Table of contents

Background
What is ChatGPT API
Implementation of ChatGPT API
Execution of ChatGPT API
Next Step

Background

I will develop AR Game with Unity, AR foundation and so on. To learn AR development, I am researching about AR and the software related it. This blog shows the research and the process of developing AR game. If you have a question, I am happy to answer it.

In my AR game, Chat GPT will be used to create automatically character dialog. Therefore, this post will show how to implement ChatGPT API on Unity.

What is ChatGPT API

These days, everyone probably knows ChatGPT. Chat GPT API is a feature that allows you to use ChatGPT via an API. Also, it is available on Unity.

Implementation of ChatGPT API

Obtain API key from Open AI

To use ChatGPT API, it is necessary to get API KEY from Open AI.

Access Open AI platform
Open AI

Click DashBoard > API keys

Click “Create new secret key”

Request

To confirm the dialog, I implemented two text filed and the button. When the button was clicked, it requests Chat GPT API.

Sample

// Open API Endpoint
var apiUrl = “https://api.openai.com/v1/chat/completions”;

// Add message into list
_messageList.Add(new ChatGPTMessageModel {role = “user”, content = userMessage});

// Header Information
var headers = new Dictionary<string, string>
{
{
“Authorization”, “Bearer “ + _apiKey
},
{
“Content-type”, “application/json”
}
};

// Request Opiton
var options = new ChatGPTCompletionRequestModel()
{
model = “gpt-3.5-turbo”,
messages = _messageList
};
var jsonOptions = JsonUtility.ToJson(options);

using var request = new UnityWebRequest(apiUrl,
“POST”)
{
uploadHandler = new UploadHandlerRaw(
Encoding.UTF8.GetBytes(jsonOptions)),
downloadHandler = new DownloadHandlerBuffer()
};

// Set Request Header
foreach (var header in headers)
{
request.SetRequestHeader(header.Key, header.Value);
}

// Request
await request.SendWebRequest();

// Process Request
if (request.result == UnityWebRequest.Result.ConnectionError || request.result == UnityWebRequest.Result.ProtocolError)
{
Debug.LogError(request.error);
throw new Exception();
}
else
{
var responseString = request.downloadHandler.text;
var responseObject = JsonUtility.FromJson<ChatGPTResponseModel>(responseString);

_messageList.Add(responseObject.choices[0].message);
return responseObject;
}

Set initial message

Dialog can be changed by setting initial message. At this time, I changed it to speak more like a German.

new ChatGPTMessageModel() {role = “system”, content = “You are German. Please reply like German in English”});

Execution of ChatGPT API on Unity

This video shows the dialog that used Chat GPT API.