A comparison study: sketch-based interface versus wimp interfaces in three-dimensional modeling tasks

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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, Departamento de Ciência da Computação Universidade Federal de Pernambuco – UFPE {tlam, asg, marcelow}@cin.ufpe.br 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
  A comparison study: sketch-based interface versus wimp interfacesin three-dimensional modeling tasks Tiago Lemos de Araujo Machado, Alex Sandro Gomes, Marcelo Walter Centro de Informática – CIn, Departamento de Ciência da ComputaçãoUniversidade Federal de Pernambuco – UFPE{tlam, asg, marcelow}@cin.ufpe.br  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 arebeing used to accomplish tasks related to geometricmodeling, 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 themore traditional WIMP modeling tools Maya & 3DS Max. We used quantitative and qualitative methods toidentify 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 acombination between the two approaches in study. Key Words: interaction styles, user studies, softwareevaluate. 1. Introduction The Sketch-Based Interface technique has been knownin the Computer Science field since the beginnings of theComputer Graphics and Human-Computer Interactionfields. In 1963, Ivan Sutherland developed Sketch Pad,one of the most influential works in Computer Science inthe last 50 years. In Sketch Pad, the user could interactwith a light pen, drawing geometric figures directly on avector display [11]. Further advances in software andhardware research since then, have developed morecomplex Sketch-Based Systems, making them availableand accessible to domestic users, according to predictionsin Sutherland’s work.Since Sutherland’s srcinal work, it took sometime for the research community to realize the potential of Sketch-Based approaches, and it was not until the 1990s that thissubject attracted attention again, for instance in the Sketchwork [23]. In 1999 the software Teddy [10], had a greatimpact on the research community, attributed by theauthors to the simplicity of usage, vis-à-vis the users,even children. The acceptance of Teddy influenced theuse of sketch-based techniques in a great number of systems such as computer games [22][7] and educationalsoftware 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, mainlyapplying sketch ideas in new applications. In spite of allthe research activity, there has been no detailed study onhow sketch-based ideas compare to traditional interaction.In this work, we investigate how sketch-basedmodeling interface compares with traditional WIMPinterface for geometric modeling tasks. We used threesystems to evaluate the techniques: Teddy [10] for itslarge repercussion in the academic field and commercialsuccess, Maya [1] and 3DS Max [19] two of the mostwell-known systems for content production in 3D. Weused a task analysis methodology to collect quantitativeand qualitative data related to the users interaction withthe two styles (in the WIMP style the users could choose between Maya or 3DS Max, based on their experiencewith these products).This paper is organized as follows: the related worksare presented in Section 2. Our methodology is presentedin Section 3. The data analysis and results are presentedand discussed in Section 4, and the conclusions withappointments for future work are presented in Section 5. 2. Related Works The main strength of Sketch-Based Interfaces is its potential to create user experiences inspired by realdrawing with pencil and paper. The ideas have been usedin a large range of applications, such as educationalsoftware [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 create3D content. Below, we discuss previous work closelyrelated to our project.Olsen and colleagues [17], introduced the themethrough a taxonomy which classifies the sketch-basedmodeling systems by the way of their creation, kind of surface, edit operations and interface paradigms. The paper presents many implementation details of thesoftware and reveals the influence of different areas in thecreation of the projects, such as HCI and Cognitive  Science. The improvement of the sketch-based interface isconsidered one of the most exciting and challengingareas.In the work presented by Seok-Hyung Bae andcolleagues in [25], an interface metaphor of pencil and paper created for professional designers, calledILoveSketch. The users can draw curves freely anddirectly on the screen, and connect them through camerarotations. Although the results are 3D models, all objectsare built through the users’ strokes, with no systeminterpretation. The researchers tested the prototype withthe collaboration of a specialist with 12 years experiencein design in the automobile industry and with toys andmovies. The choice was justified by the decision to project the system for professional users with a high levelof experience. The user carried out an intense evaluationof the system after a one-hour of training. The mainconclusion was that the user was satisfied with the greatnumbers 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 srcinal curve stroke lies inthe 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 non-formal evaluation of their system with novice users andartists. They concluded that Fibermesh is an easy to usetool, which permits evolution in the creativity tasksexecuted by the users.In the SESAME project [12], James Lin andcolleagues 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 solveconceptual design problems in three dimensions. Thework was presented in two phases: the first presented a setof guidelines to create collaborative systems for conceptual designs, and the second compared SESAMEagainst 3DS max. The main goal of the evaluation was toanalyze how designers could make a creative complexdesign 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 andcolleagues presented experimental systems where theusers can make 2D drawings, which are recognized andexhibited as 3D sketches in a display (stereo vision TV).The user can later modify the drawings, as viewed frommany view points (2D or 3D). In order to evaluate thesystem, they compared it against pencil and paper, and a3D CAD (Computer Aided Design) tool. The resultsrevealed that the ideas in terms of numbers of sketchedare much closer in this system to the numbers of sketchedin traditional pencil and paper combination.Marcus Wacker and colleagues developed The VirtualDressmaker [18], a Virtual Reality application to designclothes. The system supports advanced interactivetechniques with six degrees of freedom. The researchersargue that sketch-based techniques are more natural thanthe traditional desktop techniques. They started with a pilot test, where the user needed to position clothes on anavatar in three different systems: the Virtual Dressmaker,Maya and the CosmoWorlds. They evaluated variablessuch as the time for task completion and precisionachieved by the users. The results showed that the user’s performance was better with VirtualDressmaker. Theyalso presented points to improve the users tasks in futureversions of the software.In this work [16] Kamran Sedig and colleagues presents a methodology to evaluate the impact of usinggeometry learning software in the learning geometry process, for children at a basic educational level. Theresearch compared three versions of the same software built to teach geometry transformations. The goal was tofind ways to design effective tools to ease the knowledge- building process in learning. The research revealed thatthe present interface style brings implications in theeducation by the way users interact with the tools.Another conclusion was that the HCI elements couldimprove the cognitive capabilities of users who use thesoftware, although it can also affect the same capabilities.This work served also as an inspiration to us, since itadvances the idea that sketch-based interfaces have to bemore investigated in order to identify gains and eventuallosses that the technique can offer in different contexts.Takeo Igarahashi and colleagues introduced thesoftware Teddy [10], a gesture based system where theusers draw on a white screen with strokes in 2D (inputdata), and the result of this interaction is a 3D model(output data). Basically, all operations are a result of a setof actions (gestures) like: creation, paint, extrusion, cut,smooth, bend, etc. 3. Methodology We used a qualitative and quantitative methodology[4] to conduct our comparative study, described below. 3.1. 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 datawas analyzed and the methodology was adjusted whennecessary. We repeated this procedure until we decided  that the methodology was ready to be executed in a realcontext.In our pilot tests we had the collaboration of acomputer science student familiar with traditionalsoftware for 3D modeling (Maya in this case). Oneidentified necessity was the reduction of the experiment’slength, to avoid the user becoming tired. Although there isno limit on the time to execute the tasks, we planned it toconsume a minimum amount of the user’s time, without jeopardizing the goals of our study.An important decision taken during the pilot tests wasthe definition of the Teddy system as the selected tool toevaluate the sketch-based modeling technique. Our other choice, the software Fibermesh (which has moreinteraction possibilities than Teddy), was rejected due togreat instability in the prototype version available. Thedetails of the methodology are showed below. 3.2. Hypotheses To evaluate our study, we considered the followinghypothesis: H1 : modeling with the use of sketch (as presented inTeddy), demands less effort from the user than modelingwith the use of WIMP-like interfaces (as presented inMaya or 3DS Max). H2 : the sketch-based modeling approach (as presentedin Teddy) reduces the user’s time to complete tasks. H3 : the sketch-based modeling technique (as presentedin Teddy) produces satisfactory results.The effort (H1) and the satisfactory user’s results (H3)in this study were evaluated through the user’s answerscollected in a survey related to the two techniques presented. The time (H2) was verified through the videoregister of the user’s activities. 3.2.1. Dependent and Independent Variables. Theindependent variables involved in this study were: ã   the technique utilized (Sketch or WIMP); ã   the target object to be modeled (a bear); ã   the executed task.The dependent variables were the following: ã   user’s effort; ã   number of tries to realize the task; ã   time to execute the tasks; ã   users satisfaction; ã   Hierarchical tasks models (HTA).The user effort and satisfaction with the results werecollected through the same survey. All the other variableshave their results computed after the analysis of the user’sactivities. 3.2.2. Subjects. The profile defined users who arestudying or working in the Design, Art or Technologyfields with experience in Computer Graphics productssuch as Maya or 3DSmax. They should also have basicunderstanding of the modeling process of these tools. Allthe users were recruited as volunteers in academic or technical schools, or in design, games, and technologycompanies. 3.2.3. Collected Data. To collect the data, we defined25 users. In the study here presented we used only 6 usersto show qualitative data, our quantitative analyzecontinues and will be shown in a future work. 3.2.4. User’s Mental Model. We used the user speechto analyze, in an hierarchical form, their activities inTeddy and Maya or 3DS Max. The main objective was to build two trees of analyses, one for each approach (sketchand WIMP). By analyzing each tree, we can extractdetails of the users’ modeling activities, such as usabilitygains, needs and requirements for designing a system based on our findings. 3.2.5. Survey (personal data). A simple survey wasused to collect information about the users, such asoccupation and familiarity with the WIMP tools definedfor the study. 3.2.6. Questionnaire (System Usability Scale). Theuse of a questionnaire was necessary to collect, throughthe users’ replies, the measures for the three subjectivehypotheses (H1, H2, H3), which are related to theeasiness of use and the satisfaction with the observedresults. The questionnaire was adapted from the availablemodel developed by SUS – System Usability Scale [5]and applied to both techniques for comparison effect (theadaptation is available atwww.cin.ufpe.br/~tlam/sus_adaptation). 3.2.7. User’s Comments. Through the users answerswe collected qualitative data related to their opinionsabout satisfaction with the created 3D models, the use of creativity in the tools, and ease of use with the software. 3.3. Procedure The test sessions were composed of two phases: onededicated to introduce Teddy, and another oriented totasks execution and answering the questionnaire. In thefirst phase, the goal was to make Teddy more familiar tothe 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 atutorial help available in: http://wwwui.is.s.utokyo.ac. jp/~takeo/teddy/teddy/tutorial.html.In the second phase, the users had to execute threetasks, one only for modeling and the other two dedicatedto 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, andthe only rule was that the user needed to execute each task in each tool. The tasks were as follows: Creation - The user had to reproduce a teddy bear ( Figure 1 ) model presented in a reference picture. Thisreference was used only to show a direction of how theusers’ test could start and not to follow the referenceexactly as seen in the picture. Figure 1. The reference picture of a teddy bear. Editing - Using the bear model created in the previoustask (did not need to be complete), the user was asked tomake a drawing of a four-point star at any point on the bear’s surface. Following, they should erase this star anddraw a five-point star instead. After that, the user neededto cut one of the bear’s ears, and create a little cavity inthe bear’s body. Pointed ear - The user was asked to deform the bear’sears 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 ina 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 systemsevaluated. 4. Results For our qualitative study, we used the HierarchicalTask Analyses (HTA) technique. Based on the full videoand audio recorded during the sessions, we developed aHTA related to each task executed by the users. TheHTAs were generated with the trial version of theSoftware 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  N   S  to denote thenumber of operations in a sketch-based interface for modeling (Teddy in this case) and the definition  N  W  todenote the number of operations in a traditional desktopinterface system (Maya or 3DSMax).We collected data from six subjects, all of whom werevolunteers for the study. They were recruited in graduatecourses (Computer Science, Design and Arts) and ingame companies. All of them had little knowledge aboutsketch-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 andthe recommendation was following this study until we getthe specified amount of users’ data.According to the specialist, an analyze with only 6users 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 thestudy and soon as possible we will reveal all the achievedresults and hypotheses comments. 4.1 Task results 4.1.1. Creation. N S < N W   In task one - the creation of a 3D bear model - all theusers used less operations in the sketch-based system thanin the wimp based one( Figure 2 and Figure 3 ). Thecreation of the model in Teddy was straightforward. Theusers started this task in one of two ways: drawingdirectly on the screen with the mouse, or using theexample sphere, which starts the software. All the modelelements such as arms and legs, were generated with theextrusion set of gestures available in Teddy.In the WIMP systems, the users used geometricreferences to construct the model. The manipulation of these references, in order to build the model, forces theusers to think in some pre-defined ways. The users haveto adapt their ideas to the object seen currently on thescreen, thus resulting in additional tasks. Figure 2. A pseudocode example of the creationtask in a sketch interface (Teddy) done by one of ourtest users.
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