# Developing a BIM-Based MUVR Treadmill System for Architectural Design Review and Collaboration
## 2 Theoretical Background  
Researchers and practitioners have developed VR technology since the early 1990s. VR is a computer-generated environment with senses and objects that appear to be real. Thus, VR technology can be adopted as a communication system component that creates a simulated space and embeds humans as an integral part of the system [15]. Based on virtual displays supported by unique processing systems and non-visual sensory components, such as tactile and auditory functions, VR users can experience a truly immersive-simulated virtual environment [16]. The terminology of VR can be characterized by the 5 Is: intensive, interactive, immersive, illustrative, and intuitive [17]. Such characteristics have createdample research and application opportunities in various fields, such as automation, healthcare, and construction. Their limitations for spatial or temporal inaccessibility to realistic objects develop the need and ability to realize certain levels of accuracy in the virtual setting [10]. Moreover, space and equipment functionalities can be substantially validated through additional interaction capabilities in the virtual environment [18], achieving high efficiencies in the design review process. However, some studies proved that youths enjoy new technologies (e.g., VR applications) significantly more than adults do and had a higher willingness to adopt new technological products [19; 20]. This situation can be explained by the concept of technology readiness, which refers to people's propensity to use new technologies to achieve goals in home life and at work [21]. In the AEC industry, the extensive BIM development brings VR applications to a higher level. The integration of BIM into VR optimizes the performance as BIM-based models contain rich information that serves as a reliable basis to facilitate decision-making during the whole project life cycle, starting from planning, design, and construction to operation and maintenance stages [22]. In particular, VR has predominantly been applied in architectural design review. The incentive of its widespread adoption is the significant visual improvement arising from virtual models developed by gaming engines [10]. Architects and designers can review the design in a 1:1 scale immersive virtual environment to analyze design factors such as material types and dimensions to develop an effective building design [23]. In this highly immersive and realistic way, VR applications can judge the realistic visual impacts and technical aspects [7]. For instance, architects can better figure out the spatial relationships between building components to resolve design conflicts, check headroom compliances, and verify the required assembly detailing of the final products [24; 25]. Furthermore, VR can be adopted to produce virtual mock-ups replacing physical building models for design overviews [18]. This efficient approach enables stakeholders to consider and compare different design options simultaneously without much cost and time implication [26]. BIM-based VR applications have triggered a significant paradigm shift in the AEC industry. Construction professionals capitalize on integrating BIM into VR technology to enhance problem-solving efficiency in an immersive virtual environment. In addition, the advent of cutting-edge VR applications provides opportunities for immersive visualization that can help construction professionals to improve the sense of scale and spatial relationships of architectural and engineering design [7]. However, some challenges of using VR have been identified, such as the capability of running high-demand BIM software in VR applications, the support of multiuser applications, and the human locomotion for VR manipulations. Construction professionals come from various disciplines, so an interdisciplinary approach is vital to address today's complex engineering and construction problems.