**3. VR: AR basics**

Virtual reality (VR) is a technology with which digital environments can be built for the immersion of participants. In these environments, users have the possibility of interacting with the environment and with each other in deeply realistic ways [45]. The ultimate goal of VR is for participants to experience total immersion and prevent, in every way possible, from perceiving stimuli from the outside (real) world [45]. However, VR also involves non-immersive and semi-immersive settings (i.e., when the experience is in a desktop) [46]. On the other hand, Augmented reality (AR) concentrates on the superposition of virtual or digital elements on real world scenes. The participants can "view" the real world, but it is composited with digital items [47]. AR expands the real-world rather than constructing a virtual one. The computer-generated material improves understanding or understanding of what is happening in reality [48]. Mixed Reality (MR) is a hybrid technology where virtual objects are merged into a 3D- atmosphere or real objects are positioned into a virtual creation (**Figure 1**).

#### **Figure 1.**

*Application example for the Federal Electricity Commission in Mexico, the team of engineers works a) in a geotechnical laboratory with an application that allows them to learn more about the specimens being analyzed, share the results with supervisors (in real time) and generate the log files using the lenses; b) in discussing projects in a more immersive way in which all sources of information can be displayed to each team member can understand and discuss without bias.*

Another definition of VR is a specific collection of technologies (headset, gloves and walker) that allow participants to feel that they belong to a digitally created world through high interaction between their senses and the artificial environment [49–54]. The 3D simulation (width, height, and depth) of a real or made-up situation can be experienced visually in real-time motion (or the closest thing to this) and supported by sounds and tactile stimulus, or the necessary feedback to recreate an integral experience. With VR, users can envisage, operate, and relate multifaceted data with surprising ease [55]. Therefore, VR refers to an immersive, interactive, multi-sensory, viewer-centered, 3D computer-generated environment and the combination of technologies required to build such an environment [56, 57]. The stereoscopic ambience enables the observer experiences in deeply immersing scenes. Exploiting the human brain responses, VR dilutes the boundaries between persons and computers. Because of our ability to see the environment three-dimensionally (stereoscopic vision) VR can create right and left eyes images of an object or a scene and the observer's brain integrates these stimuli from the presented perspectives to generate a whole sensitivity of a space. The virtuality means that an illusion is created about screen objects beyond the information on 2D displays in monitors. In VR, as in other technologies (2D-CAD even the 3D version), it is tried viewers notice distance and spatial interactions, but more convincingly and precisely.
