An Emergent Approach to Game Design – Development and Play Penelope Sweetser B. InfoTech (Hons), G.C.Ed. A thesis submitted for the degree of Doctor of Philosophy School of Information Technology and Electrical Engineering The University of Queensland June 17, 2005 ii Statement of Originality The work presented in this thesis is, to the best of my knowledge and belief, original, except as acknowledged in the text, and the material has not been submitted, either in whole or in part, for a degree at this or any other university. Penelope Sweetser iii Abstract Player enjoyment is the single-most important goal of games. Games that are not enjoyable are not bought or played. Within games, enjoyment of the gameplay hinges on the game world. However, game worlds are often static and highly scripted, which leads to restricted and shallow gameplay that can detract from player enjoyment. It is possible that player enjoyment could be improved by the creation of more flexible game worlds that give players more freedom and control. One way to create more flexible game worlds is through the use of an emergent approach to designing game worlds. This thesis investigates an emergent approach to designing game worlds, as well as the issues, considerations and implications for game players and developers. The research reported in this thesis consisted of three main components. The first component involved conducting a focus group and questionnaire with players to identify the aspects of current game worlds that affect their enjoyment. The second component of the research involved investigating an emergent approach to designing game worlds, in which the Emergent Games Engine Technology (EmerGEnT) system was developed. The test-bed for the EmerGEnT system was a strategy game world that was developed using a 3D games engine, the Auran Jet. The EmerGEnT system consists of three main components: the environment, objects and agents. The third component of the research involved evaluating the EmerGEnT system against a set of criteria for player enjoyment in games, which allowed the system’s role in facilitating player enjoyment to be defined. In the player-centred studies, it was found that players are dissatisfied with the static, inconsistent and unrealistic elements of current games and that they desire more interactivity, realism and control. The development and testing of the EmerGEnT system showed that an emergent game world design, based on cellular automata, can iv facilitate emergent behaviour in a limited domain. The domain modelled by the EmerGEnT system was heat, fire, rain, fluid flow, pressure and explosions in a strategy game world. The EmerGEnT system displayed advantages relating to its ability to dynamically determine and accommodate the specific state of the game world due to the underlying properties of the cells, objects and agents. It also provided a model for emergent game worlds, which allowed more complexity than emergent objects alone. Finally, the evaluation of enjoyment revealed that incorporating an emergent game world (such as the EmerGEnT system) into a game could improve player enjoyment in terms of concentration, challenge, player skills, control and feedback by allowing more intuitive, consistent and emergent interactions with the game world. The implications of this research are that cellular automata can facilitate emergence in games, at least in a limited domain. Also, emergence in games has the potential to enhance player enjoyment in areas where current game worlds are weak. Finally, the EmerGEnT system serves as a proof of concept of using emergence in games, provides a model for simulating environmental systems in games and was used to identify core issues and considerations for future development and research of emergent game worlds. v List of Publications **Sweetser, P. & Wyeth, P. (in press) GameFlow: A Method for Evaluating Player Enjoyment in Games. ACM Computers in Entertainment 3 (3). **Sweetser, P. & Wiles, J. (in press) Combining Influence Maps and Cellular Automata for Reactive Game Agents. 6th International Conference on Intelligent Data Engineering and Automated Learning . **Sweetser, P. & Wiles, J. (in press) Using Cellular Automata to Facilitate Emergence in Game Environments. 4 th International Conference on Entertainment Computing . **Sweetser, P. & Wiles, J. (2005) Scripting versus Emergence: Issues for Game Developers and Players in Game Environment Design. International Journal of Intelligent Games and Simulations 4 (1), pp. 1-9. **Sweetser, P. & Johnson, D. (2004) Player-Centred Game Environments: Assessing Playing Opinions, Experiences and Issues. Entertainment Computing - ICEC 2004: Third International Conference, Lecture Notes in Computer Science , 3166, pp. 321-332. Sweetser, P. (2004). How to Build Neural Networks for Games. In Rabin, S. (Ed.), AI Game Programming Wisdom 2. Hingham, MA: Charles River Media, Inc. Sweetser, P. (2004). How to Build Evolutionary Algorithms for Games. In Rabin, S. (Ed.), AI Game Programming Wisdom 2. Hingham, MA: Charles River Media, Inc. vi Sweetser, P. (2004). Strategic Decision-Making with Neural Networks and Influence Maps. To be published in Rabin, S. (Ed.), AI Game Programming Wisdom 2. Hingham, MA: Charles River Media, Inc. Sweetser, P., Johnson, D., Sweetser, J., & Wiles, J. (2003) Creating Engaging Artificial Characters for Games. Proceedings of the Second International Conference on Entertainment Computing . Pittsburgh, PA: Carnegie Mellon University. Sweetser, P. & Dennis, S. (2003). Facilitating Learning in a Real Time Strategy Computer Game. Entertainment Computing: Technologies and Applications (eds. Ryohei Nakatsu and Junichi Hoshino). Kluwer Academic Publishers, Boston. Johnson, D., Gardner, J., Wiles, J., Sweetser, P. & Hollingsworth, K. (2003). The Inherent Appeal of Physically Controlled Peripherals. Entertainment Computing: Technologies and Applications (eds. Ryohei Nakatsu and Junichi Hoshino). Kluwer Academic Publishers, Boston. ** Publications related specifically to this thesis. vii This thesis is dedicated to my partner, Peter Surawski. viii Acknowledgements I would like to acknowledge several sources for funding throughout my PhD. Firstly, the School of ITEE for a departmental scholarship for my first year, as well as ongoing tutoring and lecturing throughout my studies. Second, the UQ Graduate School for providing my UQGSS scholarship for two years. Also, I would like to acknowledge the Key Centre for Human Factors and Applied Cognitive Psychology and the Australasian CRC for Interaction Design for research work that supported my study. I would like to thank my advisor, Janet Wiles, for teaching me about research and helping to bring the best out of my work. Also, I thank my associate advisor, Peta Wyeth, for her expertise in human-computer interaction and feedback on my thesis. Also, Daniel Johnson acted as an advisor on many occasions, giving me support with experimental design and statistical analysis. I also thank my sister, Jane Sweetser, for her help and advice on psychological data and analysis. I would like to thank my friend and colleague, Penny Drennan, for her support, feedback and friendship throughout this period. Finally, and most importantly, I would like to thank my family. Firstly, I thank my partner, Peter Surawski, for his ongoing support, understanding and encouragement throughout my study. I would also like to thank my parents, Bill and Gay Sweetser, for their support and encouragement throughout my study, as well as instilling me with the desire to reach for the stars and making the sacrifices that allowed me to do so. ix Contents CHAPTER 1 INTRODUCTION TO EMERENCE IN GAME WORLDS 1 1.1 Narrative versus Gameplay 1 1.2 Scripted Gameplay 3 1.3 Open Gameplay 4 1.4 Emergent Game Worlds 6 1.5 Cellular Automata in Games 7 1.6 Thesis Overview 8 1.6.1 Part I 9 1.6.2 Part II 9 1.6.3 Part III 10 1.7 Contribution 10 CHAPTER 2 SCRIPTING VERSUS EMERGENCE 13 2.1 Current Approach to Game Design 14 2.1.1 Issues for Players 14 2.1.1.1 Consistency 15 2.1.1.2 Intuitiveness and Learning 15 2.1.1.3 Emergent Gameplay and Player Expression 16 2.1.2 Issues for Developers 16 2.1.2.1 Effort in Designing, Implementing and Testing 16 2.1.2.2 Effort in Modifying and Extending 17 2.1.2.3 Level of Creative Control 17 2.1.2.4 Uncertainty and Quality Assurance 17 2.1.2.5 Ease of Feedback and Direction 17 2.1.3 Techniques for Scripting Games 18 2.1.3.1 Finite State Machines 18 2.1.3.2 Scripting 18 2.2 Emergence as an Alternative Approach 19 2.2.1 Complex Systems 20 2.2.2 Emergence 20 2.2.3 Emergence in Games 21 2.2.4 Issues for Game Developers 22 2.2.4.1 Effort in Designing, Implementing and Testing 22 2.2.4.2 Effort in Modifying and Extending 23 2.2.4.3 Level of Creative Control 23 2.2.4.4 Uncertainty and Quality Assurance 23 2.2.4.5 Ease of Feedback and Direction 23 x 2.2.5 Issues for Game Players 24 2.2.5.1 Consistency 24 2.2.5.2 Intuitiveness and Learning 24 2.2.5.3 Emergent Gameplay and Player Expression 25 2.2.6 Techniques for Emergent Games 26 2.2.6.1 Flocking 26 2.2.6.2 Cellular Automata 27 2.2.6.3 Neural Networks 28 2.2.6.4 Evolutionary Algorithms 28 2.3 Scripting-Emergence Continuum 29 PART I: IDENTIFYING THE PLAYER-CENTRED ISSUES OF INTERACTING IN GAME WORLDS CHAPTER 3 PLAYER-CENTRED GAME WORLDS 33 3.1 Defining the Player-Centred Issues 34 3.1.1 Consistency 35 3.1.2 Immersion and Suspension of Disbelief 35 3.1.3 Freedom of Player Expression 36 3.1.4 Intuitiveness 36 3.1.5 Physics 37 3.1.6 Focus Group Summary 38 3.2 Investigating