SIG/Network - Filtering of entities (i.e. omitting some entities on per connection basis)

Selectively replicating entities to different clients

Gems/Multiplayer/Code/Include/Multiplayer/IMultiplayer.h

@@ -10,6 +10,7 @@
 #include <AzCore/RTTI/RTTI.h>
 #include <AzNetworking/ConnectionLayer/IConnection.h>
 #include <AzNetworking/DataStructures/ByteBuffer.h>
+#include <Multiplayer/NetworkEntity/IFilterEntityManager.h>
 #include <Multiplayer/Components/MultiplayerComponentRegistry.h>
 #include <Multiplayer/NetworkEntity/INetworkEntityManager.h>
 #include <Multiplayer/NetworkTime/INetworkTime.h>
@@ -128,6 +129,15 @@ namespace Multiplayer
         //! @return pointer to the network entity manager instance bound to this multiplayer instance
         virtual INetworkEntityManager* GetNetworkEntityManager() = 0;
 
+        //! Sets user-defined filtering manager for entities.
+        //! This allows selectively choosing which entities to replicate on a per client connection.
+        //! See IFilterEntityManager for details.
+        //! @param entityFilter non-owning pointer, the caller is responsible for memory management.
+        virtual void SetFilterEntityManager(IFilterEntityManager* entityFilter) = 0;
+
+        //! @return pointer to the user-defined filtering manager of entities. By default, this isn't set and returns nullptr.
+        virtual IFilterEntityManager* GetFilterEntityManager() = 0;
+
         //! Retrieve the stats object bound to this multiplayer instance.
         //! @return the stats object bound to this multiplayer instance
         MultiplayerStats& GetStats() { return m_stats; }

Gems/Multiplayer/Code/Include/Multiplayer/NetworkEntity/IFilterEntityManager.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#pragma once
+
+#include <AzNetworking/ConnectionLayer/IConnection.h>
+#include <Multiplayer/NetworkEntity/NetworkEntityHandle.h>
+
+namespace Multiplayer
+{
+    //! @class IFilterEntityManager
+    //! @brief IFilterEntityManager provides an interface for filtering entities out from replication down to clients.
+    //!
+    //! By default, all entities with NetBindComponent on them are replicated to all clients.
+    //! (There is a built-in distance filtering, where only entities within vicinity of a player are sent to that player.
+    //! This is controlled by sv_ClientAwarenessRadius AZ_CVAR variable.)
+    //!
+    //! There are use cases where you want to limit the entities sent to a client, for example "fog of war" or
+    //! "out of line of sight" anti-cheating mechanic by omitting information clients should not have access to.
+    //!
+    //! By implementing IFilterEntityManager interface and setting it on GetMultiplayer()->SetFilterEntityManager()
+    //! entities can be filtered by IsEntityFiltered(...) returning true.
+    //!
+    //! Note: one cannot filter out entities in Level prefab (spawned by LoadLevel console command). Level prefabs are fully
+    //! spawned on each client. Filtering of entities is applied to dynamically spawned prefabs, and specifically
+    //! entities must have NetBindComponent on them.
+    class IFilterEntityManager
+    {
+    public:
+        AZ_RTTI(IFilterEntityManager, "{91F879F2-3DAF-43B8-B474-B312D26C0F48}");
+
+        virtual ~IFilterEntityManager() = default;
+
+        //! Return true if a given entity should be filtered out, false otherwise.
+        //! Important: this method is a hot code path, it will be called over all entities around each player frequently.
+        //! Ideally, this method should be implemented as a quick look up.
+        //!
+        //! @param entity the entity to be considered for filtering
+        //! @param controllerEntity player's entity for the associated connection
+        //! @param connectionId the affected connection should the entity be filtered out.
+        //! @return if false the given entity will be not be replicated to the connection
+        virtual bool IsEntityFiltered(AZ::Entity* entity, ConstNetworkEntityHandle controllerEntity, AzNetworking::ConnectionId connectionId) = 0;
+    };
+}

Gems/Multiplayer/Code/Source/MultiplayerSystemComponent.cpp

@@ -812,6 +812,16 @@ namespace Multiplayer
         return &m_networkEntityManager;
     }
 
+    void MultiplayerSystemComponent::SetFilterEntityManager(IFilterEntityManager* entityFilter)
+    {
+        m_filterEntityManager = entityFilter;
+    }
+
+    IFilterEntityManager* MultiplayerSystemComponent::GetFilterEntityManager()
+    {
+        return m_filterEntityManager;
+    }
+
     void MultiplayerSystemComponent::DumpStats([[maybe_unused]] const AZ::ConsoleCommandContainer& arguments)
     {
         const MultiplayerStats& stats = GetStats();

Gems/Multiplayer/Code/Source/MultiplayerSystemComponent.h

@@ -114,6 +114,8 @@ namespace Multiplayer
         AZ::TimeMs GetCurrentHostTimeMs() const override;
         INetworkTime* GetNetworkTime() override;
         INetworkEntityManager* GetNetworkEntityManager() override;
+        void SetFilterEntityManager(IFilterEntityManager* entityFilter) override;
+        IFilterEntityManager* GetFilterEntityManager() override;
         //! @}
 
         //! Console commands.
@@ -138,6 +140,8 @@ namespace Multiplayer
         NetworkEntityManager m_networkEntityManager;
         NetworkTime m_networkTime;
         MultiplayerAgentType m_agentType = MultiplayerAgentType::Uninitialized;
+        
+        IFilterEntityManager* m_filterEntityManager = nullptr; // non-owning pointer
 
         SessionInitEvent m_initEvent;
         SessionShutdownEvent m_shutdownEvent;

Gems/Multiplayer/Code/Source/ReplicationWindows/ServerToClientReplicationWindow.cpp

@@ -63,13 +63,6 @@ namespace Multiplayer
         m_controlledEntityTransform = entity ? entity->GetTransform() : nullptr;
         AZ_Assert(m_controlledEntityTransform, "Controlled player entity must have a transform");
 
-        //// this one is optional
-        //mp_ControlledFilteredEntityComponent = m_controlledEntity->FindController<FilteredEntityComponent::Authority>();
-        //if (mp_ControlledFilteredEntityComponent)
-        //{
-        //    mp_ControlledFilteredEntityComponent->AddFilteredEntityEventHandle(m_FilteredEntityAddedEventHandle);
-        //}
-
         m_updateWindowEvent.Enqueue(sv_ClientReplicationWindowUpdateMs, true);
 
         AZ::Interface<AZ::ComponentApplicationRequests>::Get()->RegisterEntityActivatedEventHandler(m_entityActivatedEventHandler);
@@ -145,21 +138,23 @@ namespace Multiplayer
             }
         );
 
-        NetworkEntityTracker* networkEntityTracker = GetNetworkEntityTracker();
+        NetworkEntityTracker* networkEntityTracker = GetNetworkEntityTracker();        
+        IFilterEntityManager* filterEntityManager = GetMultiplayer()->GetFilterEntityManager();
 
         // Add all the neighbors
         for (AzFramework::VisibilityEntry* visEntry : gatheredEntries)
         {
-            //if (mp_ControlledFilteredEntityComponent && mp_ControlledFilteredEntityComponent->IsEntityFiltered(iterator.Get()))
-            //{
-            //    continue;
-            //}
-
-            // We want to find the closest extent to the player and prioritize using that distance
             AZ::Entity* entity = static_cast<AZ::Entity*>(visEntry->m_userData);
+
+            if (filterEntityManager && filterEntityManager->IsEntityFiltered(entity, m_controlledEntity, m_connection->GetConnectionId()))
+            {
+                continue;
+            }
+
             NetBindComponent* entryNetBindComponent = entity->template FindComponent<NetBindComponent>();
             if (entryNetBindComponent != nullptr)
             {
+                // We want to find the closest extent to the player and prioritize using that distance
                 const AZ::Vector3 supportNormal = controlledEntityPosition - visEntry->m_boundingVolume.GetCenter();
                 const AZ::Vector3 closestPosition = visEntry->m_boundingVolume.GetSupport(supportNormal);
                 const float gatherDistanceSquared = controlledEntityPosition.GetDistanceSq(closestPosition);
@@ -212,10 +207,13 @@ namespace Multiplayer
         {
             if (netBindComponent->HasController())
             {
-                //if (mp_ControlledFilteredEntityComponent && mp_ControlledFilteredEntityComponent->IsEntityFiltered(newEntity))
+                if (IFilterEntityManager* filter = GetMultiplayer()->GetFilterEntityManager())
-                //{
+                {
-                //    return;
+                    if (filter->IsEntityFiltered(entity, m_controlledEntity, m_connection->GetConnectionId()))
-                //}
+                    {
+                        return;
+                    }
+                }
 
                 AZ::TransformInterface* transformInterface = entity->GetTransform();
                 if (transformInterface != nullptr)
@@ -274,6 +272,8 @@ namespace Multiplayer
 
     void ServerToClientReplicationWindow::AddEntityToReplicationSet(ConstNetworkEntityHandle& entityHandle, float priority, [[maybe_unused]] float distanceSquared)
     {
+        // Assumption: the entity has been checked for filtering prior to this call.
+
         if (!sv_ReplicateServerProxies)
         {
             NetBindComponent* netBindComponent = entityHandle.GetNetBindComponent();
@@ -314,10 +314,4 @@ namespace Multiplayer
     //        }
     //    }
     //}
-
-    //void ServerToClientReplicationWindow::OnAddFilteredEntity(NetEntityId filteredEntityId)
-    //{
-    //    ConstEntityPtr filteredEntity = gNovaGame->GetEntityManager().GetEntity(filteredEntityId);
-    //    m_replicationSet.erase(filteredEntityId);
-    //}
 }

Gems/Multiplayer/Code/Source/ReplicationWindows/ServerToClientReplicationWindow.h

@@ -54,7 +54,6 @@ namespace Multiplayer
         void OnEntityDeactivated(AZ::Entity* entity);
 
         //void CollectControlledEntitiesRecursive(ReplicationSet& replicationSet, EntityHierarchyComponent::Authority& hierarchyController);
-        //void OnAddFilteredEntity(NetEntityId filteredEntityId);
 
         void EvaluateConnection();
         void AddEntityToReplicationSet(ConstNetworkEntityHandle& entityHandle, float priority, float distanceSquared);
@@ -73,7 +72,6 @@ namespace Multiplayer
         AZ::EntityActivatedEvent::Handler m_entityActivatedEventHandler;
         AZ::EntityDeactivatedEvent::Handler m_entityDeactivatedEventHandler;
 
-        //FilteredEntityComponent::Authority* m_controlledFilteredEntityComponent = nullptr;
         //NetBindComponent* m_controlledNetBindComponent = nullptr;
 
         const AzNetworking::IConnection* m_connection = nullptr;

Gems/Multiplayer/Code/multiplayer_files.cmake

@@ -21,6 +21,7 @@ set(FILES
     Include/Multiplayer/EntityDomains/IEntityDomain.h
     Include/Multiplayer/NetworkEntity/INetworkEntityManager.h
     Include/Multiplayer/INetworkSpawnableLibrary.h
+    Include/Multiplayer/NetworkEntity/IFilterEntityManager.h
     Include/Multiplayer/NetworkEntity/NetworkEntityRpcMessage.h
     Include/Multiplayer/NetworkEntity/NetworkEntityUpdateMessage.h
     Include/Multiplayer/NetworkEntity/NetworkEntityHandle.h