Abstract

Abstract
Image matching algorithms are used in image search, classification and retrieval but are also useful to show how urban structures evolve over time. Images have the power to illustrate and evoke past events and can be used to show the evolution of structures such as buildings and other elements present in the urban landscape. The paper describes a process and a tool to provide a chronological journey through time, given a set of photographs from different time periods. The developed tool provides the ability to generate visualizations of a geographic location, given a set of related images, taken at different periods in time. It automatically processes comparisons of images and establishes relationships between them. It also offers a semi-automated method to define relationships between parts of images.

Abstract
This article addresses the problem of creating interactive mixed reality applications where virtual objects interact in images of real world scenarios. This is relevant to create games and architectural or space planning applications that interact with visual elements in the images such as walls, floors and empty spaces. These scenarios are intended to be captured by the users with regular cameras or using previously taken photographs. Introducing virtual objects in photographs presents several challenges, such as pose estimation and the creation of a visually correct interaction between virtual objects and the boundaries of the scene. The two main research questions addressed in this article include, the study of the feasibility of creating interactive augmented reality (AR) applications where virtual objects interact in a real world scenario using the image detected high-level features and, also, verifying if untrained users are capable and motivated enough to perform AR initialization steps. The proposed system detects the scene automatically from an image with additional features obtained using basic annotations from the user. This operation is significantly simple to accommodate the needs of non-expert users. The system analyzes one or more photos captured by the user and detects high-level features such as vanishing points, floor and scene orientation. Using these features it will be possible to create mixed and augmented reality applications where the user interactively introduces virtual objects that blend with the picture in real time and respond to the physical environment. To validate the solution several system tests are described and compared using available external image datasets.

Abstract
Location-based games require, among other things, obtaining or computing information regarding the players’ physical activity and real-world context. Additionally, ensuring that the players are assigned challenges that are adequate and safe for the current context (both physical and spatial) is also important, as it can improve both the gaming experience and the outcomes of the exercise. However, the impact adaptivity has in the specific case of location-based exergames still has not been researched in depth. In this paper, we present a location-based exergame and compare different play-through sessions when playing both the context sensitive and the regular versions of the game. Results show that the adaptive version provided a significantly safer gameplay experience. These results showcase the impact in player health and safety that player adaptivity achieves in location-based exergames. © Springer International Publishing AG, part of Springer Nature 2018.

Abstract

Abstract
Creating a mobile urban tourism storytelling application presents several interactivity challenges on how to convey an engaging multimedia experience on-site. This article describes a methodology for fast prototyping of a multimedia mobile applications dedicated to urban tourism storytelling. The application can be a game that takes advantage of several locationbased technologies, freely available geo-referenced media, and augmented reality for immersive gameplay. The goal is to create serious games for tourism that follow a main narrative but where the story can automatically adapt itself to the current location of the player, assimilate possible detours and allow posterior out-of-location playback. Adaptable stories can use dynamic information from map sources such as points of interest (POI), elevation or virtual buildings. The main focus is for these locationbased storytelling games to create more engagement between the tourists and the urban environment. To explore this concept, an application was designed for the city of Porto: Unlocking Porto. This location-based game with a central, yet adaptable, story engages the player into the main sights following an augmented reality path while playing small games. The article discusses and presents solutions for media acquisition, interactive storytelling, game-design interface and multi-disciplinary coordination for mobile app development.