The Tower: Design of Distinct AI Per- sonalities in Stealth-Based Games Modeling personalities with believable and consistent behaviour for NPCs in games using stealth gameplay style Master’s thesis in Game Design & Technology Marek Cernákˇ Orestis Lianoudakis Department of Computer Science and Engineering CHALMERS UNIVERSITY OF TECHNOLOGY UNIVERSITY OF GOTHENBURG Gothenburg, Sweden 2020 Master’s thesis 2020 The Tower: Design of Distinct AI Personalities in Stealth-Based Games Modeling personalities with believable and consistent behaviour for NPCs in games using stealth gameplay style Marek Černák Orestis Lianoudakis Department of Computer Science and Engineering Chalmers University of Technology University of Gothenburg Gothenburg, Sweden 2020 The Tower: Design of Distinct AI Personalities in Stealth-Based Games Modeling personalities with believable and consistent behaviour for NPCs in games using stealth gameplay style Marek Černák Orestis Lianoudakis © Marek Černák, Orestis Lianoudakis, 2020. Supervisor: Staffan Björk, Department of Computer Science and Engineering Examiner: Olof Torgersson, Department of Computer Science and Engineering Master’s Thesis 2020 Department of Computer Science and Engineering Chalmers University of Technology and University of Gothenburg SE-412 96 Gothenburg Telephone +46 31 772 1000 Typeset in LATEX Gothenburg, Sweden 2020 iv The Tower: Design of Distinct AI Personalities in Stealth-Based Games Modeling personalities with believable and consistent behaviour for NPCs in games using stealth gameplay style Marek Černák Orestis Lianoudakis Department of Computer Science and Engineering Chalmers University of Technology and University of Gothenburg Abstract Computer games using stealth situations for defining their gameplay often rely on modeling an immersive, yet exploitable non-player character behaviour. Tradition- ally, the aim of the design of such a behaviour is to provide players with memorable behaviour patterns of the in-game agents in order to facilitate the means of devising strategies used by players to finish the game levels. Although certain behaviours for the agents are usually designed to make them reactive to environment events, it is not common for commercial game titles to include the reactions based on distinct personality traits of the agents. As a part of the thesis, we research game industry methods for creation of AI agents in games. Furthermore, we explore a research in the area of modelling autonomous agents with distinct personalities. We apply these concepts to design and implement a playable game prototype, including mod- els of AI agents with distinct personalities and perform several play-tests. From the outcome of the process, we formulate guidelines for designing distinct personalities with believable and consistent behaviour for NPCs in games using stealth gameplay style. Keywords: stealth gameplay, games research, AI, NPC, autonomous agents, person- ality modeling, thesis. v Acknowledgements We would like the to thank our supervisor Staffan Björk for the advice and support during the development and writing of the thesis. We would also like to thank the people who tested the game and for the feedback they provided. We are also thankful to the University of Gothenburg for the opportunity of working on this project. Finally, we would like to thank Theodoris Michelis for evaluating the thesis’ text. Marek Černák, Orestis Lianoudakis, Gothenburg, May 2020 vii Contents List of Figures xiii List of Tables xviii List of Listings xix Glossary xx 1 Introduction1 1.1 Problem Description...........................1 1.2 Research Question............................2 1.3 Aim....................................3 1.4 Solution Constraints...........................3 2 Background5 2.1 Research Area...............................5 2.1.1 AI Personalities In Stealth Games................6 2.2 Related Work...............................6 2.2.1 Related Research.........................7 2.2.2 Application in Games.......................7 3 Theory 11 3.1 Perception................................. 13 3.1.1 Knowledge Communication................... 13 3.1.2 Sensory Systems......................... 13 3.2 Knowledge................................. 17 3.3 Personality................................ 18 3.3.1 Personality Models........................ 19 3.3.2 Emotions............................. 20 3.3.3 Mood............................... 21 3.3.4 Motivation............................. 21 3.4 Behaviour................................. 22 3.4.1 Decision Making......................... 23 3.4.2 Decision Making Based on Personalities............. 25 3.5 Design Frameworks............................ 29 3.5.1 Game Design Patterns...................... 29 3.5.2 MDA................................ 31 ix Contents 3.6 Stealth Gameplay Style.......................... 32 4 Methodology 35 4.1 Iterative Process............................. 35 4.1.1 Managerial Practices....................... 36 4.1.2 Sprint............................... 36 4.1.3 Iteration Planning........................ 36 4.1.4 Daily Meeting........................... 36 4.2 Solution Requirements.......................... 37 4.3 Computational Personality Model Prototype.............. 38 4.4 Personality Model Application...................... 39 4.4.1 Stealth Design Guidelines.................... 39 4.4.2 Stealth Design Methods..................... 40 4.5 Testing the game prototype....................... 41 4.5.1 Self-testing............................ 41 4.5.2 User Testing............................ 42 4.5.3 Data gathering.......................... 43 4.5.4 Evaluation............................. 44 4.6 Wicked Problems............................. 45 4.6.1 A definition............................ 45 4.6.2 Ties to our question....................... 47 5 Planning 49 5.1 Planning Report............................. 49 5.2 Framework Prototype Development................... 49 5.3 Thesis Finalisation............................ 51 6 Execution and Process 53 6.1 First Sprint................................ 53 6.1.1 Game AI.............................. 53 6.1.2 Stealth Level Prototype..................... 55 6.2 Second Sprint............................... 60 6.2.1 Game AI.............................. 60 6.2.2 Stealth Level Prototype..................... 63 6.3 Third Sprint................................ 65 6.3.1 Computational Personality Model................ 65 6.3.2 Stealth Level Prototype..................... 69 6.3.3 Personality Models........................ 71 6.4 Fourth Sprint............................... 72 6.4.1 Game AI.............................. 73 6.4.2 Stealth Level Prototype..................... 75 6.4.3 First Testing Session....................... 78 6.5 Fifth Sprint................................ 83 6.5.1 Game AI.............................. 84 6.5.2 Stealth Level Prototype..................... 85 6.5.3 Personality Models........................ 89 6.5.4 Second Testing Session...................... 90 x Contents 7 Results 93 7.1 Design Guidelines............................. 93 7.1.1 Consider which Computation Personality Model to work with 94 7.1.2 Consider order of design of personality and behaviour..... 95 7.1.3 Consider using intents/motivations for NPCs.......... 97 7.1.4 Motivations and personality traits should conform each other. 98 7.1.5 Reactions of the same NPC given the same environment stim- uli should not conflict each other................ 98 7.1.6 NPCs should be quite determined in finishing actions started. 99 7.1.7 Consider level design choices to fit the personality....... 100 7.1.8 Consider in which order the personalities should be shown to the player............................. 101 7.1.9 Consider personalities differentiation via audiovisual represen- tation............................... 101 7.2 The Tower: A Playable Game Prototype................ 102 7.2.1 Game System Architecture.................... 102 7.2.2 Game Level Design........................ 106 8 Discussion 113 8.1 Results................................... 113 8.1.1 Design Guidelines......................... 113 8.1.2 Game Prototype......................... 114 8.2 Methodology, Execution and Process.................. 116 8.3 Validity.................................. 117 8.4 Future Work................................ 118 8.5 Ethical considerations.......................... 119 9 Conclusion 121 References 123 A Computational Personality Model Supplement MaterialI B Description of Designed Personalities III B.1 Personalities................................ III B.1.1 Honorable Personality...................... III B.1.2 Pedantic Personality.......................IV B.1.3 Lazy Personality.........................V B.1.4 Fearful Personality........................ VII B.2 Personalities Alternatives......................... VIII B.2.1 Honorable Personality Alternatives............... VIII B.2.2 Pedantic Personality Alternatives................IX B.2.3 Lazy Personality Alternatives..................IX B.2.4 Fearful Personality Alternatives.................IX C First Gameplay User-Test Session MaterialsXI D Second Gameplay User-Test Session Materials XVII xi Contents xii List of Figures 2.1 Screenshot from Sims3 [48]. At the bottom, the status UI shows the needs of the agent. These determine the motivation of the AI....8 2.2 In Batman: Arkham City [69] the player can at anytime view the condition of their enemies. The guard in the figure is nervous with a high pulse indicating that they are aware that something is afoot. They have