From Luc Frauciel, You'll find attached a modification in ive plugin for POLYGONSTIPPLE read/write.

src/osgPlugins/ive/PolygonStipple.cpp

@@ -0,0 +1,54 @@
+/**********************************************************************
+ *
+ *    FILE:           PolygonStipple.cpp
+ *
+ *    DESCRIPTION:    Read/Write osg::PolygonStipple in binary format to disk.
+ *
+ *    CREATED BY:     Copied from LineStipple
+ *                    and modified by Luc Frauciel
+ *
+ *    HISTORY:        Created 21.3.2009
+ *
+ *    Copyright 2008 VR-C
+ **********************************************************************/
+
+#include "Exception.h"
+#include "PolygonStipple.h"
+#include "Object.h"
+
+using namespace ive;
+
+void PolygonStipple::write(DataOutputStream* out){
+    // Write CullFace's identification.
+    out->writeInt(IVEPOLYGONSTIPPLE);
+    // If the osg class is inherited by any other class we should also write this to file.
+    osg::Object* obj = dynamic_cast<osg::Object*>(this);
+    if (obj) {
+        ((ive::Object*)(obj))->write(out);
+    }
+    else
+        throw Exception("PolygonStipple::write(): Could not cast this osg::PolygonStipple to an osg::Object.");
+    // Write PolygonStipple's properties.
+    out->writeUByteArray(new osg::UByteArray(128,const_cast<GLubyte*>(getMask())));
+}
+
+void PolygonStipple::read(DataInputStream* in){
+    // Peek on LineStipple's identification.
+    int id = in->peekInt();
+    if (id == IVEPOLYGONSTIPPLE) {
+        // Read PolygonStipple's identification.
+        id = in->readInt();
+        // If the osg class is inherited by any other class we should also read this from file.
+        osg::Object*  obj = dynamic_cast<osg::Object*>(this);
+        if (obj) {
+            ((ive::Object*)(obj))->read(in);
+        }
+        else
+            throw Exception("PolygonStipple::read(): Could not cast this osg::PolygonStipple to an osg::Object.");
+        // Read PolygonStipple's properties
+        setMask((GLubyte *)in->readUByteArray()->getDataPointer());
+    }
+    else{
+        throw Exception("PolygonStipple::read(): Expected PolygonStipple identification.");
+    }
+}