Pareto-Based Narrative Planning: Making NPCs More Rational

Abstract

A narrative planner decides the actions for all characters in a story while justifying each action according to the acting characters' own individual goals. However, an action that contributes to a goal may still seem irrational when considered alongside other actions the character may take; for instance, it may sacrifice a more important goal, or expose the character to unnecessary risks. We redefine the narrative planning character model to use a multiobjective framework where character actions are chosen from a Pareto front of best and safest options. We discuss how this framework can be applied to generate a policy for how the non-player characters should behave in any given state of an interactive narrative, and how we applied such a policy in the Traffic Stop de-escalation training simulation.