http://hdl.handle.net/2117/3564 2013-05-25T15:07:13Z 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/2117/18016 Title: The ViRVIG institute Authors: Andújar Gran, Carlos Antonio; Navazo Álvaro, Isabel; Vázquez Alcocer, Pere Pau; Patow, Gustavo; Pueyo, Xavier Abstract: In this paper we present the ViRVIG Institute, a recently created institution that joins two well-known research groups: MOVING in Barcelona, and GGG in Girona. Our main research topics are Virtual Reality devices and interaction techniques, complex data models, realistic materials and lighting, geometry processing, and medical image visualization. We briefly introduce the history of both research groups and present some representative projects. Finally, we sketch our lines for future research. 2013-02-28T11:07:58Z 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/2117/16905 Title: Avatar locomotion in crowd simulation Authors: Pelechano Gómez, Núria; Spanlang, Bernhard; Beacco Porres, Alejandro Abstract: This paper presents an Animation Planning Mediator (APM) designed to synthesize animations efficiently for virtual characters in real time crowd simulation. From a set of animation clips, the APM selects the most appropriate and modifies the skeletal configuration of each character to satisfy desired constraints (e.g. eliminating foot-sliding or restricting upper body torsion), while still providing natural looking animations. We use a hardware accelerated character animation library to blend animations increasing the number of possible locomotion types. The APM allows the crowd simulation module to maintain control of path planning, collision avoidance and response. A key advantage of our approach is that the APM can be integrated with any crowd simulator working in continuous space. We show visual results achieved in real time for several hundreds of agents, as well as the quantitative ac-curacy. 2012-11-13T10:51:14Z http://hdl.handle.net/2117/16390 Title: Efficient rendering of animated characters through optimized per-joint impostors Authors: Beacco Porres, Alejandro; Andújar Gran, Carlos Antonio; Pelechano Gómez, Núria; Spanlang, Bernhard Abstract: In this paper, we present a new impostor-based representation for 3D animated characters supporting real-time rendering of thousands of agents. We maximize rendering performance by using a collection of pre-computed impostors sampled from a discrete set of view directions. Our approach differs from previous work on view-dependent impostors in that we use per-joint rather than per-character impostors. Our characters are animated by applying the joint rotations directly to the impostors, instead of choosing a single impostor for the whole character from a set of pre-defined poses. This offers more flexibility in terms of animation clips, as our representation supports any arbitrary pose, and thus, the agent behavior is not constrained to a small collection of pre-defined clips. Because our impostors are intended to be valid for any pose, a key issue is to define a proper boundary for each impostor to minimize image artifacts while animating the agents. We pose this problem as a variational optimization problem and provide an efficient algorithm for computing a discrete solution as a pre-process. To the best of our knowledge, this is the first time a crowd rendering algorithm encompassing image-based performance, small graphics processing unit footprint, and animation independence is proposed. 2012-08-27T16:35:45Z http://hdl.handle.net/2117/16104 Title: Hybrid Rugosity Mesostructures (HRMs) for fast and accurate rendering of fine haptic detail Authors: Theoktisto, Víctor; Fairén González, Marta; Navazo Álvaro, Isabel Abstract: The haptic rendering of surface mesostructure (fine relief features) in dense triangle meshes requires special structures, equipment, and high sampling rates for detailed perception of rugged models. Low cost approaches render haptic texture at the expense of fidelity of perception. We propose a faster method for surface haptic rendering using image-based Hybrid Rugosity Mesostructures (HRMs), paired maps with per-face heightfield displacements and normal maps, which are layered on top of a much decimated mesh, effectively adding greater surface detail than actually present in the geometry. The haptic probe’s force response algorithm is modulated using the blended HRM coat to render dense surface features at much lower costs. The proposed method solves typical problems at edge crossings, concave foldings and texture transitions. To prove the wellness of the approach, a usability testbed framework was built to measure and compare experimental results of haptic rendering approaches in a common set of specially devised meshes, HRMs, and performance tests. Trial results of user testing evaluations show the goodness of the proposed HRM technique, rendering accurate 3D surface detail at high sampling rates, deriving useful modeling and perception thresholds for this technique. 2012-06-20T10:05:42Z http://hdl.handle.net/2117/15934 Title: World-in-miniature interaction for complex virtual environments Authors: Trueba Hornero, Ramón; Andújar Gran, Carlos Antonio; Argelaguet Sanz, Fernando Abstract: Object occlusion is a major handicap for efficient interaction with 3D virtual environments. The well-known World in Miniature (WIM) metaphor partially solves this problem by providing an additional dynamic view point through a hand-held miniature copy of the scene. However, letting the miniature show a replica of the whole scene makes WIM metaphor suitable for only relatively simple scenes due to occlusion and level of scale issues. In this paper, the authors propose several algorithms to extend the idea behind the WIM to arbitrarily complex scenes. The main idea is to automatically decompose indoor scenes into a collection of cells that define potential extents of the miniature replica. This cell decomposition works well for general indoor scenes and allows for simple and efficient algorithms for preserving the visibility of potential targets inside the cell. The authors also discuss how to support interaction at multiple levels of scale by allowing the user to select the WIM size according to the accurazy required for accomplishing the task. 2012-05-29T10:08:08Z http://hdl.handle.net/2117/15887 Title: Visualization of large-scale urban models through multi-level relief impostors Authors: Andújar Gran, Carlos Antonio; Brunet Crosa, Pere; Chica Calaf, Antonio; Navazo Álvaro, Isabel Abstract: In this paper, we present an efficient approach for the interactive rendering of large-scale urban models, which can be integrated seamlessly with virtual globe applications. Our scheme fills the gap between standard approaches for distant views of digital terrains and the polygonal models required for close-up views. Our work is oriented towards city models with real photographic textures of the building facades. At the heart of our approach is a multi-resolution tree of the scene defining multi-level relief impostors. Key ingredients of our approach include the pre-computation of a small set of zenithal and oblique relief maps that capture the geometry and appearance of the buildings inside each node, a rendering algorithm combining relief mapping with projective texture mapping which uses only a small subset of the pre-computed relief maps, and the use of wavelet compression to simulate two additional levels of the tree. Our scheme runs considerably faster than polygonal-based approaches while producing images with higher quality than competing relief-mapping techniques. We show both analytically and empirically that multi-level relief impostors are suitable for interactive navigation through large urban models. 2012-05-17T10:31:11Z http://hdl.handle.net/2117/15886 Title: Mesh repair with user-friendly topology control Authors: Hétroy, Franck; Rey, Stéphanie; Andújar Gran, Carlos Antonio; Brunet Crosa, Pere; Vinacua Pla, Álvaro Abstract: Limitations of current 3D acquisition technology often lead to polygonal meshes exhibiting a number of geometrical and topological defects which prevent them from widespread use. In this paper we present a new method for model repair which takes as input an arbitrary polygonal mesh and outputs a valid 2-manifold triangle mesh. Unlike previous work, our method allows users to quickly identify areas with potential topological errors and to choose how to fix them in a user-friendly manner. Key steps of our algorithm include the conversion of the input model into a set of voxels, the use of morphological operators to allow the user to modify the topology of the discrete model, and the conversion of the corrected voxel set back into a 2-manifold triangle mesh. Our experiments demonstrate that the proposed algorithm is suitable for repairing meshes of a large class of shapes. 2012-05-17T10:11:40Z 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