# Bayesian Modeling Of An Human Mmorpg Player

Gabriel Synnaevea,c and Pierre Bessièreb,c a*Grenoble University* bCNRS c*E-Motion team INRIA Rhône-Alpes* 655 avenue de l'Europe 38334 Montbonnot Abstract. This paper describes an application of Bayesian programming to the control of an autonomous avatar in a multiplayer role-playing game (the example is based on World of Warcraft). We model a particular task, which consists of choosing what to do and to select which target in a situation where allies and foes are present. We explain the model in Bayesian programming and show how we could learn the conditional probabilities from data gathered during human-played sessions. Keywords: Bayesian programming, video games PACS: 07.05.Mh

## Introduction

With more and more CPU cores and more and more immersive gameplays, AI is becoming a key feature of video games. Non-player characters (NPC) acting against the player as well as by his side are required to behave realistically and interestingly. We model a massively multiplayer online role-playing game (MMORPG) player through Bayesian programming (Lebeltel, 2004). We bet that this model can learn to play as a given player he could observe and that it will yield a realistic robot, customized to the instructing player.

 A role playing game (RPG) consist in the incarnation by the human player of an avatar with a class (warrior, wizard, rogue, priest…) having different skills, spells, items, health points, stamina/energy/mana (magic energy) points. A MMORPG (e.g. World of Warcraft, AION or EVE Online) is a role-playing game in a persistent, multiplayer world. There are usually players-run factions fighting each other but we modeled a particular domain of multiplayer RPG called players versus environment (PVE). This is a cooperative task in which human players fight together against different NPC. And more specifically here, we modeled the "druid" class, which is complex because it can cast spells to deal damages or other negative effects as well as to heal allies or enhance their capacities ("buff" them).

 This model deals only with a sub-task of a global AI for autonomous NPC. The problem that we try to solve with the presented model is: how do we choose which skill to use and on which target in a PVE battle? Possible targets are all our allies and foes. Possible skills are all that we know, we aim to get a distribution over target and skills and pick the most probable combination that is as yet possible to achieve (enough energy/mana, no cooldown). For that, we first choose what should be the 