Patrick Hartling

VR Juggler: a virtual platform for virtual reality application development

Today, scientists and engineers are exploring advanced applications and uses of immersive systems that can be cost-effectively applied in their fields. However, one of the impediments to the widespread use of these technologies is the extensive technical expertise required of application developers. A software environment that provides abstractions from specific details of hardware configurations and low-level software tools is needed to provide a common base for the prototyping, development, testing and debugging of applications. This paper describes VR Juggler, a virtual platform for the creation and execution of immersive applications, that provides a virtual reality system-independent operating environment. We focus on the approach taken to specify, design and implement VR Juggler and the benefits derived from our approach.

Virtual reality interfaces using Tweek

Developers of virtual environments often face a difficult problem: users must have some way to interact with the virtual world. The application developers must determine how to map available inputs (buttons, gestures, etc.) to actions within the virtual environment (VE). As a result, user interfaces may be limited by the input hardware available with a given virtual reality (VR) system.

Implementing immersive clustering with VR juggler

Continuous, rapid improvements in commodity hardware have allowed users of immersive visualization to employ high-quality graphics hardware, high-speed processors, and significant amounts of memory for much lower costs than would be possible with high-end, shared memory computers traditionally used for such purposes. Mimicking the features of a single shared memory computer requires that the commodity computers act in concert—namely, as a tightly synchronized cluster. In this paper, we describe the clustering infrastructure of VR Juggler that enables the use of distributed and clustered computers for the display of immersive virtual environments. We discuss each of the potential ways to synchronize a cluster for immersive visualization in use today. Then, we describe the VR Juggler cluster infrastructure in detail, and we show how it allows virtual reality application developers to combine various existing clustering techniques to meet the needs of their specific applications.

Distributed virtual reality using Octopus

With the widespread popularity of the Internet and advances in distributed computing and in virtual reality, more flexibility is needed in the development and use of collaborative virtual environments. In this paper, we present Octopus, a cross-platform, object-oriented API for constructing shared virtual worlds. The list of goals for Octopus, a description of its design and a detailed discussion of its implementation are provided. The design description gives explanations of the three components of Octopus: the core that handles networking and data sharing, the interface for implementing user representations in the virtual space (avatars), and the actual implementations of the avatars.

VjControl: an advanced configuration management tool for VR Juggler applications

Virtual reality (VR) installations are often unique; every one is a complex blend of hardware devices, displays and computing resources. The configuration of VR software is therefore a difficult and time-consuming process. VR Juggler, our toolkit for VR application development, addresses these problems with a number of innovations. VR Juggler provides a unique system for organizing the configuration information for a system and minimizing the proliferation of configuration files that many systems suffer. It provides a graphical tool, called VjControl, for editing configurations, which can protect users from many common mistakes. VR Juggler also has advanced capabilities for monitoring and altering the configuration of a running immersive application.

Analyzing the performance of a cluster-based architecture for immersive visualization systems

Cluster computing has become an essential issue for designing immersive visualization systems. This paradigm employs scalable clusters of commodity computers with much lower costs than would be possible with the high-end, shared memory computers that have been traditionally used for virtual reality purposes. This change in the design of virtual reality systems has caused some development environments oriented toward shared memory computing to require modifications to their internal architectures in order to support cluster computing. This is the case of VR Juggler, which is considered one of the most important virtual reality application development frameworks based on open source code. This paper not only describes in detail the mechanisms based on cluster computing included in the internal design of VR Juggler, but also proposes a new global performance evaluation methodology. The goal of this methodology is to test the graphical performance of immersive visualization systems based on clusters of computers in terms of both network latency and number of nodes in the cluster. In this sense, a performance evaluation of VR Juggler, both in an overall and a modular approach, is presented. The obtained results show that VR Juggler can be considered as an efficient tool to support immersive visualization systems on a cluster of computers.

Open source virtual reality

This tutorial provides an overview of VR application development using Open Source software tools. We focus on the VR Juggler suite of tools (see http://www.vrjuggler.org) and various Open Source projects that can work with it. We will demonstrate how Open Source software ensures extensibility and eases integration between software tools. We will also show how leveraging existing and emerging Open Source projects can lower development times and costs while simultaneously increasing portability and stability. In particular, we will discuss several kinds of Open Source VR software: • Development frameworks for immersive VR applications (VR Juggler) • Scene graphs for managing application data. (OpenSG or OpenSceneGraph). • Clustering software for powering low-cost VR systems (NetJuggler). • Collaboration software for writing interactive, networked applications (primarily discussing software currently under development by the VR Juggler team). • Various other tools needed to write compelling applications, such as audio libraries, scripting capabilities, and navigation systems, and how they can be used by VR Jugglerbased applications.

Automated testing of virtual reality application interfaces

We describe a technique for supporting testing of the interaction aspect of virtual reality (VR) applications. Testing is a fundamental development practice that forms the basis of many software engineering methodologies. It is used to ensure the correct behavior of applications. Currently, there is no common pattern for automated testing of VR application interaction. We review current software engineering practices used in testing and explore how they may be applied to the specific realm of VR applications. We then discuss the ways in which current practices are insuficient to test VR application interaction and propose a testing architecture for addressing the problems. We present an implementation of the design written on top of the VR Juggler platform. This system allows VR developers to employ standard software engineering techniques that require automated testing methods.

Tweek: a framework for cross-display graphical user interfaces

Developers of virtual environments (VEs) face an often-difficult problem: users must have some way to interact with the virtual world. The VE application designers must determine how to map available inputs to actions within the virtual world. However, manipulating large amounts of data, entering alphanumeric information, or performing abstract operations may not map well to current VE interaction methods, which are primarily spatial. Furthermore, many VE applications are derived from mature desktop applications that typically have a very rich user interface (UI). This paper presents Tweek, a reusable, extensible framework for UI construction that allows use of the same UI on a desktop system, on a hand-held computer, or in an immersive 3D space. Designers can maintain interaction consistency across conventional visualization settings such as desktop systems and multi-screen immersive systems. This paper covers in detail the design of Tweek and its use as an input device for virtual environments.

Scalable VR application authoring

This course will provide attendees with the technical information needed to create their own compelling, scalable, interactive VR applications using VR Juggler. The, course begins with the foundations needed for building VR Juggler applications. It follows with a session on VR Juggler scalability from shared memory high-end workstations to clusters of commodity PCs. The following sessions focus on effective use of VR Juggler as a desktop-to-immersive visualization tool, including the portability of interaction methods. The course concludes with advanced VR Juggler embedded features such as virtual characters and collaboration.