William Buxton

A multi-touch three dimensional touch-sensitive tablet

A prototype touch-sensitive tablet is presented. The tablets main innovation is that it is capable of sensing more than one point of contact at a time. In addition to being able to provide position coordinates, the tablet also gives a measure of degree of contact, independently for each point of contact. In order to enable multi-touch sensing, the tablet surface is divided into a grid of discrete points. The points are scanned using a recursive area subdivision algorithm. In order to minimize the resolution lost due to the discrete nature of the grid, a novel interpolation scheme has been developed. Finally, the paper briefly discusses how multi-touch sensing, interpolation, and degree of contact sensing can be combined to expand our vocabulary in human-computer interaction.

A study in two-handed input

Two experiments were run to investigate two-handed input. The experimental tasks were representative of those found in CAD and office information systems. Experiment one involved the performance of a compound selection/positioning task. The two sub-tasks were performed by different hands using separate transducers. Without prompting, novice subjects adopted strategies that involved performing the two sub-tasks simultaneously. We interpret this as a demonstration that, in the appropriate context, users are capable of simultaneously providing continuous data from two hands without significant overhead. The results also show that the speed of performing the task was strongly correlated to the degree of parallelism employed. Experiment two involved the performance of a compound navigation/selection task. It compared a one-handed versus two-handed method for finding and selecting words in a document. The two-handed method significantly outperformed the commonly used one-handed method by a number of measures. Unlike experiment one, only two subjects adopted strategies that used both hands simultaneously. The benefits of the two-handed technique, therefore, are interpreted as being due to efficiency of hand motion. However, the two subjects who did use parallel strategies had the two fastest times of all subjects.

A comparison of input devices in element pointing and dragging tasks

An experiment is described comparing three devices (a mouse, a trackball, and a stylus with tablet) in the performance of pointing and dragging tasks. During pointing, movement times were shorter and error rates were lower than during dragging. It is shown that Fitts’ law can model both tasks, and that within devices the index of performance is higher when pointing than when dragging. Device differences also appeared. The stylus displayed a higher rate of information pmeessing than the mouse during pointing but not during dragging. The trackball ranked third for both tasks,

Realizing a video environment: EuroPARC's RAVE system

At EuroPARC, we have been exploring ways to allow physically separated colleagues to work together effectively and naturally. In this paper, we briefly discuss several examples of our work in the context of three themes that have emerged: the need to support the full range of shared work; the desire to ensure privacy without giving up unobtrusive awareness; and the possibility of creating systems which blur the boundaries between people, technologies and the everyday world.

The limits of expert performance using hierarchic marking menus

A marking menu allows 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. A hierarchic marking menu uses hierarchic radial menus and “zig-zag” marks to select from the hierarchy. This paper experimentally investigates the bounds on how many items can be in each level, and how deep the hierarchy can be, before using a marking to select an item becomes too slow or prone to errors.

Two-handed input in a compound task

Four techniques for performing a compound drawing/color selection task were studied: a unimanual technique, a bimanual technique where different hands controlled independent subtasks, and two other bimanual techniques in which the action of the right hand depended on that of the left hand. We call this latter class of two-handed technique “asymmetric dependent,” and predict that because tasks of this sort most closely conform to bimanual tasks in the everyday world, they would give rise to the best performance. Results showed that one of the asymmetric bimauual techniques, called the Toolglass technique, did indeed give rise to the best overall performance. Reasons for the superiority of this technique are discussed in terms of their implications for design. These are contrasted with other kinds of two-handed techniques, and it is shown how, if designed inappropriately, two hands can be worse than one.

A taxonomy of see-through tools

Abstract In current interfaces, users select objects, apply operations, and change viewing parameters in distinct steps that require switching attention among several screen areas. Our See-Through Interface™ software reduces steps by locating tools on a transparent sheet that can be moved over applications with one hand using a trackball, while the other hand controls a mouse cursor. The user clicks through a tool onto application objects, simultaneously selecting an operation and an operand. Tools may include graphical filters that display a customized view of application objects. Compared to traditional interactors, these tools save steps, require no permanent screen space, reduce temporal modes, apply to multiple applications, and facilitate customization. This paper presents a taxonomy of see-through tools that considers variations in each of the steps they perform. As examples, we describe particular see-through tools that perform graphical editing and text editing operations. CR Categories and Subject Descriptors: I.3.6 [Computer Graphics]: Methodology and Techniques—interaction techniques; H.5.2 [Information Interfaces and Presentation): User Interfaces—interaction styles; I.3.3 [Computer Graphics]: Picture/Image Generation—viewing algorithms; 1.3.4 [Computer Graphics]: Graphics Utilities—graphics editors

Chunking and phrasing and the design of human-computer dialogues

The use of physical gestures to reinforce cognitive chunking is discussed. The thesis presented is that muscular tension and motion can be used to phrase human-computer dialogues. These phrases can be used to reinforce the chunking of low-level tasks that correspond to the higher-level primitives of the mental model that we are trying to establish. The relationship of such gestures to the issue of compatibility is also discussed. Finally, we suggest how to improve the use of grammar-based models in analysing and designing interaction languages.

Issues in combining marking and direct manipulation techniques

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.

Towards a comprehensive user interface management system

A UIMS developed at the University of Toronto is presented. The system has two main components. The first is a set of tools to support the design and implementation of interactive graphics programs. The second is a run-time support package which handles interactions between the system and the user (things such as hit detection, event detection, screen updates, and procedure invocation), and provides facilities for logging user interactions for later protocol analysis. The design/implementation tool is a preprocessor, called MENULAY, which permits the applications programmer to use interactive graphics techniques to design graphics menus and their functionality. The output of this preprocessor is high-level code which can be compiled with application-specific routines. User interactions with the resulting executable module are then handled by the run-time support package. The presentation works through an example from design to execution in a step-by-step manner.