Added detection of active alpha channel.
Added detection of active alpha channel.


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