Building performance improvements.

Use sensible LoD range of 10km and gradual fade-out to 20km rather
than fixed 20km+ LoD range.  Also make deeper quad-tree to make
culling easier.

simgear/scene/material/mat.cxx

@@ -321,6 +321,8 @@ SGMaterial::read_properties(const SGReaderWriterOptions* options,
     building_large_min_depth = props->getFloatValue("building-large-min-depth-m", 50.0);
     building_large_max_depth = props->getFloatValue("building-large-max-depth-m", 75.0);
 
+    building_range = props->getDoubleValue("building-range-m", 10000.0);
+    
     cos_object_max_density_slope_angle  = cos(props->getFloatValue("object-max-density-angle-deg", 20.0) * osg::PI/180.0);
     cos_object_zero_density_slope_angle = cos(props->getFloatValue("object-zero-density-angle-deg", 30.0) * osg::PI/180.0);
         

simgear/scene/material/mat.hxx

@@ -211,6 +211,8 @@ public:
   inline double get_building_large_min_depth () const { return building_large_min_depth; }
   inline double get_building_large_max_depth () const { return building_large_max_depth; }
   
+  inline double get_building_range () const { return building_range; }
+  
   inline double get_cos_object_max_density_slope_angle () const { return cos_object_max_density_slope_angle; }
   inline double get_cos_object_zero_density_slope_angle () const { return cos_object_zero_density_slope_angle; }
 
@@ -415,6 +417,8 @@ private:
   double building_large_min_depth;
   double building_large_max_depth;
   
+  double building_range;
+  
   // Cosine of the angle of maximum and zero density, 
   // used to stop buildings and random objects from being 
   // created on too steep a slope.

simgear/scene/tgdb/SGBuildingBin.cxx

@@ -64,7 +64,6 @@ namespace simgear
   
 typedef std::map<std::string, osg::observer_ptr<osg::StateSet> > BuildingStateSetMap;
 static BuildingStateSetMap statesetmap;
-static int numBuildings;
 
 typedef std::map<std::string, osg::observer_ptr<Effect> > EffectMap;
 static EffectMap buildingEffectMap;
@@ -136,6 +135,8 @@ BuildingBoundingBoxCallback::computeBound(const Drawable& drawable) const
     smallBuildingFraction = mat->get_building_small_fraction();
     mediumBuildingFraction = mat->get_building_medium_fraction();
     
+    buildingRange = mat->get_building_range();
+    
     SG_LOG(SG_TERRAIN, SG_DEBUG, "Building fractions " << smallBuildingFraction << " " << mediumBuildingFraction);
     
     
@@ -753,10 +754,11 @@ BuildingBoundingBoxCallback::computeBound(const Drawable& drawable) const
     
     for (int i = 0; i < 3; i++)
     {
+      // Create a quad tree.  Only small and medium buildings are faded out.
       BuildingGeometryQuadtree
           quadbuilding(GetBuildingCoord(), AddBuildingLeafObject(),
                    SG_BUILDING_QUAD_TREE_DEPTH,
-                   MakeBuildingLeaf(20000.0, effect));
+                   MakeBuildingLeaf(buildingRange, effect, (i != 2)));
                    
       // Transform building positions from the "geocentric" positions we
       // get from the scenery polys into the local Z-up coordinate
@@ -768,8 +770,8 @@ BuildingBoundingBoxCallback::computeBound(const Drawable& drawable) const
                      BuildingInstanceTransformer(transInv));
       quadbuilding.buildQuadTree(rotatedBuildings.begin(), rotatedBuildings.end());
 
-      for (size_t i = 0; i < quadbuilding.getRoot()->getNumChildren(); ++i)
+      for (size_t j = 0; j < quadbuilding.getRoot()->getNumChildren(); ++j)
-              group->addChild(quadbuilding.getRoot()->getChild(i));
+              group->addChild(quadbuilding.getRoot()->getChild(j));
     }
       
     return group;
@@ -829,7 +831,6 @@ BuildingBoundingBoxCallback::computeBound(const Drawable& drawable) const
       
       BOOST_FOREACH(bin, buildings)
       {      
-          numBuildings = numBuildings + bin->getNumBuildings();
           ref_ptr<Group> group = bin->createBuildingsGroup(transInv, options);
           
           for (size_t i = 0; i < group->getNumChildren(); ++i)

simgear/scene/tgdb/SGBuildingBin.hxx

@@ -45,7 +45,7 @@
 #include <simgear/scene/util/StateAttributeFactory.hxx>
 #include <simgear/structure/OSGUtils.hxx>
 
-#define SG_BUILDING_QUAD_TREE_DEPTH 2
+#define SG_BUILDING_QUAD_TREE_DEPTH 4
 #define SG_BUILDING_FADE_OUT_LEVELS 4
 
 using namespace osg;
@@ -118,6 +118,9 @@ private:
   float mediumBuildingMaxDepth;
   float largeBuildingMaxDepth;
   
+  // Visibility range for buildings
+  float buildingRange;
+  
   // Shared geometries of the building set
   ref_ptr<Geometry> smallSharedGeometry;
   ref_ptr<Geometry> mediumSharedGeometry;
@@ -191,18 +194,19 @@ public:
   // Helper classes for creating the quad tree
   struct MakeBuildingLeaf
   {
-      MakeBuildingLeaf(float range, Effect* effect) :
+      MakeBuildingLeaf(float range, Effect* effect, bool fade) :
-          _range(range), _effect(effect) {}
+          _range(range), _effect(effect), _fade_out(fade) {}
       
       MakeBuildingLeaf(const MakeBuildingLeaf& rhs) :
-          _range(rhs._range), _effect(rhs._effect)
+          _range(rhs._range), _effect(rhs._effect), _fade_out(rhs._fade_out)
       {}
 
       LOD* operator() () const
       {
           LOD* result = new LOD;
           
-          // Create a series of LOD nodes so trees cover decreases slightly
+          if (_fade_out) {            
+              // Create a series of LOD nodes so buidling cover decreases
               // gradually with distance from _range to 2*_range
               for (float i = 0.0; i < SG_BUILDING_FADE_OUT_LEVELS; i++)
               {   
@@ -210,11 +214,18 @@ public:
                   geode->setEffect(_effect.get());
                   result->addChild(geode, 0, _range * (1.0 + i / (SG_BUILDING_FADE_OUT_LEVELS - 1.0)));               
               }
+          } else {
+              // No fade-out, so all are visible for 2X range
+              EffectGeode* geode = new EffectGeode;
+              geode->setEffect(_effect.get());
+              result->addChild(geode, 0, 2.0 * _range);               
+          }
           return result;
       }
       
       float _range;
       ref_ptr<Effect> _effect;
+      bool _fade_out;
   };
   
   struct AddBuildingLeafObject