Wouter Pasman

Implementation of an augmented reality system on a PDA

We present a client/server implementation for running demanding mobile AR application on a PDA device. The system incorporates various data compression methods to make it run as fast as possible on a wide range of communication networks, from GSM to WLAN.

Improving service matching and selection in ubiquitous computing environments: a user study

In large ubiquitous computing environments it is hard for users to identify and activate the electronic services that match their needs. This user study compares the newly developed service matcher system with a conventional system for identifying and selecting appropriate services. The study addresses human factors issues such as usability, trust and service awareness. With the conventional system users have to browse a hierarchical list of currently available services and activate the service that they think satisfies their current needs. With the service matcher users just enter their current need using natural language, after which a wizard, emulating an existing service matcher algorithm, searches for and activates a matching service based on the given need and the users’ location and gaze direction. This study shows that with the hierarchical list, only 66% of the tasks are solved correctly, and females score significantly worse than males. With the service matcher, the performance increases significantly to 84% correctly performed tasks and the gender difference disappears.

Accurate overlaying for mobile augmented reality

Mobile augmented reality requires accurate alignment of virtual information with objects visible in the real world. We describe a system for mobile communications to be developed to meet these strict alignment criteria using a combination of computer vision, inertial tracking and low-latency rendering techniques. A prototype low-power and low-latency renderer using an off-the-shelf 3D card is discussed.

Unreal Goal Bots

It remains a challenge with current state of the art technology to use BDI agents to control real-time, dynamic and complex environments. We report on our effort to connect the GOAL agent programming language to the real-time game UNREAL TOURNAMENT 2004. We focus in particular on the design of a suitable interface to manage agent-bot interaction and argue that the use of a recent toolkit for developing an agent-environment interface provides many advantages.It remains a challenge with current state of the art technology to use BDI agents to control real-time, dynamic and complex environments. We report on our effort to connect the GOAL agent programming language to the real-time game UNREAL TOURNAMENT 2004. BDI agents provide an interesting alternative to control bots in a game such as UNREAL TOURNAMENT to more reactive styles of controlling such bots. Establishing an interface between a language such as GOAL and UNREAL TOURNAMENT, however, poses many challenges. We focus in particular on the design of a suitable and reusable interface to manage agent-bot interaction and argue that the use of a recent toolkit for developing an agent-environment interface provides many advantages. We discuss various issues related to the abstraction level that fits an interface that connects high-level, logic-based BDI agents to a real-time environment, taking into account some of the performance issues.

Augmented reality with large 3D models on a PDA: implementation, performance and use experiences

We have implemented a client/server system for running augmented reality applications on a PDA device. The system incorporates various data compression methods to make it run as fast as possible on a wide range of communication networks, from mobile phone links to WLAN, We provide a detailed description of various implementation issues, data compression optimisations, and performance analysis of the system, Usability of the system is evaluated in a demanding architectural application, with a large virtual building rendered in an outdoors location.

Comparing simplification and image-based techniques for 3D client-server rendering systems

A mathematical model is presented for comparing geometric and image-based simplification methods. Geometric simplification reduces the number of polygons in the virtual object and image-based simplification replaces the object with an image. Our model integrates and extrapolates existing accuracy estimates, enabling the comparison of different simplification methods in order to choose the most efficient method in a given situation. The model compares data transfer and rendering load of the methods. Byte size and expected lifetime of simplifications are calculated as a function of the desired visual quality and the position and movement of the viewer. An example result is that, in typical viewing and rendering conditions and for objects with a radius in the order of one meter, imposter techniques can be used at viewing distances above 15 meters. Below that, simplified polygon objects are required and, below one meter distance, the full-resolution virtual object has to be rendered. An electronic version of the model is available on the web.

Exploring Heuristic Action Selection in Agent Programming

Rational agents programmed in agent programming lan- guages derive their choice of action from their beliefs and goals. One of the main benefits of such programming languages is that they facilitate a high-level and conceptually elegant specification of agent behaviour. Qualitative concepts alone, however, are not sufficient to specify that this behaviour is also nearly optimal, a quality typically also associated with rational agents. Optimality in this context refers to the costs and rewards associated with action execution. It thus would be useful to extend agent programming languages with primitives that allow the specification of near-optimal behaviour. The idea is that quantitative heuristics added to an agent program prune some of the options generated by the qualitative action selection mechanism. In this paper, we explore the expressivity needed to specify such behaviour in the Blocks World domain. The programming constructs that we introduce allow for a high-level specification of such heuristics due to the fact that these can be defined by (re)using the qualitative notions of the basic agent programming language again. We illustrate the use of these constructs by extending a Goal Blocks World agent with various strategies to optimize its behaviour.

Distributed low-latency rendering for mobile AR

Wearable augmented reality (AR) can help the task of a user by adding virtual objects to his view on the real world. To save power in the mobile unit, rendering can be offloaded to the backbone as much as possible. However, because of low latency requirements, images for mobile AR cannot be rendered completely in the backbone. We developed a system capable of end-to-end latencies of 10ms, with a seamless fitting dynamic level-of-detail framework extending the VRML and Inventor language, and building on current trends in QoS handling. The authors outline the structure and components of our system, and discuss a demo application projecting a statue on the campus.

Organizing ad hoc agents for human-agent service matching

Ambient intelligence, distributed agent systems, smart buildings and other emerging architectures leave the user lost between large amounts of autonomous entities or agents. With agents in cars, personal devices and other mobile systems, the set of agents available to the user can change rapidly, adding to the problems. We propose a set of agent relations to organize agents in an ad hoc situation. There are dynamic task-, location- and user relations, creating multiple relation hierarchies in agent space. These hierarchies allow robust, space- and task limited, context-sensitive search through agent space. We show how to use this structure to keep user interfaces near the user, and how it can be used to support the user in finding the agent he needs in a context-sensitive way.

Scheduling level of detail with guaranteed quality and cost

This paper presents a framework for handling and on-the-fly generation of levels of detail. The application directly controls the trade-off between the amount of resources to be used and the accuracy of the final images. The basis for this choice is an accuracy curve which explicates the trade-off. This curve is calculated and updated hierarchically, which makes it especially suited for use with a scene graph. Integration of the framework with VRML is described. Measurements on our prototype implementation show that target resource loads and accuracies can adequately be reached.