Building AI NPCs in Minutes with the Player2 Unity SDK

Announcing Player2 AI NPC Unity SDK

Prerequisites

• Unity 6 or newer

  • Scripts target .NET Standard 2.1 and use async/await.

• TextMesh Pro

  • Required for the sample chat UI.

• Newtonsoft.Json

  • Pulled in via UPM; serializes request/response payloads.

• Player2 Client

  • Download from player2.game.

Step‑by‑Step Setup

1. Add an NpcManager to Your Scene

Insert a NpcManager (singleton) under your scene root. Only one can exist per scene.

2. Configure the NpcManager

1. Game ID: Name your game or mod.

2. Functions → +: Define each action the LLM can call:

   • Name: Identifier (e.g. flame)

   • Description: Hint for the model

   • Arguments: Typed parameters (e.g. radius: number), mark required as needed.

In this example, we expose flame(radius:number) to spawn a fiery VFX cloud.

3. Attach Player2Npc to Your NPC

Select the GameObject representing your NPC (e.g. Person 1) and add Player2Npc.cs.

4. Set Up the Player2Npc Component

• Npc Manager: Drag in your scene’s NpcManager.

• Short / Full Name: For UI labels.

• Character Description: The persona text sent at spawn.

• Input Field / Output Message: Link your TextMesh Pro components.

• Persistent: Tick if the NPC should survive client restarts.

Now press Play—your NPC is live and ready to chat!

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Adding Rich NPC Functions (Optional)

To handle LLM-decided actions:

Create a handler script (e.g., ExampleFunctionHandler.cs) in your scene root:

using UnityEngine;

public class ExampleFunctionHandler : MonoBehaviour
{
    public void HandleFunctionCall(FunctionCall call)
    {
        if (call.name == "flame")
        {
            float radius = call.ArgumentAsFloat("radius", defaultValue: 3f);
            SpawnFlameCloud(radius);
        }
    }

    void SpawnFlameCloud(float r)
    {
        // Your VFX / gameplay code here
    }
}

In NpcManager → Function Handler:

• Click +

• Drag the object with ExampleFunctionHandler

• Select ExampleFunctionHandler → HandleFunctionCall

Whenever the model invokes flame, your handler runs on the main thread, so you never manually intervene.

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Under the Hood: Quick Architecture Tour

• NpcManager

  • Scene‑singleton holding configuration and the function catalog.

  • Serializes to snake_case via Newtonsoft.Json.

• Player2Npc

  • Spawns NPCs (POST /npcs) and routes UI events to SendChatMessageAsync.

• Player2NpcResponseListener

  • Consumes text/event-stream via UnityWebRequest; raises UnityEvents for text and function calls.

• ExampleFunctionHandler

  • Demonstrates reading function arguments and executing gameplay code.

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✨ That’s it! With two inspector tweaks and a tiny handler script, you have LLM‑powered, function‑calling NPCs in Unity. Layer on animations, speech synthesis, or your favorite dialogue UI—and ship your game!