ON INFORMATICS VISUALIZATION

— Virtual Reality (VR) is one of the most popular contemporary technologies and it is widely used in the videogame industry, nonetheless, this does not restrict its use in other areas of science, such as medicine or education. Due to the large commotion caused by the appearance of Covid-19, long distance virtual education technologies (e-learning) are being used. With this context, virtual reality is the focus of this study, which had the objective of understanding the work done in superior education at a distance, through the use of VR, by doing a systematic literature review (SLR; LSR in Spanish). The results reveal that the use of VR in education can improve the experience, motivation and the comprehension of abstract concepts for the students, offering them an immersive environment in which they can interact and achieve effective learning. It was concluded that the works that were reviewed regarding the topic evidence a strong growth in the application of VR in education, which in their majority, employ experimental comparative methods between groups of students which use VR when compared to others who use the traditional method.


I. INTRODUCTION
Learning is the process of interaction between those that are learning and the educators, which takes place through the use of resources and environments, such as classrooms, in order to obtain the knowledge that one desires to transmit from the educator to the learner. The most frequently used method until now was traditional teaching, nonetheless, other methods exist, such as e-learning, which is a type of education based on the use of computers and the internet; it is used to improve the learning yield with the help of technology and the advantage that it offers is that one does not need to be physically present in the classroom. Another type of technology that can be taken advantage of in order to promote learning is virtual reality (VR), which according to M. D. Smith, S. Getchell, and M. Weatherly [1] is defined as an environment generated by computers which provides three dimensional images with which the users can interact; one of the principal tools of VR is Unity 3D. An important milestone in this area was the commercialization of the Oculus Rift, HTC VIVE VR, and Oculus Quest Standalone HMD devices, which entered into the mass market due to the fact that they offered a VR experience at a low cost. Generally, these devices are used with the purpose of training, such as for videogames, though they have also been applied to areas of research such as engineering, medicine, education, and other areas.
The objective of this work was to identify the advances and learning activities of superior education students who used virtual reality technologies during the 2016 -2021 period by doing a systematic literature review in order to obtain, classify, and analyze the relevant research that has been done regarding the use of VR as a means for learning. This study will be useful for keeping specialists up to date on the topic, by making known the methods, tools, areas of study, and limitations that are found for the use of VR in education. Due to the current context of the pandemic, which started at the end of 2019 and continues to this day in 2021, distance learning is taken into account as a form of teaching for this study. The research is structured in the following fashion: in section II the methodology that was used to do this work is presented, in section III the results from the finding are described, in section IV are the conclusions, and finally in section V you find the bibliographic references.

II. MATERIALS AND METHODS
According to the process for systematically reviewing literature, the following steps should be carried out in order to elaborate the study, taking into account the methodology of the work [2]:

A. Research Questions
With the purpose of understanding the focus of the study that is being done, research questions were created in order to obtain the necessary data.
 RQ1 Which methods were used in order to evaluate the learning of those who used VR?  RQ2 Which types of VR technology were used for the research?  RQ3 What limitations appear in the application of VR as a means for learning?  RQ4 Which tools were used for the development of the research?  RQ5 How was the experience of the VR users evaluated?  RQ6 What areas of study were used in the research?
These research questions (RQ) were defined according to the context of the study. The purpose of the RQs was to respond to the questions regarding the methods used for the evaluation of the knowledge, the experience with the VR technology, the tools which were used for the studies, the limitations that were found in the studies, the types of technologies used, and the areas of study that were used in the research.

B. Review of the Reach
The reach is determined by using the PICOC rule (Population, Intervention, Comparison, Outcomes, Context):  Population: University or Superior Education Students  Intervention: Virtual Reality as a learning tool.  Comparison: There is no comparison of technologies.  Outcomes: Evaluation of the VR experience; evaluation of knowledge and the technologies.  Context: How is the experience of those who use VR evaluated?

C. Doing the Search
The strategy for doing the search of the studies consisted in identifying the terms mentioned and applied in the studies, which were: "higher education," "university education," "virtual reality," "VR," "education," "educational," "learning," and "distance education." These were created using the research questions as a reference. The selection of the database was done using digital sources, since these possess an advanced search engine, which is needed in order to carry out the research. The sources are: ACM, IEEE, SCOPUS, and SCIENCEDIRECT, and the search was done from the year 2016 to 2021. The base chain in Table I was the most used search chain for each database, with the goal of obtaining a search which was adequate, based upon the title, keywords, and abstract.

E7
Articles which only mention the terms "virtual reality" and "education" without applying it to the research. E8 Studies that do not focus on superior or university level education. Table IV shows the three phases of how the inclusion and exclusion criteria were applied for the process of filtering the studies, during which 191 studies were discarded. At the end of the process, a total of thirty six potential articles was obtained.

E. Evaluation of the Quality
In order to do an evaluation of the quality of the articles, the following questions regarding the quality were created:  Are the objectives of the study related to virtual reality and distance learning?  Is the research method appropriately described in order to reach the objective of the study?  Are the results of the study clearly expressed?  Is the article about an experimental study? Of the thirty six articles that were evaluated using these questions regarding quality, twenty seven were chosen in order to carry out this study.

F. Data Extraction
In order to obtain the study data, the following extraction indicators were established:
Exluding studies focused on augmented reality.
Excluding studies from secondary sources.
Accepting studies which use VR in their investigation of superior education.
Excludig studies which only mention the term "VR" but do not apply it.
Omitting studies that do not focus on university nor superior education.
Rejecting studies that do not deal with virtual reality nor learning.
Rejecting studies not done about distance learning. 14 articles eliminated 125 articles eliminated 52 articles eliminated obtained from different locations, of which, in two countries more studies of this type are done: The United States (29%) and China (15%), while in the rest of the countries these types of studies are hardly carried out.

Fig. 2 Geographical Locations of the Studies
Next, the results from the data extraction are described, with which the research questions are answered:

RQ1: Which methods were used in order to evaluate the learning of those who used VR?
Four principal tools for the evaluation of learning were identified, as shown in Fig. 3, below. Table V shows the evaluation tools, where the majority of the works that were reviewed were evaluated using questionnaires or tests (57%), which were made up of open and closed-ended questions. Notwithstanding, problem solving through the use of VR (22%) is the second way to evaluate learning through the use of simulation exercises or by doing activities with the device. The second method is based on surveys (14%) which were done in order to evaluate the opinion of the students with respect to their assimilation of learning. In the feedback to the students 7% indicated that the questions were asked during classes. Nonetheless, studies were also identified in which learning evaluations were not carried out [ [25]. Figure 4 shows the number of learning assessment tools that were used to evaluate those who utilized VR, with questionnaires being the most widely used; having exponential growth in recent years. In

RQ3 What limitations appear in the application of VR as a means for learning?
On the other hand, Table VII shows the limitations that are presented in the studies that were reviewed, where the following data was obtained: these limitations were the small number of participants (20%) with which the experiments were done, the problems in equipment use (13%), the time that is required to learn to use a device (9%), the budget for equipment acquisition (7%), VR sickness (7%) which is the sensation of dizziness experienced when using the devices, the lack of communication between students and teachers (6%), the lack of maturity in the VR technology (4%), the internet connection (4%), the participants quitting (2%), and the hardware and software problems (2%).   RQ4 Which tools were used for the development of the research? Table VIII shows the studies that were reviewed, where it was identified that distinct tools were used in order to carry out the research; these were categorized into programming language, services, development software, apps, and others. In the review it was found that Unity3D is the most used tool in most of the research due to the fact that it is specialized for the development of VR content.

RQ5 How was the experience of the VR users evaluated?
According to studies that were reviewed, Table IX and Fig.  5 show that there were three principal tools used in order to evaluate the user experience with a VR device, which are surveys (54%) that mainly references the students' opinions, questionnaires that also grant results of the students' perceptions, and cognitive interaction (8%) which are done in experimental sessions. On the other hand, studies are found which do not carry out this type of evaluation of the user experience [10] [7] [21] [22]. Figure 6 shows that the assessment tools for user experience were the surveys and that they have had exponential growth in recent years.  Table X shows that in the engineering branch, studies have been done in the areas of environmental, electrical, industrial, and computer engineering. Later new areas of application were identified, which were anthropology, biology, physical education, legal education, physics, and geophysics. Also, an area of teaching foreign language was identified, which was TEFL. Later other types of study such as chemistry, medicine, MLIS, psychology, silviculture, social work and zoology were identified. Nonetheless, studies were also identified which had no relation to an area of science [3]   Zoology [13] IV. CONCLUSIONS From the study it was concluded that for the evaluation of student learning through the use of VR devices, questionnaires are one of the principal tools for measuring this indicator, which is denoted from the years 2016 -2021; nonetheless, since the year 2020, the resolution of VR problems is being taken into account as another indicator of learning. It was observed that the Desktop VR technology is one of the most frequently used technologies in order to carry out experimental studies in VR, nonetheless, since the year 2019 the Google Cardboard technology has been growing, together with Desktop VR, due to the low costs of these technologies because they are HMD technologies. On the other hand, other technologies such as Oculus Rift, Samsung GearVR and HTC VIVE are not the principal tools for the studies, but it was found that these technologies are used in studies with greater complexity and which have the need for a more robust devices due to the study type. Among the limitations of the studies, it was concluded that a large part of the experiments were done with a low number of participants; an imbalance in the number of participants and the number of control groups was also found. Another principal problem that was identified was that the VR equipment can be difficult to manipulate for a large majority of the users, due to the fact that it is a technology that is being tried for the first time. The tool Unity3D is a software that is largely used for studies that are carried out in a 3D environment, however, it was identified that in some studies a decision was made to contract services that are specialized in this area in order to create the experimental environments, thus, technologies other than Unity3D, such as AutoDesk, were used for developing the environments. For the evaluation of the user experience regarding the VR device, surveys were the principal tool which were used to measure this indicator. The greatest number of studies were done in the area of engineering, together with the area of teaching languages, in comparison to the other areas that were found in the revision process.