Steering in layers above the display surface

Interaction techniques that use the layers above the display surface to extend the functionality of pen-based digitized surfaces continue to emerge. In such techniques, stylus movements are constrained by the bounds of a layer inside which the interaction is active, as well as constraints on the direction of movement within the layer. The problem addressed in this thesis is that designers currently have no model to predict movement time (MT) or quantify the difficulty, for movement (steering) in layers above the display surface constrained by thickness of the layer, its height above the display, and the width and length of the path. The problem has two main parts: first, how to model steering in layers, and second, how to visualize the layers to provide feedback for the steering task. The solution described is a model that predicts movement time and that quantifies the difficulty of steering through constrained and unconstrained paths in layers above the display surface. Through a series of experiments we validated the derivation and applicability of the proposed models. A predictive model is necessary because the model serves as the basis for design of interaction techniques in the design space; and predictive models can be used for quantitative evaluation of interaction techniques. The predictive models are important as they allow researchers to evaluate potential solutions independent of experimental conditions.Addressing the second part of the problem, we describe four visualization designs using cursors. We evaluated the effectiveness of the visualization by conducting a controlled experiment

Second Workshop on Practical Use of Coloured Petri Nets and Design/CPN.

This report contains the proceedings of the Second Workshop on Practical Use of Coloured Petri Nets and Design/CPN, October 13-15, 1999. The workshop was organised by the CPN group at the Department of Computer Science at the University of Aarhus, Denmark. The individual papers are available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop99

Using the Multi-Layer Model for Building Interactive Graphical Applications

Most interactive graphical applications that use direct manipulation are built with low-level libraries such as Xlib because the graphic and interaction models of higher-level toolkits such as Motif are not extensible. This results in high design, development and maintenance costs and encourages the development of stereotyped applications based on buttons, menus and dialogue boxes instead of direct manipulation of the applications objects. In this article we argue that these drawbacks come from the fact that high-level toolkits rely on a visualization model to manage interaction. We introduce a model that uses several graphical layers to separate the graphic entities involved in visualization from those involved in feedback and interaction management. We describe the implementation of this MultiLayer Model and we show how it can take advantage of software and hardware graphic extensions to provide good performance. We also show how it supports multiple input devices and simplifies the description of a wide variety of interaction styles. Finally, we describe our experience in using this model to implement a set of editors for a professional animation system