Added option for using the different overlay techniques.
Added option for using the different overlay techniques.


artoolkit/osg,stmh/osg,omega-hub/osg,XiaoCC/osg,koshman86/osg,koshman86/osg,stmh/osg,koshman86/osg,XiaoCC/osg,omega-hub/osg,ntoand/osg,XiaoCC/osg,artoolkit/osg,XiaoCC/osg,XiaoCC/osg,koshman86/osg,omega-hub/osg,ntoand/osg,stmh/osg,omega-hub/osg,stmh/osg,ghub/osg,ghub/osg,artoolkit/osg,ntoand/osg,stmh/osg,artoolkit/osg,ghub/osg,ghub/osg,ntoand/osg