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Item Study of the Influence of User Characteristics on the Virtual Reality Presence(The Eurographics Association, 2018) Mayor, Jesús; Sánchez, Alberto; Raya, Laura; García-Fernández, Ignacio and Ureña, CarlosIn recent years, virtual reality has grown a lot in different areas of application, including ludic, social and research, being used by a large and growing number of users with different profiles. Presence is one of the most distinctive and important features of a virtual reality experience. The aim of this article is to study the most suitable areas of application for users and to analyze the influence of different characteristics of the user's profile in the perceived presence. We have tested the interest applications indicated by 159 subjects and we have designed an immersive virtual reality experience, testing the behavior and performance of 48 users. The results obtained show that gender can influence the perceptual sensation of presence in these types of virtual environments.Item Modelling the Fluid-Boundary Interaction in SPH(The Eurographics Association, 2018) Perea, Juan J.; Cordero, Juan M.; García-Fernández, Ignacio and Ureña, CarlosSmoothed Particle Hydrodynamics (SPH) is a numerical method based on mutually interacting meshfree particles, and has been widely applied to fluid simulation in Computer Graphics. Originally SPH does not define the behaviour of the particle system in the contour, so the different variants of SPH have been solving this deficiency with different techniques. Some of these techniques are based on fictitious forces, specular particles or semi-analytic fields. However, all these proposals present a drawback, that are may introduce additional inaccuracy as a divergent behaviour of the particle dynamics or an artificial separation between the fluid limits and the contour. To solve these limitations at this paper presents a new technique based on contour particles that are used during simulation to model the interaction with the fluid. The use of contour particles had already been used in other works to construct the contour like a particle layer. That solution presents problems especially when increasing the complexity of the contour shape. In addition, unlike other techniques, this paper presents an additional advantage, the possibility of obtaining all the dynamic magnitudes for improving efficiency and versatility.Item A Procedural Approach for Thermal Visualization on Buildings(The Eurographics Association, 2018) Muñoz, David; Besuievsky, Gonzalo; Patow, Gustavo A.; García-Fernández, Ignacio and Ureña, CarlosThermal behaviour analysis on buildings is an important goal for all tasks involving energy flow simulation in urban environments. One of the most widely used simplified thermal models is based on an electrical analogy, where nodes are set to simulate and solve a circuit network. In this paper we propose a procedural approach for automatically locate the nodes of the circuit, according to the building structure. We provide a conceptual technique to efficiently visualize thermal variations over time in buildings. We show that we can simulate and visually represent the variations of the interior temperatures of a building over a period of time. We believe that the technique could be helpful for rapid analysis for changing building parameters, such as materials, dimensions or number of floors.Item A Prototype of Virtual Reality System for the Visualization, Exploration and Modeling of Huge Point Clouds(The Eurographics Association, 2018) Ortega-Donaire, José; Segura-Sánchez, Rafael Jesús; Ogáyar-Anguita, Carlos-Javier; Rueda-Ruiz, Antonio Jesús; García-Fernández, Ignacio and Ureña, CarlosThe use of specific techniques for the management and visualization of huge point clouds is necessary to solve the drawbacks of inefficiency derived from the size of the dataset and the techniques used to visualize it. This work presents a prototype of VR system for the visualization and management of extensive point clouds in 3D with the ability to edit specific points. For this, the tool incorporates multiresolution techniques, which improve the performance and efficiency of the system. The prototype also incorporates the management of the point cloud stored in an unstructured database; so the prototype can request parts of the dataset from the required fractions generated by an octree. This allows the progressive processing of 3D point clouds, which is very useful to control and visualize a large data set in real time.Item Rendering and Interacting With Volume Models in Immersive Environments(The Eurographics Association, 2018) Fons, Joan; Monclús, Eva; Vázquez, Pere-Pau; Navazo, Isabel; García-Fernández, Ignacio and Ureña, CarlosThe recent advances in VR headsets, such as the Oculus Rift or HTC Vive, at affordable prices offering a high resolution display, has empowered the development of immersive VR applications. data. In this paper we propose an immersive VR system that uses some well-known acceleration algorithms to achieve real-time rendering of volumetric datasets in an immersive VR system. Moreover, we have incorporated different basic interaction techniques to facilitate the inspection of the volume dataset. The interaction has been designed to be as natural as possible in order to achieve the most comfortable, user-friendly virtual experience. We have conducted an informal user study to evaluate the user preferences. Our evaluation shows that our application is perceived usable, easy of learn and very effective in terms of the high level of immersion achieved.Item Muscle Simulation with Extended Position Based Dynamics(The Eurographics Association, 2018) Romeo, Marco; Monteagudo, Carlos; Sánchez-Quirós, Daniel; García-Fernández, Ignacio and Ureña, CarlosRecent research on muscle simulation for Visual Effects relies on numerical methods such as the Finite Element Method or Finite Volume Method. These approaches produce realistic results, but require high computational time and are complex to set up. On the other hand Position Based Dynamics offers a fast and controllable solution to simulate surfaces and volumes, but there is no literature on how to implement constraints that could be used to realistically simulate muscles for digital creatures with this method. In this paper we extend the current state-of-the-art in Position Based Dynamics to efficiently compute realistic skeletal-muscle simulation. In particular we embed muscle fibers in the solver by adding an anisotropic component to the distance constraints between mesh points and apply overpressure to realistically model muscle volume changes under contraction. We also present a technique that consistently provides an internal structure for our muscle volumes. We use this structure to preserve the shape and extract relevant information for the activation of the muscle fibers. Finally, we propose a modification of the Extended Position Based Dynamics algorithm and describe other details for proper simulation of character’'s muscle dynamics.Item Toward Estimation of Yarn-Level Cloth Simulation Models(The Eurographics Association, 2018) Martín-Garrido, Alberto; Miguel, Eder; Otaduy, Miguel Ángel; García-Fernández, Ignacio and Ureña, CarlosEfficient and realistic cloth simulation is an unsolved problem, with yarn-level models emerging as a new alternative thanks to new hardware capabilities. Modeling yarns as flexible rods with persistent contacts enables a very robust and efficient simulation. However, this assumption also complicates the definition of elastic deformation potentials. This work explores more accurate yarn-level cloth models together with experiments that compare model features in order to detect shortcomings in the persistent contact model. In particular, we have implemented a discrete elastic model of flexible yarns with contact which treats yarns as unidimensional splines, together with a model that discretizes yarns using three-dimensional finite elements.Item On the Design of a Mixed-Reality Annotations Tool for the Inspection of Pre-fab Buildings(The Eurographics Association, 2018) García-Pereira, Inma; Gimeno, Jesús; Portalés, Cristina; Vidal-González, María; Morillo, Pedro; García-Fernández, Ignacio and Ureña, CarlosThe introduction of Augmented Reality (AR) and Virtual Reality (VR) in the inspection works carried out during the construction of prefabricated buildings can allow the early detection and elimination of deviations in their quality and energy efficiency. These new tools let us change from the traditional note taking on paper to the use of an AR application that allows to make rich annotations. The later on-site or in-office revision of the information taken as well as the remote communication while the inspection is going on can speed up and optimize the detection of errors and the maintenance of quality through the use of AR and VR. In this paper, the work in progress that is being carried out within the SIRAE project is shown. With it, we intend to implement the use of AR annotations for their visualization and modification in real time or later either in situ (AR) or from any other location (VR). The obtained first lab results are quite promising, since the usability of the system, still in development, augurs an easy adaptation of the workers to the new work tool and a substantial streamlining of the inspection processes.Item CEIG 2018: Frontmatter(Eurographics Association, 2018) García-Fernández, Ignacio; Ureña, Carlos; García-Fernández, Ignacio; Ureña, CarlosItem A Visual Interface for Feature Subset Selection Using Machine Learning Methods(The Eurographics Association, 2018) Rojo, Diego; Raya, Laura; Rubio-Sánchez, Manuel; Sánchez, Alberto; García-Fernández, Ignacio and Ureña, CarlosVisual representation of information remains a key part of exploratory data analysis. This is due to the high number of features in datasets and their increasing complexity, together with users' ability to visually understand information. One of the most common operations in exploratory data analysis is the selection of relevant features in the available data. In multidimensional scenarios, this task is often done with the help of automatic dimensionality reduction algorithms from the machine learning field. In this paper we develop a visual interface where users are integrated into the feature selection process of several machine learning algorithms. Users can work interactively with the algorithms in order to explore the data, compare the results and make the appropriate decisions about the feature selection process.
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