Papers by João Madeiras Pereira
Although the impact that Virtual Worlds and Serious Games can have on learning efficacy and effic... more Although the impact that Virtual Worlds and Serious Games can have on learning efficacy and efficiency has been recognized, there is still many open questions related to this issue. Specifically there aren't guidelines or standards to help practitioners introduce this kind of technologies in a learning environment. In this chapter, the authors describe two experiments involving virtual worlds and serious games in a learning environment. These experiments allowed the authors to understand the real potential of this kind of technology, but also some of the difficulties one can come across. The authors hope that the experiments described in this chapter can serve as a basis for similar experiments done by other practitioners. Finally, some of the pitfalls that should be avoided are described as a set of lessons learnt at the end of the chapter.
Proceedings of the 8th International Workshop on Software Specification and Design
Page 1. A Framework for Heterogeneous Concurrency Control Policies in Distributed Applications An... more Page 1. A Framework for Heterogeneous Concurrency Control Policies in Distributed Applications Ant&i0 Rito Silva, Jo50 Pereira and Jod Alves Marques INESWIST Technical University of Lisbon Lisboa, Portugal email: Rito ...
Gamification: Concepts, Methodologies, Tools, and Applications
Journal of Real-Time Image Processing, 2012
ABSTRACT Advances in both terrestrial laser scanning hardware and photogrammetric systems combine... more ABSTRACT Advances in both terrestrial laser scanning hardware and photogrammetric systems combined are creating increasingly precise and rich 3D coloured data. In this article we show how computer graphics and visualization techniques have played an important role in real-time visualization, data management, modelling, and data fusion in an increasing number of applications such as surveying engineering, structure analysis, architecture, archaeology and cultural heritage. Specifically, we describe the typical modelling steps involved in the creation of a range of digital documents provided by the 3D digitization company Artescan to customers. We present how these modelling steps were applied in the context of creating digital documents used in the preservation of Mosteiro da Batalha.
Communications in computer and information science, 2009
This book constitutes the refereed proceedings of the International Conference on Computer Vision... more This book constitutes the refereed proceedings of the International Conference on Computer Vision and Computer Graphics Theory and Applications, Visigrapp 2007, held in Barcelona, Spain, in March 2007. The 18 revised full papers presented were carefully reviewed and selected from a total of 382 submissions. The papers are organized in topical sections on geometry and modeling; animation and simulation; interactive environments; image formation and processing; image analysis; image understandungas well as motion, tracking and stereo vision.
This book constitutes the refereed proceedings of the International Conference on Computer Vision... more This book constitutes the refereed proceedings of the International Conference on Computer Vision and Computer Graphics Theory and Applications, Visigrapp 2007, held in Barcelona, Spain, in March 2007. The 18 revised full papers presented were carefully reviewed and selected from a total of 382 submissions. The papers are organized in topical sections on geometry and modeling; animation and simulation; interactive environments; image formation and processing; image analysis; image understandungas well as motion, tracking and stereo vision.
International Conference in Central Europe on Computer Graphics and Visualization, 2017
Layered Depth Images (LDI) compactly represent multiview images and videos and have widespread us... more Layered Depth Images (LDI) compactly represent multiview images and videos and have widespread usage in image-based rendering applications. In its typical use case scenario of representing a scanned environment, it has proven to be a less costly alternative than separate viewpoint encoding. However, higher quality laser scanner hardware and different user interaction paradigms have emerged, creating scenarios where traditional LDIs have considerably lower efficacy. Wide-baseline setups create surfaces aligned to the viewing rays producing a greater amount of sparsely populated layers. Free viewpoint visualization suffers from the variant quantization of depths on the LDI algorithm, reducing resolution of the dataset in uneven directions. This paper presents an alternative representation to the LDI, in which each layer of data is positioned in different viewpoints that coincide with the original scanning viewpoints. A redundancy removal algorithm based on world-space distances as opposed to to image-space is discussed, ensuring points are evenly distributed and are not viewpoint dependent. We compared our proposed representation with traditional LDIs and viewpoint dependent encoding. Results showed the multiview LDI (MVLDI) creates a smaller number of layers and removes higher amounts of redundancy than traditional LDIs, ensuring no relevant portion of data is discarded in wider baseline setups.
Springer eBooks, Dec 18, 2008
... Organization IX Nadia Magnenat-Thalmann, Switzerland Marcus Magnor, Germany Stephen Mann, Can... more ... Organization IX Nadia Magnenat-Thalmann, Switzerland Marcus Magnor, Germany Stephen Mann, Canada Michael Manzke, Ireland Michael McCool ... Fisher, UK Jan Flusser, Czech Republic Alejandro Frangi, Spain Donald Fraser, Australia Sidharta Gautama, Belgium Daniel ...
Ray Tracing is a rendering algorithm, capable of generating highly realistic images, typically em... more Ray Tracing is a rendering algorithm, capable of generating highly realistic images, typically employed in non-interactive applications that disregard real time performance and focus exclusively on image quality. As technological advances progressively improve GPU performance, many Ray Tracing algorithms have been proposed to render virtual scenes in real time with better quality than rasterization, which is more widely used in real time applications. Moreover, several works have demonstrated that ray casting is, by definition, a high performance alternative to rasterization when it comes to terrain rendering. Based on an analysis of several terrain ray tracing algorithms, a real time terrain ray tracing engine was implemented leveraging those algorithms. The implemented engine does not require conversion from heightmaps to polygonal meshes, employs a level-of-detail scheme based on the three-dimensional distance from the viewer and is also capable of secondary ray tracing for shadows, which has not been applied in previous works.
Journal of Real-time Image Processing, Nov 12, 2009
Currently, the design of aesthetic products is a process that requires a set of activities where ... more Currently, the design of aesthetic products is a process that requires a set of activities where digital models and physical mockups play a key role. Typically, these are modified (and built) several times before reaching the desired design, increasing the development time and, consequently, the final product cost. In this paper, we present an innovative design environment for CAD (Computer-aided design) surface analysis. Our system relies on a direct visuo-haptic display system, which enables users to visualize models using a stereoscopic view, and allows the evaluation of sectional curves using touch. Profile curves are rendered using an haptic device that deforms a plastic strip, thanks to a set of actuators, to reproduce the curvature of the shape co-located with the virtual model. By touching the strip users are able to evaluate shape characteristics, such as curvature or discontinuities (rendered using sound), and to assess the surface quality. We believe that future CAS(Computer-aided systems)/ CAD systems based on our approach will contribute in improving the design process at industrial level. Moreover, these will allow companies to reduce the product development time by reducing the number of physical mockups necessary for the product design evaluation and by increasing the quality of the final product, allowing a wider exploration and comparative evaluation of alternatives in the given time.
Computer Science Research Notes, Jul 1, 2023
Interactive real-time rigid body simulation is a crucial tool in any modern game engine or 3D aut... more Interactive real-time rigid body simulation is a crucial tool in any modern game engine or 3D authoring tool. The quest for fast, robust and accurate simulations is ever evolving. PBRBD (Position Based Rigid Body Dynamics), a recent expansion of PBD (Position Based Dynamics), is a novel approach for this issue. This work aims at providing a comprehensible state-of-the art comparison between Position Based methods and other real-time simulation methods used for rigid body dynamics using a custom 3D physics engine for benchmarking and comparing PBRBD (Position Based Rigid Body Dynamics), and some variants, with state-of-the-art simulators commonly used in the gaming industry, PhysX and Havok. Showing that PBRBD can produce simulations that are accurate and stable, excelling at maintaining consistent energy levels, and allowing for a variety of constraints, but is limited in its handling of stable stacks of rigid bodies due to the propagation of rotational error.
IEEE Access, 2023
The pandemic brought about an unprecedented number of virtual conferences, given the heavy restri... more The pandemic brought about an unprecedented number of virtual conferences, given the heavy restrictions on travel to in-person meetings. Despite all the advances in technology, people still complain about virtual events. There is Zoom fatigue, confinement malaise, and a longing for personal social interactions. This paper discusses our experience organizing the IEEE Virtual Reality Conference (IEEE VR) as a virtual event. IEEE VR was a success with 1200+ registered paying participants, dozens of workshops and tutorials, and hundreds of technical papers. We used (1) a virtual environment platform, together with (2) discussion tools and (3) videoconferencing/broadcast/online tools to further provide effective social interaction and increase engagement. In this paper, we explore the synergies between virtual environments and other online tools and assess user engagement by analyzing the messages exchanged between participants across different genders and geographical regions. To this end, we apply diverse engagement metrics for online conferences. Our analysis shows that these metrics have the potential to highlight engagement, diversity, and inclusion by combining textual messages, participant geographic and gender information, communities of participants, and visitation patterns in a virtual environment. Drawing on our results and experiences, we propose guidelines for organizing technical virtual events to increase diversity and social interaction. INDEX TERMS Virtual reality, virtual conferences, virtual environments, Virbela/iLRN, data analytics, guidelines, recommendations.
Real time ray tracing has been given a lot of attention in recent years in the academic and resea... more Real time ray tracing has been given a lot of attention in recent years in the academic and research community. Several novel algorithms have appeared that parallelize different aspects of the ray tracing algorithm through the use of a GPU. Among these, the creation of Bounding Volume Hierarchies (BVHs). We believe that recent approaches have failed to consider the performance impact of memory accesses in GPU and how their cost affects the overall performance of the application. In this work we show that by reducing memory bandwidth and footprint we are able to achieve significant improvements in BVH traversal times. We do this by compressing the BVH and the triangle mesh in a parallel manner after its creation, in each frame, and then decompressing it as needed while traversing the BVH.
HAL (Le Centre pour la Communication Scientifique Directe), Sep 17, 2014
Within the health sector, the effectiveness is a key factor for the deployment of Serious Games f... more Within the health sector, the effectiveness is a key factor for the deployment of Serious Games for training purposes. Engagement is central factor relating games and learning. Therefore, identifying player’s level of engagement is an important aspect to consider when assessing Serious Games effectiveness. This paper describes an approach to identify player’s engaged-behaviours based on users interaction traces. A trace is a history of users’ actions collected in real-time during their inter- action with a computer system. The process of identifying the level of engagement consists in transforming low-level behaviours (e.g. clicks) in contextualized high-level behaviours. The proposed approach is exempli- fied by applying it to the identification of engaged-behaviours in a serious game for training clinical procedures on sepsis treatment protocol.
Advances in healthcare information systems and administration book series, Jun 14, 2012
Many of the top causes of death in the world are directly related to risk factors that can be avo... more Many of the top causes of death in the world are directly related to risk factors that can be avoided with changes in lifestyle behaviors. Computers with Internet access are widely available, and their multimedia capabilities show great potential for e-learning. Furthermore, most of the frequent Internet users already look for health related information online. This chapter presents an interactive simulator that educates people on how to mitigate the risk of cardiovascular diseases. The application is named SimBody and was initially developed in the context of a Master Thesis at Technical University of Lisbon (IST), in collaboration with ZPX, a multimedia software development company. SimBody allows the users to control the behaviors of an avatar. Besides showing the contribution of each decision towards the risk of cardiovascular diseases, it offers contextualized lifestyle advices and depicts the progression of atherosclerosis. After knowledge transmission tests, the majority of the participants stated that after using SimBody they are more aware of the dangers and intend to introduce changes to their lifestyle.
Mobile devices are continuously becoming more efficient at performing computationally expensive t... more Mobile devices are continuously becoming more efficient at performing computationally expensive tasks, such as ray tracing. A lot of research effort has been put into using acceleration data structures to minimize the computational cost of ray tracing and optimize the use of GPU resources. However, with the vast majority of research focusing on desktop GPUs, there is a lack of data regarding how such optimizations scale on mobile architectures where there are a different set of challenges and limitations. Our work bridges the gap by providing a performance analysis of not only ray tracing as a whole, but also of different data structures and techniques. We implemented and profiled the performance of multiple acceleration data structures across different instrumentation tools using a set of representative test scenes. Our investigation concludes that a hybrid rendering approach is more suitable for current mobile environments, with greater performance benefits observed when using data structures that focus on reducing memory bandwidth and ALU usage.
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Papers by João Madeiras Pereira