Digital pen systems, originally designed to digitize annotations made on physical paper, are evolving to permit a wider variety of applications. Although the type and quality of pen feedback (e.g., haptic, audio, and visual) have a huge impact on advancing the digital pen technology, dynamic visual feedback has yet to be fully investigated. In parallel, miniature projectors are an emerging technology with the potential to enhance visual feedback for small mobile computing devices. In this paper we present the PenLight system, which is a testbed to explore the interaction design space and its accompanying interaction techniques in a digital pen embedded with a spatially-aware miniature projector. Using our prototype, that simulates a miniature projection (via a standard video projector), we visually augment paper documents, giving the user immediate access to additional information and computational tools. We also show how virtual ink can be managed in single and multi-user environments to aid collaboration and data management. User evaluation with professional architects indicated promise of our proposed techniques and their potential utility in the paper-intensive domain of architecture.

Inspired by our automotive and product design customers using large displays in design centers, visualization studios, and meeting rooms around the world, we have been exploring the use and potential of large display installations for almost a decade. Our research has touched on many aspects of this rich design space, from individual tools to complete systems, and has generally moved through the life cycle of a design artifact: from the creation phase, through communication and collaboration, to presentation and dissemination. As we attempt to preserve creative flow through the phases, we introduce social structures and constraints that drive the design of possible point solutions in the larger context of a digital design studio trail environment built in the lab. Although many of the interactions presented are viable across several design phases, this article focuses primarily on facilitating collaboration. We conclude with critical lessons learned of both what avenues have been fruitful and which roads to avoid. This article lightly covers the whole design process and attempts to inform readers of key factors to consider when designing for designers.

We describe a novel approach to inferring 3D curves from perspective drawings in an interactive design tool. Our methods are based on a traditional design drawing style known as analytic drawing , which supports precise image-space construction of a linear 3D scaffold. This scaffold in turn acts as a set of visual constraints for sketching 3D curves. We implement analytic drawing techniques in a pure-inference sketching interface which supports both single-and multi-view incremental construction of complex scaffolds and curve networks. A new representation of 3D drawings is proposed, and useful interactive drawing aids are described. Novel techniques are presented for deriving constraints from single-view sketches drawn relative to the current 3D scaffold, and then inferring 3D line and curve geometry which satisfies these constraints. The resulting analytic drawing tool allows 3D drawings to be constructed using exactly the same strokes as one would make on paper.

We describe a new type of graphical user interface widget called the "PieCursor." The PieCursor is based on the Tracking Menu technique and consists of a radial cluster of command wedges, is roughly the size of a cursor, and replaces the traditional cursor. The PieCursor technique merges the normal cursor function of pointing with command selection into a single action. A controlled experiment was conducted to compare the performance of rapid command and target selection using the PieCursor against larger versions of Tracking Menus and a status quo Toolbar configuration. Results indicate that for small clusters of tools (4 and 8 command wedges) the PieCursor can outperform the toolbar by 20.8% for coarse pointing. For fine pointing, the performance of the PieCursor degrades approximately to the performance found for the Toolbar condition.

Typical commercial 3D CAD tools provide modal tools such as pan, zoom, orbit, look, etc. to facilitate freeform navigation in a 3D scene. Mastering these navigation tools requires a significant amount of learning and even experienced computer users can find learning confusing and error-prone. To address this we have developed a concept called "Safe 3D Navigation" where we augment these modal tools with properties to reduce the occurance of confusing situations and improve the learning experience. In this paper we describe the major properties needed for safe navigation, the features we implemented to realize these properties, and usability tests on the effectiveness of these features. We conclude that indeed these properties do improve the learning experience for users that are new to 3D. Furthermore, many of the features we implemented for safe navigation are also very popular with experienced 3D users. As a result, these features have been integrated into six commercial 3D CAD applications and we recommend other application developers include these features to improve 3D navigation.

Literally hundreds of thousands of users of 2D computer-aided design (CAD) tools are in the difficult process of transitioning to 3D CAD tools. A common problem for these users is disorientation in the abstract virtual 3D environments that occur while developing new 3D scenes. To help address this problem, we present a novel in-scene 3D widget called the ViewCube as a 3D orientation indicator and controller. The ViewCube is a cube-shaped widget placed in a corner of the window. When acting as an orientation indicator, the ViewCube turns to reflect the current view direction as the user re-orients the scene using other tools. When used as an orientation controller, the ViewCube can be dragged, or the faces, edges, or corners can be clicked on, to easily orient the scene to the corresponding view. We conducted a formal experiment to measure the performance of the ViewCube comparing: (1) ArcBall-style dragging using the ViewCube for manual view switching, (2) clicking on face/edge/corner elements of the ViewCube for automated view switching and (3) clicking on a dedicated row of buttons for automated view switching. The results indicate that users prefer and are almost twice as fast at using the ViewCube with dragging compared to clicking techniques, independent of a number of ViewCube representations that we examined.

We describe a new interactive system for 3D design review, built to exploit the visual perception cue of motion parallax, in order to enhance shape perception and aesthetic evaluation. Traditional CAD applications typically use "bookmarked" static views for design evaluation. In our system, we replace static views with moving "shots" interspersed with cinematic visual transitions. Furthermore, users can access shots by picking object features on the 3D model, which invokes a spatial search over all shots, selects the ones deemed relevant to the feature, and plays back those shots. In this paper we describe the rationale behind this system, the main components, the implementation of the search technique, and the initial user evaluation of the system.

We describe a new interaction technique, called a spotlight, for directing the visual attention of an audience when viewing data or presentations on large wall-sized displays. A spotlight is simply a region of the display where the contents are displayed normally while the remainder of the display is somewhat darkened. In this paper we define the behavior of spotlights, show unique affordances of the technique, and discuss design characteristics. We also report on experiments that show the benefit of using the spotlight a large display and standard desktop configuration. Our results suggest that the spotlight is preferred over the standard cursor and outperforms it by a factor of 3.4 on a wall-sized display.

We describe a new interaction technique, called HoverCam, for navigating around 3D objects at close proximity. When a user is closely inspecting an object, the camera motions needed to move across its surface can become complex. For tasks such as 3D painting or modeling small detail features, users will often try to keep the camera a small distance above the surface. To achieve this automatically, HoverCam intelligently integrates tumbling, panning, and zooming camera controls into a single operation. This allows the user to focus on the task at hand instead of continuously managing the camera position and orientation. In this paper we show unique affordances of the technique and define the behavior and implementation of HoverCam. We also show how the technique can be used for navigating about data sets without well-defined surfaces such as point clouds and curves in space.

We describe a new widget and interaction technique, known as a "Frisbee," for interacting with areas of a large display that are difficult or impossible to access directly. A frisbee is simply a portal to another part of the display. It consists of a local "telescope" and a remote "target". The remote data surrounded by the target is drawn in the telescope and interactions performed within it are applied on the remote data. In this paper we define the behavior of frisbees, show unique affordances of the widget, and discuss design characteristics. We have implemented a test application and report on an experiment that shows the benefit of using the frisbee on a large display. Our results suggest that the frisbee is preferred over walking back and forth to the local and remote spaces at a distance of 4.5 feet.

We describe a new type of graphical user interface widget, known as a "tracking menu." A tracking menu consists of a cluster of graphical buttons, and as with traditional menus, the cursor can be moved within the menu to select and interact with items. However, unlike traditional menus, when the cursor hits the edge of the menu, the menu moves to continue tracking the cursor. Thus, the menu always stays under the cursor and close at hand.In this paper we define the behavior of tracking menus, show unique affordances of the widget, present a variety of examples, and discuss design characteristics. We examine one tracking menu design in detail, reporting on usability studies and our experience integrating the technique into a commercial application for the Tablet PC. While user interface issues on the Tablet PC, such as preventing round trips to tool palettes with the pen, inspired tracking menus, the design also works well with a standard mouse and keyboard configuration.

We review the Boom Chameleon, a novel input/output device consisting of a flat-panel display mounted on a tracked mechanical armature. The display acts as a physical window into 3D virtual environments, through which a one-to-one mapping between real and virtual space is preserved. The Boom Chameleon is further augmented with a touch-screen and a microphone/speaker combination. We created a 3D annotation application that exploits this unique configuration in order to simultaneously capture viewpoint, voice and gesture information. Results of an informal user study show that the Boom Chameleon annotation facilities have the potential to be an effective, and intuitive system for reviewing 3D designs.

Previous systems have explored the challenges of designing an interface for automotive styling which combine the metaphor of 2D drawing using physical tape with the simultaneous creation and management of a corresponding virtual 3D model. These systems have been limited to only 2D planar curves while typically the principal characteristic curves of an automotive design are three dimensional and non-planar. We present a system which addresses this limitation. Our system allows a designer to construct these non-planar 3D curves by drawing a series of 2D curves using the 2D tape drawing technique and interaction style. These results are generally applicable to the interface design of 3D modeling applications and also to the design of arm's length interaction on large scale display systems

This paper describes StyleCam, an approach for authoring 3D viewing experiences that incorporate stylistic elements that are not available in typical 3D viewers. A key aspect of StyleCam is that it allows the author to significantly tailor what the user sees and when they see it. The resulting viewing experience can approach the visual richness and pacing of highly authored visual content such as television commercials or feature films. At the same time, StyleCam allows for a satisfying level of interactivity while avoiding the problems inherent in using unconstrained camera models. The main components of StyleCam are camera surfaces which spatially constrain the viewing camera; animation clips that allow for visually appealing transitions between different camera surfaces; and a simple, unified, interaction technique that permits the user to seamlessly and continuously move between spatial-control of the camera and temporal-control of the animated transitions. Further, the user's focus of attention is always kept on the content, and not on extraneous interface widgets. In addition to describing the conceptual model of StyleCam, its current implementation, and an example authored experience, we also present the results of an evaluation involving real users.

We introduce the Boom Chameleon, a novel input/output device consisting of a flat-panel display mounted on a tracked mechanical boom. The display acts as a physical window into 3D virtual environments, through which a one-to-one mapping between real and virtual space is preserved. The Boom Chameleon is further augmented with a touch-screen and a microphone/speaker combination. We present a 3D annotation application that exploits this unique configuration in order to simultaneously capture viewpoint, voice and gesture information. Design issues are discussed and results of an informal user study on the device and annotation software are presented. The results show that the Boom Chameleon annotation facilities have the potential to be an effective, easy to learn and operate 3D design review system.

We present an alternate interface for 3D modeling for use on large scale displays. The interface integrates several concepts specifically selected and enhanced for large scale interaction. These include 2D construction planes spatially integrated in a 3D volume, enhanced orthographic views, smooth transitions between 2D and 3D views, tape drawing as the primary curve and line creation technique, visual viewpoint markers, and continuous two-handed interaction.

We explore the use of the non-dominant hand to control a virtual camera while the dominant hand performs other tasks in a virtual 3D scene. Two experiments and an informal study are presented which evaluate this interaction style by comparing it to the status-quo unimanual interaction. In the first experiment, we find that for a target selection task, performance using the bimanual technique was 20% faster. Experiment 2 compared performance in a more complicated object docking task. Performance advantages are shown, however, only after practice. Free-form 3D painting was explored in the user study. In both experiments and in the user study participants strongly preferred the bimanual technique. The results also indicate that user preferences concerning bimanual interaction may be driven by factors other than simple time-motion performance advantages.

Rotating a piece of paper while drawing is an integral and almost subconscious part of drawing with pencil and paper. In a similar manner, the advent of lightweight pen-based computers allow digital artwork to be rotated while drawing by rotating the entire computer. Given this type of manipulation we explore the implications for the user interface to support artwork orientation. First we describe an exploratory study to further motivate our work and characterize how artwork is manipulated while drawing. After presenting some possible UI approaches to support artwork orientation, we define a new solution called a rotating user interface (RUIs). We then discuss design issues and requirements for RUIs based on our exploratory study.

The proliferation of multiple toolbars and UI widgets around the perimeter of application windows is an indication that the traditional GUI design of a single menubar is not sufficient to support large scale applications with numerous functions. In this paper we describe a new widget which is an enhancement of the traditional menubar which dramatically increases menu-item capacity. This widget, called the Hotbox combines several GUI techniques which are generally used independently: accelerator keys, modal dialogs, pop-up/pull down menus, radial menus, marking menus and menubars. These techniques are fitted together to create a single, easy to learn yet fast to operate GUI widget which can handle significantly more menu-items than the traditional GUI menubar. We describe the design rationale of the Hotbox and its effectiveness in a large scale commercial application. While the Hotbox was developed for a particular application domain, the widget itself and the design rationale are potentially useful in other domains.

We explore a new input device and a set of interaction techniques to facilitate direct manipulation of curves and surfaces. The input device, called ShapeTapeTM, is a continuous bend and twist sensitive strip that encourages manipulations that use both hands and, at times, all 10 fingers. We explore this input and interaction design space through a set of usage scenarios for creating and editing curves and surfaces as well as consider general interactions such as command access and camera controls. This investigation is carried out by extending Alias|wavefront’s modeling and animation package, Maya. CR

Tape drawing is the art of creating sketches on large scale upright surfaces using black photographic tape. Typically used in the automotive industry, it is an important part of the automotive design process that is currently not computerized. We analyze and describe the unique aspects of tape drawing, and use this knowledge to design and implement a digital tape drawing system. Our system retains the fundamental interaction and visual affordances of the traditional media while leveraging the power of the digital media. Aside from the practical aspect of our work, the interaction techniques developed have interesting implications for current theories of human bimanual interaction.

Article Free Access Share on The Rockin'Mouse: integral 3D manipulation on a plane Authors: Ravin Balakrishnan Dept. of Computer Science, University of Toronto, Toronto, Ontario, Canada M5S 1A1 and Alias/Wavefront, 110 Richmond Street East, Toronto, Ontario, Canada M5C 1P1 Dept. of Computer Science, University of Toronto, Toronto, Ontario, Canada M5S 1A1 and Alias/Wavefront, 110 Richmond Street East, Toronto, Ontario, Canada M5C 1P1View Profile , Thomas Baudel Alias/Wavefront, 110 Richmond Street East, Toronto, Ontario, Canada M5C 1P1 Alias/Wavefront, 110 Richmond Street East, Toronto, Ontario, Canada M5C 1P1View Profile , Gordon Kurtenbach Alias/Wavefront, 110 Richmond Street East, Toronto, Ontario, Canada M5C 1P1 Alias/Wavefront, 110 Richmond Street East, Toronto, Ontario, Canada M5C 1P1View Profile , George Fitzmaurice Alias/Wavefront, 110 Richmond Street East, Toronto, Ontario, Canada M5C 1P1 Alias/Wavefront, 110 Richmond Street East, Toronto, Ontario, Canada M5C 1P1View Profile Authors Info & Claims CHI '97: Proceedings of the ACM SIGCHI Conference on Human factors in computing systemsMarch 1997 Pages 311–318https://doi.org/10.1145/258549.258778Published:27 March 1997Publication History 84citation1,262DownloadsMetricsTotal Citations84Total Downloads1,262Last 12 Months49Last 6 weeks5 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my Alerts New Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

An experimental GUI paradigm is presented which is based on the design goals of maximizing the amount of screen used for application data, reducing the amount that the UI diverts visual attentions from the application data, and increasing the quality of input. In pursuit of these goals, we integrated the non-standard UI technologies of multi-sensor tablets, toolglass, transparent UI components, and marking menus. We describe a working prototype of our new para-digm, the rationale behind it and our experiences introduc-ing it into an existing application. Finally, we presents some ot the lessons learned: prototypes are useful to break the barriers imposed by conventional GUI design and some of their ideas can still be retrofitted seamlessly into products. Furthermore, the added functionality is not measured only in terms of user performance, but also by the quality of interaction, which allows artists to create new graphic vocabularies and graphic styles.

Article Evolutionary engagement in an ongoing collaborative work process: a case study Share on Authors: Thomas P. Moran Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CAView Profile , Patrick Chiu Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CAView Profile , Steve Harrison Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CAView Profile , Gordon Kurtenbach Alias Research, 110 Richmond, Street East, Toronto, Canada M5C 1P1 and Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA Alias Research, 110 Richmond, Street East, Toronto, Canada M5C 1P1 and Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CAView Profile , Scott Minneman Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CAView Profile , William van Melle Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CAView Profile Authors Info & Claims CSCW '96: Proceedings of the 1996 ACM conference on Computer supported cooperative workNovember 1996 Pages 150–159https://doi.org/10.1145/240080.240243Published:16 November 1996 40citation654DownloadsMetricsTotal Citations40Total Downloads654Last 12 Months11Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Article Free Access Share on Implicit structure for pen-based systems within a freeform interaction paradigm Authors: Thomas P. Moran Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CAView Profile , Patrick Chiu Live Works, Inc., A Xerox Company, 2040 Fortune Drive, San Jose, CA and Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA Live Works, Inc., A Xerox Company, 2040 Fortune Drive, San Jose, CA and Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CAView Profile , William van Melle Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CAView Profile , Gordon Kurtenbach Alias Research Inc., 110 Richmond Street East, Toronto, Canada M5C 1P1 and Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA Alias Research Inc., 110 Richmond Street East, Toronto, Canada M5C 1P1 and Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CAView Profile Authors Info & Claims CHI '95: Proceedings of the SIGCHI Conference on Human Factors in Computing SystemsMay 1995 Pages 487–494https://doi.org/10.1145/223904.223970Published:01 May 1995Publication History 51citation715DownloadsMetricsTotal Citations51Total Downloads715Last 12 Months44Last 6 weeks7 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteView all FormatsPDF

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The central research issue addressed by this paper is how we can design computer interfaces that better support human attention and better maintain the fluency of work.To accomplish this we propose to use semi-transparent user interface objects.This paper reports on an experimental evaluation which provides both valuable insights into design parameters and suggests a systematic evaluation methodology.For this study, we used a variablytransparent tool palette superimposed over different background content, combining text, wire-frame or line art images, and solid images.The experiment explores the issue of focused attention and interference, by varying both visual distinctiveness and levels of transparency.

This paper describes some design refinements on marking menus and shows how these refinements embody interesting and relevant design principles for HCI. These refinements are based on the design principles of: (1) maintaining visual context, (2) hiding unnecessary information, and (3) supporting skill development by graphical feedback. The result is a new graphical representation and a more effective form of visual feedback and behavior for marking menus.

A marking menu is designed to allow a user to perform a menu selection by either popping-up a radial (or pie) menu, or by making a straight mark in the direction of the desired menu item without popping-up the menu.Previous evaluations in laboratory settings have shown the potential of marking menus.This paper reports on a case study of user behavior with marking menus in a real work situation.The study demonstrates the following: First, marking menus are used as designed.When users become expert with the menus, marks are used extensively.However, the transition to using marks is not one way.Expert users still switch back to menus to refresh their memory of menu layout.Second, marking is an extremely efficient interaction technique.Using a mark on average was 3.5 times faster than selection using the menu.Finally, design principles can be followed that make menu item/mark associations easier to learn, and interaction efficient.

Abstract Drawing a mark can be an efficient command input technique when using a pen‐based computer. However, marks are not intrinsically self‐explanatory as are other interactive techniques such as buttons and menus. We present design principles for interaction mechanisms which make marks self explanatory for novices but still allow experts to use efficient command marks. The key notion is that use of the explanation mechanism physically trains a novice to use the efficient command marks. Two novel interaction mechanisms we have developed using these principles are presented.

We describe a system to support a particular model of document creation.In this model, the document flows from the primary author to one or more collaborators.They annotate it, then return it to the author who makes the final changes.Annotations are made using conventional marks, typically using a stylus.The intent is to match the flow and mark-up of paper documents observed in the everyday world, .The system is very much modeled on Wang FreeStyle (Perkins, Blatt, Workman and Ehrlich, 1989;Francik and Akagi, 1989; & Levine and Ehrlich, in press).Our contribution is to incorporate mark recognition into the system and to explore some novel navigation tools that are enabled by the higher-level data structures that we use.The system is described and the results of initial usertesting are reported.

We describe marking menus, an extension of pie menus, which are well suited for stylus-based interfaces. Pie menus are circular menus subdivided into sectors, each of which might correspond to a different command. One moves the cursor from the center of the pie into the desired sector. Marking menus are invisible pie menus in which the movement of the cursor during a selection leaves an "ink trail" similar to a pen stroke on paper. The combination of a pie menu and a marking menu supports an efficient transition from novice to expert performance. Novices can "pop-up" a pie menu and make a selection, whereas experts can simply make the corresponding mark without waiting for the menu to appear. This article describes an experiment in which we explored both articulatory and cognitive aspects of marking menus for different numbers of items per menu and using different input devices (mouse, trackball, and stylus). The articulatory aspects are how well subjects could execute the physical actions necessary to select from pie marking menus. Articulatory aspects were investigated by presenting one group of subjects with the task of selecting from fully visible menus. Because one feature of marking menus is that users should be able to select from them without seeing the menus (by making a mark), we also ran two groups of subjects with invisible pie menus: one group with an ink trail and one without. These subjects were therefore faced with the task of either mentally representing the menu or associating marks with the commands they invoked through practice. These then are the cognitive aspects to which we refer. Our results indicate that subjects' performance degraded as the number of items increased. When menus were hidden, however, subjects performance did not degrade as rapidly when menus contained even numbers of items. We also found subjects performed better with the mouse and stylus than with the trackball.

The use of different kinds of feedback in preventing mode errors was investigated. Two experiments examined the frequency of mode errors in a text-editing task where a mode error was defined as an attempt to issue navigation commands while in insert mode, or an attempt to insert text while in command mode. In Experiment 1, the effectiveness of kinesthetic versus visual feedback was compared in four different conditions: the use of keyboard versus foot pedal for changing mode (kinesthetic feedback), crossed with the presence or absence of visual feedback to indicate mode. The results showed both kinesthetic and visual feedback to be effective in reducing mode errors. However, kinesthetic was more effective than visual feedback both in terms of reducing errors and in terms of reducing the cognitive load associated with mode changes. Experiment 2 tested the hypothesis that the superiority of this kinesthetic feedback was due to the fact that the foot pedal required subjects actively to maintain insert mode. The results confirmed that the use of a nonlatching foot pedal for switching modes provided a more salient source of information on mode state than the use of a latching pedal. On the basis of these results, we argue that user-maintained mode states prevent mode errors more effectively than system-maintained mode states.

The direct manipulation paradigm has been effective in helping designers create easy to use mouse and keyboard based interfaces.The development of flat display surfaces and transparent tablets are now making possible interfaces where a user can write directly on the screen using a special stylus.The intention of these types of interfaces is to exploit user's existing handwriting, mark-up and drawing skills while also providing the benefits of direct manipulation.This paper reports on a test bed program which we are using for exploring hand-marking types of interactions and their integration with direct manipulation interactions.