Technical Challenges of Artificial Intelligence in gaming An analysis of the use of AI in gaming and the challenges it presents to developers by Joshua Matthews.

Lets start with some positives: some early examples of great, innovative forms of AI… •  The Sims (2000) – The best selling PC game of all time, The Sims revolutionised

the AI spectrum, placing behavior responsibilities on the actors environment via Smart Objects, providing a number of basic desires for the Sims to drive their actions individually and modeling emotional interactions, allowing relationships to form. Gameplay - https://www.youtube.com/watch?v=e20QY7Hx88s

•  Halo (2001) – The first title of this successful franchise brought many innovations. The enemies use cover wisely and employ suppressive fire and grenades; the situation of the squad has an impact on its individuals (when team leader dies, team members flee); plus, there’s a lot of attention to detail. For example, enemies throw grenades back at the player and team members will respond if the player should bother them. -

•  Black & White (2001) - Published by Lionhead Studios, this god game featured interacting with a giant AI creature which can learn from examples, and takes reward and punishment. Its engine uses a solid AI architecture, rooted in cognitive science, known as belief-desire-intention (BDI) and machine learning techniques such as decision trees and neural networks are used with great success.

The mid 2000’s downfall Notice how all of those games that I just mentioned are at least 12 years old? It is said that from around the mid-2000s videogame AI nestled itself beneath a “chest-high wall” and has pretty much stayed there ever since.

Far Cry The Far Cry series has had a mixed relationship with AI over the course of its last two titles. Being open world games, this series has more aspects to cover in terms of AI, mainly revolving around its natural environment. Far Cry 2 had some great ideas for its animal AI. They developed a spawning technique that allowed them to take advantage of the fact that, in real life, Animals don’t stay in the same place. This was combined with an encounter system, that spawned various AI in the game based on what’s already there. However, less predators were actually included within the game world as the developers couldn’t control their AI and stop them from eating all the herbivores. Far Cry 3 took a more individual approach to the animals and gave them more detailed virtual minds. Ubisoft developer Hugo Desmeules explained “So now a turtle brain no longer consists of only going left and right and being crushed by a plumber, it needs to flee progressing fire, move away from an incoming vehicle, transition from ground to water navigable areas, walk, hide, swim, and care about predators like sharks.” The upgrade and developments in AI between these two games is quite impressive.

Zombies The Walking Dead: Survival Instinct had the graphics and premise to have what it takes to be a relatively decent game. After all, isn’t The Walking Dead one of the most, if not the most well known zombie franchise? Well this little mess of a game certainly died out due to its laughable AI system. The zombies didn’t share the correct focal point and often were misdirected. The zombies need to spawn and direct their attention to the player at a frequent enough rate to present a challenge and this doesn’t happen. If the zombies are even spawning through the bugged up engine, their attention isn’t focused on the player and sometimes they don’t even approach them. This would’ve been an easy behavior to imply and I believe the true reason why it wasn’t there was due to a rush of development due to a dangerously fast approaching release date. https://www.youtube.com/watch?v=dcDLnaqOeHo The Left 4 Dead franchise’s “AI Director” is the example that all future zombies games should follow. The Director is designed to detect the whereabouts of the player and spawn a challenging amount of infected accordingly. The Director will go through phases, which experienced players might even be able to judge and react to: Build Up - Upon leaving the safe zone, the Director enters Build Up mode. In this mode, Common and Special infected will spawn normally, and Mobs will appear regularly; Peak - The Director reaches "Peak" when the Survivors are at maximum Intensity. It usually occurs at the peak of combat. Infected normally stop spawning at this point.; Relax - During Relax phase, Survivors may rest and recouperate after passing through Peak phase.; The Director constantly measures how much pressure each individual Survivor is under by monitoring their Intensity. A Survivor's Intensity increases when attacked by an Infected, and by killing Infected that are close by. Survivors will immediately reach maximum Intensity when incapacitated. Survivors will not gain intensity through friendly fire, or when sniping distant Infected. https://www.youtube.com/watch?v=Ngw5DUcQAMM

Playing with the AI Over the past few years, many have uploaded videos online, demonstrating how entertaining the AI knowledge of certain game actors is in events such as combat. By enforcing some slight modifications, CPU actors can fight others without a player being involved presenting us with total simulated combat, that relies entirely on the game’s AI system. Some great examples of effective combat AI that I’ve found are that of Bully by Rockstar Games (2006), a game set in a school, where each of its ‘cliques’ have their own unique rivalries and fighting styles. Certain actions that the player does can have an effect on their reputation with that clique. For instance, if the player eggs the Jock’s gym in alliance with the Nerds, the Jocks will not take kindly to his next visit. Also, bullying certain individuals will provoke the Prefects to apprehend you. Anyway, here’s a few videos of modifications that help convey the different fighting styles and rivalries as a result of the AI. https://www.youtube.com/watch?v=alHd9UUkZmU https://www.youtube.com/watch?v=_tIRG8Xa8RM

The Last of US Rays Rays are technique that Naughty Dog used to avoid a big problem encountered within the devlopment process of their Buddy AI, that ensured the Ellie was always realistically reacting to Joels actions against enemies. It had to be restarted a few weeks before release as they saw too many weaknesses within it. Ray diagrams were used to show the different points were Ellie could stand in perespective to Joel. The developers had to analyse these points, remove the points where she would stand that would either be too close to the enemies or ridicolously out of Joel's sight and adapt that basic perspective to every instance where they meet a group of enemies, adapting in a way that doesn't enable it to look too rigid and unrealistic. Examples of points that would have to be removed include any point where Ellie is faced directly up against all wall near Joel or if she is standing so curved round to a certain angle from Joel's perspective, that she is nearer to the enemies than him. http://www.gdcvault.com/play/1020364/Ellie-Buddy-AI-in-The In the above presentation,