VRNet - a framework for multi-user virtual reality

Multi-user VR applications are challenging to develop and maintain. They are required to be highly responsive to not cause discomfort to users. Potential network issues, like delays and loss of connection, need to be taken into account. The goal of this thesis is to design and implement VRNet, a framework to provide developers with the necessary tools to aid networked VR application development. Game engines like Unreal Engine 4 (UE4) offer tools and a development environment to create complex multiplayer 3D applications. However, the underlying networking system was not designed to be used in local walkable VR scenarios. Our approach is to build the VRNet framework on top of the engine to enhance it with important functionalities. VRNet is implemented as an UE4 code plugin that extends core classes in C++. As a plugin it can easily be integrated and used in UE4 projects. It adds capabilities for networked user movement, interaction and representation in VR. Client-authoritative replication is implemented to ensure consistency between machines with optimal user experience, guarded from networking issues. Additionally, interpolation mechanisms are provided to smoothly simulate other clients. Furthermore, as a proof of concept, VRNet is integrated into a VR application that is developed in the scope of a research project by the CeMM Research Center for Molecular Medicine in cooperation with TU Wien. CeMM Holodeck is an UE4 application for visualization and interaction with biological data-networks. Another goal of this thesis is to extend the functionality of the application to allow multiple users to move around in a shared virtual environment and collaboratively interact with the data-network. The integration of VRNet was successful and showed that VRNet provides a robust and useful foundation for the creation of multi-user VR applications. Evaluation tests were conducted to investigate the performance efficiency of the VRNet framework, as well as the CeMM Holodeck. The results of the network traffic measurements show that the throughput is easily manageable for modern networks even with high network update rates. The results also indicate that resource usage is not noticeably affected by the integration of VRNet. We show that VRNet offers simplified and efficient development of multi-user VR applications that are performant and provide smooth user experience.