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Publications

Publications by Miguel Correia Melo

2023

Using Heart Rate Variability for Comparing the Effectiveness of Virtual vs Real Training Environments for Firefighters

Authors
Narciso, D; Melo, M; Rodrigues, S; Cunha, JP; Vasconcelos-Raposo, J; Bessa, M;

Publication
IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS

Abstract
The use of Virtual Reality (VR) technology to train professionals has increased over the years due to its advantages over traditional training. This paper presents a study comparing the effectiveness of a Virtual Environment (VE) and a Real Environment (RE) designed to train firefighters. To measure the effectiveness of the environments, a new method based on participants' Heart Rate Variability (HRV) was used. This method was complemented with self-reports, in the form of questionnaires, of fatigue, stress, sense of presence, and cybersickness. An additional questionnaire was used to measure and compare knowledge transfer enabled by the environments. The results from HRV analysis indicated that participants were under physiological stress in both environments, albeit with less intensity on the VE. Regarding reported fatigue and stress, the results showed that none of the environments increased such variables. The results of knowledge transfer showed that the VE obtained a significant increase while the RE obtained a positive but non-significant increase (median values, VE: before - 4 after - 7, p = .003; RE: before - 4 after - 5, p = .375). Lastly, the results of presence and cybersickness suggested that participants experienced high overall presence and no cybersickness. Considering all results, the authors conclude that the VE provided effective training but that its effectiveness was lower than that of the RE.

2023

Correlational study on novelty factor, immersive tendencies, purchase intention and memory in immersive VR e-commerce applications

Authors
Goncalves , G; Meirinhos, G; Melo, M; Bessa, M;

Publication
SCIENTIFIC REPORTS

Abstract
E-commerce is a field that changed how consumers purchase and interact with products. Although, inherent limitations such as the difficulty of testing the products first-hand before a purchase can compromise consumers' trust in online purchases. Virtual Reality (VR) has been investigated as a tool to solve limitations in several fields and how we can harness its potential to improve the overall user experience. This study analysed how immersive VR (IVR) could solve these limitations by allowing consumers to test products beforehand. We have studied how the Novelty Factor (evaluated by the users' past VR experience) and Immersive Tendencies correlate with the users' Purchase Intention and Memory (how well they remember the product's characteristics). We have analysed a sample of 38 participants (21 males) from 18 to 28 years old. Participants experienced a refrigerator with an interactive touchscreen in an IVR setup and were guided through its functionalities. Results indicated that memory of the product's characteristics was positively correlated with how recently they experienced VR. No correlations were found in the female sample. A negative correlation between Purchase Intention and Memory of the product's characteristics was found in the male sample. We concluded that IVR applications could become helpful for both consumers and online shops in an e-commerce context regardless of the Novelty Factor and Immersive Tendencies of consumers. However, differences between genders should be further investigated.

2023

Evaluation of Hands-Free VR Interaction Methods During a Fitts' Task: Efficiency and Effectiveness

Authors
Monteiro, P; Goncalves, G; Peixoto, B; Melo, M; Bessa, M;

Publication
IEEE ACCESS

Abstract
Currently, it is standard to use tracked handheld controllers for interaction in immersive virtual reality (VR). However, since VR interactions are becoming more natural with hand tracking, it is important to provide hands-free alternatives for selection and system control tasks. As such, this study aims to provide an exploratory evaluation of the effectiveness and efficiency of commonly used hands-free interfaces in selection and system control tasks. Nine interaction methods were evaluated while performing a Fitts' law task with nine advanced users of VR in a within-subject experiment. We evaluated handheld controllers as a baseline, against head gaze, eye gaze, and voice commands for pointing at the targets, and dwell time and voice commands to confirm selections. We found that using eye gaze with a 500 ms dwell time proved to be the hand-free method with the highest performance, matching the handheld controllers and being preferred by users. The evaluation also showed that using a multimodal approach to selection, especially using the voice, decreases performance, but increases effectiveness. Moreover, we verified that Fitts' law can be applied to hands-free methods, but its usage is limited when the methods have very short travel times. We then suggest selections per minute as a more robust comparative performance metric. Further studies should expand the audience and interaction tasks and focus on the confirmatory method of selection.

2011

Framework for Collaborative 3D Urban Environments

Authors
Melo, M; Bessa, M; Rocha, T; Sousa, J; Peres, E; Varajao, J; Magalhaes, L;

Publication
ENTERPRISE INFORMATION SYSTEMS, PT 2

Abstract
With Virtual Reality (VR) systems it is possible to visualize three-dimensional environments with a high level of detail and visual fidelity. The users can manipulate and interact with those virtual environments in an intuitive way, close to reality. The VR systems enable the access to digital services that can promote, amongst others, collaborative work, data sharing or e-commerce. In this paper, we present a multidisciplinary solution that can offer added value to users through a collaborative environment with an intuitive interface. This environment will use geo-referenced databases to replicate urban environments and represent real world problems in a virtual way, making possible a better and more flexible approach in order to solve them. It is also proposed an architecture and some digital services are illustrated to show its potential.

2012

A survey on HDR visualization on mobile devices

Authors
Magalhaes, L; Bessa, M; Urbano, C; Melo, M; Peres, E; Chalmers, A;

Publication
OPTICS, PHOTONICS, AND DIGITAL TECHNOLOGIES FOR MULTIMEDIA APPLICATIONS II

Abstract
There is a vast body of literature concerning the capture, storing, transmission and display of High Dynamic Range (HDR) imaging. Nevertheless, there are few works that try to address the problem of getting HDR on mobile devices. Their hardware limitations, such as processing power, storage space, graphics capabilities and screen characteristics, transform that problem in a big challenge. However, since more and more HDR content is being produced and given that in a few years it can become a standard, it is necessary to provide the means to visualize HDR images and video on mobile devices. The main goal of this paper is to present a survey on HDR visualization approaches and techniques developed specifically for mobile devices. To understand what are the main challenges that need to be addressed in order to visualize HDR on mobile devices, an overview of their main characteristics is given. The very low dynamic range of most of mobile devices' displays implies that a tone mapping operator (TMO) must be applied in order to visualize the HDR content. The current status of the research on TMO will be presented and analyzed, a special attention will be given to the ones that were developed taking in account the limited characteristics of the mobile devices' displays. Another important issue is visualization quality assessment, meaning visualize HDR content without losing the main characteristics of the original HDR content. Thus, evaluation studies of HDR content visualization on mobile devices will be presented and their results analyzed.

2012

Proposal of an Information System for a Semi-automatic Virtual Reconstruction of Archeological Sites

Authors
Adao, T; Magalhaes, L; Bessa, M; Barreira, J; Melo, M; Goncalves, M; Sousa, J; Peres, E;

Publication
4TH CONFERENCE OF ENTERPRISE INFORMATION SYSTEMS - ALIGNING TECHNOLOGY, ORGANIZATIONS AND PEOPLE (CENTERIS 2012)

Abstract
In some business areas there is the need to use representations of places or buildings in order to provide visual informations. These representations are, mainly, reconstructions of scaled real models or virtual representations produced in a Computer-Aided Design (CAD) tool. Recently, procedural modeling has been applied to generate buildings and cities in a short time and with a minimum user intervention. This methodology reveals to be a promising solution for a cost-effective alternative in models construction. One of the areas that can benefit from this kind of approach is archeology, for example to test archeological hypothesis. However, the existing solutions are not flexible enough to provide high detailed models containing building interiors and exteriors. This paper aims to present the global architecture and specification of an information system that supports the procedural modeling process, producing enhanced virtual representations of ancient places, including building facades and interiors, using the information available. (C) 2012 Published by Elsevier Ltd. Selection and/or peer review under responsibility of CENTERIS/SCIKA - Association for Promotion and Dissemination of Scientific Knowledge

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