From aa56bddefc85a15b446843d6f58dafae8036a705 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Sun, 29 Apr 2007 20:10:43 +0000
Subject: [PATCH] Added a MatrixTransform set up to provide a local origin for
 better precision.

---
 include/osgTerrain/GeometryTechnique |  8 +++++---
 src/osgTerrain/GeometryTechnique.cpp | 17 ++++++++++++++---
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/include/osgTerrain/GeometryTechnique b/include/osgTerrain/GeometryTechnique
index 88528ca95..ec0658217 100644
--- a/include/osgTerrain/GeometryTechnique
+++ b/include/osgTerrain/GeometryTechnique
@@ -14,6 +14,7 @@
 #ifndef OSGTERRAIN_GEOMETRYTECHNIQUE
 #define OSGTERRAIN_GEOMETRYTECHNIQUE 1
 
+#include <osg/MatrixTransform>
 #include <osg/Geode>
 #include <osg/Geometry>
 
@@ -110,10 +111,11 @@ class OSGTERRAIN_EXPORT GeometryTechnique : public TerrainTechnique
 
         virtual ~GeometryTechnique();
 
-        osg::ref_ptr<osg::Geode>    _geode;
+        osg::ref_ptr<osg::MatrixTransform>  _transform;
+        osg::ref_ptr<osg::Geode>            _geode;
         
-        osg::ref_ptr<TerrainGeometry> _terrainGeometry;
-        osg::ref_ptr<osg::Geometry> _geometry;
+        osg::ref_ptr<TerrainGeometry>       _terrainGeometry;
+        osg::ref_ptr<osg::Geometry>         _geometry;
 };
 
 }
diff --git a/src/osgTerrain/GeometryTechnique.cpp b/src/osgTerrain/GeometryTechnique.cpp
index 92f05c640..f8182a918 100644
--- a/src/osgTerrain/GeometryTechnique.cpp
+++ b/src/osgTerrain/GeometryTechnique.cpp
@@ -107,8 +107,19 @@ void GeometryTechnique::init()
     osg::notify(osg::NOTICE)<<"bottomLeftNDC = "<<bottomLeftNDC<<std::endl;
     osg::notify(osg::NOTICE)<<"topRightNDC = "<<topRightNDC<<std::endl;
 
+    
     _geode = new osg::Geode;
 
+    _transform = new osg::MatrixTransform;
+    _transform->addChild(_geode.get());
+
+    osg::Vec3d centerNDC = (bottomLeftNDC + topRightNDC)*0.5;
+    osg::Vec3d centerModel = (bottomLeftNDC + topRightNDC)*0.5;
+    masterLocator->convertLocalToModel(centerNDC, centerModel);
+    
+    _transform->setMatrix(osg::Matrix::translate(centerModel));
+    
+
     _terrainGeometry = 0; // new osgTerrain::TerrainGeometry;
     if (_terrainGeometry.valid()) _geode->addDrawable(_terrainGeometry.get());
 
@@ -213,7 +224,7 @@ void GeometryTechnique::init()
             osg::Vec3d model;
             masterLocator->convertLocalToModel(ndc, model);
 
-            (*_vertices)[iv] = model;
+            (*_vertices)[iv] = model - centerModel;
 
             if (colorLayer)
             {
@@ -363,9 +374,9 @@ void GeometryTechnique::update(osgUtil::UpdateVisitor* nv)
 
 void GeometryTechnique::cull(osgUtil::CullVisitor* nv)
 {
-    if (_geode.valid())
+    if (_transform.valid())
     {
-        _geode->accept(*nv);
+        _transform->accept(*nv);
     }
 }