diff --git a/include/osgDB/Serializer b/include/osgDB/Serializer
index c79ce2cc2..59cfab7b2 100644
--- a/include/osgDB/Serializer
+++ b/include/osgDB/Serializer
@@ -511,7 +511,7 @@ public:
     : ParentType(name, def), _getter(gf), _setter(sf) {}
 
     virtual bool set(osg::Object& obj, void* value) { C& object = OBJECT_CAST<C&>(obj); (object.*_setter)( *(reinterpret_cast<P**>(value)) ); return true; }
-    virtual bool get(const osg::Object& obj, void* value) { const C& object = OBJECT_CAST<const C&>(obj);*(reinterpret_cast<const P**>(value )) = (object.*_getter)(); return true; }
+    virtual bool get(const osg::Object& obj, void* value) { if (_setter!=0) { const C& object = OBJECT_CAST<const C&>(obj);*(reinterpret_cast<const P**>(value )) = (object.*_getter)(); return true; } else return false;}
 
     virtual bool read( InputStream& is, osg::Object& obj )
     {
@@ -1643,6 +1643,10 @@ public:
     wrapper->addSerializer( new osgDB::ObjectSerializer< MyClass, TYPE >( \
         #PROP, DEF, &MyClass::get##PROP, &MyClass::set##PROP), osgDB::BaseSerializer::RW_OBJECT )
 
+#define ADD_OBJECT_SERIALIZER_NO_SET(PROP, TYPE, DEF) \
+    wrapper->addSerializer( new osgDB::ObjectSerializer< MyClass, TYPE >( \
+        #PROP, DEF, &MyClass::get##PROP, 0), osgDB::BaseSerializer::RW_OBJECT )
+
 #define ADD_IMAGE_SERIALIZER(PROP, TYPE, DEF) \
     wrapper->addSerializer( new osgDB::ImageSerializer< MyClass, TYPE >( \
         #PROP, DEF, &MyClass::get##PROP, &MyClass::set##PROP), osgDB::BaseSerializer::RW_IMAGE )
diff --git a/include/osgVolume/Property b/include/osgVolume/Property
index a7e0ecc01..c749b94a0 100644
--- a/include/osgVolume/Property
+++ b/include/osgVolume/Property
@@ -82,12 +82,19 @@ class OSGVOLUME_EXPORT Property : public osg::Object
 
         META_Object(osgVolume, Property);
 
+        void dirty() { ++_modifiedCount; }
+
+        void setModifiedCount(unsigned int c) { _modifiedCount = c; }
+        unsigned int getModifiedCount() const { return _modifiedCount; }
+
         virtual void accept(PropertyVisitor& pv) { pv.apply(*this); }
         virtual void traverse(PropertyVisitor& pv) {}
 
     protected:
 
         virtual ~Property();
+
+        unsigned int _modifiedCount;
 };
 
 class OSGVOLUME_EXPORT CompositeProperty : public Property
@@ -123,7 +130,7 @@ class OSGVOLUME_EXPORT CompositeProperty : public Property
 
         const Property* getProperty(unsigned int i) const { return i<_properties.size() ? _properties[i].get() : 0; }
 
-        void addProperty(Property* property) { _properties.push_back(property); }
+        void addProperty(Property* property) { _properties.push_back(property); dirty(); }
 
         void removeProperty(unsigned int i) { _properties.erase(_properties.begin()+i); }
 
@@ -169,7 +176,7 @@ class OSGVOLUME_EXPORT SwitchProperty : public CompositeProperty
 
         /** Set which child property is active.
           * -1 disables all children.*/
-        void setActiveProperty(int i) { _activeProperty = i; }
+        void setActiveProperty(int i) { _activeProperty = i; dirty(); }
 
         /** Get the active property.*/
         int getActiveProperty() const { return _activeProperty; }
@@ -225,7 +232,7 @@ class OSGVOLUME_EXPORT ScalarProperty : public Property
         virtual void accept(PropertyVisitor& pv) { pv.apply(*this); }
 
         /** Set the value.*/
-        virtual void setValue(float v) { _uniform->set(v); }
+        virtual void setValue(float v) { _uniform->set(v); dirty(); }
 
         /** Get the value.*/
         float getValue() const { float v; _uniform->get(v); return v; }
diff --git a/include/osgVolume/VolumeSettings b/include/osgVolume/VolumeSettings
index e39d6d9de..bd14adda1 100644
--- a/include/osgVolume/VolumeSettings
+++ b/include/osgVolume/VolumeSettings
@@ -33,7 +33,7 @@ class OSGVOLUME_EXPORT VolumeSettings : public Property
         virtual void accept(PropertyVisitor& pv);
         virtual void traverse(PropertyVisitor& pv);
 
-        void setFilename(const std::string& str) { _filename = str; }
+        void setFilename(const std::string& str) { _filename = str; dirty(); }
         const std::string& getFilename() const { return _filename; }
 
         enum Technique
@@ -43,7 +43,7 @@ class OSGVOLUME_EXPORT VolumeSettings : public Property
             MultiPass
         };
 
-        void setTechnique(Technique technique) { _technique = technique; }
+        void setTechnique(Technique technique) { _technique = technique; dirty(); }
         Technique getTechnique() const { return _technique; }
 
         enum ShadingModel
@@ -54,24 +54,28 @@ class OSGVOLUME_EXPORT VolumeSettings : public Property
             MaximumIntensityProjection
         };
 
-        void setShadingModel(ShadingModel sm) { _shadingModel = sm; }
+        void setShadingModel(ShadingModel sm) { _shadingModel = sm; dirty(); }
         ShadingModel getShadingModel() const { return _shadingModel; }
 
-        void setSampleRatio(float sr) { _sampleRatioProperty->setValue(sr); }
+        void setSampleRatio(float sr) { _sampleRatioProperty->setValue(sr); dirty(); }
         float getSampleRatio() const { return _sampleRatioProperty->getValue(); }
-        SampleRatioProperty* getSampleRatioProperty() const { return _sampleRatioProperty.get(); }
+        SampleRatioProperty* getSampleRatioProperty() { return _sampleRatioProperty.get(); }
+        const SampleRatioProperty* getSampleRatioProperty() const { return _sampleRatioProperty.get(); }
 
-        void setSampleRatioWhenMoving(float sr) { _sampleRatioWhenMovingProperty->setValue(sr); }
+        void setSampleRatioWhenMoving(float sr) { _sampleRatioWhenMovingProperty->setValue(sr); dirty(); }
         float getSampleRatioWhenMoving() const { return _sampleRatioWhenMovingProperty->getValue(); }
-        SampleRatioWhenMovingProperty* getSampleRatioWhenMovingProperty() const { return _sampleRatioWhenMovingProperty.get(); }
+        SampleRatioWhenMovingProperty* getSampleRatioWhenMovingProperty() { return _sampleRatioWhenMovingProperty.get(); }
+        const SampleRatioWhenMovingProperty* getSampleRatioWhenMovingProperty() const { return _sampleRatioWhenMovingProperty.get(); }
 
-        void setCutoff(float co) { _cutoffProperty->setValue(co); }
+        void setCutoff(float co) { _cutoffProperty->setValue(co); dirty(); }
         float getCutoff() const { return _cutoffProperty->getValue(); }
-        AlphaFuncProperty* getCutoffProperty() const { return _cutoffProperty.get(); }
+        AlphaFuncProperty* getCutoffProperty() { return _cutoffProperty.get(); }
+        const AlphaFuncProperty* getCutoffProperty() const { return _cutoffProperty.get(); }
 
-        void setTransparency(float t) { _transparencyProperty->setValue(t); }
+        void setTransparency(float t) { _transparencyProperty->setValue(t); dirty(); }
         float getTransparency() const { return _transparencyProperty->getValue(); }
-        TransparencyProperty* getTransparencyProperty() const { return _transparencyProperty.get(); }
+        TransparencyProperty* getTransparencyProperty() { return _transparencyProperty.get(); }
+        const TransparencyProperty* getTransparencyProperty() const { return _transparencyProperty.get(); }
 
     protected:
 
diff --git a/src/osgVolume/Property.cpp b/src/osgVolume/Property.cpp
index 5f607bdde..f4b19a298 100644
--- a/src/osgVolume/Property.cpp
+++ b/src/osgVolume/Property.cpp
@@ -19,12 +19,14 @@
 using namespace osgVolume;
 
 
-Property::Property()
+Property::Property():
+    _modifiedCount(0)
 {
 }
 
 Property::Property(const Property& property,const osg::CopyOp& copyop):
-    osg::Object(property,copyop)
+    osg::Object(property,copyop),
+    _modifiedCount(0)
 {
 }
 
@@ -49,6 +51,7 @@ CompositeProperty::CompositeProperty(const CompositeProperty& compositeProperty,
 void CompositeProperty::clear()
 {
     _properties.clear();
+    dirty();
 }
 
 /////////////////////////////////////////////////////////////////////////////
@@ -136,6 +139,7 @@ AlphaFuncProperty::AlphaFuncProperty(const AlphaFuncProperty& afp,const osg::Cop
 
 void AlphaFuncProperty::setValue(float v)
 {
+    dirty();
     _uniform->set(v);
     _alphaFunc->setReferenceValue(v);
 }
diff --git a/src/osgWrappers/serializers/osgVolume/Property.cpp b/src/osgWrappers/serializers/osgVolume/Property.cpp
index 212a8233b..3658bce0a 100644
--- a/src/osgWrappers/serializers/osgVolume/Property.cpp
+++ b/src/osgWrappers/serializers/osgVolume/Property.cpp
@@ -8,4 +8,5 @@ REGISTER_OBJECT_WRAPPER( osgVolume_Property,
                          osgVolume::Property,
                          "osg::Object osgVolume::Property" )
 {
+    ADD_UINT_SERIALIZER_NO_SET( ModifiedCount, 0 );
 }
diff --git a/src/osgWrappers/serializers/osgVolume/VolumeSettings.cpp b/src/osgWrappers/serializers/osgVolume/VolumeSettings.cpp
index 58deec0c5..cb5518e56 100644
--- a/src/osgWrappers/serializers/osgVolume/VolumeSettings.cpp
+++ b/src/osgWrappers/serializers/osgVolume/VolumeSettings.cpp
@@ -28,4 +28,11 @@ REGISTER_OBJECT_WRAPPER( osgVolume_VolumeSettings,
     ADD_FLOAT_SERIALIZER( SampleRatioWhenMoving, 1.0f );
     ADD_FLOAT_SERIALIZER( Cutoff, 0.0f );
     ADD_FLOAT_SERIALIZER( Transparency, 1.0f );
+
+    ADD_OBJECT_SERIALIZER_NO_SET( SampleRatioProperty, osgVolume::SampleRatioProperty, NULL );
+    ADD_OBJECT_SERIALIZER_NO_SET( SampleRatioWhenMovingProperty, osgVolume::SampleRatioWhenMovingProperty, NULL );
+    ADD_OBJECT_SERIALIZER_NO_SET( CutoffProperty, osgVolume::AlphaFuncProperty, NULL );
+    ADD_OBJECT_SERIALIZER_NO_SET( TransparencyProperty, osgVolume::TransparencyProperty, NULL );
+
+
 }