## 4 Operationalization of the XR Framework for Safety Management
### Implementation Examples
#### 4.1.2 BIM Models  
First, as part of the design development process, 3D BIM models of the project are produced. These consider all the models required for the project, generally separated into three categories: architectural models, structural models and mechanical, electrical and plumbing (MEP) models. The models required will depend on what is to be implemented. For example, if safety management in concrete formwork and pouring processes is to be implemented, only the structural model may be required. The level of detail (LOD) of the BIM models will be associated with the levels of information required and the graphic quality necessary for XR environments. The first aspect will be associated with the functionalities of the XR applications and the second with the desired level of realism. In both cases, more information and realism can be provided in the XR development environments at a later stage, although this is not optimal as the ideal is to avoid rework.  
Figure 7 shows an example of the development of a BIM model of a reinforced concrete building. This was modelled based on CAD drawings (the original project did not include BIM models). Thus, the different structural elements are shown and modelled as independent elements, with a LOD 300. Each element contains geometrical information, location data, characteristics and other data of interest for the project. Different BIM software exists on the market and is useful for the development of 3D models (Autodesk Revit, ArchiCad, Tekla, others). In this example, Autodesk Revit software (version 2020) was used.  
Figure 7: BIM 3D structure model example.  
BIM models serve as inputs to reconstruct simple XR environments (from the project model only) and to analyse, for example, whether the designs proposed by engineers and architects comply with safety considerations. Here, prevention through design is relevant because the safety review is performed in the early stages of the project and the design itself can influence risk reduction.  
To perform this task, video game development engines can be used as development software for XR experiences. Unity 3D or Unreal Engine are the most commonly used, as well as other commercial software that facilitates the process of visualisation and interconnection, such as Unity Reflect (which connects Unity and Autodesk Revit). In this software, the developer will have to incorporate all the physics required for interaction with the models (typically, colliders and gravity, among others) with textures that give them realism. Figure 8 shows an example incorporating physics and textures into a BIM model (Autodesk Revit) in Unity 3D (version: 2019.4) software to develop a more realistic model for interactions. Specifically, the image shows how colliders have been applied to individual building components (e.g., walls, floors, equipment), enabling physical interactions within the XR simulation (e.g., collision detection and walking through the space). Additionally, gravity parameters have been configured to simulate realistic object behaviour in dynamic scenarios. Textures and materials have also been applied to enhance visual realism and improve immersion. These modifications are made directly in Unity's Inspector window, where the developer can assign physics components, adjust material properties, and fine-tune the visual and functional characteristics of the imported model. This setup transforms a static BIM model into an interactive, navigable XR environment suitable for safety simulations, training, or inspection tasks.