Proactive Persistent Agents - Using Situational Intelligence to Create Support Characters in Character-Centric Computer Games

Abstract

Throughout the 1990's computer game development was dominated by the improvement of game graphics. However, graphical excellence is now the norm rather than the exception, and so other technologies are coming to the fore as developers strive to make their games stand out in an ever more crowded market. Sophisticated artificial intelligence (AI) is one such technology which is now receiving a large share of game development effort as game designers attempt to create more believable computer controlled characters.

Influenced by the notion of situational intelligence, this work presents the proactive persistent agent (PPA) architecture, an intelligent agent architecture that has been developed to drive the behaviours of non player support characters in character centric computer games. The key features of the architecture are that: PPA characters display believable behaviour across a diverse range of situations, through the use of role passing and fuzzy cognitive maps; PPA based characters are capable of sophisticated social behaviours based on psychological models of personality, mood and interpersonal relationships; The architecture performs in real time on machines of modest specifications; It is relatively easy for non programmers to author characters behaviours using the architecture.

The PPA architecture has been used in two demonstration applications (an adventure game and a system for animating sophisticated virtual humans) which will also be presented. These applications have been used to perform a rigorous evaluation of the architecture, which will also be described. Evaluation is notoriously difficult in systems used to simulate the behaviour of virtual characters, as the key notion of believability is troublingly subjective. However, in spite of the difficulties involved, an evaluation scheme has been developed and used. The evaluation shows that the PPA architecture is ideal for the contol of non player support characters in character centric games.