- Presented at the CHI 2000 -
Menus beyond the desktop metaphor Fred A. Voorhorst, Helmut Krueger IHA-Ergonomie, ETH Zürich Clausiusstrasse 25 8092 Zürich, Switzerland +41 1 6325530
[email protected] ABSTRACT
Augmented Reality systems integrate real and virtual objects, allowing for a new view on the implementation of menus. This paper describes experimental research in support of making menus grasp-able, i.e. easily accessible. KEYWORDS
Graspable user interfaces, usability, AR, use of menus. INTRODUCTION
A menu can be any type of representation of an organization of tools or functions, such as pull-down menus, pop-up menus, tool pallets, and so on. The main objective of using menus is to give a structured overview of the tools and functionality at hand. Menus should, on the one hand be easily accessible, and on the other hand not crowd the workspace. Optimization of menus may improve the usability of the interface. Augmented reality systems (AR) provide the possibility to explore the use of menus in an unconstraint way. AR is a new type of VR systems emerging on the realityvirtuality continuum [4]. VR and AR open new possibilities for interface design such as e.g. gesture based HCI [3, 5]. AR ahs the additional advantage of supporting the combination of physical objects and computer generated objects. For example, a physical room can be augmented with computer images of newly designed furniture with the purpose of evaluation before the actual purchase. THE AUGMENTED REALITY SYSTEM BUILD-IT
Build-It [2, 5] is an AR based planning tool based on intuitive manipulation for the support of planning and configuration tasks. Build-It presents the user with two views: a table view showing the virtual environment in plan, and a wall projection, showing the virtual environment in perspective. The plan view contains a (virtual) camera that determines the image presented on the wall view. Build-it has a so-called graspable user interface. An interface is called graspable when each function of the interface is operated by means of a dedicated physical device. The device a function is operated with serves as a graspable function [1].
Martin Bichsel IKB, ETH Zürich Tannerstrasse 3 8092 Zürich, Switzerland +41 1 6322429
[email protected] [6]. First, a physical object naturally invites users to act. For example, a small ball invites to be squeezed while a large ball invites to be kicked. Second, the use of physical objects make it possible explicitly distinguish between functions by linking them to different actions or objects. With build-it, the interaction proceeds by means of rectangular bricks that are tracked using an infra red detection system. An object is selected by simply placing a brick on top of it. The object, when selected, can be freely moved around. The object becomes deselected when the brick is covered. IMPLEMENTING MENUS FOR BUILD-IT
The technical implementation of Build-it (two projectors and an infrared tracking system) can be used to the advantage of the implementation of menus. Both the tracking of the bricks and the projecting of the computer image is done from above the table surface.
Figure 1: A possible implementation for an AR system would be selection directly from a catalog and dragging it on the desktop.
One of the potentials of this technical set-up is the possibility to combine various information carriers such as, e.g. by combining computer images with hand drawings. Build-It gives the possibility to take the menus beyond the desktop metaphor, as allows for looking at hardware solutions such as a real catalogue, from which objects can be selected directly (see Figure 1). Implementation only requires a unique code on the page of the catalogue, that can be picked-up by the system’s infra red device. Potentially, the page layout itself can serve as coding. EXPERIMENT: MAKING MENUS GRASPABLE
In a small experiment two principles of implementing menus were tested. First, with respect to selection: a menu can be accessed either direct or through a handler. Second, with respect to interaction: the menu or handler either is virtual or real. Methods and materials
Two reasons suggest the advantage of a graspable userinterface for the development of user-friendly HCI compared to a normal graphical user-interface approach
The experiment was performed using a mock-up Build-it system, consisting of a cardboard frame on top of a table, and four real menus with real objects. The area below and extending beyond the borders of the frame represents the
virtual environment (VE) and the area above the frame is the real environment (RE). Four menus were used each with different objects (rectangular, triangle, square or bar). Figure 2 shows the four conditions of the experiment.
Figure 4: The number of times subjects changed between menus for conditions 1 to 4.
Figure 2: Conditions of the experiment. Condition 1 (upper-left): Menus are real, always visible in the RE and have to be placed inside the VE to be used. Condition 2 (upper-right): Menus are virtual and always visible in the VE. Condition 3 (lower-left): Real handlers are always visible in the RE. When placed in the VE a menu appears. Condition 4 (lower-right): Virtual handlers are always visible in the VE. When one is selected a menu appears.
Task, subjects & Hypotheses
Surprisingly, not all subjects perceive the grasp-ability of menus during condition 1 and 3. To have the preferred situation, i.e. to have more than one menu visible at the same time, was perceived by one subject only. DISCUSSION AND CONCLUSIONS
Results of the experiment demonstrate the advantage of making menus graspable but also show the importance of making perceivable this grasp-ability as not all users will fully explore the possibilities of the system. Overall, the experiment confirmed that menus should be graspable, i.e. easily accessible. REFERENCES
Figure 3: Two examples of tasks used for the experiment.
Subjects were shown a configuration (Figure 3) which they were asked to rebuild as accurately as possible. Three subjects participated in the experiment. Graspable, i.e. easily accessible, menus were assumed to have the advantage over non-graspable menus. Results
Although subjects were asked to be as good as possible, and not as fast as possible, one could expect the amount of time needed to be less for easy conditions compared to difficult conditions. However, no time differences were found. Figure 4 gives an overview of the number of times subjects switched between menus. These results indicate two types of strategies. Strategy 1 is the optimization of menu access and is used when menus are difficult accessible (condition 4). Subjects optimize the number of changes between menus by accessing each menu only once. Strategy 2 is the optimization of task performance and is used when menus are easily accessible (e.g. condition 2). Subjects selected freely from different menus, depending on the menu item that is needed.
1. Fitzmaurice, G. W., Buxton, W., 1997, An empirical evaluation of graspable user-interfaces: towards specialized space-multiplexed input: CHI 97: Looking to the future. 2. Fjeld, M., Bichsel, M., Rauterberg, M., (1998), Build-It: A brick based tool for direct interaction: Engineering, Psychology and Cognitive Ergonomics, v. 3: Ashgate, Hampshire, 5 p. 3. Hummels, C. J., Stappers, P.J., 1998, Meaningful gestures for human computer interaction: beyond hand postures: Proceedings 3rd Int. Conference on Automatic Face & Hand recognition, p. 591 - 596. 4. Milgram, P., Takemura, H., Utsumi, A. & Kishino, K., (1994) Augmented Reality, a class of displays on the reality-virtuality continuum: SPIE, v. 2351. 5. Rauterberg, M., Fjeld, M., Krueger, H., Bichsel, M., Leonhardt, U. & Meier, M., 1997, BUILD-IT: a video-based interaction technique of a planning tool for construction and design.: Proceedings of Work With Display Units -- WWDU'97, p. 175-176. 6. Voorhorst, F.A & Krueger, H. (1999) User-friendly by making the interface graspable. In: Proceedings of 8th HCI conference. Eds: M.J. Smith, G. Salvendy & R.J. Koubek. Volume 1. Pp.416-420
