Distributed Virtual Environments Research Articles

A Multiplayer Virtual Intelligent System Based on Distributed Virtual Reality

Distributed Virtual Reality (DVR) is a combination of network and virtual reality technology, it could facilitate to construct a uniformly shared Distributed Virtual Environment (DVE) by using network to connect geographically distributed multiplayers. This paper concentrates on the theoretical research and practical development about Multiplayer Virtual Intelligent System (MVIS), and the main contribution could be summarized as two points. (1) Based on the DVR technology, this paper presented some theoretical research on MVIS, including the classification of virtual entities, communication pattern of entities, and the behavioral consistency research. Furthermore, a Multiplayer Earliest Deadline First (MEDF) program was proposed in order to guarantee the consistency of entities. (2) A prototype algorithm experiment system, called Multiplayer Graph-algorithm Intelligent System (MGIS), was designed. MGIS not onlyefficiently solves many problems in traditional computer algorithm teaching, such as high-abstraction, difficulty to understand, and lack of interaction mechanism; but also extends the application of DVR to cultural tourism, because MGIS is developed on the 3D scene of Lushan Mountain, which is one of the notable tourist attractions in China, and was included in the UNESCO World Heritage list in 1996. What i’s more, MGIS illustrates the ability of expression, applicability and generality of the theoretical research about MVIS.

Consensus Based Networking of Distributed Virtual Environments.

Distributed virtual environments (DVEs) are challenging to create as the goals of consistency and responsiveness become contradictory under increasing latency. DVEs have been considered as both distributed transactional databases and force-reflection systems. Both are good approaches, but they do have drawbacks. Transactional systems do not support Level 3 (L3) collaboration: manipulating the same degree-of-freedom at the same time. Force-reflection requires a client-server architecture and stabilisation techniques. With Consensus Based Networking (CBN), we suggest DVEs be considered as a distributed data-fusion problem. Many simulations run in parallel and exchange their states, with remote states integrated with continous authority. Over time the exchanges average out local differences, performing a distribued-average of a consistent, shared state. CBN aims to build simulations that are highly responsive, but consistent enough for use cases such as the piano-movers problem. CBN's support for heterogeneous nodes can transparently couple different input methods, avoid the requirement of determinism, and provide more options for personal control over the shared experience. Our work is early, however we demonstrate many successes, including L3 collaboration in room-scale VR, 1000's of interacting objects, complex configurations such as stacking, and transparent coupling of haptic devices. These have been shown before, but each with a different technique; CBN supports them all within a single, unified system.

Phaneros: Visibility‐based framework for massive peer‐to‐peer virtual environments

AbstractContemporary distributed virtual environments are growing out of terabytes of 3D content and hundreds of thousands of users. Server–client architectures have become inadequate for fulfilling the scalability requirements. The peer‐to‐peer architectures provide inherently scalable, cost‐effective distributed solutions for distributed virtual environments. We present a fully distributed peer‐to‐peer framework, Phaneros, which is capable of providing necessary means to realize more efficient and more scalable massive distributed virtual environments. Using the presented visibility‐aware interest management, Phaneros performs better than existing overlays, achieving single‐hop update dissemination while having lower bandwidth requirements. The provided visibility‐aware 3D streaming scheme distributes 3D content more efficiently without creating any significant load on the server. Our test results show significant improvements over existing frameworks.

Consistency and fairness in real-time distributed virtual environments: Paradigms and relationships

Distributed real-time virtual environments entail a well-known set of trade-offs resulting in a lack of state consistency across simulation nodes. This lack of consistency gives rise to a number of challenges that must be addressed by system designers to ensure users remain engaged and satisfied. This paper surveys several approaches to defining, measuring, and controlling the consistency of simulation state data and relates them to the concepts of fairness and fitness for purpose. The interplay between consistency and fairness, in relation to fitness for purpose, must be carefully considered by system engineers to ensure appropriate design trade-offs.

A Fairness Oriented Consistency Control Method in Distributed Virtual Environment Systems

The distributed virtual environment (DVE) system needs to adopt the consistency control method to maintain the state consistency of each node. Existing consistency control methods mainly consider how to increase the consistency of the whole system with a small overhead, and often neglect the important role of fairness in the virtual environment system. In fact, in many DVE systems, the fairness of all users in the virtual world plays an important role in the usability of the system. In this paper, we propose a new fairness-oriented consistency control method, which ensures the fairness of each node in terms of inconsistency degree by adjusting the ahead deviation time of each node, thus improving the usability of the system. Experimental results show that our method can significantly improve the fairness of the distributed virtual environment system.

A Dynamic Load Balancing Method in Hexagonal Cell Based DVE Systems

Load balancing problem is one of the key issues in multi-server architecture Distributed Virtual Environment (DVE) system. Existing load balancing methods are mainly for the one-dimensional cutting based DVE system or square cell based DVE system, and it is difficult to apply them to the hexagonal cell based DVE system. In this paper, we propose a new load balancing method for hexagonal cell virtual environment system, which can effectively reduce the number of overloaded server at run time and reduce the client migrations between servers by selecting appropriate migration cells. The experimental results show that the proposed method can effectively keep the load balance among servers in the virtual environment system based on hexagon partitioning and reduce the probability of client migrations, thus improving the usability of the system.

On designing and testing distributed virtual environments

SummaryDistributed real‐time (DRT) systems are among the most complex software systems to design, test, maintain, and evolve. The existence of components distributed over a network often conflicts with real‐time requirements, leading to design strategies that depend on domain‐specific and even application‐specific knowledge. Distributed virtual environment (DVE) systems are DRT systems that connect multiple users instantly with each other and with a shared virtual space over a network. DVE systems deviate from traditional DRT systemsx in the importance of the quality of the end user experience. We present an analysis of important, but challenging, issues in the design, testing, and evaluation of DVE systems through the lens of experiments with a concrete DVE, OpenSimulator. We frame our observations within six dimensions of well‐known design concerns: correctness, fault tolerance/prevention, scalability, time sensitivity, consistency, and overhead of distribution. Furthermore, we place our experimental work in a broader historical context, showing that these challenges are intrinsic to DVEs and suggesting lines of future research. Copyright © 2016 John Wiley & Sons, Ltd.

Object-Based Viewpoint For Large-Scale Distributed Virtual Environment

Distributed Virtual Environment (DVE) is a shared application consisting many objects, which can be accessed by many users. There have been many methods used to scale the DVE such as dividing simulation workload, dynamic load balancing among servers, and creating alternative architectures. However, they may not accommodate many objects and users. In this paper, we explore all approaches used to scale the DVE and then determine the characteristics of the existing approaches. With those characteristics, we compared existing approaches based on three parameters: the number of simulation per region, implementation, and the number of objects managed by simulator. The results show that all approaches use the same viewpoint, called present viewpoint, in developing the DVE. It views DVE as a world where all objects and activities are managed by a simulator. The results also show that this viewpoint contributes in terms of limitations of the current DVEs performance. In response to these results, we further propose a new viewpoint, called object-based viewpoint, to generate object-based simulators architecture. The experiment results show that our proposed architecture can provide a large scale DVE with better performances than the previous architectures.

Consistency-Aware Zone Mapping and Client Assignment in Multi-Server Distributed Virtual Environments

In Distributed Virtual Environments (DVEs), the primary task is to maintain a consistent view of the virtual world among all users. Multi-server architecture has been shown to have good scalability to support a large population of users in DVEs. In the zone-based Multi-server Distributed Virtual Environment (MSDVE), zone mapping and client assignment are two key issues in the design of an efficient and scalable MSDVE. Most of the existing work on the zone mapping and client assignment issues in MSDVE aims to either balance workload among servers, reduce inter-server communication, and/or reduce transmission delay. In this paper, we study the zone mapping and client assignment issues from a new perspective aiming to reduce the inconsistency of a DVE. Using the time-space inconsistency metric, we formally formulate the problem as a mix integer programming problem. The zone mapping and client assignment strategy is proposed which consists of a centralized algorithm for initialization and a distributed adaptive tuning algorithm for running system. Extensive experiments were conducted both by simulation and real system for evaluating the performance of the proposed solutions and results are reported in the paper.

On View Consistency in Multi-Server Distributed Virtual Environments

A distributed virtual environment (DVE) is a shared virtual environment (VE) that allows remote users to interact with each other through networks. DVEs are becoming very popular due to some prominent applications, such as online games and virtual worlds. To support a large number of users, a multi-server DVE architecture may be adopted, with each server managing a subset of users. However, there are two critical problems with this architecture: view inconsistency caused by delays and server overloading caused by uneven distribution of users. While the first problem affects users' perception of the VE and causes user disputes, the second problem affects the system response time. In this paper, we first show that the view inconsistency problem and the load balancing problem are conflicting objectives. We then propose an efficient joint optimization framework to address both problems. Our results show that the proposed method can improve the view inconsistency problem significantly, which is important to the interactivity of DVE applications.

Space-Time Matching Algorithms for Interest Management in Distributed Virtual Environments

Interest management in Distributed Virtual Environments (DVEs) is a data-filtering technique designed to reduce bandwidth consumption and therefore enhances the scalability of the system. This technique usually involves a process called interest matching , which determines what data should be sent to the participants as well as what data should be filtered. Although most of the existing interest matching approaches have been shown to meet their runtime performance requirements, they have a fundamental disadvantage—they perform interest matching at discrete time intervals. As a result, they would fail to report events between discrete timesteps. If participants of the DVE ignore these missing events, they would most likely perform incorrect simulations. This article presents a new approach called space-time interest matching , which aims to capture the missing events between discrete timesteps. Although this approach requires additional matching effort, a number of novel algorithms are developed to significantly improve its runtime efficiency.

ICO2: A Networked Game for Collecting Large-Scale Eco-Driving Behavior Data

iCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is a networked game that aims to collect human driving behavior data at scale and help researchers better understand how people apply eco-driving practices. iCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is an integrated multiplatform game that can be accessed via Web client on Facebook and iPad clients, and supports a shared traffic experience among its users. Here, the authors describe iCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and discuss two key efforts and their results. First, they investigated the scalability of Distributed Virtual Environments (DiVE), the networking framework they developed for multiuser 3D virtual world applications. The "area of interest" method that DiVE uses was tested in a laboratory setting and showed promising results on two important metrics: bandwidth and frames per second. Second, they ran a small marketing campaign to collect data from users interacting with the iPad version of iCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> "in the wild." They then analyzed the users' acceleration behavior, an important aspect of eco-driving.

An efficient caching algorithm for peer-to-peer 3D streaming in distributed virtual environments

Recent technical progress on the Internet and virtual reality has enabled the proliferation of the applications of distributed virtual environments (DVEs). In a DVE, high-resolution 3D contents may generate huge data while peer-to-peer (P2P) streaming takes advantages to carry these huge traffic in a cost-effective manner. In this P2P paradigm, peers can cache and share DVE data cooperatively to reduce server workload and improve streaming quality. Nevertheless, it is critical to maintain and update the cached contents in each peer efficiently. In this paper, we propose an efficient caching algorithm for a P2P 3D content streaming framework. The proposed caching algorithm is based on a new preservation metric that is defined for balancing visual saliency, reusability and potential relevance of cached 3D objects. Then, these cached 3D objects in each peer are updated adaptively with the ascendant order in importance quantified using this new metric. We implemented the proposed caching algorithm in a simulated DVE platform for P2P-based 3D streaming. We conducted a comprehensive simulation study and our experimental results demonstrate that the proposed peer-to-peer streaming method outperforms the classic 3D streaming methods (including FLoD and MRM) in terms of fill ratio, base latency, requests by nodes and requests to the server.

Ambient Privacy with Wireless Grids: Forging New Concepts of Relationship in 21st Century Information Society

This study combines ambient intelligence with wireless grids to investigate ambient privacy in socio-technical interactions in emerging and next generation technology-pervasive environments. The research literature on 21 st century social sciences, ambient intelligence, wireless grids, futures studies, and privacy provides a theoretical framework for the exploration of ambient privacy in 21 st century environments. Use experience with WeJay social radio is explored in a virtual distributed environment. The research design incorporates a case study approach, employing multiple methods of inquiry and analysis. Findings related to ambient privacy at the early design stage of an awareenabled wireless grid product draw on the concepts of underdesign, privacy by design (PbD), and sensitive information, contributing to the forging of new technology-people-information relationships and understandings. This paper makes a contribution to the literature in several domains through development of the ambient privacy concept. This research proposes an ambient privacy interaction dynamic; an ambient privacy research framework; and an agenda to guide ambient privacy research and practice for a 21 st century information society.

Dynamic load balancing in distributed virtual environments using heat diffusion

Distributed virtual environments (DVEs) are attracting a lot of attention in recent years, due to the increasing popularity of online gaming and social networks. As the number of concurrent users of a DVE increases, a critical problem is on how the workload among multiple servers can be balanced in order to maintain real-time performance. Although a number of load balancing methods have been proposed, they either try to produce high quality load balancing results and become too slow or emphasize on efficiency and the load balancing results become less effective. In this article, we propose a new approach to address this problem based on heat diffusion. Our work has two main contributions. First, we propose a local and a global load balancing methods for DVEs based on heat diffusion. Second, we investigate two performance factors of the proposed methods, the convergence threshold and the load balancing interval. We have conducted a number of experiments to extensively evaluate the performance of the proposed methods. Our experimental results show that the proposed methods outperform existing methods in that our methods are effective in reducing server overloading while at the same time being efficient.

Update schedules for improving consistency in multi-server distributed virtual environments

Distributed Virtual Environments (DVEs) have been widely used in online games, military training and collaborative engineering applications, etc. In DVEs, the primary task is to maintain a consistent view of the virtual world among all users. Multi-server architecture has been shown to have good scalability to support a large population of users in DVEs. However, servers can still get saturated with network bandwidth due to several reasons. In this case, state updates cannot be disseminated timely and the consistency of the virtual world cannot be guaranteed. This paper investigates update schedules to prioritize state updates from a global perspective for improving consistency in multi-server DVEs where each server has a limit on upload bandwidth. Using time–space inconsistency (TSI) metric, we analyze the problem using Lagrange Multipliers for a DVE in an ideal situation with unchanged configurations and the results are then used to develop an updating algorithm in practical systems. Experimental results show that the proposed algorithm significantly improves the consistency compared to other existing update algorithms.

Reducing view inconsistency by predicting avatars' motion in multi-server distributed virtual environments

Multi-server distributed virtual environment (DVE) system contains a set of servers to support a huge number of geographically distributed users. It provides a shared virtual scenario where users represented by avatars participate in and interact with each other through networks. However, there are two technical challenges in designing an efficient DVE system with this architecture: view inconsistency caused by network delays and server overloading caused by uneven distribution of users. While the first problem affects users' perception of the VE and causes user disputes, the second problem affects the system response time. We present a new partitioning framework to simultaneously address the two problems, in which the DVE scenario is divided into a set of disjoint grids called virtual cells. The virtual cells are then indexed by a region quadtree and an algorithm is proposed to search the region quadtree so as to equally partition avatars among servers. By using probabilistic models to predict each avatar's future motion and the virtual region its area of interest (AOI) will cover, a density-based method is proposed to help each server construct avatar clusters from its local avatars in parallel. By estimating the possible distances of avatar's future position to the geometry center of each cluster, an algorithm is proposed to repartition non-assigned avatars among servers so as to reduce view inconsistency and preserve workload balancing among the servers. We conducted comprehensive experiments to evaluate our method by comparing it with other approaches.

Tangible mixed reality for remote design review: a study understanding user perception and acceptance

Abstract Background The design review process is often expensive due to the need for face-to-face meetings between the involved parties. Distributed design collaboration is made possible by advances in networking techniques. A tangible Mixed Reality (MR)-based virtual design prototype was created as a distributed virtual environment (DVE) for the purpose of improving remote design review collaboration. This tangible MR system has been developed to a point that experimental evaluation is necessary in order to understand the strengths and weaknesses of various features of the system. Methods In this paper, we evaluated the tangible MR system against a commercial 3D distributed design review system in three aspects: the investigation of how users experienced virtual models in the tangible MR system as compared with the commercial system, the measurement of the users’ attitude towards the effectiveness of the tangible MR system, and the discoveries of usability issues involved in the tangible MR interface through usability studies. Results The findings from user feedback suggest that the tangible MR system may facilitate problem-solving and the quantity of work in a given amount of time and that virtual design displayed in the mixed scene was a useful aid in the design error detection task. Conclusion These findings are useful for the improvement of future generations of the MR system. Also the suggestions can be further generalized to become usability guidelines for the MR developers in other applications and domains.

Dynamic causal order control approach in distributed virtual environment on wide area network

In a Distributed Virtual Environment(DVE) system running on Wide Area Network(WAN),the control effect of causal order consistency is determined by both the correctness of causality and the real-time due to the large network transmission delay.In order to achieve a better trade-off between the quality of causal order consistency and real-time in a DVE,a new dynamic causal order control approach was proposed.The core idea of this approach was to dynamically adjust and balance the amount of blocked effect messages and that of delayed causal messages on each site in a DVE system,so as to meet the demands of causality correctness and real-time requirement on message ordering delivery.The evaluation results demonstrate that the proposed approach can outperform the previous ones by effectively improving the quality of causal order control while simultaneously preserving the real-time property of DVE systems.

Caffe Neve

The popularization of podcasting provides Internet users more opportunities to access interesting and entertaining multimedia content. The podcasting content hosting sites became the shared platforms for all Internet users to access third-party contributions. More and more Internet users are encouraged to become active content providers that share their resources and multimedia productions. Building a large scale multi-user 3D application can benefit from the same content distribution pattern as the development cost can be distributed if the application implementation is outsourced. The application is constructed by integrating 3D content from various third-party service providers. In addition, the implementation outsourcing can inspire contributors to provide creative application content. Unfortunately, sharing and distributing 3D resources are more challenging and the podcasting framework cannot resolve the problems effectively. We introduce a standardized framework that supports the seamless integration of distributed 3D resources as coarse-grained components of constructed Distributed Virtual Environments (DVEs). Component Application Framework For Extensible NEtworked Virtual Environments (Caffe Neve) uses service-oriented architecture (SOA) and incorporates streaming technology for dynamic content delivery. Using Caffe Neve, third-party developers can create distributed services to stream 3D content. The framework provides an application integrator that constructs a shared virtual environment and delivers the application content to the end users. In this paper we describe the framework details. The application integration infrastructure of the framework is designed based on a distributed Model-View-Controller model. The framework uses an ontology to support the semantic level content integration and service coordination. In addition, the framework incorporates streaming within the architecture for the real-time data delivery and improved performance. By deploying services within the framework, 3D resource owners can conveniently podcast or broadcast their 3D content to the end users. In the end, we demonstrate how to use the framework to construct 3D podcast and broadcast applications. Regardless of the type of 3D applications and delay tolerance, performance is important and has to be carefully studied. We evaluate the framework performance by examining the sample application and present the analysis results. We also present the experiment results on the simulated framework application in large scale by using simulation tools.