NetCode For GameObjects

Installation

  1. Import Netcode sample.

  2. Install NetCode for GameObjects package.

  3. Add the CUSTOM_NETWORK scripting define in Project Settings > Player > Scripting Define Symbols.

  4. Unpack DotsCity/Packages/Upgrades/NetcodeGOPrefabs package.

  5. In the Cull Config, set the calculation mode to Multiplayer Calculate Distance or Multiplayer Camera View.

  6. Drag & drop NGOPrefabRoot into the scene & in that root, in the PrefabRootResolve component, press the Resolve Refs button (new scene only).

  7. In the CityEntryPoint object on the scene, uncheck the Auto Bootstrap option in the SceneBootstrap component (new scene only).

  8. Install Multiplayer Play Mode package to simulate multiple local players (optional).

  9. Open NGODemo sample scene.

    Note

    By default, only the NGODemo scene works out of the box.

Architecture & Code Structure

The Netcode for GameObjects (NGO) integration in DotsCity provides a network transport layer, object wrappers, and efficient serialization wrappers for traffic, pedestrians, and traffic lights.

System Services & Providers

System-level services and infrastructure providers that handle network session setup, low-level messaging, and object lifetime:

  • NgoProviderSO: A ScriptableObject provider (NetworkProviderSO) that initializes the NGO network stack, registers all message types in UniversalNetworkService, and creates the PedestrianBroadcaster.

  • NgoTransport: Implements INetworkTransport using NGO’s CustomMessagingManager. Handles server/client session lifecycle, message sending (Reliable / Unreliable), and event callbacks.

  • NgoMessageRegistry: A static registry that links internal network messages (traffic batches, pedestrian spawns, traffic light states, etc.) with their respective NGO serialization wrappers.

  • NgoPlayerSpawnerSO: ScriptableObject spawner that handles server-side instantiation and NGO NetworkObject spawning with client ownership assignment.

  • NgoVehicleNetworkSync: Central scene/system manager that synchronizes vehicle ownership and state between NGO and the DOTS/Mono hybrid traffic system. Manages driver assignment, physics toggling, ownership changes, and enables/disables NetworkTransform components upon entering/exiting vehicles.

Player-Attached Components

Components and adapters attached directly to the Player Prefab:

  • NgoPlayerMovementAdapter: Attached to the player prefab. Controls movement activation and input handling, enabling local simulation exclusively for the owning client.

  • NgoPlayerRpcTransport: Attached to the player prefab. Transmits vehicle enter/exit ServerRPCs and ClientsRPCs, bridging client interactions with PlayerNetworkInteractionBridge.

  • NgoPlayerSpawnNotifier: Attached to the player prefab. Handles player lifecycle events, registers spawned instances in PlayerRegistry, and notifies local spawners upon client initialization.

Vehicle-Attached Components

Components and adapters attached directly to Vehicle Prefabs:

  • NgoNetworkVehicleObserver: Attached to vehicle prefabs. Synchronizes unique vehicle IDs via NetworkVariable<int> and triggers client-side vehicle spawn/despawn hooks in NgoVehicleNetworkSync.

  • NgoVehicleInputSyncAdapter: Attached to vehicle prefabs. Synchronizes vehicle control inputs (throttle, steering, handbrake) from owner clients to the server via ServerRPCs and distributes them using NetworkVariable.

Scene & Culling Adapters

  • NgoCullPointAdapter: Attached to camera/cull point GameObjects. Acts as a network bridge for CullPointCore, streaming client camera position and view projection matrix to the server ECS via SubmitCullPointServerRpc.

  • NgoIdentityWrapper & NgoBehaviourWrapper: Generic Mono/NGO adapters for NetworkObject and NetworkBehaviour components, conforming them to internal INetworkIdentity and INetworkBehaviour interfaces.

Data Serialization & Wrappers

To minimize GC allocations and optimize bandwidth, custom serialization wrappers implementing INetworkSerializable are used:

  • Vehicles: NgoTrafficBatchBroadcast, VehicleSpawnDataWrapper, and VehicleDespawnDataWrapper. Uses NgoVehicleSnapshotSerializers with pre-allocated static read buffers.

  • Traffic Lights: NgoTrafficLightBroadcast serializes traffic light states using reusable array buffers.

  • Pedestrians: Wrappers including PedestrianSpawnBroadcastWrapper, PedestrianTransformBroadcastWrapper, PedestrianStateBroadcastWrapper, PedestrianRagdollBroadcastWrapper, and initial state sync wrappers.

  • Player Signals: NgoPlayerReadySignalWrapper for synchronization of player readiness signals.