Abstract Information Visualization in Interactive 3D Virtual Environments:
Conceptualization and Usability Evaluation Kaveh Bazargan Harandi
Codirection de thèse :
M. Gilles Falquet, professeur
Mme Claudine Métral, professeure
Abstract Information Visualization in Interactive 3D Virtual Environments:
Conceptualization and Usability Evaluation
THÈSE
présentée à la Faculté des sciences économiques et sociales de l’Université de Genève
par
Kaveh BAZARGAN HARANDI
sous la codirection de
M. Gilles FALQUET, professeur Mme Claudine METRAL, professeure
pour l’obtention du grade de
Docteur ès sciences économiques et sociales mention systèmes d’information
Membres du jury de thèse:
M. Gilles FALQUET, Professeur, Co-directeur de thèse, Université de Genève Mme Claudine METRAL, Professeure, Co-directrice de thèse, Université de Genève
M. Dimitri KONSTANTAS, Professeur, Président du jury, Université de Genève M. Laurent MOCCOZET, Maître d'Enseignement et de Recherche, Université de Genève
M. Patrick ROTH, Informaticien, Groupe NTICE, Université de Genève M. Ahmed SEFFAH, Professeur, Concordia University, Canada
Thèse no 747 Genève, 14 mars 2011
ABSTRACT INFORMATION VISUALIZATION IN INTERAC- TIVE 3D VIRTUAL ENVIRONMENTS: CONCEPTUALIZATION AND USABILITY EVALUATION
Thèse présentée à la Faculté des sciences économiques et so- ciales de l’Université de Genève
Par Kaveh Bazargan Harandi pour l’obtention du grade de
Docteur ès sciences économiques et sociales mention : systèmes d’information
Membres du jury de thèse :
M. Gilles Falquet, Professeur, Co-directeur de thèse, Université de Genève Mme Claudine Métral, Professeure, Co-directrice de thèse, Université de Genève M. Dimitri Konstantas, Professeur, Président du jury, Université de Genève
M. Laurent Moccozet, Maître d'Enseignement et de Recherche, Université de Genève M. Patrick Roth, Informaticien, Groupe NTICE, Université de Genève
M. Ahmed Seffah, Professeur, Concordia University, Canada
Thèse N° 747
Genève, le 14 mars 2011
La Faculté des sciences économiques et sociales, sur préavis du jury, a autorisé l’impression de la présente thèse, sans entendre, par là, n’émettre aucune opinion sur les propositions qui s’y trouvent énoncées et qui n’engagent que la responsabilité de leur auteur.
Genève, le 14 mars 2011
Le doyen
Bernard MORARD
Impression d'après le manuscrit de l'auteur.
© Kaveh Bazargan Harandi, 2011. Tout droit réservés.
ISBN 978-2-88903-005-7
Editions SES - Université de Genève
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A raindrop tricked from a cloud and was discomfited to see the ocean’s with:
“Where there’s the ocean, who am I? If it exists, then truly I do not!”
But, while with disparagement’s eye it saw itself, an oyster-shell within its bosom dearly cherished it;
And heaven at length so far advanced it cause that it became an imperial pearl, renowned:
Elevation it discovered by first becoming lowly, Nothingness’ door it pounded until existence came to be!
(Chapter 4, On Humility, The Bustan of Saadi)
Source: Saadi Shirazi, M. [Persian poet of the 13th century] The Bustan of Sheikh-e Ajal Saadi, translated (from Persian) by G.M. Wickns. The Iranian Commission for UNESCO, Tehran, 1985
Table of Contents
Abstract ... xiii
Résumé ... xv
Acknowledgments ... xvii
List of Figures ... xix
List of Tables ... xxv
1. INTRODUCTION ... 1
1.1 Motivation ... 1
1.2 Challenges ... 2
1.3 Application Domains ... 3
1.3.1 Cultural Heritage and Tourism ... 4
1.3.2 Public Participation in Sustainable Urban Planning ... 5
1.3.3 Advertising, Marketing and Commerce ... 6
1.3.4 Training and Simulation ... 8
1.3.5 Serious Games and In-Game Advertising ... 9
1.4 Problem Statement ... 11
1.5 Research Questions ... 12
1.6 Research Methodology ... 13
1.7 Organization of this Dissertation ... 15
2. STATE OF THE ART ... 17
2.1 Interactive 3D Virtual Environments ... 17
2.1.1 Developing Interactive 3D User Interfaces and 3DVEs ... 17
2.1.2 Reference Models for Interactive 3DVEs ... 18
2.1.3 View Management and Spatial Configuration ... 20
2.2 Abstract Information Visualization Techniques ... 22
2.2.1 Abstract Information ... 22
2.2.2 Layout Space of Abstract Info. Visualization Techniques ... 25
2.2.3 Comparison of Abstract Info. Visualization Techniques ... 32
2.2.4 Taxonomies Related to Abstract Info. Visualization ... 37
2.2.5 Information Rich Virtual Environments ... 40
2.3 Evaluation of Interactive 3D Virtual Environments ... 41
2.3.1 Navigation Problems in Interactive 3DVEs ... 41
2.3.2 Metrics for the Evaluation of Interactive 3DVEs ... 42
2.3.3 Evaluation Methods for Interactive 3DVEs ... 47
2.3.4 Design Guidelines for the Dev. of Interactive DVEs ... 59
2.3.5 Specific Characteristics of Interactive 3DVEs Evaluation ... 60
2.4 Summary ... 61
3. AN INTERACTIVE 3DVE FOR USABILITY TESTING ... 63
3.1 Conceptual Model ... 63
3.1.1 Reference 3D Scene ... 63
3.1.2 Type of Abstract Information ... 64
3.1.3 User Context and Target Object Context ... 64
3.1.4 Type of Tasks ... 65
3.1.5 Type of Abstract Information Visualization Technique ... 69
3.2 Methodological Approach ... 70
3.2.1 Selection of a Reference 3D Scene ... 71
3.2.2 Selection of Related Abstract Information ... 71
3.2.3 Selection of User Contexts and Target Object Contexts ... 72
3.2.4 Definition of the Type of Tasks ... 77
3.2.5 Implementation of Visualization Techniques ... 78
3.3 Constrained Navigation Approach ... 84
3.3.1 Controlling the Navigation Skill Variable ... 84
3.3.2 Implementation of Constrained Navigation Interactors ... 85
3.3.3 Using a Gamepad as Input Device ... 86
3.4 Summary ... 88
4. USABILITY TESTING METHODOLOGY ... 91
4.1 Interactive 3DVE Prototyping Toolkit ... 92
4.1.1 Testing Environment ... 92
4.1.2 Technological Setup ... 93
4.2 Selecting the Participants ... 93
4.2.1 Target Population and Number of Participants ... 93
4.2.2 Profile and Selection Protocol ... 93
4.3 Tasks ... 94
4.3.1 Task List ... 94
4.3.2 Training Tasks and Formal Tasks ... 95
4.4 Experimental Design ... 95
4.4.1 Within vs. Between Subject Design ... 95
4.4.2 Dependant and Independent Variables ... 97
4.5 Method and Procedure ... 98
4.5.1 Participant General Instructions and Task Instructions ... 98
4.5.2 Procedure ... 99
4.6 Usability Metrics and Measurements ... 101
4.6.1 Metrics and Measurements: Effectiveness and Efficiency . 101 4.6.2 Metrics and Measurements for Satisfaction ... 101
4.7 Data Collection, Analysis and Presentation ... 102
4.7.1 Data Collection and Anaysis ... 102
4.7.2 Data Presentation ... 102
4.8 Summary ... 103
5. CASE STUDIES: EXPERIMENTATIONS & RESULTS ... 105
5.1 Applying the Methodological Approach ... 105
5.1.1 Reference 3D Scene ... 105
5.1.2 Related Abstract Information ... 106
5.1.3 User Contexts and Target Object Contexts ... 107
5.1.4 Type of Tasks ... 112
5.1.5 Abstract Information Visualization Techniques ... 113
5.2 Applying the Usability Testing Methodology ... 115
5.2.1 Setup ... 115
5.2.2 Participants ... 116
5.2.3 Tasks ... 117
5.2.4 Experimental Design ... 118
5.2.5 Method and Procedure ... 119
5.2.6 Measurements and Data Collection ... 120
5.3 Experiment 1: Effect of Constrained Navigation Approach ... 121
5.3.1 Objective: Impact of Constrained Navigation on Presence 121 5.3.2 Results and Descriptive Statistics ... 122
5.3.3 Discussions ... 129
5.4 Experiment 2: Comparison of Two Visualization Techniques . 131 5.4.1 Objective: Comparison of WS-KB and VS-KB Techniques 131 5.4.2 Results and Descriptive Statistics ... 132
5.4.3 Discussions ... 140
5.5 Summary ... 141
6. CONCLUSION AND PERSPECTIVES ... 143
6.1 Summary ... 143
6.2 Contributions ... 144
6.3 Limitations ... 145
6.4 Practical Impact: Towards a Decision Support KB ... 147
6.5 Future Work ... 148
REFERENCES ... 151
APPENDIX ... 169
A. Pre-questionnaire for selecting participants ... 169
B. Consent Form ... 172
C. Igroup Presence Questionnaire ... 173
D. Screenshots Illustrating Contexts and Techniques ... 176
Abstract
Abstract information refers to information that a user can’t directly obtain just by visualizing the spatial information of objects in a 3D virtual envi- ronment (3DVE). Many interactive visualization techniques have been created to augment 3DVEs with abstract information. Developers of in- teractive 3DVEs who want to augment their 3D models with abstract in- formation have to determine which visualization technique has the highest level of usability for their needs according to different tasks and user con- texts. Therefore, a usability evaluation toolkit is needed to help them compare the usability of different abstract information visualization tech- niques according to specific design needs and contexts.
The first part of this thesis reviews the state of the art on interactive 3DVEs development, abstract information visualization techniques and the evaluation of interactive 3DVEs. The layout space of abstract infor- mation visualization techniques, according to a preliminary comparison, is proposed. Taxonomies related to abstract information visualization are analyzed. Specific evaluation considerations related to navigation prob- lems, evaluation metrics and methods and design guidelines for the de- velopment of interactive 3DVEs are presented.
Then, in the second part, this thesis presents a conceptual model, reusable toolkit and usability evaluation methodology for comparing the usability of different abstract information visualization techniques. The conceptual model is composed of five elements: reference 3D scene, type of abstract information, user and target object contexts, type of tasks and type of ab- stract information visualization technique. We characterize the design space of any abstract information visualization techniques in interactive 3DVEs by using five layout dimensions: space, shape, location, interac- tion and scale. In order to control the navigation skill variable, the design of a constrained navigation approach for teleporting the user from one user context to another is proposed.
Finally, the third part of this thesis presents case studies for validating the proposed conceptual model, the toolkit and the usability evaluation me- thodology by performing usability testing experiments and analyzing their results. A first experiment has been designed to evaluate and validate the constrained navigation approach for controlling the navigation skill varia- ble of the users. The experimental results provide clear evidence that the sense of presence, which is a user satisfaction factor in interactive 3DVEs, is not significantly affected by the constrained navigation ap- proach during the usability testing session. A second experiment has been
designed to validate the conceptual model, the reusable toolkit and the usability testing methodology. This was done trough evaluating and com- paring the usability of two techniques for displaying virtual panels. The conceptual model, the reusable toolkit and the usability evaluation me- thodology have been validated by the experimental results.
The contributions of this thesis are a reusable conceptual model, toolkit and usability evaluation methodology for measuring and comparing the usability of abstract information visualization techniques in interactive 3DVEs.
Keywords: Human Computer Interaction, Interactive 3D Virtual Envi- ronment, Abstract Information Visualization, Usability Evaluation Me- thodology, Presence
Résumé
L’information abstraite fait référence à l’information que l’on ne peut pas directement obtenir juste en visualisant les informations spatiales des ob- jets dans un environnement virtuel 3D (EV3D). Il existe plusieurs techni- ques de visualisation de l’information abstraite dans les EV3D interactifs.
Afin de pouvoir augmenter leurs modèles 3D avec des informations abs- traites, les développeurs d’EV3D interactifs doivent pouvoir identifier quelle technique de visualisation possède le niveau d’utilisabilité le plus élevé en fonction des différentes tâches et contextes utilisateur. Par conséquent, un outil est nécessaire pour comparer l’utilisabilité de diffé- rentes techniques de visualisation de l’information abstraite en fonction des besoins de conception et des contextes.
Dans une première partie, cette thèse propose un état de l’art sur le déve- loppement des EV3D interactifs, les techniques de visualisation d’information abstraites et l’évaluation des EV3D interactifs. L’espace d’affichage pour classifier les techniques de visualisation d’information abstraites, selon une comparaison préliminaire, est proposé. Des taxono- mies relatives à la visualisation d’informations abstraites sont analysées.
Des aspects spécifiques relatifs aux problèmes de navigation, aux métri- ques et méthodes d’évaluation et aux heuristiques de développement des EV3D sont présentés.
Puis, dans une deuxième partie, cette thèse présente un modèle concep- tuel, un outil et une méthodologie d’évaluation réutilisable pour comparer l’utilisabilité des différentes techniques de visualisation de l’information abstraite. Le modèle conceptuel est composé de cinq éléments : une scène 3D de référence, type d’information abstraite, contextes de utilisateur et de l’objet cible, type de tâche et technique de visualisation d’information abstraite. L'espace de conception des techniques de visualisation d’information abstraites est caractérisé selon cinq dimensions: espace, forme, emplacement, interaction et échelle. Une approche de navigation contrainte est présentée afin de pouvoir contrôler la variable relative à l’habileté de navigation.
Enfin, dans une troisième partie, cette thèse présente des études de cas pour la mise en ouvre et la validation de l’approche conceptuelle, de l’outil et de la méthodologie d’évaluation réutilisable en réalisant des tests d’utilisabilité et en analysant leurs résultats. Une première expérience a été conduite pour évaluer et valider l’approche de navigation contrainte pour contrôler la variable relative à l’habilité de navigation des utilisa- teurs. Les résultats permettent de confirmer que la sensation de présence,
qui est un facteur de satisfaction majeur dans les EV3D interactifs, n’est pas significativement influencée par l’approche de navigation contrainte durant les tests d’utilisabilité. Une seconde expérience a été conduite afin de valider le modèle conceptuel, l’outil et la méthodologie d’évaluation réutilisable. Pour ce faire, l’utilisabilité de deux techniques de visualisa- tion pour des panneaux virtuels a été évaluée et comparée. Le modèle conceptuel, l’outil et la méthodologie d’évaluation réutilisable ont étés validées par les résultats des expériences.
Les contributions de cette thèse sont un modèle conceptuel, un outil et une méthodologie d’évaluation réutilisables pour mesurer et comparer l’utilisabilité des techniques de visualisation de l’information abstraite dans les EV3D interactifs.
Keywords: Interaction Homme Machine, Environnement Virtuel 3D In- teractif, Technique de Visualisation d’Information Abstraite, Méthodolo- gie pour les Tests d’Utilisabilité, Présence
Acknowledgments
First and foremost, I’d like to thank my devoted research supervisors:
Prof. Gilles Falquet and Prof. Claudine Métral.
My interest in human computer interaction research, in general, and usa- bility evaluation and testing, in particular, started with my participation in a post-graduate course, given by Professor Gilles Falquet, entitled: “In- formation System’s Interfaces”. I gradually got involved in an academic atmosphere where I learned the salient feature of interdisciplinary re- search in information systems and human computer interaction.
Being a graduate of the Swiss Federal Institute of Technology (EPFL) in applied mathematics, I appreciated to enter the domain of academic uni- versity research. In this regard, Prof. Gilles Falquet, opened the door of his Information System Interfaces (ISI) Lab and guided me in the explora- tion of the topics related to human computer interactions.
I had the great opportunity to enter the domain of 3D user interfaces by working on a project co-supervised by Prof. Didier Buchs and Prof. Gilles Falquet. I also enjoyed participating in teaching and learning activities of the ISI Lab and assisting him in guiding of bachelor and master degrees students who took projects with us.
Without Prof. Gilles Falquet’s dedicated guidance and support this re- search could never be accomplished.
I am thankful to Prof. Claudine Métral who offered me the opportunity to participate in the research activities and projects that she was involved.
More specially, in assisting her with teaching and learning activities by providing advanced training for using Google SketchUp and in the con- text of projects related to semantically enriched 3D city models projects.
By doing so, she has given me the chance to clarify my research objec- tives and enhance my knowledge and understanding of domain specific 3D applications. Her advices and recommendations have been essential towards completing this research.
I would also like to thank all the members of my jury for their valuable comments and suggestions.
Prof. Dimitri Konstantas, President of the jury, provided me with signifi- cant advices and precious recommendations for the advancement process related to my Ph.D. completion.
The references and resources that Dr. Laurent Moccozet shared with me have been very helpful in completing the state of the art.
Without Dr. Patrick Roth’s support I would have had a very hard time designing and running up my usability tests. I thank him for sharing rele- vant usability specific textbooks and practical research resources with me.
Prof. Ahmed Sheffah valuable comments, constructive remarks and chal- lenging questions about the usability testing methodology were very help- ful in improving my Ph.D. dissertation report. I specially thank him for suggesting me to follow the structure of the Common Industry Format (CIF) for usability test reports. I have been honored to receive his glorious comment about my thesis:
“The thesis contributions are novel and the research done is timely accu- rate and original. Through the thesis, the candidate demonstrated also his expertise in the area of HCI and his capacity in conducting a challenging research.”
Special thanks are also due to my colleagues Alain, Nizar, Jean-Pierre, Jacques, Mathieu, Claire-Lise, Mustapha, Hélène, Camille and many oth- er members of the CUI (Centre Universitaire d’Informatique).
Many thanks to Marie-France, Elie, Dorothée, Amélia, Daniel and Nico- las. They have always been a great support in case of need at the CUI.
I would also like to thank all the students from the University of Geneva who have participated in the usability tests.
Finally, I would like to say “thank you” and express all my gratitude to my dedicated parents, Dr. Farideh Mashayekh (Bazargan) and Prof. Ab- bas Bazargan, who are lifelong learners in their own filed of research.
Their continuous affection and support helped me overcome all the diffi- culties and obstacles towards achieving my research objectives.
List of Figures
Figure 1: VCF-3D: spatial information before user click ... 5
Figure 2: VCF-3D: spatial and related abstract information ... 5
Figure 3: 3DVEP: state before user click on a target building ... 6
Figure 4: 3DVEP: state after user click on a target building ... 6
Figure 5: Fanevenues interactive 3D seating and pricing ... 7
Figure 6: 9/11 Memorial informational balloons ... 7
Figure 7: 2D Web browsers as objects inside an interactive 3DVE ... 7
Figure 8: 3D-Driving interactive driving training ... 8
Figure 9: RapidLearning interactive 3DVE training application ... 8
Figure 10: Text message displayed as overlay ... 9
Figure 11: Text message displayed in the right toolbar ... 10
Figure 12: Advertisement panel in Second Life ... 10
Figure 13: Reference model for virtual reality (Fuchs et al., 1999) ... 18
Figure 14: VEDS components overview (Eastgate, 2001) ... 19
Figure 15: Spatial configurations of 3DVEs (Tyndiuk, 2005) ... 22
Figure 16: Data State Model (Chi, 2000) ... 24
Figure 17: World-fixed and display-fixed windows (Feiner et al., 1993) 25 Figure 18: 2D windows display states (Stoev et al., 2002) ... 26
Figure 19: Object space technique [four different views] (Aubry, 2007) 26 Figure 20: World space technique (Bazargan et al., 2009) ... 27
Figure 21: User space technique (Bowman et al., 2003) ... 27
Figure 22: Display space technique used to identify buildings ... 28
Figure 23: Viewport space technique used to identify buildings ... 28
Figure 24: 3D city model without any abstract information ... 29
Figure 25: Postcard image displayed with the object space technique .... 29
Figure 26: Short text displayed with the object space technique ... 30
Figure 27: Postcard image displayed with the world space technique ... 30
Figure 28: Short text displayed with world space technique ... 30
Figure 29: Short text displayed with user space technique ... 31
Figure 30: Postcard image displayed with user space technique ... 31
Figure 31: Postcard image displayed with viewport space technique ... 31
Figure 32: Postcard image displayed with display space technique ... 31
Figure 33: Illustrative Shadows technique (Ritter et al., 2003) ... 33
Figure 34: Virtual PDA technique (Bazargan and Falquet, 2009) ... 34
Figure 35: Croquet 3D Windows and buttons (Kadobayashi et al., 2006) ... 34
Figure 36: Croquet 3D Interactors (Kadobayashi et al., 2006) ... 34
Figure 37: Interactive 2D Media Layer technique (Bazargan and Falquet, 2009) ... 35
Figure 38: Sidebar technique (Bazargan and Falquet, 2009) ... 35
Figure 39: 3D Labels technique (Maass and Döllner, 2008) ... 36
Figure 40: Text display techniques (Chen et al., 2004) ... 37
Figure 41: Description of the ring menu technique using the taxonomy . 38 Figure 42: Classification of occlusion management techniques (Elmqist and Tsigas, 2007) ... 39
Figure 43: Single Usability Metric (SUM) model (Sauro and Kindlund, 2005b) ... 44
Figure 44: Classification of 3DVEs usability evaluation methods (Bowman et al., 2002) ... 48
Figure 45: Testbed evaluation (Bowman et al., 1999) ... 49
Figure 46: Sequential evaluation (Bowman et al., 1999) ... 50
Figure 47: Classification of publications by evaluation method (Dünser et al., 2008) ... 52
Figure 48: Guideline for the property identifiable object (Kaur et al., 1999) ... 54
Figure 49: 3DVE usability criteria assed by MAUVE (Stanney et al., 2003) ... 57
Figure 50: Overview of the global architecture of 3DUI-EF (Domingues et al., 2010) ... 58
Figure 51: ConcurTaskTrees (CTT) task types (Paternò et Lecerof, 1997) ... 67
Figure 52: Task model for goal directed exploration and navigation ... 68
Figure 53: Generic task model for user interaction ... 69
Figure 54: Five layout dimensions of abstract information visualization techniques ... 70
Figure 55: Importing a 3D model from the 3D Warehouse into SketchUp ... 71
Figure 56: Sample page of the 3D-Llanes project ... 72
Figure 57: Sample text page (1D data type) ... 72
Figure 58: Sample virtual panel ... 72
Figure 59: Sample HTML file ... 72
Figure 60: Top view of the 3D scene ... 73
Figure 61: Visual markers positioned inside the 3D scene ... 73
Figure 62: Initial orientation and viewpoint in the 1st user context ... 74
Figure 63: Initial orientation and viewpoint in the 2nd user context ... 74
Figure 64: Initial orientation and viewpoint in the 3rd user context ... 75
Figure 65: Initial orientation and viewpoint in the 4th user context ... 75
Figure 66: Initial orientation and viewpoint in the 5th user context ... 76
Figure 67: Target object example: newspaper kiosk as a component ... 76
Figure 68: Goal directed exploration generic task ... 77
Figure 69: Scene 4 saved with “Magazine-racks” layer set as invisible (unchecked right box) ... 79 Figure 70: Searching and importing the “Magazine-racks” component inside the model ... 79 Figure 71: Scene 4-bis saved with “Magazine-racks” active layer set as visible ... 79 Figure 72: Customizing the kiosk’s DCs attributes with the onClick and GoToScene functions ... 80 Figure 73: Clicking on the kiosk results in displaying the stand rack with some magazine images ... 80 Figure 74: Characterization of the out_of_the_box-KB technique using the five layout dimensions ... 81 Figure 75: WS-VP-KB abstract information visualisation technique ... 82 Figure 76: Characterization of the WS-VP-KB technique ... 82 Figure 77: Augmenting the 3DVE with a virtual panel using the VS- Virtual_Panel-KB technique ... 83 Figure 78: Characterization of the VS-VP-KB technique ... 83 Figure 79: Constrained navigation interactors (Bazargan et al., 2010) .... 84 Figure 80: Positioning the constrained navigation interactors DCs in the 3D scene (Bazargan, 2010) ... 85 Figure 81: Top view of the constrained navigation interactors DCs in the 3D scene (Bazargan, 2010) ... 86 Figure 82: Saitek dual action USB gamepad ... 87 Figure 83: Usability testing environment and setup ... 92 Figure 84: Karnak temple 3D model with modifications ... 105 Figure 85: Text and images concerning Obelisk Unique ... 106 Figure 86: Virtual panel about Obelisk Unique ... 106 Figure 87: Initial position and orientation in the 1st user context ... 107 Figure 88: Initial viewpoint of the user in the 1st user context ... 108 Figure 89: Initial position and orientation in the 2nd user context ... 108 Figure 90: Initial viewpoint of the user in the 2nd user context ... 109 Figure 91: Initial position and orientation in the 3rd user context ... 109 Figure 92: Initial viewpoint of the user in the 3rd user context ... 110 Figure 93: Initial position and orientation in the 4th user context ... 110 Figure 94: Initial viewpoint of the user in the 4th user context ... 111 Figure 95: Initial position and orientation in the 5th user context ... 111 Figure 96: Initial viewpoint of the user in the 5th user context ... 112 Figure 97: Goal directed exploration generic task ... 112 Figure 98: VS-VP-KB reusable DCs ... 114 Figure 99 : WS-VP-KB reusable DCs ... 114
Figure 100: Using the WS-VP-KB technique DCs to augment the 3DVE ... 114 Figure 101: Using the VS-VP-KB technique DCs to augment the 3DVE ... 114 Figure 102: General setting of the usability testing room ... 115 Figure 103: Monitor and participant during the usability testing session ... 116 Figure 104: Initial positions and field of views for all the five user contexts ... 121 Figure 105: Overall responses to the IPQ (Spatial Presence) [n=14] .... 122 Figure 106: Individual responses to the IPQ (Spatial Presence - General Question) [n=14] ... 123 Figure 107: Individual responses to the IPQ (Spatial Presence) [n=14] 124 Figure 108: Overall responses to the IPQ (Involvement) [n=14]... 125 Figure 109: Individual responses to the IPQ (Involvement) ... 126 Figure 110: Overall responses to the IPQ (Experienced Realism) [n=14]
... 127 Figure 111: Individual responses to the IPQ (Experienced Realism) .... 128 Figure 112: Initial positions and orientation for all the five user contexts ... 131 Figure 113: Effect of visualization technique on task completion time (sec) for Task 1 to 5 (Mean time) ... 133 Figure 114: Effect of visualization technique on task completion time (sec) for Task 1 to 5 (Mean time) ... 133 Figure 115: Effect of visualization technique on task completion time (sec) for Task 1 to 5 (Median time) ... 134 Figure 116: Effect of visualization technique on task completion time (sec) for Task 1 to 5 (Geometrical mean time) ... 134 Figure 117: Effect of visualization technique on task completion time (sec) for Task 1 ... 135 Figure 118: Effect of visualization technique on task completion time (sec) for Task 2 ... 136 Figure 119: Effect of visualization technique on task completion time (sec) for Task 3 ... 137 Figure 120: Effect of visualization technique on task completion time (sec) for Task 4 ... 138 Figure 121: Effect of visualization technique on task completion time (sec) for Task 5 ... 139 Figure 122: Speed-accuracy tradeoff curve (Bowman et al., 2008) ... 141 Figure 123: Displaying the virtual panel with the viewport space technique in the 1st user context ... 176
Figure 124: Displaying the virtual panel with the world space technique in the 1st user context ... 176 Figure 125: Zoom-in on the virtual panel with the world space technique in the 1st user context ... 176 Figure 126: Displaying the virtual panel with the viewport space technique in the 2nd user context ... 177 Figure 127: Displaying the virtual panel with the world space technique in the 2nd user context ... 177 Figure 128: Zoom-in on the virtual panel with the world space technique in the 2nd user context ... 177 Figure 129: Displaying the virtual panel with the viewport space technique in the 3rd user context ... 177 Figure 130: Displaying the virtual panel with the world space technique in the 3rd user context ... 178 Figure 131: Zoom-in on the virtual panel with the world space technique in the 3rd user context ... 178 Figure 132: Displaying the virtual panel with the viewport space technique in the 4th user context ... 178 Figure 133: Displaying the virtual panel with the world space technique in the 4th user context ... 178 Figure 134: Zoom-in on the virtual panel with the world space technique in the 4th user context ... 179 Figure 135: Displaying the virtual panel with the viewport space technique in the 5th user context ... 179 Figure 136: Displaying the virtual panel with the world space technique in the 5th user context ... 179 Figure 137: Zoom-in on the virtual panel with the world space technique in the 5th user context ... 179
List of Tables
Table 1: Comparison of selected abstract information visualization techniques (Bazargan and Falquet, 2009) ... 33 Table 2: IRVE design matrix: abstract information display (Polys, 2006) ... 40 Table 3: Objective and subjective measures from measuring usability (Hornbaek, 2006) ... 43 Table 4: IPQ subscales and related criteria (I-Group, 2008) ... 46 Table 5: Usability issues of 3DVE users (Gabbard, 1997) ... 53 Table 6: Usability issues of 3DVE users tasks (Gabbard, 1997) ... 53 Table 7: Usability issues of the user presentation (Gabbard, 1997) ... 53 Table 8: Counterbalancing of task order for tasks and techniques ... 97 Table 9: Usability DataLogger tool: list of worksheets ... 102 Table 10: Participants profile and main characteristics ... 117 Table 11: Counterbalancing of task order for fourteen participants, five tasks and two techniques ... 119 Table 12: Raw data on responses to the IPQ (Spatial Presence Questions) ... 122 Table 13: Raw data on responses to the IPQ (Involvement Questions) . 125 Table 14: Raw data on responses to the IPQ (Experienced Realism) .... 127 Table 15: Task completion time (sec) for each task with each technique ... 132 Table 16: Descriptive statistics for task completion time (sec) for each task with each technique ... 132 Table 17: Statistics for evaluating the effect of visualization technique on task completion time (sec) for Task 1 ... 135 Table 18: Statistics for evaluating the effect of visualization technique on task completion time (sec) for Task 2 ... 136 Table 19: Statistics for evaluating the effect of visualization technique on task completion time (sec) for Task 3 ... 137 Table 20: Statistics for evaluating the effect of visualization technique on task completion time (sec) for Task 4 ... 138 Table 21: Statistics for evaluating the effect of visualization technique on task completion time (sec) for Task 5 ... 139 Table 22: Elements for the construction of a decision support knowledge base for the selection of abstract information visualization techniques . 147
1. INTRODUCTION 1.1 Motivation
An interactive virtual environment (3DVE) is a computer-generated 3D world in which a user can interact with computer-generated objects. Spa- tial data for building 3DVEs applications exist in many activity domains such as geosciences, medicine and neuroscience, manufacturing indus- tries, industrial design, automotive engineering and transport, architec- ture, urbanism, landscape design, archeology and cultural heritage.
In the majority of these applications, symbolic or abstract information can be added to 3D spatial data to enhance user understanding in order to con- struct meaning from 3D spatial data and abstract information. Abstract information refers to information that a user can’t directly obtain just by visualizing the spatial information of objects in a 3DVE. Abstract infor- mation can be considered as attribute centric or semantic information re- lated to objects that are present in an interactive 3DVE
For instance, in archeology and cultural heritage, object semantics is typi- cally just as important as the actual geometry for some specific tasks.
Embedding abstract information related to, namely, the original source, date, design and existing knowledge on associated objects can contribute both to the effectiveness and efficient work of a cultural heritage profes- sional and overall user experience of an interactive 3DVE visitor.
There are many ways in which abstract information can be added to 3D scenes in order to help the user perform specific tasks within the 3DVEs applications. Once a mode is selected by a 3DVE author or designer, a fundamental question is how to provide the user with tools to interact with the 3DVE and its objects. This is usually done via a 3DVE authoring development tool which is an application that supports the construction of a 3DVE and the definition of objects in that environment.
These authoring tools do not provide 3DVEs designers with relevant solu- tion to select a specific mode for adding abstract information to 3D scenes. The reason for this lack of solution is the large variety of repre- sentation schemas and data formats for 3D data and the necessity to make the semantic descriptions independent from the geometric representation of the 3D models.
In a study of scientific and technological challenges of virtual reality, Durlach and Mavor (1995) point out that there has been a tendency to
ignore or minimize the evaluation of 3DVEs applications. They indicate the need for expert guidance and new toolkits for 3DVEs. Fifteen years later, reflecting on authoring and the design and implementation issues of interactive 3DVEs, Wingrave and LaViola (2010) explain why in contrast to the great advances in 3D data acquisition, digitization, processing and rendering power available for 3DVEs, little has changed regarding their design, implementation and usability evaluation.
Although great technological progress has been achieved, the involve- ment of real human end users in the evaluation of 3DVEs applications is still limited compared with the efforts to include virtual humans (Arnold et al., 2008) in, for instance, complex architectural models, reacting in real-time.
Understanding the usability of 3DVEs is therefore essential for the im- provement of present and future interfaces which will increasingly inte- grate 3D data with dynamic objects and contents that the users will be able to interact with.
1.2 Challenges
Authors and designers of interactive 3DVEs have to find the best ways to integrate additional information into 3D scenes while ensuring end user satisfaction and usability. The designing process thus requires a clear identification and understanding of what different alternatives are and how a specific choice might improve an application for a given task.
In order to improve interactive 3DVEs displaying abstract information, designers must be able to measure and compare the impact of different techniques. This process is quite challenging as it requires multiple im- plementations, prototyping and testing with real end users in order to col- lect data and find out which technique is most relevant for a given setting.
Although, the field of usability engineering and testing in human comput- er interaction and more specifically 2D user interface design are now well documented with a rich body of academic literature including solid theo- retical frameworks and proven experimental results, much has to be done to adapt and apply such methodologies in the design of 3DVE.
The limitations of current usability engineering practices show up when a designer needs to make informed decisions about issues which are 3D specific such as the impact of input device on 3D navigation and interac- tion controls.
The game design industry has done extensive research and experimenta- tions to study the impact of input device and controller-related issues in designing video games. But, putting apart few exception, the results of such studies have not always been shared with the academic community.
As a consequence, designers who are willing to create new interaction techniques and devices have to find their own way for comparing the re- sult of what they’ve created with existing techniques.
To make this happen, there is a need for a kind of step by step ben- chmarking procedure and toolkit which can be used by any designer. The results of usability evaluation performed with the toolkit can then be shared with other researchers and reused. A fundamental obstacle to de- signing such usability evaluation toolkit for interactive 3DVE is the inte- roperability with existing 3D modeling and authoring softwares and ease of use. These softwares can’t be used quickly and intuitively without learning and practice.
For example, 3D modeling professionals work with different softwares which don’t provide all 3D data formats for exporting and importing files.
Besides, adding interactivity to objects within interactive 3DVEs is also done via different dedicated authoring softwares. From an end user pers- pective, it is essential to be able to take into consideration the variety of development tools for building interactive 3DVEs and keep the toolkit easy to learn and use.
To be successful and to assist interactive 3DVE designers and developers in comparing the usability of different abstract information visualization techniques in different settings, we must first identify and then overcome many constraints and challenges.
We are fully aware that it is doubtable to overcome these problems and challenges all at once and build a comprehensive usability evaluation toolkit which would fit each and every interactive 3DVE designers need.
Yet, these important challenges are worth the scientific research efforts.
1.3 Application Domains
We present five application domains in which visualizing abstract infor- mation in domain specific 3DVEs is necessary in order to motivate our problem statement.
1.3.1 Cultural Heritage and Tourism
Visitors are attracted to travel and discover many cultural heritage sites trough the world. The United Nations Educational, Scientific and Cultural Organization (UNESCO) seeks to encourage the identification, protection and preservation of cultural and natural heritage around the world consi- dered to be of outstanding value to humanity. The World Heritage List includes 704 cultural, 180 natural and 27 mixed properties in 151 States Parties (UNESCO-WHC, 2010). Many are unable to travel to these sites for personal reasons such as financial costs.
Many visualization strategies are available for the inclusion of 2D and 3D digital technologies in cultural heritage applications (Foni et al., 2010).
While extensive efforts have been made to document and present cultural heritage sites to online visitors via dedicated websites such as (1001WONDERS, 2010), rich interactive 3DVE applications are still very limited.
In addition, once 3D models of selected cultural heritage sites are gener- ated, the related websites mostly provide links to readymade videos and animations. Therefore, the online visitor can’t take an active role by navi- gating, freely exploring the 3D model and accessing abstract information about specific objects.
For example, the geometrical 3D reconstruction models of sites such as Persepolis (PERSEPOLIS-3D, 2010) or Bam (BAM3DCG, 2010) should be enhanced with abstract information, related to different architectural elements, in order to construct online interactive 3DVEs.
The Virtual Forbidden City (VFC-3D, 2008) is an online interactive 3DVE where visitors can virtually experience the Forbidden City in Bei- jing. To help online visitors to gain a deeper understanding of the objects that they encounter during their explorations, most impressive artifacts and buildings have additional textual information, photos and multimedia content available to provide a deeper understanding of their purpose and construction. Interactive virtual guided tours lead the visitors to places that help explore important themes about the design and use of the For- bidden City (Figures 1, 2).
Designers of the VFC-3D project have been confronted with the chal- lenge of integrating text, images and video content with 3D models to build an interactive 3DVE (VFC-3D, 2008).
Figure 1: VCF-3D: spatial informa- tion before user click
Figure 2: VCF-3D: spatial and related abstract information
1.3.2 Public Participation in Sustainable Urban Planning
Sustainable urban planning action consists of a process of complex se- quential stages which start with conception and ends with implementa- tion. It is important to mention that both the population’s and administra- tion involvement and participation, as well as of other interested parties, is a decisive factor for the success of this process.
According to a recent study by Amadao and his colleagues (2010), the feedbacks and constructive comments received by the administration from the population are essential during specific process such as road design, buildings density settings, public spaces and facilities location.
Consensus needs to be obtained among a broad group to exert strong in- fluence. Tools are therefore needed to share concerns, examine alterna- tives, and propose solutions through collaborative citizen based examina- tion and discussion.
Therefore the main concern should be how to ensure the dialogue be- tween the administration’s design team and the local population which do not have the same professional knowledge and background. Many people find it difficult to visualize what a development will look like from 2D plans and understand how planning decisions are made and how their comments are taken into account. Métral and her colleagues (2008, 2009) have proposed to build semantically enriched 3D city models in order to improve decision support.
In response to these problems, 3D Virtual Environmental Planning (3DVEP) tools allow people to view and make comments on planning developments in 3D within the context of an existing landscape or citys- cape (VEP, 2007). Counsell and his colleagues provide detailed explana-
tions about the need for systematic use of 3DVEPs for public participa- tion in order to influence the final decision outcomes (Counsell et al., 2006). A user evaluation of selected 3DVEP tools indicates that usability of such tools must be improved (Counsell et al., 2009). The researchers also clearly point out the need for integration of 3D data with 2D data and additional information in 3DVEP tools.
For instance, the directors of the PAV urban zone project within the Re- public and Canton of Geneva in Switzerland have launched an open con- sultation to collect views, comments and requests on the issue of existing public spaces and facilities from the inhabitants. The outcomes of this open consultation have been published in a report (BAZARURBAIN, 2010) which has been made available to the population online (PAV, 2010). For few specific public buildings, parts of the consultation out- comes could be integrated into the 3DVEP tool (SITG, 2010) which in- cludes all the spatial and identification data related to new buildings (Fig- ures 3, 4).
Figure 3: 3DVEP: state before user click on a target building
Figure 4: 3DVEP: state after user click on a target building
1.3.3 Advertising, Marketing and Commerce
In recent years, technological developments have made it possible to build interactive 3D models of objects and interactive 3DVE that can be experienced through the Web, using common, low-cost personal comput- ers (Chittaro and Ranon, 2007). Online interactive 3D marketing and product configurator development softwares, such as the ones provided by Aarkid (Aarkid, 2010), have modified the paradigm of conventional merchant / client relationship to a new level where clients can explore, customize and adapt the final product based on their personal desires.
Häubl and Figueroa (2002) have conducted experiments which show that the availability of interactive 3D product presentations instead of static images may affect some important aspects of buyer behavior, including the amount of time spent examining products and purchase likelihood.
Guo and Barnes (2007) provide the same type of analysis after analyzing why people spend real money and time to buy virtual items in virtual.
Papastamatiou et al. (2009) present a methodology for the development of interactive 3D virtual reality applications for commercial use. In addition to spatial data, such applications must display textual and graphical in- formation to document and explain some attributes of selected 3D objects.
For example, the Fanevenues (FANVENUES3D, 2010) interactive 3D seating maps and online ticketing service displays additional pricing in- formation outside the 3D scene (Figure 5). The National 9/11 Memorial and Museum interactive 3DVE (9/11-3D, 2010) displays abstract infor- mation inside informational balloons that overlay the 3D scene. This way of displaying abstract information creates occlusion problems as the in- formation bubble can’t be moved or resized by the user (Figure 6).
The interactive 3DVE of the Linnean Society of London (LINNEAN-3D, 2010) contains 2D Web browser that can display any Web page interac- tively on any surface in the 3D world (Figure 7). Improving the usability of abstract information display within such 3D applications is a crucial success factor which can increase both user experience and sales.
Figure 5: Fanevenues interactive 3D seating and pricing
Figure 6: 9/11 Memorial informa- tional balloons
Figure 7: 2D Web browsers as objects inside an interactive 3DVE
1.3.4 Training and Simulation
3D simulators are virtual recreations of equipment that allow learners to practice via specific human computer interactions and interfaces. Jackson and Batstone (2008) explain how instructional strategies and learning activities are enhanced with 3D simulations. Research has proven that interactive 3D learning improves comprehension, retention and on-the-job performance and costs less than product mockups, physical simulations, and other approaches. Bacim and his colleagues (2010) have conducted case studies for improving the structural understanding of 3D forms and structures by providing cognitive scaffolding in Web3D learning systems.
For example, Cortona3D RapidLearning (CORTONA3D, 2009) is a learning toolkit for producing digital interactive 3DVE training applica- tions using animated 3D simulations which include existing technical manuals and documents (Figure 8). The 3D Driving School (3D- DRIVING, 2009) is an interactive driving training simulator in real-time 3D which displays additional graphical and textual information inside the cockpit view (Figure 9).
Figure 8: 3D-Driving interactive driving training
Figure 9: RapidLearning interac- tive 3DVE training application Although replication of the reality works well for training scenarios, it’s not the case for educational scenarios. Many 3DVEs designers in the field of education have attempted to mimic the traditional classroom teaching / learning paradigm by recreating dedicated virtual worlds and spaces. The real added value of 3D for training and simulation will probably not be achieved in this way. Instead, the true potential of 3DVE for learning will be realized by creating relevant learning activities which engage the learner into doing actions in order to learn.
Learning in 3D is the title of a newly published book by Kapp and O'Driscoll (2010) which advocates the opportunities and advantage of learning and collaborating in interactive 3DVEs for learning. The process of achieving the desired learning objectives, in such environments, takes place at the moment when the lack of knowledge or capability of the learner intersects with the need to have that knowledge or capability to overcome a specific challenge or complete a specific task.
According to the authors: “In designing interactive 3DVE for learning, content is the king, but context is the kingdom.” Context is provided by definitions of concepts, topics, procedures and principals which should be available to the learner during his interactions with the environment. Such context can be considered as abstract information which has to be pre- sented to the learner within the 3DVE.
1.3.5 Serious Games and In-Game Advertising
A video game is a game played with a computer according to certain rules for entertainment and recreation." Zyda (2005) defines a serious games as: “a game played with a computer in accordance with specific rules that uses entertainment to further government or corporate training, educa- tion, health, public policy, and strategic communication objectives.”.
In serious games, users are engaged in 3DVEs that are interesting, informative and interactive (Konstantas et al., 2008). Based on previous research, Djaouti and his collegues (2008, 2010) have created the online Serious Game Classification (Alvarez et al., 2010) according to multiple criteria.
In a study concerning serious games dedicated to strengthening programming skills for virtual reality applications, Muratet et al. (2009) explain why usability is a critical success factor in design serious games.
For exemple, FoodForce (UN-WFP, 2010) is the first humanaterian serious video game created by the United Nations World Food Programme (Figure 10).
Figure 10: Text message displayed as overlay
CyberCIEGE (2007) is a serious game which provides cyber security training (Cone et al., 2007) and awareness tools that can support organizational security training objectives while engaging typical users in an engaging 3D security adventure (Figure 11). In a project aimed at assessing the usability and effectiveness of CyberCIEGEG, Greitzer et al.
(2007) discuss the need to improve the way textual and graphical information is presented within the game’s 3DVE.
Figure 11: Text message displayed in the right toolbar
In-game adverstising is the practice of using video games to deliver advertising. On technique consists of displaying advertising content directly within the 3D world (Figure 12). Richards (2009) indicates that most gamers like advertising in the game because it adds to the realism provided it doesn’t interfeer with the ease of use and user experience.
Figure 12: Advertisement panel in Second Life
1.4 Problem Statement
The main problem that this research intended to investigate is situated within the design phase of interactive 3DVEs conception. The problem occurs when the designer must select a visualization technique, among a set of available techniques, in order to augment 3D worlds with abstract information related to specific objects in different situations. The type of abstract information can range from a simple textual annotation to text and image in form of a hypertext or any other kind of configuration.
We presume that the abstract information to display is already available with a given visual representation and the designer of an interactive 3DVE will use it as it is without modifying it’s visual representation prior to augmenting the 3D world. Therefore, it should be noted that we do not study the underlying problem of abstract information visual representa- tion which is sometime called information visualization. Such problems include, for example, the appropriateness of information encoding and the readability of visual representations.
Evaluating information visualization for the above-mentioned perspective has it’s own challenges which has been well studied by the related com- munity and synthetically reported by Sheelagh (2008). Bowman and his colleagues (2003) has proposed the new research area of information-rich virtual environments (IRVE) as the combination of information visualiza- tion and 3D virtual environments for building integrated information spaces. An IRVE connects abstract information with a 3DVE in a way that it is possible to navigate in a 3D perceptual environment that is enc- hanted with the display of abstract information. From the perspective of IRVE, our main problem is thus to explore how different techniques of abstract information visualization for augmenting interactive 3DVE with abstract information in different situations can be evaluated.
In order to investigate the above problem, we first need to review the state of the art on interactive 3DVEs development, abstract information visua- lization techniques and the evaluation of interactive 3DVEs. Taxonomies related to abstract information visualization should be analyzed. Specific evaluation considerations related interactive 3DVEs should also be re- viewed.
The second objective of this research was to propose a conceptual model in order to support developers of interactive 3DVEs in either identifying an appropriate visualization technique, in terms of usability, for augment- ing their 3D models with abstract information or creating new techniques.
Then, in order to evaluate abstract information visualization techniques used to augment 3DVEs, the third objective was to build an interactive 3DVE prototyping toolkit. This toolkit should provide the designers of interactive 3DVEs with an infrastructure and methodology for imple- menting selected techniques for augmenting 3DVEs with abstract infor- mation.
The fourth objective was to define the usability evaluation methodology which goes along with the toolkit.
Finally, the fifth and last objective was to validate the above mentioned approaches and toolkit by doing case studies in form of experimentations for comparing the usability of two abstract information visualization techniques.
1.5 Research Questions
In the general programming approach for the development of interactive 3DVEs, the developers usually directly code and implement some ab- stract information visualization techniques without having any kind of interaction with the end user.
Understanding how users interact with 3DVEs is essential for performing usability evaluation of abstract information visualization techniques in interactive 3DVEs. In this regard, we have examined the state of the art on interactive 3DVEs, abstract information visualization techniques and the evaluation of interactive 3DVEs. Navigation in 3DVEs is obviously different from navigation in 2D user interfaces (2DUIs) as it requires dif- ferent skills and tools. The spatial configurations of interactive 3DVEs, a combination of the user’s viewpoint reference frame and movement refer- ence fame, have a great impact on navigation design. Therefore, depend- ing on the spatial configuration, our first question was:
(1) What criteria need to be considered when evaluating interactive 3DVEs with regard to navigation? More specifically, how is it possible to control the navigation skill variable when evaluating interactive 3DVEs?
One of the main differences between interactive 3DVE and 2DUIs is the ability to generate presence which is the sense of being there. As presence affects the user’s interaction experience, it therefore impacts usability evaluation. Thus, we must figure out what metrics should be used to
measure presence in interactive 3DVEs. Many well established metho- dology and authoring tools are available for building 2DUIs prototypes for usability testing. In contrast, to our knowledge, very few tools are at developer’s disposal to build interactive 3DVEs prototypes for usability testing. This is a major obstacle for developers of interactive 3DVEs who want to test and compare different abstract information visualization technique according to different elements. Hence, our second question was:
(2) What reusable conceptual model and toolkit can be defined and im- plemented to build interactive 3DVEs in order to perform usability tests according to different elements?
Designing usability studies for 2DUIs is well documented and best prac- tices are known and used by practitioners to make related measurements and analyze the results. But when it comes to applying the same metho- dology for evaluating the effect of a specific abstract information visuali- zation technique in interactive 3DVEs, some additional considerations and recommendations should be taken into account. These considerations are mainly related to specific characteristics of interactive 3DVEs. So, with respect to usability testing methodology our third question was:
(3) What kind of usability testing methodology should be used for per- forming usability tests to compare the usability of abstract information visualization techniques with the toolkit? How should the observations and measurements be carried out as part of the usability evaluation of interactive 3DVEs?
1.6 Research Methodology
We first approached our research questions by performing a comprehen- sive state of the art, with a stepwise refinement approach, that started with analyzing the state of the art on related work and ended with focused re- search that has already been accomplished. To this end, we searched and collected relevant references by keeping our three research questions in mind. The main concern was to identify theoretical and practical frame- works that could be reused and extended with regard to our research ob-
jectives. It was also important to highlight and understand what the limi- tations of the existing contributions and results are.
After completing the review of background work and the state of art, we started to develop our conceptual model, methodological approach and constrained navigation approach. One of our objectives was to enable any developer to use the conceptual model along with any interactive 3DVE development application. Therefore, we adopted an application indepen- dent description of the conceptual model. Nevertheless, we had to illu- strate and practically explain how to use the conceptual model in order to set up and perform usability tests for measuring and comparing the usabil- ity of different abstract information visualization techniques.
Therefore, we compared different applications for developing interactive 3DVEs and finally selected Google SketchUp Pro (SketchUp, 2010) software as a starting point for prototyping tool. Our choice was moti- vated by it’s ease of use and unique features for creating 3DVEs by com- bining models imported via the Google Warehouse and adding interactivi- ty to them. Therefore, we provided a guiding example on how to imple- ment the conceptual model with SketchUp. The description of the con- strained navigation approach was also done with application independent explanations and then illustrated with reusable interactors with SketchUp.
We also designed and conducted few pilot studies for selecting the input device. The results of the pilot studies and evidence form published re- sults and recommendations motivated the selection of a gamepad as input device.
We then used the Common Industry Format (CIF) (ISO/IEC 25062) in order to describe the usability testing methodology with goes along with our toolkit. The CIF guarantees a common format for describing the usa- bility test method and context of testing which can be reused by other developers, researchers and usability professionals. The CIF was also used to provide usability professionals with a standard format for evaluat- ing the technical merit of the usability testing methodology and the usa- bility of abstract information visualization techniques.
We finally conducted two cases studies in form of experimentations. The purpose of the first experiment was to validate the constrained navigation approach for controlling the navigation skill variable. The second experi- ment was designed to put the reusable conceptual model, usability testing toolkit and methodology into practice. Key contributions, limitations, practical impacts and future work were also discussed in the conclusion.
1.7 Organization of this Dissertation
Chapter 1 presents the motivations, challenges, applications domains, problem statement, research questions and research methodology.
Chapter 2 reviews the state of the art on interactive 3DVEs development, abstract information visualization techniques and the evaluation of inter- active 3DVEs. A general introduction to developing interactive 3DVEs is first given. The impact of view management and spatial configuration on the type of interactive 3DVE application is discussed.
Abstract information is defined and the layout space dimension of ab- stract information visualization techniques is discussed. A preliminary comparison of few abstract information visualization techniques is pro- vided. The layout space of abstract information visualization techniques, according to the preliminarily comparison, is proposed. Taxonomies re- lated to abstract information visualization and information rich virtual environments are presented.
Then, the evaluation of interactive 3DVEs is reviewed. Navigation prob- lems in interactive 3DVEs, metrics and methods for usability evaluation in interactive 3DVEs are presented. Design guidelines for interactive 3DVEs development are analyzed. Finally the concept of usability eval- uation is extended to interactive 3DVEs by taking into consideration spe- cific issues such as navigation problems.
Chapter 3 focuses on building an interactive 3DVE prototyping toolkit for usability testing. In order to evaluate the usability of abstract informa- tion visualization techniques, we have first developed a conceptual model composed of five elements: a reference 3D scene, type of abstract infor- mation, user contexts and target object contexts, type of tasks and type of abstract information visualization technique. The conceptual model is reusable as it is independent from any specific technological and software solution.
In the second part of this chapter we present the methodological approach which goes along with the conceptual model by using SketchUp. Finally, we define and implement a constrained navigation approach for control- ling the navigation skill variable. In addition, we also justify the selection of a gamepad as input device for controlling the navigation, selection and interaction.
Chapter 4 describes the specific usability testing methodology for mea- suring and comparing the usability of different abstract information visua-
