# Virtual Reality for Spatial Planning and Emergency Situations: Challenges and Solution Directions
## 4 Results
### Application Design Approaches  
Regarding the approaches for the application design, 13 papers focused primarily on digitally creating/recreating an actual 3D building model. The choice of starting first with the building model construction over asset content is justified by the authors of [16], who state that it is ideal to create a building model for an application in an early stage of the development process. This is because the model influences later choices in the development process. [PERSON] et al. [26] pay considerable attention to the properties that a model for a VR application should have in the case of wayfinding. They argue that the model does not need to be photorealistic and, therefore, does not need to be highly detailed. Instead, it is more significant that indicators for improving the participants' perception of distances and depth are represented. Moreover, the building model should represent the real environment's geometry and spatial relations exactly, including recognizable objects at the same location as in the real environment. Approaches for creating a high-quality model can be realized by collecting floorplans, photos and videos of the real environment. Here, high-quality refers to a significant level of convenience [27] (e.g., playability, realism and elimination of errors). The authors also mention that ambiance, such as the correct color schemes, can contribute to creating an optimal model. After the model is completed, it can be imported into a game engine. Overall, for the development process, five software programs were used in total to work on the model development. An overview of the software and hardware that were used per paper is provided in Table 2.  
Figure 3: Radial histogram keyword frequency. The dominant game engine in the selected papers was Unity (\(n\) = 14), which is different to the one in the works by [22], which imported to Unreal. Regarding the importing process, three challenges were identified [26]. First, the 3D coordinate system of the modelling software is often different than the system used in the game engine. Typically, this problem can be solved using the export settings, but is nonetheless recognized in the articles. Second, imported objects might end up being invisible because they are inverted. An example of a solution to this problem is to create a custom material that colors objects or polygons that are inverted or pre-process the model to flip the normal prior to exporting. Third, the Z-fighting phenomenon might occur. This results in two or more objects flickering because they are in the exact same (XYZ) location, thus causing conflict during the render process. This, of course, can be solved by moving one of the objects slightly. [PERSON] et al. [33] continue by improving their model with objects that were obtained from the Unity Asset Store. From there, they downloaded their doors and some pieces of furniture that were not available in their chosen modelling software. To be able to use a VR hardware device, a support package corresponding to the chosen VR headset should be downloaded and integrated. Next, walkable areas should be added using floor colliders, and mesh colliders should be added to other objects [37]. A bounding box should be used to make sure the user of the application does not go outside of the walkable area. Next, a first-person controller (FPC) should be integrated. This FPC is essential for a wayfinding VR application, as without it, the user cannot move through the model or scene. With this FPC, the speed can be edited, and the exact location and movement of the participant can be recorded [38]. Recording this is needed to obtain results, and for this process, [36] used a custom logger script to export the exact location and movement to a.CSV file. Similarly, [22; 38] recorded the positions at a frequency of 10 Hz. Another example is the research of [35], who even recorded information at a frequency of 90 Hz.