Added prelimnary KdTree data structure and automatic kdtree build support

into osgDB::Registry/osgTerrain so that newly created subgraphs can have 
KdTree built on all osg::Geometry automatically on load/creation.

src/osg/KdTree.cpp

@@ -0,0 +1,67 @@
+/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield 
+ *
+ * This library is open source and may be redistributed and/or modified under  
+ * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
+ * (at your option) any later version.  The full license is in LICENSE file
+ * included with this distribution, and on the openscenegraph.org website.
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
+ * OpenSceneGraph Public License for more details.
+*/
+
+#include <osg/KdTree>
+#include <osg/Geode>
+
+using namespace osg;
+
+
+////////////////////////////////////////////////////////////////////////////////
+//
+// KdTree
+
+bool KdTree::build(osg::Geometry* geometry)
+{
+    osg::notify(osg::NOTICE)<<"KdTree::build("<<geometry<<")"<<std::endl;
+    return true;
+}
+
+bool KdTree::intersect(const osg::Vec3& start, const osg::Vec3& end, LineSegmentIntersections& intersections)
+{
+    return false;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+//
+// KdTreeBuilder
+KdTreeBuilder::KdTreeBuilder():
+    osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ALL_CHILDREN),
+    _maxNumLevels(16),
+    _targetNumTrianglesPerLeaf(4),
+    _numVerticesProcessed(0)
+{            
+    _kdTreePrototype = new osg::KdTree;
+}
+
+
+void KdTreeBuilder::apply(osg::Geode& geode)
+{
+    for(unsigned int i=0; i<geode.getNumDrawables(); ++i)
+    {            
+
+        osg::Geometry* geom = geode.getDrawable(i)->asGeometry();
+        if (geom)
+        {
+            osg::KdTree* previous = dynamic_cast<osg::KdTree*>(geom->getShape());
+            if (previous) continue;
+
+            osg::ref_ptr<osg::KdTree> kdTree = dynamic_cast<osg::KdTree*>(_kdTreePrototype->cloneType());
+
+            if (kdTree->build(geom))
+            {
+                geom->setShape(kdTree.get());
+            }
+        }   
+    }
+}