DESIGNING AND TESTING HUMAN COMPUTER ...

Appeared in D. Roller (Ed.). Conference proceedings of the 31th International Symposium on Automotive Technology and Automation (ISATA) pp. 27-34, 1998, Automotive Automotion Limited, , Croydon

DESIGNING AND TESTING HUMAN COMPUTER INTERACTION: A CASE STUDY IN VIRTUAL CLAY MODELLING Mrs C.C.M. Hummels and Dr C.J. Overbeeke Delft University of Technology The Netherlands 98ME038 ABSTRACT In this paper we present an interaction design method that starts from the user and his task. This implies that the designer has to develop perceivable actions for the user, based on the task to perform and the perceptual-motor skills of the user. Technical or time constraints of the design project must not hamper the natural performance of the task. Finally, the interaction designer should design a HCI system by extensively performing user tests with low fidelity prototypes with high (inter)action relevance. We tested this interaction design method for virtual clay modelling. The results support our belief that this method is of use in developing intuitive systems.

1. INTRODUCTION In this paper we introduce a method for designing human computer interaction. This method consists of four layers. The interface designer has to take the steps successively from bottom to top when designing human computer interaction, see Figure 1.

Figure 1. The interaction design method We will explain the interaction design method (IDM) and exemplify the IDM with virtual clay modelling (VCM). VCM is the computer-aided version of traditional clay modelling. The modeller can make car models with virtual clay which exists of an infinite of minuscule 3D units. VCM is developed within the European project ‘Innovative styling applications in computer-aided environments’ (INSTANCE)1 . 1

Brite EuRam III Project 95-2151, in co-operation with BMW AG (D), Coventry University (UK), IWF TU Berlin

(D), Sintef (N) and Deskartes (SF).

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Within INSTANCE we study the feasibility of intuitive computer-aided tools in the automotive design process, which incorporate the skill-based expressive wealth of traditional methods. INSTANCE seeks to cover the entire styling design process with an integrated solution for a workflow from a 2D digital sketch to a milled full size model. The process starts with digital/digitised 2D sketches which are converted into a fairly simple 3D computer model. This 3D model preserves the expressivity of the sketches by mapping the sketch back onto the model (for details, see Overbeeke et al. 1997). After an iterative design process, the 3D model (without sketch mapping) is fed into a virtual clay modelling system for further detailed modifications. This paper concentrates on developing the VCM module. Finally the virtual car model is sent to a five-axis milling machine to manufacture a physical 3D (full size) car model. The four layers of the interaction design method will be explained separately in the next four sections and illustrated in section six. We start with the first layer: a new user- and task-oriented human computer interaction approach.

2. A NEW HCI APPROACH Technical advancements are achieved enormously fast nowadays, contrary to usability advancements. These technical developments sometimes even lead to the decline of usability. For example, Microsoft Word 6.0 is a word processor which incorporates so many features, presents them in so many different ways ( more than 10 toolbars, extendible menus etc.) and consequently becomes so slow, that users can hardly perform their task, that is writing a text. Future user interfaces must allow users to focus on the task instead of controlling a computer. You can compare it with writing on paper. You are focused on the text and not on the pen, unless the pen is preventing you from writing (e.g. when you have run out of ink). Traditional user interfaces are function-oriented or object-oriented, which means that they depend on strict syntax-rules. In function-oriented programming the function is given precedence, e.g. the user commands the computer to “copy file A”. In object-oriented programming the objects is given precedence, e.g. “file A must be copied”. Future user interfaces will be user-oriented and taskoriented. This means that they do not depart from strict syntax-rules and commands, but they will unify the function and the object into one (Nielsen, 1993). For example, a drawing can be deleted on a handheld computer by crossing out the drawing with a pen, instead of selecting the drawing or the delete-function first. Consequently, the user can concentrate on the task. So the ‘interface design’ has to become an ‘out of my face design’ according to Buxton (1997). The traditional interface, an obstacle between a user and a computer, is replaced by a context for action. The computer is assimilated in the environment (Nielsen, 1993; Buxton, 1997; Laurel, 1993). The new HCI approach implies that an interface designer has to design actions and a context for these actions, instead of objects or functions (We therefore prefer to call him interaction designer instead of interface designer). Designing actions means designing perceivable actions: how can the user see what his possibilities are? These possibilities should not be visualised by metaphorical icons as is done in graphical user interfaces, because the metaphor depicts the object instead of the actions. The possibilities should be offered through affordances, i.e. formal characteristics of objects that show us 2

possibilities to act (Smets, 1995). So a cup affords us grasping and drinking, but also throwing when we are angry. In HCI these affordances can be offered through virtual 3D objects and real 3D objects. To summarise the first step of the interaction design method for virtual clay modelling: The interaction designer should become aware that he has to design perceivable actions that fit in with the task of a virtual clay modeller. This first layer becomes the zero level when this new human computer interaction approach becomes common practice and replaces the traditional approaches. The interaction designer can then start the interaction design method with step 2 in Figure 1. In the next section we define this second layer: task and the perceptual motor skills of the (virtual) clay modeller.

3. SKILLS AND TASK ANALYSIS FOR VCM Designing a virtual clay modelling system asks for a skills and task analysis. One wonders why commercially available computer aided styling (CAS) applications hardly bother about these analyses. The highly skilled clay modeller creates 3D car models with these CAS applications through a complex set of mouse or pen strokes and numerical inputs. Furthermore, these models are largely built in orthogonal views on 21-inch monitors. CAS applications lack the skill-based and expressive wealth that forms the basis for styling design process and is essential to capture the expressivity of cars (Hummels et al, 1997; Overbeeke et al, 1997). Nevertheless the modellers are asked to make models resulting in the same accuracy as full scale 3D clay models. So it is not surprising that within the styling design process little use is made of computing. If we want to optimise the virtual clay modelling task for car styling we must support exactly the skills and sensitivities of those clay modellers. We should aim at conserving existing skills instead of acquiring new skills (Buxton, 1997). So, what is it the goal of the clay modeller and what perceptualmotor skills does he use to reach it? Generally, 3D clay models are made to develop and evaluate the aesthetic aspects of a car design, to supply information to the engineers and to determine manufacturing aspects and marketing opportunities. The clay modellers must be able to transform 2D visual information from the stylist into a 3D model. This model consists of extremely accurate (complex) curved surfaces and form and feature lines. Clay offers the modellers the visual and tactile opportunities to do so. Before modelling can begin, a structure is made from metal, wood and foam, that stays about 15 cm within the boundary of the expected surface. (Within INSTANCE the virtual clay modeller starts with a simple virtual 3D model). On top of this structure the modeller uses a special kind of wax-based clay, that allows both soft, smooth handling and hard, carving methods depending on the temperature. They use many different tools like templates, sweeps, scrapers, spatulas, slicks and tape which they use with both hands and experience as a natural extension of their hands. The hands themselves are also very powerful tools, because the modellers ‘see’ the surface through their hands. Further information is obtained mainly through reflections of the light (Birtley, 1990). To summarise the second step of the interaction design method for virtual clay modelling:

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Figure 4. The slick always snaps to the surface. These two approaches have formed the basis for the next phase: designing the virtual clay modelling actions and affordances. Several alternatives were designed and visualised with scenarios and storyboards, see Figure 5. Examples of affordances shown in this figure are the turntable (affords grasping and rotating) and the physical tool (affords grasping and cutting).

Figure 5. A part from the storyboard ‘virtual clay modelling using a slick’. The modelling environment is designed for action with tools and objects that afford interaction like grasping and manipulating. The working area is divided in three areas: a clay modelling area, a tool development area and a storage of models area. The interactions visualised in these different scenarios were thereupon tested with physical mock-ups. Paper, cardboard, transparent synthetics, wire, ‘shaving foam’ etc. were used to make a working mockup, see Figure 6. We used a Wizard of Oz approach to test the concept.

Figure 6. A working prototype of the virtual clay modelling concept. A final set-up could be built to test the effect of absence of force feedback by offering the modeller a 3D image of the filmed mock-up which he can operate using a Wizard of Oz approach. This user test stretches beyond the limits of INSTANCE. The virtual clay modelling concept is currently implemented. 7

6. CONCLUSIONS If the new HCI approach becomes common practice, the interaction designer develops perceivable actions for a user. In this paper we have stated that the designer has to develop a context for action based on the task and the perceptual-motor skills of a specific user. Furthermore, technical or time constraints of the design project should not hamper the natural performance of the user’s task. And finally, the designer should develop a HCI concept by extensively performing user tests with low fidelity prototypes with high (inter)action relevance. We have tested this approach for virtual clay modelling. The results support our believe that this method is of use in developing a computerised automotive design process that will be used with delight by the intended users. We therefore continue our work, both on an the automotive design process and on HCI in general.

REFERENCES Birtley, N. (1990). The conventional automobile styling process. Internal report Coventry Polytechnic Department of Industrial Design. Buxton, W. (1997). Out from behind the glass and the outside-in squeeze. Invited presentation at CHI’97, Conference on human factors in computing systems. Atlanta, Georgia. Gould, J.D. (1995). How to design a usable system. In R.M. Baecker, J. Grudin, W.A.S. Buxton and S. Greenberg (eds.) Readings in Human-Computer Interaction: Towards the year 2000. San Francisco: Morgan Kaufmann Publishers, Inc. Hummels, C., Paalder, A., Overbeeke, C., Stappers, P.J. and Smets, G. (1997). Two-handed gesture-based car styling in a virtual environment. in D. Roller (ed.) Conference Proceedings of the 30th ISATA, nr. 97ME081., Croydon: Automotive Automation Ltd., pp. 227-234. Hummels, C., Smets, G. and Overbeeke, K. (1998). An intuitive two-handed gestural interface for computer supported product design. in I. Wachsmuth and M. Fröhlich (eds.) Gesture and signlanguage in human computer interaction: proceedings of Bielefeld gesture workshop 1997. Berlin: Springer-Verlag. (in press) Laurel, B. (1993). Computers as theatre. Addison-Wesley Publishing Company. Nielsen, J. (1993). Noncommand user interfaces. Communications of the ACM, Vol. 36, No. 4 (April), pp. 83-99. (Revised version on http://useit.com) Overbeeke, C., Kehler, T., Hummels, C. and Stappers, P.J. (1997). Exploiting the expressive: Rapid entry of car designers' conceptual sketches into a CAD environment. In D. Roller (Ed.) Conference Proceedings of the 30th ISATA, nr. 97ME082., Croydon: Automotive Automation Ltd., pp. 243250.

Rettig, M. (1994). Prototyping for tiny fingers. Communications of the ACM, Vol. 37, No. 4 (April), pp. 21-27. Smets, G.J.F. (1995). Industrial design engineering and the theory of direct perception and action. Ecological Psychology, Vol. 7, No. 4, pp. 329-374.

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