From Christopher Blaesius,

"Soft shadow mapping is basically the same as hard shadow mapping beside that
it uses a different fragment shader.
So for me it makes sense that osgShadow::SoftShadowMap is derived from
osgShadow::ShadowMap, this makes it easier to maintain the two classes.
Additional SoftShadowMap also provides the same Debug methods as ShadowMap."

include/osgShadow/ShadowMap

@@ -91,9 +91,9 @@ class OSGSHADOW_EXPORT ShadowMap : public ShadowTechnique
         virtual ~ShadowMap(void) {};
 
         /** Create the managed Uniforms */
-        void createUniforms();
+        virtual void createUniforms();
 
-        void createShaders();
+        virtual void createShaders();
 
         osg::ref_ptr<osg::Camera>       _camera;
         osg::ref_ptr<osg::TexGen>       _texgen;