scenery()->get_elevation_m(geod, elev, &mat))
         return naNil();
     naRef vec = naNewVector(c);
     naVec_append(vec, naNum(elev));