Pong Multiplayer Demo (Unity + Namazu Elements + Crossfire)

Overview

This is a Unity-based multiplayer Pong demo that demonstrates:

• Integration with Namazu Elements for user management and matchmaking.
• Use of Unity Netcode for GameObjects (NGO) with WebRTC for networked gameplay.
• CPU player simulation using ParrelSync for cloned projects.
• Scene management and pre-placed vs spawned network objects.

The project is designed to let the host player login manually, while a cloned instance automatically logs in as a CPU player.

This project is based (with permission) on the unity-pong-tutorial project found here.

---

Features

• Manual Player Login (create account or log back in)
• CPU Player Auto Login (detected in cloned projects via ParrelSync)
• Matchmaking using Namazu Elements + Crossfire plugin
• WebRTC Peer-to-Peer Connection via Unity Netcode
• Networked Pong Gameplay (paddles, ball, scoring)
• Scene flow: Login → PongMulti → gameplay

---

Project Setup

Requirements

1. Unity 2021.3+ (or compatible LTS version)
2. Namazu Elements + Crossfire services running
3. A created application in Elements, in this case named Pong
4. A matchmaking configuration in Elements (FIFO recommended), named default
5. ParrelSync (for CPU player detection in cloned projects)

Setup Steps

1. Clone the Project with ParrelSync

   • ParrelSync allows creating a "clone" Unity instance.
   • The cloned project will automatically detect itself and login as the CPU player.

2. Configure Elements Client

   • Ensure ElementsProperties.ELEMENTS_ROOT_URL points to your running Namazu Elements instance.
   • Ensure the application name (Pong) matches your Elements setup.

3. Network Prefabs & Scenes

   • Pre-place NetworkObjects (ball, host paddle, client paddle) in the PongMulti scene.
   • Do NOT call Spawn() manually on pre-placed scene objects — NGO will spawn them automatically.
   • Add any dynamically spawned prefabs (e.g., projectiles, power-ups) to NetworkManager → NetworkPrefabs.

4. Startup Flow

   • The project starts in the Login scene.
   • Host player logs in manually (create account or sign in).
   • CPU player clone logs in automatically using CPUPlayerLoader.
   • After login, players can find or join a match using the default matchmaking configuration.
   • Once connected, a WebRTC P2P connection is established via NGO + Crossfire plugin.
   • The PongMulti scene is loaded automatically, and gameplay begins.

---

NGO Gotchas (Important Notes)

1. Scene Objects vs Prefabs

   • Scene objects (pre-placed in the scene) are automatically spawned by NGO. Do not call Spawn() on them.
   • Only dynamically instantiated objects should be spawned manually.

2. NetworkVariables

   • Do not write to NetworkVariables before the NetworkObject has spawned.
   • Initialize variables and subscribe to OnValueChanged in OnNetworkSpawn().

3. Ownership

   • For pre-placed paddles or ball objects, use ChangeOwnership(clientId) to assign control.
   • Do not try to InstantiateAndSpawn scene objects — this causes hash mismatches and spawn failures.

4. WebRTC / DataChannel Timing

   • Ensure NetworkManager.Singleton.StartHost() or StartClient() completes before sending any network messages.
   • For proper synchronization, all initial game setup should happen in OnNetworkSpawn() on both host and clients.

5. Score & UI Updates

   • Use NetworkVariable hooks to update UI across clients.
   • Do not attempt to directly set UI text from server logic — always update through OnValueChanged callbacks.

---

Scenes

Scene Name	Description
Login	Player login / account creation / CPU player detection
PongMulti	Multiplayer Pong gameplay

---

Code Structure

• LoginViewController – Handles manual login, account creation, and profile management.
• CPUPlayerLoader – Automatically logs in CPU player in cloned projects.
• GameManager – Manages gameplay: networked paddles, ball, score, round logic.
• ElementsAuthService – Utility class to handle shared authentication logic (login, signup, profile fetching).

---

Running the Demo

1. Open the main project → Start Unity.
2. Open the Login scene.
3. For CPU vs host testing:
   • Use ParrelSync → Create Clone.
   • Start clone → CPU automatically logs in.
4. Log in manually in the main project.
5. Matchmaking starts automatically.
6. Once connection established → PongMulti scene loads → game starts.

---

References

Unity Netcode for GameObjects

Namazu Elements Docs

ParrelSync GitHub

---

Mermaid Flow Diagram

flowchart TD
    A[Main Project Host Player] --> B[Fetch Profile]
    C[Cloned Project CPU Player] --> D[Ensure Profile Exists]
    B --> E[Matchmaking]
    D --> E
    E --> F[WebRTC Connection]
    F --> G[PongMulti Scene]
    G --> H[NetworkObjects Spawned]
    G --> I[Ownership Assigned]
    G --> J[Gameplay Begins]
    G --> K[NGO Gotchas]

Loading