Virtual Actors’ Behaviour for 3D Interactive Storytelling

In this paper, we describe a method for implementing intelligent behaviour for artificial actors in the context of interactive storytelling. We have developed a fully implemented prototype based on the UnrealTM game engine and carried experiments with a simple sitcom-like scenario. We discuss the central role of artificial actors in interactive storytelling and how real-time generation of their behaviour participates to the creation of a dynamic storyline. We follow previous work describing the behaviour of artificial actors through AI planning formalisms, and adopt a search-based approach to planning. The set of all possible behaviours, accounting for many different instantiations of a basic plot, can be represented through an AND/OR graph. Under certain formal conditions, the solution plan can be obtained by directly searching the graph with the AO* algorithm. We describe our implementation of AO* and how it addresses the specific issues of 3D interactive storytelling, such as interaction with the virtual world and user intervention.