Fix for "falling through ground" problem

The LOD far range on the tile entry scenegraph node was initialized to
0. This meant that any traverals of active children that happened
before the tile manager updated the node would ignore the node
altogether. Among these is the groundcache traversal which was failing
at startup even though scenery was loaded.

Also added a function to dump scene graph nodes to files; very handy
in gdb.

src/FDM/groundcache.cxx

@@ -249,8 +249,8 @@ public:
     FGGroundCache::GroundProperty oldGp = mGroundProperty;
     if (!enterNode(geode))
       return;
-
-    for(unsigned i = 0; i < geode.getNumDrawables(); ++i)
+    unsigned int numDrawables = geode.getNumDrawables();
+    for(unsigned i = 0; i < numDrawables; ++i)
       fillWith(geode.getDrawable(i));
     sphIsec = oldSphIsec;
     mGroundProperty = oldGp;
@@ -438,12 +438,14 @@ public:
 
 FGGroundCache::FGGroundCache() :
   ground_radius(0.0),
+  _type(0),
+  _material(0),
   cache_ref_time(0.0),
   wire_id(0),
   reference_wgs84_point(SGVec3d(0, 0, 0)),
   reference_vehicle_radius(0.0),
-  found_ground(false),
-  _material(0)
+  down(0.0, 0.0, 0.0),
+  found_ground(false)
 {
 }
 

src/Main/renderer.cxx

@@ -1077,5 +1077,11 @@ fgDumpTerrainBranchToFile(const char* filename)
                                  filename );
 }
 
+// For debugging
+bool
+fgDumpNodeToFile(osg::Node* node, const char* filename)
+{
+    return osgDB::writeNodeFile(*node, filename);
+}
 // end of renderer.cxx
     

src/Scenery/tileentry.cxx

@@ -151,6 +151,10 @@ FGTileEntry::FGTileEntry ( const SGBucket& b )
     _node->setCullCallback(new TileCullCallback);
     tileFileName += ".stg";
     _node->setName(tileFileName);
+    // Give a default LOD range so that traversals that traverse
+    // active children (like the groundcache lookup) will work before
+    // tile manager has had a chance to update this node.
+    _node->setRange(0, 0.0, 10000.0);
 }
 
 
@@ -569,6 +573,11 @@ bool ReaderWriterSTG::acceptsExtension(const string& extension) const
             || osgDB::equalCaseInsensitive(extension, "stg"));   
 }
 
+//#define SLOW_PAGER 1
+#ifdef SLOW_PAGER
+#include <unistd.h>
+#endif
+
 osgDB::ReaderWriter::ReadResult
 ReaderWriterSTG::readNode(const string& fileName,
                           const osgDB::ReaderWriter::Options* options) const
@@ -589,6 +598,10 @@ ReaderWriterSTG::readNode(const string& fileName,
     osg::Node* result
         = FGTileEntry::loadTileByName(osgDB::getNameLessExtension(stgFileName),
                                       globals->get_fg_scenery());
+    // For debugging race conditions
+#ifdef SLOW_PAGER
+    sleep(5);
+#endif
     if (result)
         return result;           // Constructor converts to ReadResult
     else