diff --git a/include/osg/Drawable b/include/osg/Drawable
index 07680a10c..06ed34233 100644
--- a/include/osg/Drawable
+++ b/include/osg/Drawable
@@ -462,6 +462,9 @@ class SG_EXPORT Drawable : public Object
             void setMultiTexSupported(bool flag) { _isMultiTexSupported=flag; }
             bool isMultiTexSupported() const { return _isMultiTexSupported; }
 
+			void setOcclusionQuerySupported(bool flag) { _isOcclusionQuerySupported=flag; }
+			bool isOcclusionQuerySupported() const { return _isOcclusionQuerySupported; }
+
             void glSecondaryColor3ubv(const GLubyte* coord) const;
             void glSecondaryColor3fv(const GLfloat* coord) const;
 
@@ -486,6 +489,13 @@ class SG_EXPORT Drawable : public Object
             void glBufferSubData (GLenum target, GLintptrARB offset, GLsizeiptrARB size, const GLvoid *data) const;
             void glDeleteBuffers (GLsizei n, const GLuint *buffers) const;
 
+	    void glGenOcclusionQueries( GLsizei n, GLuint *ids ) const;
+	    void glDeleteOcclusionQueries( GLsizei n, const GLuint *ids ) const;
+	    GLboolean glIsOcclusionQuery( GLuint id ) const;
+	    void glBeginOcclusionQuery( GLuint id ) const;
+	    void glEndOcclusionQuery() const;
+	    void glGetOcclusionQueryiv( GLuint id, GLenum pname, GLint *params ) const;
+	    void glGetOcclusionQueryuiv( GLuint id, GLenum pname, GLuint *params ) const;
 
         protected:
 
@@ -508,13 +518,22 @@ class SG_EXPORT Drawable : public Object
             typedef void (APIENTRY * BufferSubDataProc) (GLenum target, GLintptrARB offset, GLsizeiptrARB size, const GLvoid *data);
             typedef void (APIENTRY * DeleteBuffersProc) (GLsizei n, const GLuint *buffers);
 
-            ~Extensions() {}
+	    typedef void (APIENTRY * GenOcclusionQueriesProc) ( GLsizei n, GLuint *ids );
+	    typedef void (APIENTRY * DeleteOcclusionQueriesProc) ( GLsizei n, const GLuint *ids );
+	    typedef GLboolean (APIENTRY * IsOcclusionQueryProc) ( GLuint id );
+	    typedef void (APIENTRY * BeginOcclusionQueryProc) ( GLuint id );
+	    typedef void (APIENTRY * EndOcclusionQueryProc) ();
+	    typedef void (APIENTRY * GetOcclusionQueryivProc) ( GLuint id, GLenum pname, GLint *params );
+	    typedef void (APIENTRY * GetOcclusionQueryuivProc) ( GLuint id, GLenum pname, GLuint *params );
+
+	    ~Extensions() {}
 
             bool _isVertexProgramSupported;
             bool _isSecondaryColorSupported;
             bool _isFogCoordSupported;
             bool _isMultiTexSupported;
- 
+	    bool _isOcclusionQuerySupported;
+
             FogCoordProc _glFogCoordfv;
 
             SecondaryColor3ubvProc _glSecondaryColor3ubv;
@@ -538,6 +557,14 @@ class SG_EXPORT Drawable : public Object
             BufferDataProc      _glBufferData;
             BufferSubDataProc   _glBufferSubData;
             DeleteBuffersProc   _glDeleteBuffers;
+
+            GenOcclusionQueriesProc _glGenOcclusionQueries;
+            DeleteOcclusionQueriesProc _glDeleteOcclusionQueries;
+            IsOcclusionQueryProc _glIsOcclusionQuery;
+            BeginOcclusionQueryProc _glBeginOcclusionQuery;
+            EndOcclusionQueryProc _glEndOcclusionQuery;
+            GetOcclusionQueryivProc _glGetOcclusionQueryiv;
+            GetOcclusionQueryuivProc _glGetOcclusionQueryuiv;
         };
 
         /** Function to call to get the extension of a specified context.
diff --git a/src/osg/Drawable.cpp b/src/osg/Drawable.cpp
index bea82343c..2716fde7c 100644
--- a/src/osg/Drawable.cpp
+++ b/src/osg/Drawable.cpp
@@ -470,6 +470,7 @@ Drawable::Extensions::Extensions(const Extensions& rhs):
     _isSecondaryColorSupported = rhs._isSecondaryColorSupported;
     _isFogCoordSupported = rhs._isFogCoordSupported;
     _isMultiTexSupported = rhs._isMultiTexSupported;
+    _isOcclusionQuerySupported = rhs._isOcclusionQuerySupported;
     _glFogCoordfv = rhs._glFogCoordfv;
     _glSecondaryColor3ubv = rhs._glSecondaryColor3ubv;
     _glSecondaryColor3fv = rhs._glSecondaryColor3fv;
@@ -489,6 +490,13 @@ Drawable::Extensions::Extensions(const Extensions& rhs):
     _glBufferData = rhs._glBufferData;
     _glBufferSubData = rhs._glBufferSubData;
     _glDeleteBuffers = rhs._glDeleteBuffers;
+    _glGenOcclusionQueries = rhs._glGenOcclusionQueries;
+    _glDeleteOcclusionQueries = rhs._glDeleteOcclusionQueries;
+    _glIsOcclusionQuery = rhs._glIsOcclusionQuery;
+    _glBeginOcclusionQuery = rhs._glBeginOcclusionQuery;
+    _glEndOcclusionQuery = rhs._glEndOcclusionQuery;
+    _glGetOcclusionQueryiv = rhs._glGetOcclusionQueryiv;
+    _glGetOcclusionQueryuiv = rhs._glGetOcclusionQueryuiv;
 }
 
 
@@ -498,6 +506,7 @@ void Drawable::Extensions::lowestCommonDenominator(const Extensions& rhs)
     if (!rhs._isSecondaryColorSupported) _isSecondaryColorSupported = false;
     if (!rhs._isFogCoordSupported) _isFogCoordSupported = false;
     if (!rhs._isMultiTexSupported) _isMultiTexSupported = false;
+    if (!rhs._isOcclusionQuerySupported) _isOcclusionQuerySupported = false;
 
     if (!rhs._glFogCoordfv) _glFogCoordfv = 0;
     if (!rhs._glSecondaryColor3ubv) _glSecondaryColor3ubv = 0;
@@ -520,6 +529,14 @@ void Drawable::Extensions::lowestCommonDenominator(const Extensions& rhs)
     if (!rhs._glBufferData) _glBufferData = 0;
     if (!rhs._glBufferSubData) _glBufferSubData = 0;
     if (!rhs._glDeleteBuffers) _glDeleteBuffers = 0;
+
+    if (!rhs._glGenOcclusionQueries) _glGenOcclusionQueries = 0;
+    if (!rhs._glDeleteOcclusionQueries) _glDeleteOcclusionQueries = 0;
+    if (!rhs._glIsOcclusionQuery) _glIsOcclusionQuery = 0;
+    if (!rhs._glBeginOcclusionQuery) _glBeginOcclusionQuery = 0;
+    if (!rhs._glEndOcclusionQuery) _glEndOcclusionQuery = 0;
+    if (!rhs._glGetOcclusionQueryiv) _glGetOcclusionQueryiv = 0;
+    if (!rhs._glGetOcclusionQueryuiv) _glGetOcclusionQueryuiv = 0;
 }
 
 void Drawable::Extensions::setupGLExtenions()
@@ -528,6 +545,7 @@ void Drawable::Extensions::setupGLExtenions()
     _isSecondaryColorSupported = isGLExtensionSupported("GL_EXT_secondary_color");
     _isFogCoordSupported = isGLExtensionSupported("GL_EXT_fog_coord");
     _isMultiTexSupported = isGLExtensionSupported("GL_ARB_multitexture");
+    _isOcclusionQuerySupported = osg::isGLExtensionSupported( "GL_NV_occlusion_query" );
 
     _glFogCoordfv = ((FogCoordProc)osg::getGLExtensionFuncPtr("glFogCoordfv","glFogCoordfvEXT"));
     _glSecondaryColor3ubv = ((SecondaryColor3ubvProc)osg::getGLExtensionFuncPtr("glSecondaryColor3ubv","glSecondaryColor3ubvEXT"));
@@ -551,7 +569,15 @@ void Drawable::Extensions::setupGLExtenions()
     _glBufferSubData = ((BufferSubDataProc)osg::getGLExtensionFuncPtr("glBufferSubData","glBufferSubDataARB"));
     _glDeleteBuffers = ((DeleteBuffersProc)osg::getGLExtensionFuncPtr("glDeleteBuffers","glDeleteBuffersARB"));
 
+    _glGenOcclusionQueries = ((GenOcclusionQueriesProc)osg::getGLExtensionFuncPtr("glGenOcclusionQueries","glGenOcclusionQueriesNV"));
+    _glDeleteOcclusionQueries = ((DeleteOcclusionQueriesProc)osg::getGLExtensionFuncPtr("glDeleteOcclusionQueries","glDeleteOcclusionQueriesNV"));
+    _glIsOcclusionQuery = ((IsOcclusionQueryProc)osg::getGLExtensionFuncPtr("glIsOcclusionQuery","_glIsOcclusionQueryNV"));
+    _glBeginOcclusionQuery = ((BeginOcclusionQueryProc)osg::getGLExtensionFuncPtr("glBeginOcclusionQuery","glBeginOcclusionQueryNV"));
+    _glEndOcclusionQuery = ((EndOcclusionQueryProc)osg::getGLExtensionFuncPtr("glEndOcclusionQuery","glEndOcclusionQueryNV"));
+    _glGetOcclusionQueryiv = ((GetOcclusionQueryivProc)osg::getGLExtensionFuncPtr("glGetOcclusionQueryiv","glGetOcclusionQueryivNV"));
+    _glGetOcclusionQueryuiv = ((GetOcclusionQueryuivProc)osg::getGLExtensionFuncPtr("glGetOcclusionQueryuiv","glGetOcclusionQueryuivNV"));
 }
+
 void Drawable::Extensions::glFogCoordfv(const GLfloat* coord) const
 {
     if (_glFogCoordfv)
@@ -779,3 +805,89 @@ void Drawable::Extensions::glDeleteBuffers(GLsizei n, const GLuint *buffers) con
         notify(WARN)<<"Error: glBufferData not supported by OpenGL driver"<<std::endl;
     }
 }
+
+void Drawable::Extensions::glGenOcclusionQueries( GLsizei n, GLuint *ids ) const
+{
+    if (_glGenOcclusionQueries)
+    {
+        _glGenOcclusionQueries( n, ids );
+    }
+    else
+    {
+        osg::notify(osg::WARN)<<"Error: glGenOcclusionQueries not supported by OpenGL driver"<<std::endl;
+    }    
+}
+
+void Drawable::Extensions::glDeleteOcclusionQueries( GLsizei n, const GLuint *ids ) const
+{
+    if (_glDeleteOcclusionQueries)
+    {
+        _glDeleteOcclusionQueries( n, ids );
+    }
+    else
+    {
+        osg::notify(osg::WARN)<<"Error: glDeleteOcclusionQueries not supported by OpenGL driver"<<std::endl;
+    }    
+}
+
+GLboolean Drawable::Extensions::glIsOcclusionQuery( GLuint id ) const
+{
+    if (_glIsOcclusionQuery)
+    {
+        return _glIsOcclusionQuery( id );
+    }
+    else
+    {
+        osg::notify(osg::WARN)<<"Error: glIsOcclusionQuery not supported by OpenGL driver"<<std::endl;
+    }    
+
+    return GLboolean( 0 );
+}
+
+void Drawable::Extensions::glBeginOcclusionQuery( GLuint id ) const
+{
+    if (_glBeginOcclusionQuery)
+    {
+        _glBeginOcclusionQuery( id );
+    }
+    else
+    {
+        osg::notify(osg::WARN)<<"Error: glBeginOcclusionQuery not supported by OpenGL driver"<<std::endl;
+    }    
+}
+
+void Drawable::Extensions::glEndOcclusionQuery() const
+{
+    if (_glEndOcclusionQuery)
+    {
+        _glEndOcclusionQuery();
+    }
+    else
+    {
+        osg::notify(osg::WARN)<<"Error: glEndOcclusionQuery not supported by OpenGL driver"<<std::endl;
+    }    
+}
+
+void Drawable::Extensions::glGetOcclusionQueryiv( GLuint id, GLenum pname, GLint *params ) const
+{
+    if (_glGetOcclusionQueryiv)
+    {
+        _glGetOcclusionQueryiv( id, pname, params );
+    }
+    else
+    {
+        osg::notify(osg::WARN)<<"Error: glGetOcclusionQueryiv not supported by OpenGL driver"<<std::endl;
+    }    
+}
+
+void Drawable::Extensions::glGetOcclusionQueryuiv( GLuint id, GLenum pname, GLuint *params ) const
+{
+    if (_glGetOcclusionQueryuiv)
+    {
+        _glGetOcclusionQueryuiv( id, pname, params );
+    }
+    else
+    {
+        osg::notify(osg::WARN)<<"Error: glGetOcclusionQueryuiv not supported by OpenGL driver"<<std::endl;
+    }    
+}