José M. Noguera

A mobile 3D-GIS hybrid recommender system for tourism

The amount of touristic and travel information existing on the Internet is overwhelming. Recommender systems are typically used to filter irrelevant information and to provide personalized and relevant services to tourists. In this context, mobile devices are particularly useful because of their ubiquitous nature that turns them into an attractive platform for assisting on-the-move tourists to choose points of interest to visit according to their physical location. However, mobile devices also present several usability limitations that should be considered in order to provide information in a direct and intuitive way. In this paper, we present a novel mobile recommender system that brings together a hybrid recommendation engine and a mobile 3D GIS architecture. This system allows tourists to benefit from innovative features such as a 3D map-based interface and real-time location-sensitive recommendations. The details related to the design and implementation of the proposed solution are also presented, along with an empirical evaluation of user experience with the mobile application.

Navigating large terrains using commodity mobile devices

Abstract We describe a hybrid client–server technique for remote adaptive streaming and rendering of large terrains in resource-limited mobile devices. The technique has been designed to achieve an interactive rendering performance on a mobile device connected to a low-bandwidth wireless network. The rendering workload is split between the client and the server. The terrain area close to the viewer is rendered in real-time by the client. The terrain located far from the viewer is portrayed as view-dependent impostors, rendered by the server on demand. A prototype has been built and an exhaustive set of experiments covering several platforms, wireless networks and a wide range of viewer velocities has been conducted. Results show that the approach is feasible, effective and robust.

A Context-Aware Mobile Recommender System Based on Location and Trajectory

Recommender systems have typically been used in tourism applications to filter out irrelevant information and to provide personalized recommendations to the users. With the advent of mobile devices and ubiquitous computing, RSs have begun to incorporate Location Based Services (LBS) into mobile tourism guides to provide users with interesting points of interest (POIs) according to their contextual information, mainly physical location. In this paper, we propose a context-aware system for mobile devices that incorporates some implicit contextual information that is scarcely used in the literature: the user’s speed and his trajectory. This system has been specifically crafted to assist travelling users by providing them with smart and personalized POIs along their route taking into account their current location and driving speed.

A scalable architecture for 3D map navigation on mobile devices

Mobile devices such as smart phones or tablets are rapidly increasing their graphics and networking capabilities. However, real-time visualization of 3D maps is still a challenging task to accomplish on such limited devices. In this paper, we describe the principles involved in the design and development of a scalable client–server architecture for delivering 3D maps over wireless networks to mobile devices. We have developed a hybrid adaptive streaming and rendering method that distributes the 3D map rendering task between the mobile clients and a remote server. This architecture provides support for efficient delivery of 3D contents to mobile clients according to their capabilities. As a proof of concept, we have implemented a prototype and carried out exhaustive experiments considering different scenarios and hundreds of concurrent connected clients. The analysis of the server workload and the mobile clients performance show that our architecture achieves a great scalability and performance even when using low-end hardware.

A flooding algorithm for extracting drainage networks from unprocessed digital elevation models

A new method for extracting the drainage network from a digital elevation model (DEM) is presented. It is based on the well-known D8 approach that simulates the overland flow but uses a more elaborate water transfer model that is inspired by the natural behaviour of water. The proposed solution has several advantages: it works on unprocessed DEMs avoiding the problems caused by pits and flats, can generate watercourses with a width greater than one cell and detects fluvial landforms like lakes, marshes or river islands that are not directly handled by most previous solutions.

Mobile Volume Rendering: Past, Present and Future

Volume rendering has been a relevant topic in scientific visualization for the last decades. However, the exploration of reasonably big volume datasets requires considerable computing power, which has limited this field to the desktop scenario. But the recent advances in mobile graphics hardware have motivated the research community to overcome these restrictions and to bring volume graphics to these ubiquitous handheld platforms. This survey presents the past and present work on mobile volume rendering, and is meant to serve as an overview and introduction to the field. It proposes a classification of the current efforts and covers aspects such as advantages and issues of the mobile platforms, rendering strategies, performance and user interfaces. The paper ends by highlighting promising research directions to motivate the development of new and interesting mobile volume solutions.

Interaction and visualization of 3D virtual environments on mobile devices

The advent of low energy-consumption Graphics Processing Units (GPUs) [1] has boosted the graphics capabilities of mobile devices, opening the door to the development of interactive 3D applications that were inconceivable just a few years ago [2]. The mobile market is strongly competitive, and an attractive visual interface is an important advantage in creating a successful device. As a result, mobile device manufacturers have rapidly adopted this new hardware, and the market is demanding new applications featuring advanced 3D graphics and interactive virtual worlds. This scenario opens a wide and interesting research area. Virtual reality applications, until now limited to desktop computers, can now take full advantage of the unique attributes provided by mobile computing: ubiquity, connectivity, context-awareness, and multimodal interfaces. However, these advantages come at a cost. By definition, mobile devices must be small and powered by batteries. These two factors severely limit both their computing power and graphics capabilities. As applications require the handling of larger and more complex 3D scenes, more intelligent and power-efficient techniques will be required. In addition, the nature of handheld devices raises new unprecedented usability issues. The small display sizes, coupled with the limited input technologies, motivate the study of new ways of interacting with the 3D applications. The goal of this theme issue of Personal and Ubiquitous Computing is to investigate the implications of adopting 3D graphics and virtual environments in the field of mobile computing. The papers collected in this issue present current research efforts and useful applications that employ 3D graphics with particular focus on addressing the unique features of mobile devices. Submissions to this theme issue came from an open call for papers. We selected five papers to publish after two rounds of rigorous reviews. A large number of reviewers assisted us in the review process. In order to ensure high reviewing standards, three to four reviewers evaluated each paper.

Flexible queries on relational databases using fuzzy logic and ontologies

Combines fuzzy logic and semantic techniques to perform flexible queries in a relational database.Alternative method to fuzzy logic, to execute flexible queries on non-scalar attributes.Answers are ordered according with the accomplishment degree to the query.Ontologies are used as an attribute domain frame to return semantically similar information to the query.Fuzzy logic are used on scalar attributes. Nowadays there are many proposals that allow users to perform fuzzy queries on relational databases. Regardless of these proposals, fuzzy queries are really useful on scalar values where fuzzy sets can be adjusted to the user needs and domains, but non-scalar values are a more complex task. Here, we extend non-scalar attribute management in fuzzy queries with the use of ontologies. Thus, we allow to compute this kind of queries not only with the similarity relationships defined explicitly on a fuzzy set but with semantically interrelated terms modeled as a domain ontology as well. Moreover, we present the architecture of a novel system that combines both techniques to return an answer as much complete as possible and ordered by a degree of accomplishment. Finally, a qualitative and quantitative study about the use of flexible queries on relational databases is included in this work, as well.

Optimized Generation of Stereoscopic CGI Films by 3D Image Warping

The generation of a stereoscopic animation film requires doubling the rendering times and hence the cost. In this paper, we address this problem and propose an automatic system for generating a stereo pair from a given image and its depth map. Although several solutions exist in the literature, the high standards of image quality required in the context of a professional animation studio forced us to develop specially crafted algorithms that avoid artefacts caused by occlusions, anti‐aliasing filters, etc. This paper describes all the algorithms involved in our system and provides their GPU implementation. The proposed system has been tested with real‐life working scenarios. Our experiments show that the second view of the stereoscopic pair can be computed with as little as 15% of the effort of the original image while guaranteeing a similar quality.

Voxelización de Sólidos Mediante Instanciación de Geometría

Resumen En este artículo analizamos un algoritmo para calcular la voxelización de un sólido que es simple, eficiente, robusto y que aprovecha gran parte del potencial del hardware gráfico 3D. La nueva generación de hardware gráfico ha aportado innovadoras características tales como la instanciación de geometría y el procesador de geometría. Describimos cómo estas nuevas características pueden emplearse para implementar de manera sencilla y eficiente un algoritmo de voxelización. Se consigue así reducir el tiempo necesario para subir el modelo a la GPU. Se presentan dos implementaciones del algoritmo. La primera hace uso de la instanciación de geometría, y la segunda emplea conjuntamente la instanciación y el procesador de geometría.