# End-Users' Augmented Reality Utilization for Architectural Design Review
## 2 Literature Review  
### End-User Involved Design Review and Visualized Building Information  
Design review is a co-creation process, which involves the representatives of designers, project teams, subcontractors, suppliers, and even clients to review designs and share different perspectives to address potential issues [2]. By gathering all actors involved in a project at an early stage, it allows professionals and clients to create building project design in a collaborative way. An effective and efficient design review can improve the quality of the final product and ultimately reduce the project's cost and duration [11]. In particular, the participation of end-users is critical, since they will occupy most of the building's life cycle as inhabitants, external service providers, operation and maintenance personnel, or building administration. For these reasons, end-user involvement during design review is considered as an essential phase that can elaborate on the end-user's requirements to significantly improve overall design quality and satisfaction. In this regard, when it comes to sharing design information with end-users, appropriate and effective visualization of building information is required during the iterative presentation and evaluation phases. This is because design proposals should be reviewed by various participants, such as clients or a design review board [4, 12]. However, in the past, it was common for clients to only be provided with images of 2D drawings or 3D physical models as the visual component in communication. Even if a 3D virtual model is used, it was common to present a 3D model of a building through a 2D environment, such as a printed copy or monitor display [13]. In general, end-users have various backgrounds, limited experience in design review, and are not familiar with design representation language or information used by experts. These types of information prepared by experts rely on their skills for mutual understanding, which may lead to a misunderstanding of information for non-experts. Furthermore, it does not allow end-users to actively understand the building design, which makes it difficult for experts to interpret the client's perception of design. As a result, end-user involvement in design review is often minimized or ignored due to the lack of appropriate resources [14]. Meanwhile, with the recent advancements of computing technology, VR and AR have shown the potential of presenting more realistic representations of virtual models to end-users [15]. VR and AR can also provide non-technical parties with an increased sense of presence and immersion, which is not easily possible with 2D-based traditional methods [16].  
With the potential of becoming new visualization platforms, VR and AR-related technologies have been rapidly accepted by the field of architecture, engineering, and construction (AEC), allowing BIM models to be visualized more intuitively [6]. VR and AR are the two main visual presentation platforms that are used for building information. VR has been defined as a simulated virtual environment in which a user experiences telepresence (the feeling of being present in the current environment) and can freely navigate, manipulate, and interact with virtual objects [17; 18]. Examples of a virtual environment often include graphic simulations using a computer with either a monitor-based or immersive head-mounted device [19]. The term mixed reality (MR) refers to environments where real and virtual objects are presented together within a single display [20]. Specifically, MR incorporates virtual objects into reality or introduces real-world objects to a virtual environment [21]. AR is placed within the range of MR since it allows the presentation of virtual objects in a real environment by using see-through and monitor-based displays. AR simulates virtual prototypes into the real world and provides a connection between the virtual and real-world while maintaining the flexibility of the virtual world [22; 23].