Abstract
The present study aims (a) to translate and adapt the Igroup Presence Questionnaire (IPQ) to the Portuguese context (semantic equivalence/ conceptual and content validity) and (b) to examine its psychometric properties (reliability and factorial validity). The sample consisted of 478 subjects (285 males and 193 females). The fidelity of the factors varied between 0.53 and 0.83. The confirmatory factor analysis results produced a 14-item version of IPQ-PT, accepting covariance between residual errors of some items of the instrument, as the best structural representation of the data analyzed. The CFA was conducted based on a three-variable model. The fit indexes obtained were X-2/df = 2.647, GFI = .948, CFI = .941, RSMEA = .059, and AIC = 254. These values demonstrate that the proposed Portuguese translation of the IPQ maintains its original validity, demonstrating it to be a robust questionnaire to measure the sense of presence in virtual reality studies. It is therefore recommended for use in presence research when using Portuguese samples.

Abstract
The effort of generating large city scenes is greatly reduced when using procedural modelling techniques. Nonetheless. users are limited to defining rules and tuning parameters in a define-generation reanalyse cycle, reducing direct control. Describing buildings with split-based operations may disrupt the creative process by forcing the user to focus on how to describe a building instead of how a building should look. We use planar shapes and two-dimensional boo lean operations allowing procedural descriptions that are More aligned with humans' perceptions of buildings while letting users directly manipulate shapes (e.g., by dragging) in an interactive application.

Abstract
Interactive visualization of virtual environments is an active research topic. There is a multiplicity of applications such as simulation systems, augmented and mixed reality environments, computer games, amongst others, which endlessly demand for greater levels of realism and interaction. At every stage of the process, including modeling, image synthesis, transmission and navigation, there are identifiable circumstances which may compromise the achievement of high quality solutions for the posed problems. For many of these problems, an effective use of optimization tools can play a major role in order to achieve solutions with better quality. Within this context, an innovative optimization architecture is presented regarding to two major principles. The first principle comprises the possibility to integrate, with reduced effort, the optimization tools with existent applications and systems. Thus, we propose an agent-based framework where the optimization application may operate as an independent process in respect to the visualization application where communication is achieved by means of a specifically developed high-level message based protocol. The second principle establishes on the utilization of a class of intelligent optimization methods, known as metaheuristics, which major distinguishing quality is their great level of problem-independence, thus, enabling a wider application. The paper describes conducted experiments and presents results that demonstrate the utility and efficacy of the proposed framework.

Abstract
This paper proposes an interactive annotation technique for 360 degrees videos that allows the use of traditional video editing techniques to add content to immersive videos. Using the case study of immersive journalism the main objective is to diminish the entry barrier for annotating 360 degrees video pieces, by providing a different annotation paradigm and a set of tools for annotation. The spread of virtual reality systems and immersive content has been growing substantially due to technological progress and cost reductions in equipment and software. From all the technologies employed in virtual reality systems, 360 degrees video is one that currently presents unique conditions to be widely used by various industries -especially for communication purposes. From the various areas that can benefit from the usage of virtual reality systems, the communication field is one that requires innovation in the way that narratives are built, especially in virtual reality systems. In the case of immersive journalism, 360 degrees video technology is currently one of the most used mediums by several media outlets. This kind of news content, whose innovative role should be highlighted, is still being studied in the field of journalism, needing a clearly defined set of rules and good practises. In order to improve the introduction of virtual elements in the 360 degrees videos this paper proposes a set of annotation paradigms for 1) Media information display and 2) Narrative and attention focusing. In this paper we present a list of possible techniques that solve the problem of immersive annotation, as well as a description of a prototype that was developed to test these concepts. The prototype implements an annotation technique based on masked videos and the extension of standard subtitle file formats. Finally a fast-track user study was developed to evaluate the acceptance of the visualisation techniques and to refine the set of tools.

Abstract
The effort of creating virtual city environments is reduced using procedural modelling techniques. However, these typically use split-based approaches which can impose limitations on the final geometry, usually enforcing a grid-like structure and require complex geometry to be imported. Layered shape grammars can increase the variability of procedural buildings, while the vectorial definition of shapes introduces the possibility of creating complex shapes that seamlessly blend into the model. We evaluate the contributions with a modelling example and a comparison with split-based procedural modelling techniques. Results show that layers allow more flexibility than split-based techniques in creating variations. Vectorially defined shapes are a step forward in shape grammar expressiveness.

Abstract
The purpose of this study was to measure the subject's sense of presence while they performed a task (riding a bicycle downhill) in a virtual reality (VR) environment and to compare it by body position (standing vs. sitting) and gender. The sample consisted of 35 subjects (19 male and 16 female) between 17 and 33 years of age. A translated and validated Portuguese version of the lgroup Presence Questionnaire (IPQp) and the Reflexive Motor Acts (RMAs), based on direct observation, were used as metrics. The results showed significant differences between body position at the level of Experienced Realism, Spatial Presence and Overall Sense of Presence. When measuring RMAs, it was demonstrated that people in the sitting position presented a higher frequency. We concluded that body position influences perceptions of credibility, which has an impact on the sense of presence. No differences were identified between the genders.