Sketch-Based Interfaces versus WIMP Interfaces in Three Dimensional

2009 Latin American Web Congress

A comparison study: sketch-based interface versus WIMP interfaces in three-dimensional modeling tasks Tiago Lemos de Araujo Machado, Alex Sandro Gomes, Marcelo Walter Centro de Informática – CIn Universidade Federal de Pernambuco – UFPE Recife, Brazil {tlam, asg, marcelow}@cin.ufpe.br applying sketch ideas in new applications. In spite of all the research activity, there has been no detailed study on how sketch-based ideas compare to traditional interaction. In this work, we investigate how sketch-based modeling interface compares with traditional WIMP interface for geometric modeling tasks. We used three systems to evaluate the techniques: Teddy [10] for its large repercussion in the academic field and commercial success, Maya [1] and 3DS Max [19] two of the most well-known systems for content production in 3D. We used a task analysis methodology to collect quantitative and qualitative data related to the users interaction with the two styles (in the WIMP style the users could choose between Maya or 3DS Max, based on their experience with these products). This paper is organized as follows: the related works are presented in Section 2. Our methodology is presented in Section 3. The data analysis and results are presented and discussed in Section 4, and the conclusions with appointments for future work are presented in Section 5.

Abstract Sketch-Based Interfaces are becoming a popular interaction style for many applications. The interaction style tries to recreate the experience of sketching that is similar to real paper and pencil drawings. They are being used to accomplish tasks related to geometric modeling, animation, architecture, design, music, and learning, among others. In this work we evaluate and compare two interaction approaches, Sketch and WIMP, in tasks for modeling 3D objects. We used two distinct tools: Teddy – a sketch based modeling software, and the more traditional WIMP modeling tools Maya & 3DS Max. We used quantitative and qualitative methods to identify benefits from both techniques from the users’ perspective. These data will be turned into requirements for a future prototype based on the usability gains of a combination between the two approaches in study. Key Words: interaction styles, user studies, software evaluate.

I. INTRODUCTION The Sketch-Based Interface technique has been known in the Computer Science field since the beginnings of the Computer Graphics and Human-Computer Interaction fields. In 1963, Ivan Sutherland developed Sketch Pad, one of the most influential works in Computer Science in the last 50 years. In Sketch Pad, the user could interact with a light pen, drawing geometric figures directly on a vector display [11]. Further advances in software and hardware research since then, have developed more complex Sketch-Based Systems, making them available and accessible to domestic users, according to predictions in Sutherland’s work. Since Sutherland’s original work, it took sometime for the research community to realize the potential of SketchBased approaches, and it was not until the 1990s that this subject attracted attention again, for instance in the Sketch work [23]. In 1999 the software Teddy [10], had a great impact on the research community, attributed by the authors to the simplicity of usage, vis-à-vis the users, even children. The acceptance of Teddy influenced the use of sketch-based techniques in a great number of systems such as computer games [22][7] and educational software like Alice [2]. Also, in the steps of Teddy, research activity in this topic increased with the publication of many papers in the last few years, mainly

978-0-7695-3856-3/09 $26.00 © 2009 IEEE DOI 10.1109/LA-WEB.2009.22

II. RELATED WORKS The main strength of Sketch-Based Interfaces is its potential to create user experiences inspired by real drawing with pencil and paper. The ideas have been used in a large range of applications, such as educational software [6], computer games [8][22], physics simulation, manipulation of mathematical symbols [13][14][15][24], prototyping of web pages [11], architecture [9], animation [19], and the creation of presentations [20]. Our work concentrates on the evaluation of systems to create 3D content. Below, we discuss previous work closely related to our project. Olsen and colleagues [17], introduced the theme through a taxonomy which classifies the sketch-based modeling systems by the way of their creation, kind of surface, edit operations and interface paradigms. The paper presents many implementation details of the software and reveals the influence of different areas in the creation of the projects, such as HCI and Cognitive Science. The improvement of the sketch-based interface is considered one of the most exciting and challenging areas. 29

avatar in three different systems: the Virtual Dressmaker, Maya and the CosmoWorlds. They evaluated variables such as the time for task completion and precision achieved by the users. The results showed that the user’s performance was better with VirtualDressmaker. They also presented points to improve the users tasks in future versions of the software. In this work [16] Kamran Sedig and colleagues presents a methodology to evaluate the impact of using geometry learning software in the learning geometry process, for children at a basic educational level. The research compared three versions of the same software built to teach geometry transformations. The goal was to find ways to design effective tools to ease the knowledgebuilding process in learning. The research revealed that the present interface style brings implications in the education by the way users interact with the tools. Another conclusion was that the HCI elements could improve the cognitive capabilities of users who use the software, although it can also affect the same capabilities. This work served also as an inspiration to us, since it advances the idea that sketch-based interfaces have to be more investigated in order to identify gains and eventual losses that the technique can offer in different contexts. Takeo Igarahashi and colleagues introduced the software Teddy [10], a gesture based system where the users draw on a white screen with strokes in 2D (input data), and the result of this interaction is a 3D model (output data). Basically, all operations are a result of a set of actions (gestures) like: creation, paint, extrusion, cut, smooth, bend, etc.

In the work presented by Seok-Hyung Bae and colleagues in [25], an interface metaphor of pencil and paper created for professional designers, called ILoveSketch. The users can draw curves freely and directly on the screen, and connect them through camera rotations. Although the results are 3D models, all objects are built through the users’ strokes, with no system interpretation. The researchers tested the prototype with the collaboration of a specialist with 12 years experience in design in the automobile industry and with toys and movies. The choice was justified by the decision to project the system for professional users with a high level of experience. The user carried out an intense evaluation of the system after a one-hour of training. The main conclusion was that the user was satisfied with the great numbers of features of the system. The software Fibermesh [3] is an evolution of Teddy. It brings even more power to the user in the task of creation of 3D models. The original curve stroke lies in the model. It makes possible to manipulate the object in a practical way with operations directly applied in the curve by user actions. The researchers presented also a nonformal evaluation of their system with novice users and artists. They concluded that Fibermesh is an easy to use tool, which permits evolution in the creativity tasks executed by the users. In the SESAME project [12], James Lin and colleagues studied ways to provide support to the work of designers in the initial stages of the designing process. SESAME was created to explore different visions to solve conceptual design problems in three dimensions. The work was presented in two phases: the first presented a set of guidelines to create collaborative systems for conceptual designs, and the second compared SESAME against 3DS max. The main goal of the evaluation was to analyze how designers could make a creative complex design in the least amount of time, and what sets of operations they need to execute during the task. With the GODZILLA [26] system, S. Tano and colleagues presented experimental systems where the users can make 2D drawings, which are recognized and exhibited as 3D sketches in a display (stereo vision TV). The user can later modify the drawings, as viewed from many view points (2D or 3D). In order to evaluate the system, they compared it against pencil and paper, and a 3D CAD (Computer Aided Design) tool. The results revealed that the ideas in terms of numbers of sketched are much closer in this system to the numbers of sketched in traditional pencil and paper combination. Marcus Wacker and colleagues developed The Virtual Dressmaker [18], a Virtual Reality application to design clothes. The system supports advanced interactive techniques with six degrees of freedom. The researchers argue that sketch-based techniques are more natural than the traditional desktop techniques. They started with a pilot test, where the user needed to position clothes on an

III. METHODOLOGY We used a qualitative and quantitative methodology [4] to conduct our comparative study, described below. A. Pilot Tests We executed a great number of pilot tests [18] in order to decide the tools to be used, to evaluate and improve our methodology. After the pilot sessions, the collected data was analyzed and the methodology was adjusted when necessary. We repeated this procedure until we decided that the methodology was ready to be executed in a real context. In our pilot tests we had the collaboration of a computer science student familiar with traditional software for 3D modeling (Maya in this case). One identified necessity was the reduction of the experiment’s length, to avoid the user becoming tired. Although there is no limit on the time to execute the tasks, we planned it to consume a minimum amount of the user’s time, without jeopardizing the goals of our study. An important decision taken during the pilot tests was the definition of the Teddy system as the selected tool to evaluate the sketch-based modeling technique. Our other choice, the software Fibermesh (which has more

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WIMP). By analyzing each tree, we can extract details of the users’ modeling activities, such as usability gains, needs and requirements for designing a system based on our findings. 5) Survey (personal data): A simple survey was used to collect information about the users, such as occupation and familiarity with the WIMP tools defined for the study. 6) Questionnaire (System Usability Scale): The use of a questionnaire was necessary to collect, through the users’ replies, the measures for the three subjective hypotheses (H1, H2, H3), which are related to the easiness of use and the satisfaction with the observed results. The questionnaire was adapted from the available model developed by SUS – System Usability Scale [5] and applied to both techniques for comparison effect (the adaptation is available at www.cin.ufpe.br/~tlam/sus_adaptation ). 7) User’s Comments: Through the users answers we collected qualitative data related to their opinions about satisfaction with the created 3D models, the use of creativity in the tools, and ease of use with the software.

interaction possibilities than Teddy), was rejected due to great instability in the prototype version available. The details of the methodology are showed below. B. Hypotheses To evaluate our study, we considered the following hypothesis: H1: modeling with the use of sketch (as presented in Teddy), demands less effort from the user than modeling with the use of WIMP-like interfaces (as presented in Maya or 3DS Max). H2: the sketch-based modeling approach (as presented in Teddy) reduces the user’s time to complete tasks. H3: the sketch-based modeling technique (as presented in Teddy) produces satisfactory results. The effort (H1) and the satisfactory user’s results (H3) in this study were evaluated through the user’s answers collected in a survey related to the two techniques presented. The time (H2) was verified through the video register of the user’s activities.

IV. PROCEDURE

1) Dependent and Independent Variables: The independent variables involved in this study were:

The test sessions were composed of two phases: one dedicated to introduce Teddy, and another oriented to tasks execution and answering the questionnaire. In the first phase, the goal was to make Teddy more familiar to the users. They filled a simple questionnaire about their experience with the tools and their occupations. The users had time to test the system functions with a tutorial help available in: http://wwwui.is.s.utokyo.ac. jp/~takeo/teddy/teddy/tutorial.html. In the second phase, the users had to execute three tasks, one only for modeling and the other two dedicated to editing the model previously created. Each task was performed with both Teddy and Maya (or 3DS Max). There was not a time limit to conclude the tasks, and the only rule was that the user needed to execute each task in each tool. The tasks were as follows:

• the technique utilized (Sketch or WIMP); • the target object to be modeled (a bear); • the executed task. The dependent variables were the following: • user’s effort; • number of tries to realize the task; • time to execute the tasks; • users satisfaction; • Hierarchical tasks models (HTA). The user effort and satisfaction with the results were collected through the same survey. All the other variables have their results computed after the analysis of the user’s activities. 2) Subjects: The profile defined users who are studying or working in the Design, Art or Technology fields with experience in Computer Graphics products such as Maya or 3DSmax. They should also have basic understanding of the modeling process of these tools. All the users were recruited as volunteers in academic or technical schools, or in design, games, and technology companies. 3) Collected Data:. To collect the data, we defined 25 users. In the study here presented we used only 6 users to show qualitative data, our quantitative analyze continues and will be shown in a future work. 4) User’s Mental Model: We used the user speech to analyze, in an hierarchical form, their activities in Teddy and Maya or 3DS Max. The main objective was to build two trees of analyses, one for each approach (sketch and

Creation - The user had to reproduce a teddy bear (Fig. 1) model presented in a reference picture. This reference was used only to show a direction of how the users’ test could start and not to follow the reference exactly as seen in the picture.

Figure 1. The reference picture of a teddy bear.

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1) The creation of the model in Teddy was straightforward. The users started this task in one of two ways: drawing directly on the screen with the mouse, or using the example sphere, which starts the software. All the model elements such as arms and legs, were generated with the extrusion set of gestures available in Teddy. In the WIMP systems, the users used geometric references to construct the model. The manipulation of these references, in order to build the model, forces the users to think in some pre-defined ways. The users have to adapt their ideas to the object seen currently on the screen, thus resulting in additional tasks.

Editing - Using the bear model created in the previous task (did not need to be complete), the user was asked to make a drawing of a four-point star at any point on the bear’s surface. Following, they should erase this star and draw a five-point star instead. After that, the user needed to cut one of the bear’s ears, and create a little cavity in the bear’s body. Pointed ear - The user was asked to deform the bear’s ears to make it look like a cat’s ear. To do this task, the previously created ears must be used. After the conclusion of the third task, the users filled in a questionnaire about the tests and talked about their experience when performing the tasks. The tasks were defined in this way to cover a set of basic operations presented in the 3D modeling systems evaluated. V. RESULTS For our qualitative study, we used the Hierarchical Task Analyses (HTA) technique. Based on the full video and audio recorded during the sessions, we developed a HTA related to each task executed by the users. The HTAs were generated with the trial version of the Software Task Architect [27]. We adopted the number of units generated in the tasks to define the usability gains of the techniques. We will use the definition NS to denote the number of operations in a sketch-based interface for modeling (Teddy in this case) and the definition NW to denote the number of operations in a traditional desktop interface system (Maya or 3DSMax). We collected data from six subjects, all of whom were volunteers for the study. They were recruited in graduate courses (Computer Science, Design and Arts) and in game companies. All of them had little knowledge about sketch-based systems, but some experience with Maya or 3DSMax in different levels, varying from beginner to professional, according to their use of these tools in their leisure time or in their professional lives. Unfortunatelly we didn’t´ reach a large number of users (we defined 25) to generate enough data. We have a consulting with a specialist in statistics and the recommendation was following this study until we get the specified amount of users’ data. According to the specialist, an analyze with only 6 users is insufficient to give effective results. By these reasons this paper section analyze our qualitative data exclusively. We continue to work with the quantitative part of the study and soon as possible we will reveal all the achieved results and hypotheses comments.

Figure 2. A pseudocode example of the creation task in a sketch interface (Teddy) done by one of our test users.

A. Task results Creation. NS < NW: In task one - the creation of a 3D bear model - all the users used less operations in the sketch-based system than in the wimp based one(Fig. 2 and Fig. 3).

Figure 3. A pseudocode example of the creation task in a WIMP interface (Maya) done by one of our user´s test.

2) Editing. NS ~= Nw : In this task, the number of operations was close in both approaches. We will present

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without loss of time and concentration in long searches over interface menus. This reduced set of instructions can be repetitive and tedious in great projects or in the user’s time task along a computer, but it could not be observed in the tasks analyzed.In our sessions, we could observe that the users created the model basically with a simple extrude function. In the case of WIMP-based systems, the use of several menus and dialog boxes cause some mistakes and difficulties to get a solution for a specified task. The users have to acquire a great knowledge of the options presented in the system interface even to create simple objects.

the result of this task according to their subtasks: cut operation, drawing (and erase) a star, and creating a cavity. a) Editing: cut operation. NS ~= NW: In this subtask, with only a single stroke in Teddy, the users can cut the ear off the bear. In the WIMP-based system, two techniques were used: some preferred to use the “delete face” function, whereas others preferred the Boolean operation to cut the ear. b) Editing: drawing (and erase) a star. NS ~= NW: Most of the results in this subtask showed that the number of operations is closer in both systems. In fact, all the users used the same approach in the sketch-based system, i.e., they made strokes directly on the model’s surface to create the stars and then scribbled to erase it. In the WIMP-based systems, the users defined a few points to connect edges in the surface model. The stars were built in this way. To erase it, they used the delete command. Another user preferred to use the function Star available in the system. But this function added more tasks related to typing the number of vertices to form the star which increases the effort (NS < NW) in an WIMP interface. c) Editing: creating a cavity. NS ~= NW: To create a cavity in the sketch-based system the users only needed to apply the extrusion function. In the WIMP-based systems the users executed the task by selecting some

B. Creation We could observe that the best usability gain that the sketch-based interface technique brings to the 3D modeling task, is in the creation phase. On this task, the number of user operations was consistently less than when realizing the same tasks in a WIMP-based interface. Creating a model in this way was very practical to our users, since the sketch technique is a straightforward way for users to express their ideas, without having to make technical decisions about the object to be generated.

vertices and pushing one to define the cavity. 3) Pointed ear. NS > NW: In this task, the number of operations was greater in the sketch-based system (Fig. 4 & and Fig. 5). In the sketch approach almost all users used cut and extrude operations to give the ears of the bear a pointed view look. One user tried the bend function, the most common alternative to this task, but he did not finish his action because a system fail locked the system. Another user tried the bend function with success. In the WIMP approach, all users selected a set of vertices or faces defining the ear, and pulled these to give the bear’s ear with a pointed view look. VI. CONCLUSIONS In this section we present our main conclusions, grouped by our impressions regarding: the reduced instruction set gestures presented by Teddy in our test sessions, the creation and the editing phase of the procedure, and their implications in the user activities.

Figure 4. A example of the first and second try in the Pointed ear task in a sketch interface (Teddy). The user used the bend function without success, so he made the ear pointed with an extrusion function.

A. Reduced Instruction Set Gestures The sketch-based system Teddy has a reduced instruction set of gestures. This characteristic implies that the user can generate 3D models in a faster and easier way. They can interact with the computer environment

Figure 5. Pointed task in the WIMP approach.

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Methodology session. We continue to collect data from new user’s tests and we hope to show the results in a future as a natural evolution of this research.

In the WIMP-based systems, the users need to plan ahead, or to have a well-defined idea to minimize their time and effort in the selection sets to construct their models. The technical background required to manipulate these interfaces is also higher, if the user wants to make full use or their creativity throughout the project. A high level experience in the use of these interfaces is needed to reach the same level of interaction as in the sketch-based systems.

ACKNOWLEDGEMENT We would like to thanks CNPQ for finatial support, the members of our research groups – Ciências Cognitivas e Tecnologias Educacionais and Mídia & Interação, Playlore Gameworks for the users, the teacher Richard Lane and Cultura Inglesa for the technical review of this paper, the teacher Renata Souza for consulting and all the users who participated in a volunteer way of this study.

C. Editing The editing operations revealed more usability gains in the WIMP-based systems. In task 2 (Editing) of our experiment, we could observe that the number of operations was very close, but in the task 3 (Bend) we observed that number of operations was greater in the sketch-based system. The possibility of direct manipulation of vertices and faces, and the use of keyboard commands to copy and paste, showed that these familiar computational and geometry instructions are more remarkable than some new gesture-based instructions.

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VII. REQUIREMENTS AND FUTURE WORKS We are developing a 3D geometric modeling prototype using sketch-based ideas for the interface, and we plan to use the gathered results from this study as requirements for this prototype. The evaluation of the HTAs and the user comments, showed us that a system combining the two approaches (sketch and WIMP) could be built with the following characteristics:

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A. Manipulation of vertices and faces We observed that the manipulation of vertices and faces that define the models, is an operation for editing objects very popular with by the users. Editing a model at the level of a vertex or a face was very useful and simple in our tests sessions in the WIMP approach. In the sketch approach, although the interaction can be very simple too, the users have to make some effort to find the right stroke which will generate the desired modification.

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B. Copy and paste functions Another functionality which reduces the users' efforts is the copy and paste functions. All users use it to avoid modeling similar objects from scratch several times. In a WIMP context, this use is very simple with selected options through the graphical interface or keyboard commands. But in the sketch software, this function was not available and the users had to develop similar objects from the scratch every time they needed to use them.

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