From Terrex and Andrew Sampsom and Don Tidrow and Robert Osfield,

email comments from Andew Sampson,

"I've contacted Terrex, and obtained the 2.2 version
of their trpage library.  The library included a
fork of OSG 0.9.8's txp plugin, modified to load 2.1+
txp DBs.

I've done the work of incorporating the changes made
to OSG's txp plugin since 0.9.8 into Terrex's fork.
The forked version is now up-to-date with the changes
made to OSG 0.9.9 and 1.0.

Terrex made a lot of changes (especially differences
in whitespace), so the diff between the forked version

and OSG 1.0's txp plugin is yucky.  I did my best, but

keep in mind that this is the result of a 4-way merge
(kinda... terrex-0.9.8, stock-0.9.8, stock-0.9.9,
stock-1.0).

I really want to see this forked version merged back
into the main OSG branch.  The new features offered by

this version of the plugin (2.1+ support, variable
LOD support, bug fixes) are worth the trouble."

--

Don Tidrow then took this code and added his work.

--

Robert Osfield then fixed all the warnings that abound in the trpage code base.

src/osgPlugins/txp/TXPNode.cpp

@@ -20,6 +20,41 @@ using namespace osg;
 
 
 
+class RetestCallback : public osg::NodeCallback
+{
+
+public:
+    RetestCallback()
+    {
+	timer = osg::Timer::instance(); // get static timer
+        prevTime = 0; // should this be instantiated with current time?
+    }
+
+    virtual void operator () ( osg::Node * node, osg::NodeVisitor * nv )
+    {
+        osg::Group *pLOD = (osg::Group *) node; 
+        osg::Group *n = NULL;
+        if ((pLOD->getNumChildren() > 0) &&
+            (n = (osg::Group *) pLOD->getChild(0)) &&
+            (n->getNumChildren() == 0))
+        {
+	    osg::Timer_t curTime = timer->tick();
+            if ((prevTime + 2.0/timer->getSecondsPerTick() ) < curTime)
+            {
+                prevTime = curTime;
+                pLOD->removeChildren( 0, pLOD->getNumChildren());
+            }
+        }
+
+        NodeCallback::traverse( node, nv );
+    }
+
+protected:
+    const osg::Timer* timer;
+    osg::Timer_t prevTime;
+};
+
+
 
 #define TXPNodeERROR(s) osg::notify(osg::NOTICE) << "txp::TXPNode::" << (s) << " error: "
 
@@ -29,6 +64,7 @@ _originX(0.0),
 _originY(0.0)
 {
     setNumChildrenRequiringUpdateTraversal(1);
+	setCullingActive(false);
 }
             
 TXPNode::TXPNode(const TXPNode& txpNode,const osg::CopyOp& copyop):
@@ -52,18 +88,18 @@ void TXPNode::traverse(osg::NodeVisitor& nv)
 {
     switch(nv.getVisitorType())
     {
-      case osg::NodeVisitor::CULL_VISITOR:
-      {
+    case osg::NodeVisitor::CULL_VISITOR:
+    {
                 
         osgUtil::CullVisitor* cv = dynamic_cast<osgUtil::CullVisitor*>(&nv);
         if (cv)
         {
-//#define PRINT_TILEMAPP_TIMEINFO        
-#ifdef PRINT_TILEMAPP_TIMEINFO        
+//#define PRINT_TILEMAPP_TIMEINFO
+#ifdef PRINT_TILEMAPP_TIMEINFO
             const osg::Timer& timer = *osg::Timer::instance();
             osg::Timer_t start = timer.tick();
             std::cout<<"Doing visible tile search"<<std::endl;
-#endif // PRINT_TILEMAPP_TIMEINFO        
+#endif // PRINT_TILEMAPP_TIMEINFO
         
             osg::ref_ptr<TileMapper> tileMapper = new TileMapper;
             tileMapper->setLODScale(cv->getLODScale());
@@ -92,11 +128,11 @@ void TXPNode::traverse(osg::NodeVisitor& nv)
     
         updateEye(nv);
         break;
-      }
-      case osg::NodeVisitor::UPDATE_VISITOR:
+    }
+    case osg::NodeVisitor::UPDATE_VISITOR:
         updateSceneGraph();
         break;
-      default:
+    default:
         break;
     }
     Group::traverse(nv);
@@ -186,7 +222,10 @@ bool TXPNode::loadArchive()
     _archive->GetHeader()->GetLodSize(0,tileSize);
 
     _pageManager = new TXPPageManager;
-    _pageManager->Init(_archive.get());
+
+    // We are going to use _pageManager to manage lod 0 only, all other lod
+    // are managed by this OSG plugin
+    _pageManager->Init(_archive.get(), 1);
 
     return true;
 }
@@ -227,7 +266,7 @@ void TXPNode::updateEye(osg::NodeVisitor& nv)
             tile->GetTileLoc(x,y,lod);
             if (lod==0)
             {
-                osg::Node* node = addPagedLODTile(x,y,lod);
+                osg::Node* node = addPagedLODTile(x,y);
                 tile->SetLocalData(node);
                 //osg::notify(osg::NOTICE) << "Tile load: " << x << " " << y << " " << lod << std::endl;
             }
@@ -237,8 +276,12 @@ void TXPNode::updateEye(osg::NodeVisitor& nv)
     }
 }
 
-osg::Node* TXPNode::addPagedLODTile(int x, int y, int lod)
+osg::Node* TXPNode::addPagedLODTile(int x, int y)
 {
+    // For TerraPage 2.1 and over this method must only be use with lod = 0.
+    // If you look at the code that calls it, it is effectively called only when
+    // lod = 0. So all is OK
+    int lod = 0;
     char pagedLODfile[1024];
     sprintf(pagedLODfile,"%s\\tile%d_%dx%d_%d.txp",_archive->getDir(),lod,x,y,_archive->getId());
 
@@ -254,6 +297,7 @@ osg::Node* TXPNode::addPagedLODTile(int x, int y, int lod)
     pagedLOD->setCenter(info.center);
     pagedLOD->setRadius(info.radius);
     pagedLOD->setNumChildrenThatCannotBeExpired(1);
+    pagedLOD->setUpdateCallback(new RetestCallback);
 
     const trpgHeader* header = _archive->GetHeader();
     trpgHeader::trpgTileType tileType;
@@ -274,9 +318,10 @@ osg::Node* TXPNode::addPagedLODTile(int x, int y, int lod)
     }
     else
     {
-        _nodesToAdd.push_back(pagedLOD);
-        return pagedLOD;
-    }
+    _nodesToAdd.push_back(pagedLOD);
+    
+    return pagedLOD;
+}
 }
 
 void TXPNode::updateSceneGraph()