http://hdl.handle.net/2117/3567 2013-05-26T09:36:51Z http://hdl.handle.net/2117/19368 Title: Full high-dynamic range images for dynamic scenes Authors: Ramírez Orozco, Raissel; Martín, Ignacio; Loscos, Céline; Vázquez Alcocer, Pere Pau Abstract: The limited dynamic range of digital images can be extended by composing photographs of the same scene taken with the same camera at the same view point at di erent exposure times. This is a standard procedure for static scenes but a challenging task for dynamic ones. Several methods have been presented but few recover high dynamic range within moving areas. We present a method to recover full high dynamic range (HDR) images from dynamic scenes, even in moving regions. Our method has 3 steps. Firstly, areas a ected by motion are detected to generate a ghost mask. Secondly, we register dynamic objects over a reference image (the best exposed image in the input sequence). Thirdly, we combine the registered input photographs to recover HDR values in a whole image using a weighted average function. Once matching is found, the assembling step guarantees that all aligned pixels will contribute to the nal result, including dynamic content. Tests were made on more than 20 sets of sequences, with moving cars or pedestrians and di erent background. Our results show that Image Mapping Function approach detects best motion regions while Normalized Cross Correlation o ers the best deal speed-accuracy for image registration. Results from our method o ers better result when moving object are roughly rigid and their movement is mostly rigid. The nal composition is an HDR image with no ghosting and all dynamic content present in HDR values. 2013-05-22T08:40:29Z http://hdl.handle.net/2117/18017 Title: Accurate multi-modal image registration using compression Authors: Vázquez Alcocer, Pere Pau; Marco Gómez, Jordi Abstract: Image registration is an important task in medicine, especially when images have been acquired by different scanner/sensor types, since they provide information on different body structures (bones, muscles, vessels...). Several techniques have been proposed in the past, and among those, Normalized Mutual Information has been proven as successful in many cases. Normalized Compression Distance has been proposed as a simple yet effective technique for image registration. It is especially suitable for the case of CT-MRI registration. However, other image modalities such as PET pose some problems and do not achieve accurate registration. In this paper we analyse and propose a valid approach for image registration using compression that works properly for different combinations of CT, MRI and PET images. 2013-02-28T11:31:21Z http://hdl.handle.net/2117/17117 Title: Biomechanical validation of upper-body and lower-body joint movements of kinect motion capture data for rehabilitation treatments Authors: Fernández-Baena, Adso; Susín Sánchez, Antonio; Lligadas, Xavier Abstract: ew and powerful hardware like Kinect introduces the possibility of changing biomechanics paradigm, usually based on expensive and complex equipment. Kinect is a markerless and cheap technology recently introduced from videogame industry. In this work we conduct a comparison study of the precision in the computation of joint angles between Kinect and an optical motion capture professional system. We obtain a range of disparity that guaranties enough precision for most of the clinical rehabilitation treatments prescribed nowadays for patients. This way, an easy and cheap validation of these treatments can be obtained automatically, ensuring a better quality control process for the patient’s rehabilitation. 2012-12-12T11:23:43Z http://hdl.handle.net/2117/15881 Title: Relief impostor selection for large scale urban rendering Authors: Andújar Gran, Carlos Antonio; Díaz Iriberri, José; Brunet Crosa, Pere Abstract: Image-based rendering techniques are often the preferred choice to accelerate the exploration of massive outdoor models and complex human-made structures. In the last few years, relief mapping has been shown to be extremely useful as a compact representation of highly-detailed 3D models. In this paper we describe a rendering system for interactive, high-quality visualization of large scale urban models through a hierarchical collection of properly-oriented relief-mapped polygons. At the heart of our approach is a visibilityaware algorithm for the selection of the set of viewing planes supporting the relief maps. Our selection algorithm optimizes both the sampling density and the coverage of the relief maps and its running time is mostly independent on the underlying geometry. We show that our approach is suitable for navigating through large scale urban models at interactive rates while preserving both geometric and appearance details. 2012-05-17T07:49:54Z http://hdl.handle.net/2117/15854 Title: Affordable immersive projection system for 3d interaction Authors: Andújar Gran, Carlos Antonio; Fairén González, Marta; Brunet Crosa, Pere Abstract: This paper describes an affordable Virtual Reality system designed and developed by a group of researchers at the Polytechnic University of Catalunya (UPC). The system allows direct selection and manipulation of virtual 3D objects. The interaction is based on stereoscopic images projected over the user’s working space and on devices tracking the user’s natural movements. The system includes a screen being adjustable both in orientation and height, sensors tracking the head and hand movements, and a tactile device for the forefinger providing touch sense. A prototype of the system is currently exhibited at the Virtual Reality Center of Barcelona and it is being used in different application fields like architecture, medicine and industrial design. 2012-05-15T11:20:15Z http://hdl.handle.net/2117/15853 Title: ATLAS, a platform for transparently developing distributed applications Authors: Fairén González, Marta; Vinacua Pla, Álvaro Abstract: We discuss the design and implementation of a software development platform that allows unsophisticated programmers to include advanced features to their applications with no or very little extra information and effort. These features include the splitting of the application in distinct processes that may be distributed over a network, a powerful configuration and scripting language, and several tools including an input system to easily construct reasonable interfaces. We attempt to describe both the techniques used to achieve transparency for the programmer and what exactly a user must do to build new ATLAS modules. 2012-05-15T10:36:42Z http://hdl.handle.net/2117/15851 Title: Comparison of crowd simulation for building evacuation and an alternative approach Authors: Pelechano Gómez, Núria; Malkawi, Ali Abstract: This paper presents an overview of crowd simulation models, their limitations, and an alternative agent-based approch. First we introduce several methods and then we focus on two widely used and validated simulation tools that use grid-based models. We discus the artifacts that these models introduce regarding the way they treat the space and the implication that this has in the movement of the agents during the simulation. We also describe the limitations that current commercial software tools have in terms of simulating human psychology and physiology. The paper discusses an agent-based alternative approach developed to overcome these limitations. The model allows for the simulation of human movement that can provide results more closely describing behavior of real people during an emergency situation. Flow rates, densities and speeds emerge in our model from the physical interactions between people instead of being predefined. 2012-05-15T09:02:01Z http://hdl.handle.net/2117/15711 Title: La realidad virtual en el aprendizaje de historia mediante la interacción con humanoides virtuales Authors: Muñoz, Albert; Besora, Isaac; Creus López, Carles; Pelechano Gómez, Núria; Brunet Crosa, Pere; Beacco Porres, Alejandro Abstract: La realidad virtual ofrece la posibilidad de interactuar de manera inmersiva en mundos virtuales 3D. Estos mundos virtuales pueden ser representaciones de otros momentos históricos que permiten al usuario explorar los modelos virtuales como si de una visita turística al pasado se tratase. En este proyecto se ha realizado una reconstrucción virtual de la antigua ciudad romana de Tarragona (Tarraco) para ofrecer un entorno interactivo en el que los visitantes a la exposición puedan navegar por diferentes partes de la ciudad así como interactuar con humanoides virtuales representando romanos que ayudarán al usuario a recopilar información histórica y aprender mediante un sencillo juego interactivo. 2012-04-05T12:25:06Z http://hdl.handle.net/2117/15707 Title: Rendering detailed haptic textures Authors: Theoktisto, Víctor; Fairén González, Marta; Navazo Álvaro, Isabel; Monclús Lahoya, Eva Abstract: Rendering haptic textures seamlessly out of triangle meshes just by using geometry requires heavy work and does not allow high sampling rates for detailed, rugged models. Better approaches simulate surface texture without increasing much the complexity or processing cost, at the expense of fidelity of perception. We propose a method for rendering local height field maps out of an underlying triangle mesh, which relies in a space subdivision representation based on octrees for collision detection, and rendering individual surface detail by modulating force response using local height fields. We compare our method against a force mapping implementation for rendering/perceiving the same models with textures using normal maps. The proposed technique allows for real time perception of 3D surface detail, allowing the user to perceive the best haptic rendering alternative for a given model. Some experimental results are presented to show the goodness of the approach. 2012-04-04T11:45:37Z http://hdl.handle.net/2117/15704 Title: Feeling crowded? Exploring presence in virtual crowds Authors: Pelechano Gómez, Núria; Stocker, Catherine; Allbeck, Jan; Badler, Norman Abstract: Virtual reality experiments with virtual crowds are necessary to study human behavior under panic or stressful situations that cannot be evaluated in the real world (i.e., building evacuation due to fire). In order to carry out those experiments it is necessary to use a crowd simulation model in which a real person is seamlessly immersed and experiences a high sense of presence when interacting with such a crowd. This paper studies several crowd simulation models in order to determine which could best enhance presence for a user within a virtual environment. Egocentric features that affect presence are considered in the evaluation. Once we have a realistic simulation, we could use it to study human behavior and obtain relevant data. That data could then be used to update agent behaviors in the simulation system to further improve the overall realism of large groups of autonomous agents. 2012-04-04T08:52:07Z http://hdl.handle.net/2117/15701 Title: Multi-scale manipulation in indoor scenes with the World in Miniature Metaphor Authors: Trueba Hornero, Ramón; Andújar Gran, Carlos Antonio; Argelaguet Sanz, Fernando Abstract: The World in Miniature Metaphor (WIM) allows users to select, manipulate and navigate efficiently in virtual environments. In addition to the first-person perspective offered by typical VR applications, the WIM offers a second dynamic viewpoint through a hand-held miniature copy of the environment. In this paper we explore different strategies to allow the user to interact with the miniature replica at multiple levels of scale. Unlike competing approaches, we support complex indoor environments by explicitly handling occlusion. We discuss algorithms for selecting the part of the scene to be included in the replica, and for providing a clear view of the region of interest. Key elements of our approach include an algorithm to recompute the active region from a subdivision of the scene into cells, and a view-dependent algorithm to cull-away occluding geometry through a small set of slicing planes roughly oriented along the main occluding surfaces. We present the results of a user-study showing that our technique clearly outperforms competing approaches on spatial tasks performed in densely-occluded scenes. 2012-04-03T10:06:57Z http://hdl.handle.net/2117/15695 Title: Octree detection of closed compartments Authors: Brunet Crosa, Pere; Navazo Álvaro, Isabel; Vinacua Pla, Álvaro Abstract: The present paper addresses the problem of detecting closed compartments produced by a set of planar faces in the space. The topology of the set is general, and edges in the final piecewise planar surface can belong to one, two or more faces; boundary representations for non-manifold solids are particular cases. An octree structure (dubbed compartment Octree) that defines a 3D graph through the volume defined by the set of faces is proposed, and it is shown that a seed propagation algorithm on the graph can be used to detect the existing closed compartments. The algorithm can either compute the total number of compartments or detect if the set of faces define a closed solid volume, the outside part being considered as a separate compartment. 2012-04-02T09:54:48Z http://hdl.handle.net/2117/13076 Title: S3Dc: a 3Dc-based volume compression algorithm Authors: Yela Reneses, Héctor; Navazo Álvaro, Isabel; Vázquez Alcocer, Pere Pau Abstract: Volumes acquired for medical purposes are continuously increasing in size, faster than graphic cards memory capacity. Large volumetric datasets do not fit into GPU memory and therefore direct rendering is not possible. Even large volumes that still fit into GPU memory make frame rates decay. In order to reduce the size of large volumetric models, we present a new compression scheme. In this paper we present S3Dc, a lossy volume compression algorithm suitable for scalar values. It is inspired in hardware-accelerated 3Dc normal compression technique. S3Dc allows us to compress the volume in CPU up to a 4:1 or 8:1 ratio, while still yielding good quality results. We provide details on the compression scheme and show how to render directly from a S3Dc compressed texture. Furthermore, we analyze the image quality theoretical error and the average error with several images in order to assess the results. 2011-07-29T09:10:51Z http://hdl.handle.net/2117/13067 Title: Octree-based view-dependent triangle meshes Authors: Fairén González, Marta; Trueba Hornero, Ramón Abstract: In this paper we present a new technique for view-dependent LOD rendering, where the scene is represented through an octree model from which we can obtain a triangle mesh corresponding to a view-dependent LOD. We present the construction of this octree model and the visualization algorithm that generates on-the-fly a closed and valid triangle mesh for each frame of the visualization. This visualization algorithm is a depth-first traversal algorithm which also allows to re-use triangles from one frame to another. 2011-07-28T08:29:20Z http://hdl.handle.net/2117/13062 Title: Portalada: a virtual reconstruction of the entrance of the Ripoll Monastery Authors: Scopigno, Roberto; Ranzuglia, Guido; Besora, Isaac; Brunet Crosa, Pere; Callieri, Marco; Chica Calaf, Antonio; Corsini, Massimiliano; Dellepiane, Matteo; Morales, Daniel; Moyés, Jordi Abstract: The dichotomy between detail representation and data management is still a big issue in the context of the acquisition and visualization of 3D objects, especially in the field of Cultural Heritage. New technologies give the possibility to acquire very detailed geometry, but very often it’s very hard to process the amount of data produced. In this paper we present a project which aimed at virtually reconstructing the impressive (7x11 m.) portal of the Ripoll Monastery, Spain. The monument was acquired using triangulation laser scanning technology, producing a dataset of more than 2000 range maps for a total of more than 1 billion triangles. All the steps of the entire project are described, from the acquisition planning to the final setup for the dissemination to the public. In particular, we show how timeof-flight laser scanning data can be used to obtain a speed up in the alignment process, and how, after model creation and imperfections repairing, an interactive and immersive setup gives the public the possibility to navigate and visualize the high detail representation of the portal. This paper shows that, after careful planning and with the aim of new algorithms, it’s now possible to preserve and visualize the highly detailed information provided by triangulation laser scanning also for very large surfaces. 2011-07-27T11:09:43Z