Addressed PR feedback

Signed-off-by: antonmic <56370189+antonmic@users.noreply.github.com>

Gems/Atom/Feature/Common/Code/Include/Atom/Feature/Mesh/MeshFeatureProcessor.h

@@ -153,7 +153,7 @@ namespace AZ
 
             Data::Instance<RPI::Model> GetModel(const MeshHandle& meshHandle) const override;
             Data::Asset<RPI::ModelAsset> GetModelAsset(const MeshHandle& meshHandle) const override;
-            AZStd::vector<Data::Instance<RPI::ShaderResourceGroup>>& GetObjectSrgs(const MeshHandle& meshHandle) const override;
+            const AZStd::vector<Data::Instance<RPI::ShaderResourceGroup>>& GetObjectSrgs(const MeshHandle& meshHandle) const override;
             void QueueObjectSrgForCompile(const MeshHandle& meshHandle) const override;
             void SetMaterialAssignmentMap(const MeshHandle& meshHandle, const Data::Instance<RPI::Material>& material) override;
             void SetMaterialAssignmentMap(const MeshHandle& meshHandle, const MaterialAssignmentMap& materials) override;

Gems/Atom/Feature/Common/Code/Include/Atom/Feature/Mesh/MeshFeatureProcessorInterface.h

@@ -61,12 +61,15 @@ namespace AZ
             virtual Data::Instance<RPI::Model> GetModel(const MeshHandle& meshHandle) const = 0;
             //! Gets the underlying RPI::ModelAsset for a meshHandle.
             virtual Data::Asset<RPI::ModelAsset> GetModelAsset(const MeshHandle& meshHandle) const = 0;
-            //! Gets the ObjectSrg for a meshHandle.
+
-            //! Updating the ObjectSrg should be followed by a call to QueueObjectSrgForCompile,
+            //! Gets the ObjectSrgs for a meshHandle.
-            //! instead of compiling the srg directly. This way, if the srg has already been queued for compile,
+            //! Updating the ObjectSrgs should be followed by a call to QueueObjectSrgForCompile,
-            //! it will not be queued twice in the same frame. The ObjectSrg should not be updated during
+            //! instead of compiling the srgs directly. This way, if the srgs have already been queued for compile,
+            //! they will not be queued twice in the same frame. The ObjectSrgs should not be updated during
             //! Simulate, or it will create a race between updating the data and the call to Compile
-            virtual AZStd::vector<Data::Instance<RPI::ShaderResourceGroup>>& GetObjectSrgs(const MeshHandle& meshHandle) const = 0;
+            //! Cases where there may be multiple ObjectSrgs: if a model has multiple submeshes and those submeshes use different
+            //! materials with different object SRGs.
+            virtual const AZStd::vector<Data::Instance<RPI::ShaderResourceGroup>>& GetObjectSrgs(const MeshHandle& meshHandle) const = 0;
             //! Queues the object srg for compile.
             virtual void QueueObjectSrgForCompile(const MeshHandle& meshHandle) const = 0;
             //! Sets the MaterialAssignmentMap for a meshHandle, using just a single material for the DefaultMaterialAssignmentId.

Gems/Atom/Feature/Common/Code/Mocks/MockMeshFeatureProcessor.h

@@ -19,7 +19,7 @@ namespace UnitTest
         MOCK_METHOD1(CloneMesh, MeshHandle(const MeshHandle&));
         MOCK_CONST_METHOD1(GetModel, AZStd::intrusive_ptr<AZ::RPI::Model>(const MeshHandle&));
         MOCK_CONST_METHOD1(GetModelAsset, AZ::Data::Asset<AZ::RPI::ModelAsset>(const MeshHandle&));
-        MOCK_CONST_METHOD1(GetObjectSrgs, AZStd::vector<AZStd::intrusive_ptr<AZ::RPI::ShaderResourceGroup>>&(const MeshHandle&));
+        MOCK_CONST_METHOD1(GetObjectSrgs, const AZStd::vector<AZStd::intrusive_ptr<AZ::RPI::ShaderResourceGroup>>&(const MeshHandle&));
         MOCK_CONST_METHOD1(QueueObjectSrgForCompile, void(const MeshHandle&));
         MOCK_CONST_METHOD1(GetMaterialAssignmentMap, const AZ::Render::MaterialAssignmentMap&(const MeshHandle&));
         MOCK_METHOD2(ConnectModelChangeEventHandler, void(const MeshHandle&, ModelChangedEvent::Handler&));

Gems/Atom/Feature/Common/Code/Source/Mesh/MeshFeatureProcessor.cpp

@@ -215,7 +215,7 @@ namespace AZ
             return {};
         }
 
-        AZStd::vector<Data::Instance<RPI::ShaderResourceGroup>>& MeshFeatureProcessor::GetObjectSrgs(const MeshHandle& meshHandle) const
+        const AZStd::vector<Data::Instance<RPI::ShaderResourceGroup>>& MeshFeatureProcessor::GetObjectSrgs(const MeshHandle& meshHandle) const
         {
             static AZStd::vector<Data::Instance<RPI::ShaderResourceGroup>> staticEmptyList;
             return meshHandle.IsValid() ? meshHandle->m_objectSrgList : staticEmptyList;

Gems/AtomLyIntegration/EMotionFXAtom/Code/Source/AtomActorInstance.cpp

@@ -880,7 +880,7 @@ namespace AZ
         {
             if (m_meshHandle)
             {
-                AZStd::vector<Data::Instance<RPI::ShaderResourceGroup>>& wrinkleMaskObjectSrgs = m_meshFeatureProcessor->GetObjectSrgs(*m_meshHandle);
+                const AZStd::vector<Data::Instance<RPI::ShaderResourceGroup>>& wrinkleMaskObjectSrgs = m_meshFeatureProcessor->GetObjectSrgs(*m_meshHandle);
 
                 for (auto& wrinkleMaskObjectSrg : wrinkleMaskObjectSrgs)
                 {