Abstract

Abstract
Navigation through immersive virtual environments is a key concept for virtual reality as it allows users to explore those environments. Therefore, it is important to understand virtual reality navigation interfaces and their impact on the users' experience. This paper presents an objective performance evaluation of two types of navigation: natural (real walking and walk-in-place) vs. unnatural (gamepad). Steering Law was the objective performance metric chosen since it captures the relationship between the time to travel a path and the difficulty of that path. In addition to performance, subjective metrics were also considered, namely the feeling of presence, cybersickness and user satisfaction. The experiments consisted of having participants complete a series of paths with different indexes of difficulty and the time that a participant took to walk each path was measured. Overall results show that the navigation through real walking yielded better results when it comes to performance, cybersickness, and user satisfaction than the walk-in-place and gamepad navigation interfaces.

Abstract
This investigation concerns the translation and validation of the ITC - Sense of Presence Inventory (ITC-SOPI) for the Portuguese-speaking population (in Europe), estimating the validity of the content and concepts and the maintenance of an equivalent semantics. It also sought to verify its psychometric properties, namely its factorial validity and internal consistency. The sample consisted of 459 individuals, 274 males and 185 females. The fidelity of the subscales varied between 0.67 and 0.89. Confirmatory factor analysis revealed a theoretical model of 35 items, divided by four factors. After fixing some of the residual errors between items, the following adjustment indexes were calculated: chi(2)/df = 2.301; goodness fit index = 0.860; comparative fitness index = 0.889; root mean square error of approximation = 0.053; Akaike's information criterion = 1420. Based on the observed results and the robustness of the sample size used, the obtained theoretical model shows that the ITC-SOPI is recommended to measure presence in virtual reality research projects with samples of Portuguese language speakers.

Abstract
New virtual reality technologies allow the user to gain a greater sense of presence in virtual environments. One of the areas where these technologies can have a major impact is the area of games that allow users to explore these environments and interact with them by receiving feedback from their actions in real time. The present study aimed to evaluate if the use of physiological signals to update the virtual environment in real-time could be used to increase the feeling of presence. To perform this study, an experimental study was designed based on a game that allowed the use of physiological data to calculate the participant's arousal in real-time and, based on that, modify certain elements of the virtual environment where the participants were asked to fulfill a task. With the analysis of the data obtained, it was possible to verify that the use of biofeedback did not reveal statistically significant differences for the variables tested, however, it can be concluded that the use of biofeedback improves some subscales of presence, being the users with more experience in games and more computer knowledge susceptible to such changes.

Abstract
With the appearance of innovative virtual reality (VR) technologies, the need to create immersive content arose. Although there are already some non-immersive solutions to address immersive audio-visual content, there are no solutions that allow the creation of immersive multisensory content. This work proposes a novel architecture for a collaborative immersive tool that allows the creation of multisensory VR experiences in real-time, thus promoting the expeditious development, adoption, and use of immersive systems and enabling the building of custom-solutions that can be used in an intuitive manner to support organizations' business initiatives. To validate the presented proposal, two approaches for the authoring tools (Desktop interface and Immersive interface) were subjected to a set of tests and evaluations consisting of a usability study that demonstrated not only the participants' acceptance of the authoring tool but also the importance of using immersive interfaces for the creation of such VR experiences.

Abstract
Virtual reality (VR) games have the potential to produce immersive experiences. To better explore the potential of VR games, it becomes necessary to understand what affects the player's presence in VR games. This work measures and compares the levels of presence and cybersickness in VR environments. Two games with different levels of interaction and narrative were compared. Presence and cybersickness were measured in a sample of 32 subjects using the IPQp questionnaire and a Portuguese version of the SSQ respectively. The results indicate that there were no differences in presence and cybersickness between the interaction and the narrative dimensions. To extend the study, the gender of participants was also considered an independent variable where we found significant differences in the metrics of presence and experienced realism, nausea and disorientation with female participants getting higher scores. © 2018 IEEE.