Creating Believable Emotional Virtual Characters by Neesha Desai a Thesis Submitted in Partial Fulfillment of the Requirements F
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Creating Believable Emotional Virtual Characters by Neesha Desai A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Computing Science University of Alberta c Neesha Desai, 2015 Abstract Believable, realistic video game character behaviour continues to lag behind the improve- ments in graphics, stories and game play in video games. In this dissertation we focus on the use of two techniques, emotional gaits and emotional incidents, as a way to add easily identifiable, non-verbal, and non-facial emotion to background game characters, thereby increasing the believability of these characters. Emotional gaits refers to the body posture, hand/arm positioning, walk and walking speed of the characters. An emotional incident is an emotion-specific interaction between characters or between characters and props within the game world. The selection and implementation of the techniques was designed to be easily scaled to large numbers of characters and require a minimal number of additional animations. These techniques (emotional gaits and emotional incidents) were analyzed through six different user studies. The examination focused on three aspects: 1) the ease of emotion identification when the behaviour was isolated, 2) whether the gender of the participants and characters affected the results, and 3) emotion identification when observed during normal game play. The results show that participants were able to accurately identify the emotions, that the combination of both emotional gaits and emotional incidents was best overall (but some emotions could be equally achieved with only one), that there were some small differences based on participant gender, and that participants could easily and quickly learn to identify the character emotions when observed within a game world. ii Preface All user studies described in this dissertation received ethics approval from the Research Ethics Office at the University of Alberta. • Study 1 - Identifying Character Emotion in Video Games Pro00025530, Chapter 4 • Study 2 - Gender perceptions of video game character emotion Pro00030705, Chapter 5 • Study 3 - Emotional Characters and Game Play Pro00038529, Chapter 7 • Study 3.5 - Believable Emotional Characters Pro00038930, Chapter 7 • Study 4 - Changing Characters Emotion Pro00042256, Chapter 7 • Study 5 - Guess Who - Video Game Character Study Pro00046111, Chapter 8 • Study 6 - Identifying Character Emotion in Project Spark Pro00050746, Chapter 9 Key results from Chapter 4 have appeared in a published paper: Neesha Desai, and Duane Szafron. Enhancing the Believability of Character Behav- iors Using Non-Verbal Cues, Proceedings of the Eighth AAAI Conference on Artificial In- telligence and Interactive Digital Entertainment (AIIDE), Stanford, USA, October, 2012, 130-135. iii Acknowledgements Grad school is not a solitary experience. It requires many supporters along the way. First up, I would like to thank my family. My parents, Nancy and Pete, and my sisters, Raani and Soni (and their families )have been there for me the entire way. They listened to my rants, cooked me meals and worked to cheer me up when times were tough. Next, my supervisor (Duane Szafron) and the Believe research group (both past and present members) were always available for bouncing ideas off, testing out experiments and so much more. I have been lucky to have made great friendships within the department but also within the startup community in Edmonton. The people who have climbed with me, shared a beer, or helped launch Alieo, have all helped keep me sane during the highs and lows of research. Finally, I would be remiss if I did not thank the Natural Sciences and Engineering Research Council of Canada, Alberta Innovates Technology Futures, and the GRAND-NCE, all of whom helped fund my research. iv Contents 1 Introduction 1 1.1 Contributions . 4 2 Creating Recognizable Emotions 7 2.1 Constraints . 9 2.2 Problem . 10 2.3 Techniques . 11 2.3.1 Emotional Gaits . 12 2.3.2 Emotional Incidents . 13 2.4 Conclusion . 16 3 Related Work 18 3.1 Emergent Game Play . 18 3.2 Gender . 19 3.3 Benefits of Game Play . 20 3.4 Emotions . 21 3.4.1 Emotions versus Moods versus Personality . 22 3.4.2 Emotion as represented through non-verbal cues . 22 3.4.3 Theories of Emotion . 25 3.4.4 Emotion as seen in Animation and Games . 28 4 Identifying Emotions 30 4.1 Experimental Design . 31 4.1.1 Participants . 33 4.1.2 Experiment Limitations . 33 4.2 Results . 34 v 4.2.1 Confusion Matrices . 34 4.3 Overall Results . 35 4.3.1 Gait . 35 4.3.2 Incident . 36 4.3.3 Combination - Gait plus Incident . 36 4.3.4 Comparison of Techniques . 37 4.4 Which technique(s) to use? . 39 4.4.1 Use in Entertainment Games . 39 4.4.2 Use in Serious Games . 40 4.5 Anecdotes . 40 4.6 Conclusion . 41 5 Gender Differences 42 5.1 Experimental Design . 43 5.1.1 Participants . 44 5.1.2 Experiment Limitations . 44 5.1.3 Statistical Techniques . 45 5.2 Results . 45 5.2.1 Female vs Male Participants . 45 5.2.2 Female vs Male Characters . 47 5.2.3 Consistency . 49 5.2.4 Gamers vs Non-Gamers . 50 5.3 Conclusion . 51 6 Creating self-determined Emotion Behaviour 52 6.1 Consistency . 53 6.2 Unpredictability . 54 6.3 Emotion Architecture . 54 6.4 Basic Character Behaviour . 57 6.5 Triggering Character Incident . 58 6.6 Character Incidents . 59 6.7 Animation Controller . 60 6.8 Prop Incidents . 64 vi 6.9 Emotional Incidents in the Park . 64 6.9.1 Probability Factor . 66 6.10 Conclusion . 67 7 Experiments on adding emotional characters into games - Studies 3 and 4 68 7.1 Return Tablet - Study 3 . 69 7.1.1 Experimental Design . 69 7.1.2 Participants . 72 7.1.3 Results . 73 7.1.4 Return Tablet version 2 - Study 3.5 . 74 7.2 Changing Emotions - Study 4 . 75 7.2.1 Experimental Design . 75 7.2.2 Participants . 76 7.2.3 Results . 76 7.3 Conclusion - Lessons Learned . 78 7.3.1 Tutorials . 78 7.3.2 Game Play . 79 7.3.3 Questions . 79 8 Guess Who? - Study Five 81 8.1 Implementation . 82 8.2 Experimental Design . 84 8.2.1 Tutorial . 84 8.2.2 Games 1 and 2 - Guess Who . 84 8.2.3 Game Three - Identifying Emotion . 87 8.3 Participants . 88 8.3.1 Experiment Limitations . 88 8.4 Results . 88 8.4.1 Believable Characters . 89 8.4.2 Playing Strategies . 90 8.4.3 Learning . 91 8.4.4 Time Spent Playing . 92 vii 8.4.5 Identifying Emotion . 92 8.5 Conclusion . 93 9 Easy construction of animation and incidents - Study Six 96 9.1 Related Work . 97 9.1.1 Kodu . 97 9.1.2 Scratch . 98 9.1.3 Alice . 98 9.1.4 Kano . 99.