Added export to the height field class.
Added export to the height field class.


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