Key Technologies for Networked Virtual Environments

Thanks to the improvements experienced in technology in the last few years, most especially in virtual reality systems, the number and potential of networked virtual environments or NVEs and their users are increasing. NVEs aim to give distributed users a feeling of immersion in a virtual world and the possibility of interacting with other users or with virtual objects inside it, like when they interact in the real world. Being able to provide that feeling and natural interactions when the users are geographically separated is one of the goals of these systems. Nevertheless, this goal is especially sensitive to different issues, such as different connections with heterogeneous throughput or different network latencies, which can lead to consistency and synchronization problems and, thus, to a worsening of the users' quality of experience or QoE. With the purpose of solving these issues, researchers have proposed and evaluated numerous technical solutions, in fields like network architectures, data distribution and filtering, resource balancing, computing models, predictive modeling and synchronization in NVEs. This paper gathers and classifies them, summarizing their advantages and disadvantages, using a new way of classification. With the current increase of the number of NVEs and the multiple solutions proposed so far, this work aims to become a useful tool and a starting point not only for future researchers in this field but also for those who are new in NVEs development, in which guaranteeing a good users' QoE is essential.Comment: Submitted to Springer Multimedia System

Collaborative Distributed Virtual Sculpting

A lot of effort is now being put into developing collaborative distributed virtual environments. However, very few projects address collaborative virtual sculpting in which the shapes of the target objects are likely changing continuously. Some major issues including user interaction, data transmission, concurrent object editing by multiple clients and rendering of deforming objects must be addressed in a real-time context. In this paper, we propose a framework for collaborative virtual sculpting in a distributed virtual environment. The system is based on a hybrid model which merges the client-server and the peer-to-peer architectures to allow fast data replication. To support real-time deformation and rendering of deformable objects, we model each of these objects using NURBS surfaces and render them using the real-time deformable NURBS rendering method that we have developed. We will present a data structure for the transmission of these deformable objects. We will also introduce the idea of editing region and the corresponding locking mechanism for simultaneous editing of the same object by multiple clients. Toward the end of the paper, we will show some performance results of the prototype system.

Collaborative Distributed Virtual Sculpting

A lot of effort is now being put into developing collaborative distributed virtual environments. Howevel; very few projects address collaborative virtual sculpting in which the shapes of the target objects are likely changing continuously. Some major issues including user interaction, data transmission, concurrent object editing by multiple clients and rendering of deforming objects must be addressed in a real-time context. In this papel; we propose a framework for collaborative virtual sculpting in a distributed virtual environment. The system is based on a hybrid model which merges the client-server and the peer-to-peer architectures to allow fast data replication. To support real-time deformation and rendering of deformable objects, we model each of these objects using NURBS surfaces and render them using the real-time deformable NURBS rendering method that we have developed. We will present a data structure for the transmission of these deformable objects. We will also introduce the idea of editing region and the corresponding locking mechanism for simultaneous editing of the same object by multiple clients. Toward the end of the papel; we will show some pe~ormance results of the prototype system.