Integrating GPT-4 into Unity

When I began developing LEAF, I didn’t know exactly what this project would become. I just knew I wanted a game character that could actually respond to me - one that didn’t follow a fixed or pre-defined script. I was drawn to the idea of using generative AI to power interactions that felt unpredictable and personal. This post walks through the first steps towards the development of LEAF: bringing GPT-4 into Unity.

GPT-4 is capable of generating text that feels natural and responsive. I had no idea of how it would work in a game setting, but I wanted to try. My early thinking was: what if I could just type something to a character, and it would answer back? Not through code or dialogue trees, but through actual AI-driven reasoning. Unity offered flexibility for building the game systems, visual elements, and AI integration. It also allows me to build a prototype quickly while testing multiple gameplay systems in parallel.

Before i could do anything in Unity though, I needed access to GPT-4. I signed up with an OpenAI account and acquired an API key. What I didn’t realize at the time was that each call to GPt-4 costs money, and that it works on a credit system. That immediately made me think carefully about how often the game should talk to the AI. In Unity, I created a secure method to store my API key and build a simple input / output test to see if I could get a response.

Once the API was installed into Unity, all that was required was to write a script that sends a prompt request to the GPT-4 endpoint and await a response. I started by passing in a predetermined prompt, something simple like “You are a companion character in a game. Start by introducing yourself.” After a few attempts of making sure the script was set up properly, I received my first response that already made an attempt to roleplay.

At this point, the integration wasn’t doing anything fancy. There was no game character, no companion system, goals or objectives. But seeing GPT-4 respond inside the Unity console told me this could work, and reinforced the idea that what I’m building isn’t just a game, but a system to make characters feel more alive within games.

A few notes from my first interaction with the GPT-4 API within Unity has made me realize that there is some latency and it can take a few seconds to respond. I’ve navigated around this by adding in a loading state at the beginning of the game, preventing any input from being made until after the first API response has been confirmed. I will look into designing a method of masking around this delay with intentional moments of pause, like with loading screens, animations, or pre-loaded responses.

I’ve also come to the realization that each prompt costs tokens, making me realize that I would have to find a way of optimizing the usage. Excessive API calls can prove costly if not careful. GPT-4 also returns a lot of text when roleplaying. I would need to find a way to trim or shape that into something usable in gameplay.