Precise 3D manipulation in virtual reality (VR) is essential for effectively aligning virtual objects. However, state-of-the-art VR manipulation techniques have limitations when high levels of precision are required, including the unnaturalness caused by scaled rotations and the increase in time due to degree-of-freedom (DoF) separation in complex tasks. We designed two novel techniques to address these issues: AMP-IT, which offers direct manipulation with an adaptive scaled mapping for implicit DoF separation, and WISDOM, which offers a combination of Simple Virtual Hand and scaled indirect manipulation with explicit DoF separation. We compared these two techniques against baseline and state-of-the-art manipulation techniques in a controlled experiment. Results indicate that WISDOM and AMP-IT have significant advantages over best-practice techniques regarding task performance, usability, and user preference.

State management is a fundamental requirement of multi-user applications like distributed simulations or networked games. The quality of the experience of such applications heavily depends on synchronous communication. The movement of an entity from one logical zone into another initiates reorganization of the peer-to-peer structure and eventually ruins synchronous interactions. The frequent nature of such event in the distributed simulations has significant impact on the performance and cannot be ignored. In this paper, we present a performance enhancement mechanism considering the physical attributes of the entities. We demonstrate that clustering the entities based on their physical characteristics or behavior significantly reduces peer- to-peer structural reformation penalties. The effectiveness of such clustering mechanism is simulated and analyzed in the context MMOG.

Synchronous communication is a primary concern for multi-user virtual environments like Massively Multiplayer Online Games (MMOGs). Most of the MMOGs offer discrete view for the avatars and follow logical zone layout for easy state management. The avatar movement, from one logical zone to another, causes reorganization at the P2P overlay structure. Its recurrent nature along with unintelligent zone crossing approaches eventually hampers synchronous communication. In this paper, we present performance enhancement mechanisms to reduce P2P overlay reorganization penalties based on avatars ’ physical characteristics. Avatars ’ unpredictable movement around the zone boundaries also incur repeated connections and disconnections either among the zone masters or among the multiple peers in the overlay networks. Interest driven zone crossing, dynamic shared region between adjacent zones, and clustering of the entities based on their attributes significantly alleviates these problems and also provides continuous view and seamless region crossing to players. The technical contribution of this paper is to present the effectiveness of object clustering mechanism and interest driven zone crossing with dynamic shared region between each adjacent zones to enhance the gaming experience of MMOG players or users of other types of networked virtual environments (VE).

Abstract Grid services provide an important abstract layer on top of heterogeneous components (hardware and software) that take part in a Grid environment. In this scenario, applications such as scientific visualization require access to data of non‐conventional data types, such as fluid path geometry, and the evaluation of special user programs and algebraic operators, such as spatial hash‐join, on these data. In order to support such applications we are developing a Configurable Data Integration Middleware System for the Grid (CoDIMS‐G). CoDIMS‐G provides a query execution environment adapted to the heterogeneity and variations found in a Grid environment by offering a node scheduling algorithm and an adaptive query execution strategy. The latter both adapts to performance variations in a scheduled node and deals efficiently with repetitive evaluation of a query execution plan fragment, as needed for computing a particle's, trajectory. Copyright © 2005 John Wiley & Sons, Ltd.

Abstract In this paper we propose a middleware infrastructure adapted for supporting scientific visualization applications over a Grid environment. We instantiate a middleware system from CoDIMS, which is an environment for the generation of configurable data integration middleware systems. CoDIMS adaptive architecture is based on the integration of special components managed by a control module that executes users workflows. We exemplify our proposal with a middleware system generated for computing particles' trajectories within the constraints imposed by a Grid environment. Copyright © 2004 John Wiley & Sons, Ltd.

Collaborative virtual environment (CVE) concepts have been used in many systems. The architectures available today provide support for a number of users but they fail if too many users are together in a small "space" in the virtual world. This paper introduces VELVET, an adaptive hybrid architecture which allows a greater number of users to interact through a CVE. VELVET introduces a novel adaptive area of interest management, which supports heterogeneity amongst the various participants.

Many critics of the Java language have pointed performance deficiencies as a barrier to acceptable support of Collaborative Multimedia Systems. This paper presents four MCRLab products, fully written in Java that support collaboration amongst a group of users, and successfully demonstrate that Java collaboration frameworks are not only possible but also can perform at acceptable levels of quality, if designed correctly.

The concept of collaborative virtual environments has been deployed in many systems in the past few years. Applications of such technology have been used anywhere from military combat simulations to various civilian commercial applications. We present a specific system developed for industrial teletraining. The system, which aims to reduce the cost of training, consists of an interactive 3D environment with collaboration and management capabilities that allows a trainer to lead and control a session attended by many trainees.