# Designing a Large-Scale Immersive Visit in Architecture, Engineering, and Construction
### Related Works: Large-Scale 3D Models in Urban Area  
In [2], a detailed review of the applications of 3D city models was given. This study showed that 3D city models are employed in about 30 use cases that are a part of a multitude of application domains for environmental simulations and decision support, valuable for several purposes beyond visualization. Interested readers can refer to [3] for digital twins from the point of view of the city stakeholders. We focused our work on 3D city models characterized by a high Level Of Detail (LOD), a measure that indicates their grade and scale, for architectural and art purposes mainly. The 3D city models are derived from various acquisition techniques such as photogrammetry, radar and laser scanning [4; 5; 6], cadastral drawings [7], extrusion from 2D footprints [8], or crowdsourced geoinformation [9; 10]; all are GIS-based sources of information that can sensed and measured because the infrastructure exists. Another more precise kind of data are architectural BIM models [11], which are high-level-of-detail models and are already available for future construction or real estate development in progress. Few city models based on professional BIM are described in the literature. For instance, in [12], the authors linked an existing BIM to generic simulation models of construction activities implemented as script game components within a game engine, but only one BIM was used that modeled a sample house. A meta-analysis of the work available in the field of BIM's application can be found in [13]. However, as underlined in [14], there is limited literature about virtual reality technologies and BIM in AEC: the most-common uses of VR are safety training [15], project schedule control, collaborative projects [16], design issues, and construction site layout. However, to our knowledge, no publication has explained the necessary steps required for the building of a 3D city model based on professional BIM files. Let us cite some examples of realizations with GIS data. Aerometrex created a 3D model of the entire city of Adelaide, using a combination of photogrammetry data captured via helicopters and the real-time archviz tool TwinMotion [17]. The firm used the real-time architectural visualization tool TwinMotion to create a 3D model of Adelaide and the area surrounding it--around 1000 sq km--using photogrammetry data captured via fixed-wing aircraft and helicopters. AccuCities [18] designed a visualization of London's architectural evolution and the growth of the city over 1 km\({}^{2}\) tiles and its 3D model. The digital city model was captured from three separate aerial surveys conducted in 2016, 2019, and 2022. The 3D mapping operation created the 3D model using manual stereophotogrammetry. A simple 3D city model was first created by extruding building footprint polygons, then updated at a finer level of detail. They used the archviz tool Unreal Engine as a graphical engine. The CityGML database 3 DCityDB [19] is a repository of free 3D models useful for urban context display. These are low-level-of-detail models useful to integrate with your high-LOD architectural BIM. Interested users can see, for instance, a 3D city model of Berlin portaldeveloper by the Technische Universitat Munchen [20]. The interface exploits publicly available open data in CityGML format, which contain around 550,000 LoD2 building objects (basic roof shape and orientation) within the whole city area (890 km\({}^{2}\)). In [21], the authors described how to derive CityGML building models from BIM data. The conversion of BIM data to GIS data has several challenges due to the differences in the reference system, level of granularity, and geometric representation methods, as well as semantic mismatches between BIM and GIS data models. Our approach is the other way around, since we only integrated GIS data for the urban context of LaVallee into our city model made of a collection of BIM data.