Disallow trying to traverse through nodes in definition as there is a…

…n issue with trying to render the root of std surface,

and there is not mechanism to traverse out of a functional graph to it's instance and downstream.

source/MaterialXGraphEditor/Graph.cpp

@@ -735,6 +735,18 @@ void Graph::setRenderMaterial(UiNodePtr node)
         mx::StringSet testPaths;
         if (mtlxNode)
         {
+            mx::ElementPtr parent = mtlxNode->getParent();
+            if (parent->isA<mx::NodeGraph>())
+            {
+                // There is no logic to support traversing from inside a functional graph
+                // to it's instance and hence downstream so skip this from consideration.
+                // The closest approach would be to "flatten" all definitions to compound graphs.
+                mx::NodeGraphPtr parentGraph = parent->asA<mx::NodeGraph>();
+                if (parentGraph->getNodeDef())
+                {
+                    return;
+                }
+            }
             testPaths.insert(mtlxNode->getNamePath());
         }
         else if (mtlxNodeGraph)
@@ -3755,11 +3767,7 @@ void Graph::drawGraph(ImVec2 mousePos)
                     {
                         setRenderMaterial(_currUiNode);
                     }
-                    else if (_currUiNode->getNodeGraph())
-                    {
-                        setRenderMaterial(_currUiNode);
-                    }
-                    else if (_currUiNode->getOutput())
+                    else if (_currUiNode->getNodeGraph() || _currUiNode->getOutput())
                     {
                         setRenderMaterial(_currUiNode);
                     }