# VIS-HAPT: A Methodology Proposal to Develop Visuo-Haptic Environments in Education 4.0
## 3 Authors' Previous Work  
The authors of this work have contributed important efforts in the development of visuo-haptic applications focused on education. In this section, the main results of these studies are summarized, including the scenarios that will be discussed in Section 5 below. In [PERSON] et al. (2015) [28], three visuo-haptic simulators designed to feel the strength nature of electric forces were presented: point charge; line charge; and plane charge. The purpose of this preliminary study was to compare the dependence of the electric forces with the distance for these charge distributions. These simulators were developed with Chai 3D and Open-GL. From a perception survey, undergraduate engineering students revealed that most of them expressed a very positive opinion on the use of the visuo-haptic simulators and expressed that these facilitated their understanding of the nature and origin of electric forces. Preliminary learning gain studies with experimental and control groups of students have suggested that students from the experimental group achieve a better understanding than those from the control group. [PERSON] et al. (2018) [22] developed four visuo-haptic environments for understanding classical mechanics concepts: (i) block on a rough incline; (ii) rotating door; (iii) double Atwood's machine; and (iv) rolling reel. The visualization of the visuo-haptic simulators was displayed in two dimensions. An architecture for developing the scenarios was presented. The visuo-haptic environments were developed with Chai 3D and Open-GL, and similar students' perception and learning gains studies were performed. Very good students' perceptions were obtained, and statistically significant learning gains for experimental group students were also achieved for the _block on a rough incline_ and the _double Atwood's machine_ scenarios. [PERSON] et al. (2020) [9] proposed a novel architecture for the fast development of interactive visuo-haptic applications in game engines. They validated the architecture developing and implementing a plugin for coupling the haptic device with UNITY, named the Haptic Device Integration for Unity (_HaDIU_). Their approach allowed achieving remarkably better visualizations than those obtained in existing single-purposeapplications. Additionally, their results suggested that a faster development of interactive visuo-haptic simulators could be achieved by implementing this approach than using traditional techniques, especially in terms of reducing the times used for developing the technological model and for the calibration and testing phase of the methodology. In a recent work, [PERSON] et al. (2020) [PERSON] et al. (2020) presented a new version of the visuo-haptic simulators for the electric forces of the preliminary work by [PERSON] et al. (2020), which included the new architecture and the _HaDIU_ plugin proposed by [PERSON] et al. (2020). Moreover, several design elements were incorporated to improve the 3D perception of the simulators. A pre-test and post-test were applied to a student sample before and after working with the simulators, respectively, and statistically significant average learning gains were obtained for the comprehension of the force dependence in the case of the _line charge_ and _plane charge_ visuo-haptic environments. These results suggested that the use of the visuo-haptic simulators may help students to better identify the dependence of electric forces on distance. It was also observed that the potential effect of improving the understanding of electric interactions was higher among students with lower previous familiarity with these topics as compared to more advanced students. Additionally, through perception surveys, it was found that the students very much liked the haptic activity. The aforementioned visuo-haptic developments used diverse architectures and technological approaches requiring diverse amounts of effort and development time.