Developing Games Using AI

In this article, MicaelDaGraça, the author of the book, Practical Game AI Programming, we will be covering the following points to introduce you to using AI Programming for games for exploratory data analysis.

• A brief history of and solutions to game AI
• Enemy AI in video games
• From simple to smart and human-like AI
• Visual and Audio Awareness

A brief history of and solutions to game AI

To better understand how to overcome the present problems that game developers are currently facing, we need to dig a little bit on the history of video game development and take a look to the problems and solutions that was so important at the time, where some of them was so avant-garde that actually changed the entire history of video game design itself and we still use the same methods today to create unique and enjoyable games.

One of the first relevant marks that is always worth to mention when talking about game AI is the chess computer programmed to compete against humans. It was the perfect game to start experimenting artificial intelligence, because chess usually requires a lot of thought and planning ahead, something that a computer couldn't do at the time because it was necessary to have human features in order to successfully play and win the game. So the first step was to make it able for the computer to process the game rules and think for itself in order to make a good judgment of the next move that the computer should do to achieve the final goal that was winning by check-mate. The problem, chess has many possibilities so even if the computer had a perfect strategy to beat the game, it was necessary to recalculate that strategy, adapting it, changing or even creating a new one every time something went wrong with the first strategy.

Humans can play differently every time, what makes it a huge task for the programmers to input all the possibility data into the computer to win the game. So writing all the possibilities that could exist wasn't a viable solution, and because of that programmers needed to think again about the problem. Then one day they finally came across with a better solution, making the computer decide for itself every turn, choosing the most plausible option for each turn, that way the computer could adapt to any possibility of the game. Yet this involved another problem, the computer would only think on the short term, not creating any plans to defeat the human in the future moves, so it was easy to play against it but at least we started to have something going on. It would be necessary decades until someone defined the word "Artificial Intelligence" by solving the first problem that many researchers had by trying to create a computer that was capable of defeating a human player. Arthur Samuel is the person responsible for creating a computer that could learn for itself and memorize all the possible combinations. That way there wasn't necessary any human intervention and the computer could actually think for its own and that was a huge step that it's still impressive even for today standards.

Enemy AI in video games

Now let's move to the video game industry and analyze how the first enemies and game obstacles were programmed, was it that different from what we are doing now? Let's find out.

Single player games with AI enemies started to appear in the 70's and soon some games started to elevate the quality and expectations of what defines a video game AI, some of those examples were released for the arcade machines, like Speed Race from Taito (racing video game) and Qwak(duck hunting using a light gun) or Pursuit(aircraft fighter) both from Atari. Other notable examples are the text based games released for the first personal computers, like Hunt the Wumpus and Star Trek that also had enemies. What made those games so enjoyable was precisely the AI enemies that didn't reacted like any other before because they had random elements mixed with the traditional stored patterns, making them unpredictable and a unique experience every time you played the game. But that was only possible due to the incorporation of microprocessors that expanded the capabilities of a programmer at that time. Space Invaders brought the movement patterns,Galaxian improved and added more variety making the AI even more complex, Pac-Man later on brought movement patterns to the maze genre.

The influence that the AI design in Pac-Man had is just as significant as the influence of the game itself. This classic arcade game makes the player believe that the enemies in the game are chasing him but not in a crude manner. The ghosts are chasing the player (or evading the player) in a different way as if they have an individual personality. This gives people the illusion that they are actually playing against 4 or 5 individual ghosts rather than copies of a same computer enemy.

After that Karate Champ introduced the first AI fighting character, Dragon Quest introduced tactical system for the RPG genre and over the years the list of games that explored artificial intelligence and used it to create unique game concepts kept expanding and all of that came from a single question, how can we make a computer capable of beating a human on a game.

All the games mentioned above have a different genre and they are unique in their style but all of them used the same method for the AI, that is called Finite State Machine. Here the programmer input all the behaviors necessary for the computer to challenge the player, just like the first computer that played chess. The programmer defined exactly how the computer should behave in different occasions in order to move, avoid, attack or perform any other behavior in order to challenge the player and that method is used even in the latest big budget games of today.

From simple to smart and human-like AI

Programmers face many challenges while developing an AI character but one of the greatest challenges is adapting the AI movement and behavior in relation to what the player is currently doing or will do in future actions. The difficulty exists because the AI is programmed with pre-determined states, using probability or possibility maps in order to adapt his movement and behavior according to the player. This technic can become very complex if the programmer extends the possibilities of the AI decisions, just like the chess machine that has all the possible situations that may occur on the game. It's a huge task for the programmer because it's necessary to determine what the player can do and how the AI will react to each action of the player and that takes a lot of CPU power. To overcome that challenge programmers started to mix possibility maps with probabilities and other technics that let the AI decide for itself on how it should react according to the player actions. These factors are important to consider while developing an AI that elevates the game quality as we are about to discover.

Games kept evolving and players got even more exigent, not only with the visual quality, as well with the capabilities of the AI enemies and also with the allied characters. To deliver new games that took in consideration the player expectations, programmers started to write even more states for each character, creating new possibilities, more engaging enemies implementing important allies characters, more things for the player to do and a lot more features that helped re-defined different genres and creating new ones. Of course this was also possible because of the technology that also kept improving, allowing the developers to explore even more the artificial intelligence in the video games. A great example of this that is worth to mention is Metal Gear Solid, the game brought a new genre to the video game industry by implementing stealth elements, instead of the popular straight forward and shooting. But those elements couldn't be fully explored as Hideo Kojima intended because of the hardware limitations at the time. Jumping forward from the 3th to the 5th generation of consoles, Konami and Hideo Kojima presented the same title but this time with a lot more interactions, possibilities and behaviors from the AI elements of the game, making it so successful and important in the video game history that it's easy to see its influence in a large number of games that came after Metal Gear Solid.

Metal Gear Solid - Sony Playstation 1

Visual and Audio Awareness

The game in the above screenshot implemented visual and audio awareness to the enemy. This feature stablished the genre that we know today as a stealth game. So the game uses Pathfinding and Finite States Machine, features that already came from the beginning of the video game industry but in order to create something new they also created new features such as Interaction with the Environment, Navigation Behavior, Visual/Audio Awareness and AI interaction. A lot of things that didn't existed at the time but that is widely used today even on different game genres such as Sports, Racing, Fighting or FPS games were also introduced.

After that huge step for game design, developers still faced other problems or should i say, this new possibilities brought even more problems, because it was not perfect. The AI still didn't react as a real person and many other elements was necessary to implement, not only on stealth games but in all other genres and one in particular needed to improve their AI to make the game feel realistic. We are talking about sport games, especially those who tried to simulate the real world team behaviors such as Basketball or Football. If we think about it, the interaction with the player is not the only thing that we need to care about, we left the chess long time ago, where it was 1 vs 1. Now we want more and watching other games getting realistic AI behaviors, sport fanatics started to ask that same features on their favorite games, after all those games was based on real world events and for that reason the AI should react realistically as possible.

At this point developers and game designers started to take in consideration the AI interaction with itself and just like the enemies from Pac-Man, the player should get the impression that each character on the game, thinks for itself and reacts differently from the others. If we analyze it closely the AI that is present on a sports game is structured like an FPS or RTS game is, using different animation states, general movements, interactions, individual decisions and finally tactic and collective decisions. So it shouldn't be a surprise that sports games could reach the same level of realism as the other genres that greatly evolved in terms of AI development, .However there's a few problems that only sport games had at the time and it was how to make so many characters on the same screen react differently but working together to achieve the same objective. With this problem in mind, developers started to improve the individual behaviors of each character, not only for the AI that was playing against the player, but also the AI that was playing alongside with the player. Once again Finite State Machines made a crucial part of the Artificial Intelligence but the special touch that helped to create a realistic approach in the sports genre was the anticipation and awareness used on stealth games. The computer needed to calculate what the player was doing, where the ball was going and coordinate all of that, plus giving a false impression of a team mindset towards the same plan. Combining the newly features used on the new genre of stealth games with a vast number of characters on the same screen, it was possible to innovate the sports genre by creating a sports simulation type of game that has gained so much popularity over the years. This helps us to understand that we can use almost the same methods for any type of game even if it looks completely different, the core principles that we saw on the computer that played chess it's still valuable to the sport game released 30 years later.

Let's move on to our last example that also has a great value in terms of how an AI character should behave to make it more realistic, the game is F.E.A.R. developed by Monolith Productions. What made this game so special in terms of Artificial Intelligence was the dialogues between the enemy characters. While it wasn't an improvement in a technical point of view, it was definitely something that helped to showcase all of the development work that was put on the characters AI and this is so crucial because if the AI don't say it, it didn't happen. This is an important factor to take in consideration while creating a realistic AI character, giving the illusion that it's real, the false impression that the computer reacts like humans and humans interact so AI should do the same. Not only the dialogues help to create a human like atmosphere, it also helps to exhale all of the development put on the character that otherwise the player wouldn't notice that it was there. When the AI detects the player for the first time, he shouts that he found it, when the AI loses sight of the player, he also express that emotion. When the squad of AI's are trying to find the player or ambush him, they speak about that, living the player imagining that the enemy is really capable of thinking and planning against him. Why is this so important? Because if we only had numbers and mathematical equations to the characters, they will react that way, without any human feature, just math and to make it look more human it's necessary to input mistakes, errors and dialogues inside the character AI, just to distract the player from the fact that he's playing against a machine.

The history of video game artificial intelligence is still far away from perfect and it's possible that it would take us decades to improve just a little bit what we achieve from the early 50's until this present day, so don't be afraid of exploring what you are about to learn, combine, change or delete some of the things to find different results, because great games did it in the past and they had a lot of success with it.

Summary

In this article we learned about the AI impact in the video game history, how everything started from a simple idea to have a computer to compete against humans in traditional games and how that naturally evolved into the the world of video games. We also learned about the challenges and difficulties that were present since the day one and how coincidentally programmers kept facing and still face the same problems.