diff --git a/include/osgUtil/Optimizer b/include/osgUtil/Optimizer
index 1f67f1673..6ec599577 100644
--- a/include/osgUtil/Optimizer
+++ b/include/osgUtil/Optimizer
@@ -44,12 +44,14 @@ class OSGUTIL_EXPORT Optimizer
             SHARE_DUPLICATE_STATE = 0x8,
             MERGE_GEOMETRY = 0x10,
             CHECK_GEOMETRY = 0x20,
+            SPATIALIZE_GROUPS = 0x40,
             ALL_OPTIMIZATIONS = FLATTEN_STATIC_TRANSFORMS |
                                 REMOVE_REDUNDANT_NODES |
                                 COMBINE_ADJACENT_LODS |
                                 SHARE_DUPLICATE_STATE |
                                 MERGE_GEOMETRY |
-                                CHECK_GEOMETRY
+                                CHECK_GEOMETRY |
+                                SPATIALIZE_GROUPS
         };
 
         /** traverse the node and its subgraph with a series of optimization
@@ -213,6 +215,24 @@ class OSGUTIL_EXPORT Optimizer
                 static bool mergePrimitive(osg::DrawElementsUInt& lhs,osg::DrawElementsUInt& rhs);
 
         };
+
+        /** Spatialize scene into a balanced quad/oct tree.*/
+        class OSGUTIL_EXPORT SpatializeGroupsVisitor : public osg::NodeVisitor
+        {
+            public:
+
+                SpatializeGroupsVisitor():osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ALL_CHILDREN) {}
+                
+                virtual void apply(osg::Group& group);
+                
+                bool divide(unsigned int maxNumTreesPerCell=8);
+                
+                bool divide(osg::Group* group, unsigned int maxNumTreesPerCell);
+                
+                typedef std::set<osg::Group*> GroupsToDivideList;
+                GroupsToDivideList _groupsToDivideList;
+
+        };
 };
 
 }
diff --git a/src/osgUtil/Optimizer.cpp b/src/osgUtil/Optimizer.cpp
index b6d3850ca..c27477858 100644
--- a/src/osgUtil/Optimizer.cpp
+++ b/src/osgUtil/Optimizer.cpp
@@ -110,7 +110,13 @@ void Optimizer::optimize(osg::Node* node, unsigned int options)
         node->accept(mgv);
     }
 
-
+    if (options & SPATIALIZE_GROUPS)
+    {
+        SpatializeGroupsVisitor sv;
+        node->accept(sv);
+        sv.divide();
+        
+    }
 
 }
 
@@ -1525,3 +1531,190 @@ bool Optimizer::MergeGeometryVisitor::mergePrimitive(osg::DrawElementsUInt& lhs,
     lhs.insert(lhs.end(),rhs.begin(),rhs.end());
     return true;
 }
+
+////////////////////////////////////////////////////////////////////////////////////////////
+//
+//  Spatialize the scene to accelerate culling
+//
+
+void Optimizer::SpatializeGroupsVisitor::apply(osg::Group& group)
+{
+    if (typeid(group)==typeid(osg::Group) || group.asTransform())
+    {
+        _groupsToDivideList.insert(&group);
+    }
+    traverse(group);
+}
+
+bool Optimizer::SpatializeGroupsVisitor::divide(unsigned int maxNumTreesPerCell)
+{
+    bool divided = false;
+    for(GroupsToDivideList::iterator itr=_groupsToDivideList.begin();
+        itr!=_groupsToDivideList.end();
+        ++itr)
+    {
+        if (divide(*itr,maxNumTreesPerCell)) divided = true;
+    }
+    return divided;
+}
+
+bool Optimizer::SpatializeGroupsVisitor::divide(osg::Group* group, unsigned int maxNumTreesPerCell)
+{
+    if (group->getNumChildren()<=maxNumTreesPerCell) return false;
+    
+    // create the original box.
+    osg::BoundingBox bb;
+    unsigned int i;
+    for(i=0;i<group->getNumChildren();++i)
+    {
+        bb.expandBy(group->getChild(i)->getBound().center());
+    }
+    
+    float radius = bb.radius();
+    float divide_distance = radius*0.7f;
+    bool xAxis = (bb.xMax()-bb.xMin())>divide_distance;
+    bool yAxis = (bb.yMax()-bb.yMin())>divide_distance;
+    bool zAxis = (bb.zMax()-bb.zMin())>divide_distance;
+
+    std::cout<<"Dividing "<<group->className()<<"  num children = "<<group->getNumChildren()<<"  xAxis="<<xAxis<<"  yAxis="<<yAxis<<"   zAxis="<<zAxis<<std::endl;
+    
+    unsigned int numChildrenOnEntry = group->getNumChildren();
+    
+    typedef std::pair< osg::BoundingBox, osg::ref_ptr<osg::Group> > BoxGroupPair;
+    typedef std::vector< BoxGroupPair > Boxes;
+    Boxes boxes;
+    boxes.push_back( BoxGroupPair(bb,new osg::Group) );
+
+    // divide up on each axis    
+    if (xAxis)
+    {
+        unsigned int numCellsToDivide=boxes.size();
+        for(unsigned int i=0;i<numCellsToDivide;++i)
+        {
+            osg::BoundingBox& orig_cell = boxes[i].first;
+            osg::BoundingBox new_cell = orig_cell;
+
+            float xCenter = (orig_cell.xMin()+orig_cell.xMax())*0.5f;
+            orig_cell.xMax() = xCenter;
+            new_cell.xMin() = xCenter;
+
+            boxes.push_back(BoxGroupPair(new_cell,new osg::Group));
+        }
+    }
+
+    if (yAxis)
+    {
+        unsigned int numCellsToDivide=boxes.size();
+        for(unsigned int i=0;i<numCellsToDivide;++i)
+        {
+            osg::BoundingBox& orig_cell = boxes[i].first;
+            osg::BoundingBox new_cell = orig_cell;
+
+            float yCenter = (orig_cell.yMin()+orig_cell.yMax())*0.5f;
+            orig_cell.yMax() = yCenter;
+            new_cell.yMin() = yCenter;
+
+            boxes.push_back(BoxGroupPair(new_cell,new osg::Group));
+        }
+    }
+
+    if (zAxis)
+    {
+        unsigned int numCellsToDivide=boxes.size();
+        for(unsigned int i=0;i<numCellsToDivide;++i)
+        {
+            osg::BoundingBox& orig_cell = boxes[i].first;
+            osg::BoundingBox new_cell = orig_cell;
+
+            float zCenter = (orig_cell.zMin()+orig_cell.zMax())*0.5f;
+            orig_cell.zMax() = zCenter;
+            new_cell.zMin() = zCenter;
+
+            boxes.push_back(BoxGroupPair(new_cell,new osg::Group));
+        }
+    }
+
+
+    // create the groups to drop the children into
+    
+
+    // bin each child into associated bb group
+    typedef std::vector< osg::ref_ptr<osg::Node> > NodeList;
+    NodeList unassignedList;
+    for(i=0;i<group->getNumChildren();++i)
+    {
+        bool assigned = false;
+        osg::Vec3 center = group->getChild(i)->getBound().center();
+        for(Boxes::iterator itr=boxes.begin();
+            itr!=boxes.end() && !assigned;
+            ++itr)
+        {
+            if (itr->first.contains(center))
+            {
+                // move child from main group into bb group.
+                (itr->second)->addChild(group->getChild(i));
+                assigned = true;
+            }
+        }
+        if (!assigned)
+        {
+            unassignedList.push_back(group->getChild(i));
+        }
+    }
+
+
+    // now transfer nodes across, by :
+    //      first removing from the original group,
+    //      add in the bb groups
+    //      add then the unassigned children.
+    
+    
+    // first removing from the original group,
+    group->removeChild(0,group->getNumChildren());
+    
+    // add in the bb groups
+    typedef std::vector< osg::ref_ptr<osg::Group> > GroupList;
+    GroupList groupsToDivideList;
+    for(Boxes::iterator itr=boxes.begin();
+        itr!=boxes.end();
+        ++itr)
+    {
+        // move child from main group into bb group.
+        osg::Group* bb_group = (itr->second).get();
+        if (bb_group->getNumChildren()>0)
+        {
+            if (bb_group->getNumChildren()==1)
+            {
+                group->addChild(bb_group->getChild(0));
+            }
+            else
+            {
+                group->addChild(bb_group);
+                if (bb_group->getNumChildren()>maxNumTreesPerCell)
+                {
+                    groupsToDivideList.push_back(bb_group);
+                }
+            }
+        }
+    }
+    
+    
+    // add then the unassigned children.
+    for(NodeList::iterator nitr=unassignedList.begin();
+        nitr!=unassignedList.end();
+        ++nitr)
+    {
+        group->addChild(nitr->get());
+    }
+
+    // now call divide on all groups that require it.
+    for(GroupList::iterator gitr=groupsToDivideList.begin();
+        gitr!=groupsToDivideList.end();
+        ++gitr)
+    {
+        divide(gitr->get(),maxNumTreesPerCell);
+    }
+
+    return (numChildrenOnEntry<group->getNumChildren());
+    
+}