From Torben Dannhauer, "I added radial fog functionality be using the OpenGL extension 'GL_NV_fog_distance'."

include/osg/Fog

@@ -1,4 +1,4 @@
-/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield 
+/* -*-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 
@@ -17,6 +17,17 @@
 #include <osg/StateAttribute>
 #include <osg/Vec4>
 
+#ifndef GL_FOG_DISTANCE_MODE_NV
+    #define GL_FOG_DISTANCE_MODE_NV 0x855A
+#endif
+#ifndef GL_EYE_PLANE_ABSOLUTE_NV
+    #define GL_EYE_PLANE_ABSOLUTE_NV 0x855C
+#endif
+#ifndef GL_EYE_RADIAL_NV
+    #define GL_EYE_RADIAL_NV 0x855B
+#endif
+
+
 #ifndef GL_FOG_COORDINATE
     #define GL_FOG_COORDINATE   0x8451
 #endif
@@ -52,7 +63,8 @@ class OSG_EXPORT Fog : public StateAttribute
             _start(fog._start),
             _end(fog._end),
             _color(fog._color),
-            _fogCoordinateSource(fog._fogCoordinateSource) {}
+            _fogCoordinateSource(fog._fogCoordinateSource),
+            _useRadialFog(fog._useRadialFog)    {}
 
         META_StateAttribute(osg, Fog,FOG);
         
@@ -70,6 +82,7 @@ class OSG_EXPORT Fog : public StateAttribute
             COMPARE_StateAttribute_Parameter(_end)
             COMPARE_StateAttribute_Parameter(_color)
             COMPARE_StateAttribute_Parameter(_fogCoordinateSource)
+            COMPARE_StateAttribute_Parameter(_useRadialFog)
 
             return 0; // passed all the above comparison macro's, must be equal.
         }
@@ -98,8 +111,11 @@ class OSG_EXPORT Fog : public StateAttribute
         inline void  setEnd( float end )          { _end = end; }
         inline float getEnd() const               { return _end; }
 
-        inline void  setColor( const Vec4 &color )      { _color = color; }
-        inline const Vec4& getColor() const             { return _color; }
+        inline void  setColor( const Vec4 &color ) { _color = color; }
+        inline const Vec4& getColor() const        { return _color; }
+        
+        inline void setUseRadialFog( bool useRadialFog ) { _useRadialFog = useRadialFog; }
+        inline bool getUseRadialFog() const              { return _useRadialFog; }
         
         enum FogCoordinateSource
         {
@@ -122,6 +138,7 @@ class OSG_EXPORT Fog : public StateAttribute
         float   _end;
         Vec4    _color;
         GLint   _fogCoordinateSource;
+        bool    _useRadialFog;
 };
 
 }

src/osg/Fog.cpp

@@ -29,6 +29,7 @@ Fog::Fog()
     _end     = 1.0f;
     _color.set( 0.0f, 0.0f, 0.0f, 0.0f);
     _fogCoordinateSource = FRAGMENT_DEPTH;
+    _useRadialFog = false;
 }
 
 
@@ -51,11 +52,21 @@ void Fog::apply(State& state) const
     glFogf( GL_FOG_END,      _end );
     glFogfv( GL_FOG_COLOR,    (GLfloat*)_color.ptr() );
     
-    static bool fogCoordExtensionSuppoted = osg::isGLExtensionSupported(state.getContextID(),"GL_EXT_fog_coord");
-    if (fogCoordExtensionSuppoted)
+    static bool fogCoordExtensionSupported = osg::isGLExtensionSupported(state.getContextID(),"GL_EXT_fog_coord");
+    if (fogCoordExtensionSupported)
     {
         glFogi(GL_FOG_COORDINATE_SOURCE,_fogCoordinateSource);
     }
+
+    static bool fogDistanceExtensionSupported = osg::isGLExtensionSupported(state.getContextID(),"GL_NV_fog_distance");
+    if (fogDistanceExtensionSupported)
+    {
+        if(_useRadialFog)
+            glFogf(GL_FOG_DISTANCE_MODE_NV, GL_EYE_RADIAL_NV);
+        else
+            glFogf(GL_FOG_DISTANCE_MODE_NV, GL_EYE_PLANE_ABSOLUTE_NV);
+    }
+
 #else
     OSG_NOTICE<<"Warning: Fog::apply(State&) - not supported."<<std::endl;
 #endif

src/osgWrappers/serializers/osg/Fog.cpp

@@ -19,4 +19,5 @@ REGISTER_OBJECT_WRAPPER( Fog,
     ADD_FLOAT_SERIALIZER( Density, 1.0f );  // _density
     ADD_VEC4_SERIALIZER( Color, osg::Vec4() );  // _color
     ADD_GLENUM_SERIALIZER( FogCoordinateSource, GLint, GL_NONE );  // _fogCoordinateSource
+    ADD_BOOL_SERIALIZER( UseRadialFog, false );    // _useRadialFog
 }