From Ulrich Hertlein, "attached is a stencil buffer-based constant-width outline f/x with example. I've also modified osgfxbrowser to setup the stencil buffer accordingly."

examples/osgfxbrowser/osgfxbrowser.cpp

@@ -320,6 +320,12 @@ int main(int argc, char *argv[])
 
     viewer.setThreadingModel(threading);
 
+    // setup stencil buffer for Outline f/x.
+    osg::DisplaySettings::instance()->setMinimumNumStencilBits(1);
+    unsigned int clearMask = viewer.getCamera()->getClearMask();
+    viewer.getCamera()->setClearMask(clearMask | GL_STENCIL_BUFFER_BIT);
+    viewer.getCamera()->setClearStencil(0);
+ 
     // any option left unread are converted into errors to write out later.
     arguments.reportRemainingOptionsAsUnrecognized();