Department of Computer, Control and Management Engineering

Virtual Reality (VR) is now a well-established technology which offers realistic and immersive virtual worlds to the user usually by means of Head-Mounted Displays (HMDs). Actually, these devices can also be backed by a cloud server which can host the game server or even directly render the virtual world, as in the well-known cloud gaming paradigm. However, due to the drastically low latencies that technology requires, it is more convenient, when possible, to use servers that are as close to the users as possible. As a consequence, implementing the game or the render server in the Fog Computing layer is a concrete possibility. A research investigation has been carried out by using the Meta Quest 2 device, which are the QoE trade-offs, in terms of graphic quality and network performance, both in the case in which the HMD performs the 3d rendering locally by using a sample game written with Unreal Engine and in the case in which the 3d rendering is done in the Fog by means of the nVidia CloudXR framework and Oculus Air Link. The results of the proposed experiments reveal that the remote rendering offers a stable frame rate against a higher quality image. Instead, local rendering sets the best possible graphics quality against the optimal frame rate. Additionally, the utilization of remote rendering to perform video compression in the case of decreasing the available bandwidth to adjust graphics quality and FPS has also been analyzed. The same does not hold for Motion-to-Photon latency, which increases with distance, reducing the general QoE.