Ssg tweaks.

Better handling of missing tiles.
Added a range selector so we can completely ignore tiles that are beyond
  our visibility range.
Added a routine to prep the ssg nodes before rendering by updating the
  transform and range selector values.

src/Scenery/tilecache.cxx

@@ -137,10 +137,13 @@ FGTileCache::fill_in( int index, const FGBucket& p )
 
     tile_cache[index].mark_loaded();
     tile_cache[index].tile_bucket = p;
-    ssgBranch *new_tile = fgObjLoad( tile_path.str(), &tile_cache[index] );
     tile_cache[index].branch_ptr = new ssgTransform;
-    tile_cache[index].branch_ptr->addKid( new_tile );
-    // tile_cache[index].branch_ptr->addKid( penguin );
+    tile_cache[index].range_ptr = new ssgRangeSelector;
+    ssgBranch *new_tile = fgObjLoad( tile_path.str(), &tile_cache[index] );
+    if ( new_tile != NULL ) {
+	tile_cache[index].range_ptr->addKid( new_tile );
+    }
+    tile_cache[index].branch_ptr->addKid( tile_cache[index].range_ptr );
     terrain->addKid( tile_cache[index].branch_ptr );
 
     // cout << " ncount before = " << tile_cache[index].ncount << "\n";

src/Scenery/tileentry.cxx

@@ -42,7 +42,10 @@ FG_USING_STD(mem_fun_ref);
 // Constructor
 FGTileEntry::FGTileEntry ( void )
     : ncount(0),
-      state(Unused)
+      state(Unused),
+      vtlist(NULL),
+      vnlist(NULL),
+      tclist(NULL)
 {
     nodes.clear();
 }
@@ -73,9 +76,15 @@ FGTileEntry::free_tile()
     fragment_list.erase( begin(), end() );
 
     // delete the ssg used structures
+    if ( vtlist != NULL ) {
 	delete vtlist;
+    }
+    if ( vnlist != NULL ) {
 	delete vnlist;
+    }
+    if ( tclist != NULL ) {
 	delete tclist;
+    }
 
     // delete the ssg branch
 

src/Scenery/tileentry.hxx

@@ -109,7 +109,21 @@ public:
     sgVec3 *vnlist;
     sgVec2 *tclist;
 
-    // pointer to ssg branch;
+    // ssg tree structure for this tile is as follows:
+    // ssgRoot(scene)
+    //     - ssgBranch(terrain)
+    //        - ssgTransform(tile)
+    //           - ssgRangeSelector(tile)
+    //              - ssgEntity(tile)
+    //                 - kid1(fan)
+    //                 - kid2(fan)
+    //                   ...
+    //                 - kidn(fan)
+
+    // pointer to ssg range selector for this tile
+    ssgRangeSelector *range_ptr;
+
+    // pointer to ssg transform for this tile
     ssgTransform *branch_ptr;
 
 public:

src/Scenery/tilemgr.cxx

@@ -734,6 +734,42 @@ update_tile_geometry( FGTileEntry *t, GLdouble *MODEL_VIEW)
 }
 
 
+// Prepare the ssg nodes ... for each tile, set it's proper
+// transform and update it's range selector based on current
+// visibilty
+void FGTileMgr::prep_ssg_nodes( void ) {
+    FGTileEntry *t;
+
+    int tile_diameter = current_options.get_tile_diameter();
+
+    float ranges[2];
+    ranges[0] = 0.0f;
+    ranges[1] = current_weather.get_visibility();
+
+    // traverse the potentially viewable tile list and update range
+    // selector and transform
+    for ( int i = 0; i < (tile_diameter * tile_diameter); i++ ) {
+	int index = tiles[i];
+	t = global_tile_cache.get_tile(index);
+
+	if ( t->is_loaded() ) {
+	    // set range selector (LOD trick)
+	    t->range_ptr->setRanges( ranges, 2 );
+
+	    // calculate tile offset
+	    t->SetOffset( scenery.center );
+
+	    // calculate ssg transform
+	    sgCoord sgcoord;
+	    sgSetCoord( &sgcoord,
+			t->offset.x(), t->offset.y(), t->offset.z(),
+			0.0, 0.0, 0.0 );
+	    t->branch_ptr->setTransform( &sgcoord );
+	}
+    }
+}
+
+
 // Render the local tiles
 void FGTileMgr::render( void ) {
     FGInterface *f;
@@ -744,7 +780,6 @@ void FGTileMgr::render( void ) {
     fgFRAGMENT *frag_ptr;
     FGMaterialSlot *mtl_ptr;
     int i;
-    int tile_diameter;
     int index;
     int culled = 0;
     int drawn = 0;
@@ -753,7 +788,7 @@ void FGTileMgr::render( void ) {
     f = current_aircraft.fdm_state;
     v = &current_view;
 
-    tile_diameter = current_options.get_tile_diameter();
+    int tile_diameter = current_options.get_tile_diameter();
 
     // moved to fgTileMgrUpdate, right after we check if we need to
     // load additional tiles:
@@ -775,13 +810,6 @@ void FGTileMgr::render( void ) {
 	    // calculate tile offset
 	    t->SetOffset( scenery.center );
 
-	    // calculate ssg transform
-	    sgCoord sgcoord;
-	    sgSetCoord( &sgcoord,
-			t->offset.x(), t->offset.y(), t->offset.z(),
-			0.0, 0.0, 0.0 );
-	    t->branch_ptr->setTransform( &sgcoord );
-
 	    // Course (tile based) culling
 	    if ( viewable(t->offset, t->bounding_radius) ) {
 		// at least a portion of this tile could be viewable
@@ -854,6 +882,6 @@ void FGTileMgr::render( void ) {
     // traverse the transient per-material fragment lists and render
     // out all fragments for each material property.
     xglPushMatrix();
-    // material_mgr.render_fragments();
+    material_mgr.render_fragments();
     xglPopMatrix();
 }

src/Scenery/tilemgr.hxx

@@ -108,6 +108,11 @@ public:
     double current_elev_new( const FGBucket& p );
     double current_elev( double lon, double lat, const Point3D& abs_view_pos );
 
+    // Prepare the ssg nodes ... for each tile, set it's proper
+    // transform and update it's range selector based on current
+    // visibilty
+    void prep_ssg_nodes( void );
+
     // Render the local tiles --- hack, hack, hack
     void render( void );
 };