From Farshid Lashkari,

"I've made some changes to osg which I think make it easier to control
the render order of CameraNode's. Instead of using the built-in orders
(PRE_RENDER, POST_RENDER, NESTED_RENDER), you can specify an integer
order. Values less than zero are pre rendered in order. Values greater
than zero are post rendered in order. And a value of 0 is equivalent
to NESTED_RENDER.

The changes should be fully backward compatible. Also, I changed the
RenderStageList type from a vector to a list because I needed to be
able to insert values anywhere in the list.

The reason I made these changes was because I wanted to be able to set
the render order of a CameraNode at runtime without having to reorder
it in the scenegraph."

and later in the final submission message (relating to what has been finally been merged)    :

"I've rethought my implementation and came up with something a little
better. The setRenderOrder will continue to take an enum, but will
have an optional orderNum parameter which can be both positive and
negative. I think this method is more intuitive and flexible."

include/osg/CameraNode

@@ -181,11 +181,14 @@ class OSG_EXPORT CameraNode : public Transform, public CullSettings
         /** Set the rendering order of this camera's subgraph relative to any camera that this subgraph is nested within.
           * For rendering to a texture, one typically uses PRE_RENDER.
           * For Head Up Displays, one would typically use POST_RENDER.*/
-        void setRenderOrder(RenderOrder order) { _renderOrder = order; }
+        void setRenderOrder(RenderOrder order, int orderNum = 0) { _renderOrder = order; _renderOrderNum = orderNum; }
         
         /** Get the rendering order of this camera's subgraph relative to any camera that this subgraph is nested within.*/
         RenderOrder getRenderOrder() const { return _renderOrder; }
 
+        /** Get the rendering order number of this camera relative to any sibling cameras in this subgraph.*/
+        int getRenderOrderNum() const { return _renderOrderNum; }        
+
         /** Return true if this Camera is set up as a render to texture camera, i.e. it has textures assigned to it.*/
         bool isRenderToTextureCamera() const;
 
@@ -366,6 +369,7 @@ class OSG_EXPORT CameraNode : public Transform, public CullSettings
         Matrixd                     _viewMatrix;
         
         RenderOrder                 _renderOrder;
+        int                         _renderOrderNum;
         
         GLenum                      _drawBuffer;
         GLenum                      _readBuffer;

src/osg/CameraNode.cpp

@@ -20,6 +20,7 @@ CameraNode::CameraNode():
     _clearMask(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT),
     _transformOrder(PRE_MULTIPLY),
     _renderOrder(POST_RENDER),
+    _renderOrderNum(0),
     _drawBuffer(GL_NONE),
     _readBuffer(GL_NONE),
     _renderTargetImplementation(FRAME_BUFFER),
@@ -39,6 +40,7 @@ CameraNode::CameraNode(const CameraNode& camera,const CopyOp& copyop):
     _projectionMatrix(camera._projectionMatrix),
     _viewMatrix(camera._viewMatrix),
     _renderOrder(camera._renderOrder),
+    _renderOrderNum(camera._renderOrderNum),
     _drawBuffer(camera._drawBuffer),
     _readBuffer(camera._readBuffer),
     _renderTargetImplementation(camera._renderTargetImplementation),

src/osgUtil/CullVisitor.cpp

@@ -1208,11 +1208,11 @@ void CullVisitor::apply(osg::CameraNode& camera)
         // dependancy list.
         switch(camera.getRenderOrder())
         {
-            case osg::CameraNode::PRE_RENDER :
-                getCurrentRenderBin()->getStage()->addPreRenderStage(rtts.get());
+            case osg::CameraNode::PRE_RENDER:
+                getCurrentRenderBin()->getStage()->addPreRenderStage(rtts.get(),camera.getRenderOrderNum());
                 break;
-            default :
-                getCurrentRenderBin()->getStage()->addPostRenderStage(rtts.get());
+            default:
+                getCurrentRenderBin()->getStage()->addPostRenderStage(rtts.get(),camera.getRenderOrderNum());
                 break;
         }
 

src/osgUtil/RenderStage.cpp

@@ -124,7 +124,7 @@ void RenderStage::reset()
         pre_itr != _preRenderList.end();
         ++pre_itr)
     {
-        (*pre_itr)->reset();
+        pre_itr->second->reset();
     }
 
     RenderBin::reset();
@@ -133,7 +133,7 @@ void RenderStage::reset()
         post_itr != _postRenderList.end();
         ++post_itr)
     {
-        (*post_itr)->reset();
+        post_itr->second->reset();
     }
 
     _preRenderList.clear();
@@ -146,7 +146,7 @@ void RenderStage::sort()
         pre_itr != _preRenderList.end();
         ++pre_itr)
     {
-        (*pre_itr)->sort();
+        pre_itr->second->sort();
     }
 
     RenderBin::sort();
@@ -155,18 +155,44 @@ void RenderStage::sort()
         post_itr != _postRenderList.end();
         ++post_itr)
     {
-        (*post_itr)->sort();
+        post_itr->second->sort();
     }
 }
 
-void RenderStage::addPreRenderStage(RenderStage* rs)
+void RenderStage::addPreRenderStage(RenderStage* rs, int order)
 {
-    if (rs) _preRenderList.push_back(rs);
+    if (rs)
+    {
+        RenderStageList::iterator itr;
+        for(itr = _preRenderList.begin(); itr != _preRenderList.end(); ++itr) {
+            if(order < itr->first) {
+                break;
+            }
+        }
+        if(itr == _preRenderList.end()) {
+            _preRenderList.push_back(RenderStageOrderPair(order,rs));
+        } else {
+            _preRenderList.insert(itr,RenderStageOrderPair(order,rs));
+        }
+    }
 }
 
-void RenderStage::addPostRenderStage(RenderStage* rs)
+void RenderStage::addPostRenderStage(RenderStage* rs, int order)
 {
-    if (rs) _postRenderList.push_back(rs);
+    if (rs)
+    {
+        RenderStageList::iterator itr;
+        for(itr = _postRenderList.begin(); itr != _postRenderList.end(); ++itr) {
+            if(order < itr->first) {
+                break;
+            }
+        }
+        if(itr == _postRenderList.end()) {
+            _postRenderList.push_back(RenderStageOrderPair(order,rs));
+        } else {
+            _postRenderList.insert(itr,RenderStageOrderPair(order,rs));
+        }
+    }
 }
 
 void RenderStage::drawPreRenderStages(osg::State& state,RenderLeaf*& previous)
@@ -178,7 +204,7 @@ void RenderStage::drawPreRenderStages(osg::State& state,RenderLeaf*& previous)
         itr!=_preRenderList.end();
         ++itr)
     {
-        (*itr)->draw(state,previous);
+        itr->second->draw(state,previous);
     }
     //cout << "Done Drawing prerendering stages "<<this<< "  "<<_viewport->x()<<","<< _viewport->y()<<","<< _viewport->width()<<","<< _viewport->height()<<std::endl;
 }
@@ -940,7 +966,7 @@ void RenderStage::drawPostRenderStages(osg::State& state,RenderLeaf*& previous)
         itr!=_postRenderList.end();
         ++itr)
     {
-        (*itr)->draw(state,previous);
+        itr->second->draw(state,previous);
     }
     //cout << "Done Drawing prerendering stages "<<this<< "  "<<_viewport->x()<<","<< _viewport->y()<<","<< _viewport->width()<<","<< _viewport->height()<<std::endl;
 }
@@ -954,7 +980,7 @@ bool RenderStage::getStats(Statistics& stats) const
         pre_itr != _preRenderList.end();
         ++pre_itr)
     {
-        if ((*pre_itr)->getStats(stats))
+        if (pre_itr->second->getStats(stats))
         {
             statsCollected = true;
         }
@@ -964,7 +990,7 @@ bool RenderStage::getStats(Statistics& stats) const
         post_itr != _postRenderList.end();
         ++post_itr)
     {
-        if ((*post_itr)->getStats(stats))
+        if (post_itr->second->getStats(stats))
         {
             statsCollected = true;
         }