Don't assume the emitter node is a Group (Fixes #3082)

This would be a correct assumption by default, but is no longer true when the NifLoader::optimize() function optimizes the graph.

apps/openmw/mwphysics/physicssystem.cpp

@@ -580,7 +580,7 @@ namespace MWPhysics
                 int recIndex = it->first;
                 int shapeIndex = it->second;
 
-                NifOsg::FindRecIndexVisitor visitor(recIndex);
+                NifOsg::FindGroupByRecIndex visitor(recIndex);
                 mPtr.getRefData().getBaseNode()->accept(visitor);
                 if (!visitor.mFound)
                 {

components/nifosg/nifloader.cpp

@@ -887,7 +887,7 @@ namespace NifOsg
                 // This seems to be true for all NIF files in the game that I've checked, suggesting that NIFs work similar to OSG with regards to update order.
                 // If something ever violates this assumption, the worst that could happen is the culling being one frame late, which wouldn't be a disaster.
 
-                FindRecIndexVisitor find (partctrl->emitter->recIndex);
+                FindGroupByRecIndex find (partctrl->emitter->recIndex);
                 rootNode->accept(find);
                 if (!find.mFound)
                 {

components/nifosg/particle.cpp

@@ -276,7 +276,7 @@ void Emitter::emitParticles(double dt)
         int randomRecIndex = mTargets[(std::rand() / (static_cast<double>(RAND_MAX)+1.0)) * mTargets.size()];
 
         // we could use a map here for faster lookup
-        FindRecIndexVisitor visitor(randomRecIndex);
+        FindGroupByRecIndex visitor(randomRecIndex);
         getParent(0)->accept(visitor);
 
         if (!visitor.mFound)
@@ -306,21 +306,25 @@ void Emitter::emitParticles(double dt)
     }
 }
 
-FindRecIndexVisitor::FindRecIndexVisitor(int recIndex)
+FindGroupByRecIndex::FindGroupByRecIndex(int recIndex)
     : osg::NodeVisitor(TRAVERSE_ALL_CHILDREN)
     , mFound(NULL)
     , mRecIndex(recIndex)
 {
 }
 
-void FindRecIndexVisitor::apply(osg::Node &searchNode)
+void FindGroupByRecIndex::apply(osg::Node &searchNode)
 {
     if (searchNode.getUserDataContainer() && searchNode.getUserDataContainer()->getNumUserObjects())
     {
         NodeUserData* holder = dynamic_cast<NodeUserData*>(searchNode.getUserDataContainer()->getUserObject(0));
         if (holder && holder->mIndex == mRecIndex)
         {
-            mFound = static_cast<osg::Group*>(&searchNode);
+            osg::Group* group = searchNode.asGroup();
+            if (!group)
+                group = searchNode.getParent(0);
+
+            mFound = group;
             mFoundPath = getNodePath();
             return;
         }

components/nifosg/particle.hpp

@@ -172,11 +172,12 @@ namespace NifOsg
         osg::Vec3f mCachedWorldDirection;
     };
 
-    // NodeVisitor to find a child node with the given record index, stored in the node's user data container.
-    class FindRecIndexVisitor : public osg::NodeVisitor
+    // NodeVisitor to find a Group node with the given record index, stored in the node's user data container.
+    // Alternatively, returns the node's parent Group if that node is not a Group (i.e. a leaf node).
+    class FindGroupByRecIndex : public osg::NodeVisitor
     {
     public:
-        FindRecIndexVisitor(int recIndex);
+        FindGroupByRecIndex(int recIndex);
 
         virtual void apply(osg::Node &searchNode);