HYDRA-934 : Fix reload of a scene with a Usd stage.

lib/mayaHydra/hydraExtensions/sceneIndex/registration.cpp

@@ -41,7 +41,8 @@
 #include <maya/MFnDependencyNode.h>
 #include <maya/MItDag.h>
 #include <maya/MMessage.h>
-#include <maya/MNodeMessage.h>
+#include <maya/MSceneMessage.h>
+#include <maya/MFileIO.h>
 #include <maya/MFnPlugin.h>
 #include <maya/MGlobal.h>
 
@@ -218,11 +219,16 @@ MayaHydraSceneIndexRegistry::MayaHydraSceneIndexRegistry(const std::shared_ptr<F
     id = MDGMessage::addNodeAddedCallback(
         _SceneIndexNodeAddedCallback, kMayaUsdProxyShapeNode, this, &status);//We need only to monitor the MayaUsdProxyShapeNode
     if (TF_VERIFY(status == MS::kSuccess, "NodeAdded callback registration failed."))
-        _sceneIndexDagNodeMessageCallbacks.append(id);
+        _DGCallbackIds.append(id);
     id = MDGMessage::addNodeRemovedCallback(
         _SceneIndexNodeRemovedCallback, kMayaUsdProxyShapeNode, this, &status);//We need only to monitor the MayaUsdProxyShapeNode
     if (TF_VERIFY(status == MS::kSuccess, "NodeRemoved callback registration failed."))
-        _sceneIndexDagNodeMessageCallbacks.append(id);
+        _DGCallbackIds.append(id);
+
+    //Because we cannot process a node while loading a maya file, we are storing them in an array in _SceneIndexNodeAddedCallback 
+    // and process them once the after load has completed through _AfterOpenCallback.
+    _AfterOpenCBId = MSceneMessage::addCallback(MSceneMessage::kAfterOpen, _AfterOpenCallback, this, &status);
+    TF_VERIFY(status == MS::kSuccess, "MSceneMessage::kAfterOpen callback registration failed.");
 
     static const MTypeId MAYAUSD_PROXYSHAPE_ID(0x58000095); //Hardcoded
 
@@ -267,8 +273,12 @@ MayaHydraSceneIndexRegistry::GetRegistrations() const
 
 MayaHydraSceneIndexRegistry::~MayaHydraSceneIndexRegistry()
 {
-    MDGMessage::removeCallbacks(_sceneIndexDagNodeMessageCallbacks);
-    _sceneIndexDagNodeMessageCallbacks.clear();
+    MDGMessage::removeCallbacks(_DGCallbackIds);
+    _DGCallbackIds.clear();
+    if (_AfterOpenCBId){
+        MSceneMessage::removeCallback(_AfterOpenCBId);
+    }
+    _AfterOpenCBId = 0;
     _registrationsByObjectHandle.clear();
     _registrations.clear();
 }
@@ -451,10 +461,28 @@ void MayaHydraSceneIndexRegistry::_AddSceneIndexForNode(MObject& dagNode)
 
 void MayaHydraSceneIndexRegistry::_SceneIndexNodeAddedCallback(MObject& dagNode, void* clientData)
 {
-    if (dagNode.isNull() || dagNode.apiType() != MFn::kPluginShape)
+    if (dagNode.isNull() || dagNode.apiType() != MFn::kPluginShape){
         return;
-    auto renderOverride = static_cast<MayaHydraSceneIndexRegistry*>(clientData);
-    renderOverride->_AddSceneIndexForNode(dagNode);
+    }
+
+    auto mayaHydraSceneIndexRegistry = static_cast<MayaHydraSceneIndexRegistry*>(clientData);
+    if (MFileIO::isOpeningFile()){
+        //We cannot process a node while loading a file
+        mayaHydraSceneIndexRegistry->_AppendNodeToProcessAfterOpenScene(dagNode);
+    }else{
+        mayaHydraSceneIndexRegistry->_AddSceneIndexForNode(dagNode);
+    }
+}
+
+//We need to check if some nodes that need to be processed were added to our array during a file load
+void MayaHydraSceneIndexRegistry::_AfterOpenCallback(void *clientData) 
+{
+    if (! clientData){
+        return;
+    }
+
+    auto mayaHydraSceneIndexRegistry = static_cast<MayaHydraSceneIndexRegistry*>(clientData);
+    mayaHydraSceneIndexRegistry->_ProcessNodesAfterOpen();
 }
 
 void MayaHydraSceneIndexRegistry::_SceneIndexNodeRemovedCallback(MObject& dagNode, void* clientData)
@@ -465,4 +493,15 @@ void MayaHydraSceneIndexRegistry::_SceneIndexNodeRemovedCallback(MObject& dagNod
     renderOverride->_RemoveSceneIndexForNode(dagNode);
 }
 
+void MayaHydraSceneIndexRegistry::_ProcessNodesAfterOpen()
+{
+    for (auto& dagNode : _nodesToProcessAfterOpenScene){
+        if (dagNode.isNull() || dagNode.apiType() != MFn::kPluginShape){
+            continue;
+        }
+        _AddSceneIndexForNode(dagNode);
+    }
+    _nodesToProcessAfterOpenScene.clear();
+}
+
 PXR_NAMESPACE_CLOSE_SCOPE

lib/mayaHydra/hydraExtensions/sceneIndex/registration.h

@@ -30,6 +30,8 @@
 #include <maya/MNodeMessage.h>
 #include <maya/MObject.h>
 #include <maya/MObjectHandle.h>
+#include <maya/MObjectArray.h>
+
 #include <ufe/rtid.h>
 #include <ufe/ufe.h>
 
@@ -98,9 +100,20 @@ class MayaHydraSceneIndexRegistry
     bool        _RemoveSceneIndexForNode(const MObject& dagNode);
     static void _SceneIndexNodeAddedCallback(MObject& obj, void* clientData);
     static void _SceneIndexNodeRemovedCallback(MObject& obj, void* clientData);
+    static void _AfterOpenCallback (void *clientData);
+
+    // Append a node to the list of nodes that need to be processed after the scene is opened.
+    void _AppendNodeToProcessAfterOpenScene(const MObject& node) {_nodesToProcessAfterOpenScene.append(node);}
+    //We need to check if some nodes that need to be processed were added to our array during a file load
+    void _ProcessNodesAfterOpen();
+
     const std::shared_ptr<Fvp::RenderIndexProxy> _renderIndexProxy;
 
-    MCallbackIdArray _sceneIndexDagNodeMessageCallbacks;
+    MCallbackIdArray _DGCallbackIds;
+    MCallbackId _AfterOpenCBId {0};
+
+    // Maintain a list of nodes that need to be processed after the scene is opened. We cannot process them during file load.
+    MObjectArray    _nodesToProcessAfterOpenScene;
 
     Registrations _registrations;
     // Maintain alternative way to retrieve registration based on MObjectHandle. This is faster to

lib/mayaHydra/mayaPlugin/renderOverride.cpp

@@ -1218,6 +1218,10 @@ void MtohRenderOverride::_InitHydraResources(const MHWRender::MDrawContext& draw
     //Add the scene index as an input scene index of the merging scene index
     _renderIndexProxy->InsertSceneIndex(_mayaHydraSceneIndex, SdfPath::AbsoluteRootPath());
 
+    if (!_sceneIndexRegistry) {
+        _sceneIndexRegistry.reset(new MayaHydraSceneIndexRegistry(_renderIndexProxy));
+    }
+
     _CreateSceneIndicesChainAfterMergingSceneIndex(drawContext);
 
     if (auto* renderDelegate = _GetRenderDelegate()) {
@@ -1321,10 +1325,6 @@ void MtohRenderOverride::_CreateSceneIndicesChainAfterMergingSceneIndex(const MH
     _selectionSceneIndex->SetDisplayName("Flow Viewport Selection Scene Index");
     _lastFilteringSceneIndexBeforeCustomFiltering  = _selectionSceneIndex;
 
-    if (!_sceneIndexRegistry) {
-        _sceneIndexRegistry.reset(new MayaHydraSceneIndexRegistry(_renderIndexProxy));
-    }
-
     // Add display style scene index
     _lastFilteringSceneIndexBeforeCustomFiltering = _displayStyleSceneIndex =
             Fvp::DisplayStyleOverrideSceneIndex::New(_lastFilteringSceneIndexBeforeCustomFiltering);