From Aurelien Albert, "In the DXF plugin, DXF layers are decoded and each layer is added in a separate group, which is very usefull to retrieve a layer or display a list of all layers in the aplication.

But the layers are not always children of the "model root" node : there can be a matrix transform between "model root" and "layers parent", so I've added the name "Layers" on the node which contains all layers to easily retrieve the layers groups from application code."

src/osgPlugins/dxf/scene.h

@@ -379,6 +379,9 @@ public:
             child = root;
         }
 //            root = mt;
+
+        child->setName("Layers");
+
         for (std::map<std::string, osg::ref_ptr<sceneLayer> >::iterator litr = _layers.begin();
             litr != _layers.end(); ++litr) {
             sceneLayer* ly = (*litr).second.get();