Almost all modern computer games utilize realistic, high quality 3D animated graphics and 3D sound effects. These two aspects work very well to give the illusion of realism. However, this impression of reality can be smashed if the behaviour of the Non Player Characters (NPCs) is not natural or just doesn’t “feel right”.
The AI in most computer games isn’t really the same as academic AI. It’s more of a mix of techniques that are related to A.I. and are mainly concerned with giving a believable appearance of intelligence. AI doesn’t have to be incredibly complex as very little is required to fool the human brain, a complex A.I would actually be hidden and therefore hard for the player to spot. “The concept of “less is more” can therefore be applied to AI in computer games.” The biggest requirement for creating a captivating illusion of intelligence in games would be managing and controlling perception, I.e. organising and evaluating data from an agents environment which would mostly be sensory data but would also include the communication between multiple agents within a game world.
“The decision cycle of those NPCs constantly executes
three steps [van Lent et al 1999]:
1. perceive (accept information about the environment – sensor information)
2. think (evaluate perceived information & plan according actions)
3. act (execute the planned actions)”
At first glimpse this appears to be a very simple approach which may be inappropriate for creating captivating and entertaining game play. However, most computer games do not really need NPCs that are extremely capable, possibly even more so than the player themselves, as games are meant to be fun to play. If the game is too challenging, causing the player to constantly loose, it will loose it’s attraction and will therefore not be played.
AI was used in early games to produce believable adversaries to challenge the player. Depending on the genre of the game, RPG, arcade, RTS, different techniques and methods were used to create the A.I system, but the end result was always the same – create a believably life like adversary to give the player a challenging but fun and rewarding game play experience.
As games expanded and grew with the constantly evolving computers that ran them, incidentals, background agents, that did not contribute to the main story line started to make an appearance to help enrich the game universe. Game agents that could move about in the background, living out their ‘lives’.
High quality graphics no longer make a computer game stand out any longer. This has led to game developers increasing the complexity and believability of agents within the game universe. To make an agent seem life-like and intelligent, it needs to exhibit natural looking behaviour.
Since game agents have to work in real time, developers have to exclude many AI techniques so illusion is not spoilt by agents reacting slowly. One of the main issues affecting the real time requirements of AI is the fact that the AI has to be processed along with the games graphics, physics, sound, input, networking etc etc. Generally game AI was not viewed as hugely important and did not receive much attention, therefore not much processor times was reserved for it. With the advent of graphics accelerators in the mid 90’s, AI started to receive more attention as greater amounts of graphics processing was being moved onto dedicated graphics hardware.
The game agents in most modern computer games face the problems of
1. Path finding or path planning
2. Decision making
3. Steering or motion control
It is a combination of relatively simple methods applied to these problems that create the illusion of artificial intelligence in computer games.
Both games and the AI techniques used in games have come a long way over the past two and a half decades. Usually the most favourable choices for AI techniques are the older, more established ones. These techniques have actually varied very little over time.
“However over the past decade more and more novel ideas and methods for games AI have filtered into the game development process [Sweetser 2003] “
agents – Intelligent agents are NPCs that have the ability to make decisions and are made up from a combination of AI techniques.
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