From Michael Platings and Robert Osfield, added support for controlling,

via StateSet::setNestedRenderBin(bool) whether the new RenderBin should be nested
with the existing RenderBin, or be nested with the enclosing RenderStage.

src/osg/StateSet.cpp

@@ -1,4 +1,4 @@
-/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield 
+/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2008 Robert Osfield 
  *
  * This library is open source and may be redistributed and/or modified under  
  * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
@@ -81,7 +81,8 @@ bool osg::isTextureMode(StateAttribute::GLMode mode)
 }
 
 StateSet::StateSet():
-    Object(true)
+    Object(true),
+    _nestRenderBins(true)
 {
     _renderingHint = DEFAULT_BIN;
     
@@ -91,7 +92,8 @@ StateSet::StateSet():
     setRenderBinToInherit();
 }
 
-StateSet::StateSet(const StateSet& rhs,const CopyOp& copyop):Object(rhs,copyop)
+StateSet::StateSet(const StateSet& rhs,const CopyOp& copyop):Object(rhs,copyop),
+    _nestRenderBins(rhs._nestRenderBins)
 {
     _modeList = rhs._modeList;
 

src/osgUtil/CullVisitor.cpp

@@ -140,6 +140,8 @@ void CullVisitor::reset()
     //
     
     CullStack::reset();
+    
+    _renderBinStack.clear();
 
     _numberOfEncloseOverrideRenderBinDetails = 0;
 

src/osgWrappers/osg/StateSet.cpp

@@ -426,6 +426,16 @@ BEGIN_OBJECT_REFLECTOR(osg::StateSet)
 	          __C5_std_string_R1__getBinName,
 	          "Get the render bin name. ",
 	          "");
+	I_Method1(void, setNestRenderBins, IN, bool, val,
+	          Properties::NON_VIRTUAL,
+	          __void__setNestRenderBins__bool,
+	          "By default render bins will be nested within each other dependent upon where they are set in the scene graph. ",
+	          "This can be problematic if a transparent render bin is attached to an opaque render bin which is attached to another transparent render bin as these render bins will be sorted separately, giving the wrong draw ordering for back-to-front transparency. Therefore, to prevent render bins being nested, call setNestRenderBins(false). ");
+	I_Method0(bool, getNestRenderBins,
+	          Properties::NON_VIRTUAL,
+	          __bool__getNestRenderBins,
+	          "Get whether associated RenderBin should be nested within parents RenderBin. ",
+	          "");
 	I_Method1(void, setUpdateCallback, IN, osg::StateSet::Callback *, ac,
 	          Properties::NON_VIRTUAL,
 	          __void__setUpdateCallback__Callback_P1,
@@ -623,6 +633,9 @@ BEGIN_OBJECT_REFLECTOR(osg::StateSet)
 	I_SimpleProperty(osg::StateSet::ModeList &, ModeList, 
 	                 __ModeList_R1__getModeList, 
 	                 __void__setModeList__ModeList_R1);
+	I_SimpleProperty(bool, NestRenderBins, 
+	                 __bool__getNestRenderBins, 
+	                 __void__setNestRenderBins__bool);
 	I_ArrayProperty(osg::Object *, Parent, 
 	                __Object_P1__getParent__unsigned_int, 
 	                0,