# Developing a BIM-Based MUVR Treadmill System for Architectural Design Review and Collaboration
## 2 Theoretical Background
As such, the concept of MUVR disrupts the limitations of the conventional single-user VR setting where VR has used a gaming PC, yielding challenges when running the latest construction applications. The typical MUVR platform is set up by using a client-server model [27; 28; 29]. Unlike traditional single-user VR applications, MUVR platforms are established to enable real-time interactions and communications between multiple stakeholders in a shared virtual environment. A server is integrated to manage over system displays, and each client can access a data copy to be displayed, either on a local drive by the local area network or a shared network drive by the wide area network. Once a client is connected to the server, the server can update the display and synchronize the client's view regularly. On the other side, each client transmits pose information from its headsets and controllers to the server, relayed to other clients for displays. This framework also supports different modes that enable users to read particular results individually without sharing them with other clients. This setup of MUVR platforms effectively supports real-time interactions between users in the shared virtual environment [27]. In most current VR applications, users are only limited to moving in the predetermined physical space, which may constrain the natural interaction in the virtual environment. The gaming treadmills can be an option to offer user movement ability in the virtual environment by fixing users on a stationary point and reducing their foot friction, so that they can walk in a stationary platform naturally [30]. VR treadmills have been popularly adopted in the E-sport entertainment and healthcare industry [31; 32]. The self-paced VR treadmills can be bowl-shaped or flat-shaped, and their integration into VR applications can provide users with an immersive walking experience [13]. Moreover, VR treadmills provide great potential in becoming a safe simulator that enables active human locomotion in the virtual environment. For instance, the omnidirectional treadmill is a VR platform designed to bring the user back to the center of the active surface when he moves in any direction and steps off the active surface, avoiding walking over the edge of the platform [33]. Human locomotion and usability in the virtual environment are the critical aspects of the omnidirectional treadmill [34]. This kind of VR treadmill offers benefits such as allowing users to run and jump naturally on a designated platform during VR simulation, as every foot movement is tracked by the hardware. The average enjoyment level during physical activities in VR on treadmills is higher, because this movement can increase user participation in the virtual environment [35]. Thus, there is great potential to adopt VR treadmills in the AEC industry to enhance the users' immersive experience, as the current VR applications are limited to the conventional way without human locomotion. Significantly, the setup of multiple treadmills can avoid real-world collisions between users operating MUVR platforms in the same shared physical room.