From Eric Sokolowsky, "osgviewer (and all other OSG-based utilities) fails to provide help for the OSG_NOTIFY_LEVEL environment variable. This submission fixes that problem."

src/osg/Notify.cpp

@@ -11,6 +11,7 @@
  * OpenSceneGraph Public License for more details.
 */
 #include <osg/Notify>
+#include <osg/ApplicationUsage>
 #include <string>
 #include <stdlib.h>
 #include <iostream>
@@ -18,6 +19,8 @@
 
 using namespace std;
 
+static osg::ApplicationUsageProxy Notify_e0(osg::ApplicationUsage::ENVIRONMENTAL_VARIABLE, "OSG_NOTIFY_LEVEL <mode>", "FATAL | WARN | NOTICE | DEBUG_INFO | DEBUG_FP | DEBUG | INFO | ALWAYS");
+
 osg::NotifySeverity g_NotifyLevel = osg::NOTICE;
 
 void osg::setNotifyLevel(osg::NotifySeverity severity)