http://hdl.handle.net/2117/3296 2013-05-21T14:44:01Z http://hdl.handle.net/2117/18983 Title: Skeletal representations of orthogonal shapes Authors: Martínez Bayona, Jonás; Pla García, Núria; Vigo Anglada, Marc Abstract: Orthogonal shapes are polygons orpolyhedra enclosed byaxis-aligned edges orfaces, respectively. Inthis paper wepresent two skeletal representatio nsoforthogonal shapes: the cube skeleton and a family ofskeletal represe ntations provided bythe scale cube skeleton. Both skeletal represe ntations rely onthe L1 metric. Weshow that the cube skeleton is homotopically equivalent to its original shape,reduces its dimension,and it is composed of line segments orplanar polygons with restricted orientation. We also present analgorithm to compute the scale cube skeleton oforthogonal polygons and compare the presented skeletons with other skeletal represe ntations. 2013-04-25T11:11:36Z http://hdl.handle.net/2117/18255 Title: Juegos digitales en el aula: un caso de estudio Authors: Contreras Espinosa, Ruth S.; Eguía Gómez, Jose Luis; Solano Albajés, Lluís Abstract: Durante el año 2011 se diseño, implementó y estudió un juego digital que muestra la vida de un científico Catalán: El paleontólogo Mi - quel Crusafont. El juego fue creado como un recurso para el aprendizaje cognitivo y posteriormente fue utilizado en aulas de primaria con el fin de obtener la visión de los profesores involucrados. Como método de recolec - ción de datos se ha utilizado la observación, la entrevista en profundidad y el grupo focal. El objetivo principal de este estudio se centra en reunir la visión de profesores de primaria, al hacer uso de juegos en el aula. Las conclusiones nos muestran las percepciones que los miembros del grupo de estudio tiene sobre el uso de juegos digitales. 2013-03-13T12:23:04Z http://hdl.handle.net/2117/17576 Title: A scalable architecture for 3D map navigation on mobile devices Authors: Noguera, José María; Segura, Rafael; Ogáyar, Carlos; Joan Arinyo, Robert Abstract: Mobile devices such as smart phones or tablets are rapidly increasing their graphics and networking capabilities. However, real-time visualization of 3D maps is still a challenging task to accomplish on such limited devices. In this paper, we describe the principles involved in the design and development of a scalable client–server architecture for delivering 3D maps over wireless networks to mobile devices. We have developed a hybrid adaptive streaming and rendering method that distributes the 3D map rendering task between the mobile clients and a remote server. This architecture provides support for efficient delivery of 3D contents to mobile clients according to their capabilities. As a proof of concept, we have implemented a prototype and carried out exhaustive experiments considering different scenarios and hundreds of concurrent connected clients. The analysis of the server workload and the mobile clients performance show that our architecture achieves a great scalability and performance even when using low-end hardware. 2013-02-05T10:36:33Z http://hdl.handle.net/2117/16877 Title: Os games digitais como um recurso cognitivo na aprendizagem: um estudo de caso Authors: Eguía Gómez, Jose Luis; Contreras Espinosa, Ruth S.; Solano Albajés, Lluís Abstract: Os games digitais possuem um valor educativo importante e têm sido reconhecidos pelos educadores como um rico e produtivo espaço que proporciona conteúdos de aprendizagem para os estudantes, melhorando, através dele, o desenvolvimento cognitivo do aluno. Este artigo explora as oportunidades cognitivas dos games digitais como uma ferramenta de aprendizagem e mostra um estudo de caso: o jogo de Joan de Peratallada. O objetivo desse estudo é promover o diálogo e a possível colaboração entre um jogo digital cognitivo aplicado as escolas primárias de forma a colaborar com a ensino de historia de Catalunha, Espanha. 2012-11-12T09:16:12Z http://hdl.handle.net/2117/16466 Title: Computing parameter ranges in constructive geometric constraint solving: Implementation and correctness proof Authors: Hidalgo, Marta; Joan Arinyo, Robert Abstract: In parametric design, changing values of parameters to get different solution instances to the problem at hand is a paramount operation. One of the main issues when generating the solution instance for the actual set of parameters is that the user does not know in general which is the set of parameter values for which the parametric solution is feasible. Similarly, in constraint-based dynamic geometry, knowing the set of critical points where construction feasibility changes would allow to avoid unexpected and unwanted behaviors. We consider parametric models in the Euclidean space with one internal degree of freedom. In this scenario, in general, the set of values of the variant parameter for which the parametric model is realizable and defines a valid shape is a set of intervals on the real line. In this work we report on our experiments implementing the van der Meiden Approach to compute the set of parameter values that bound intervals for which the parametric object is realizable. The implementation is developed on top of a constructive, ruler-and-compass geometric constraint solver. We formalize the underlying concepts and prove that our implementation is correct, that is, the approach exactly computes all the feasible interval bounds. 2012-09-12T07:22:06Z http://hdl.handle.net/2117/15727 Title: Efficient algorithms for boundary extraction of 2D and 3D orthogonal pseudomanifolds Authors: Vigo Anglada, Marc; Pla García, Núria; Ayala Vallespí, M. Dolors; Martínez Bayona, Jonás Abstract: In this paper we present algorithms to extract the boundary representation of orthogonal polygons and polyhedra, either manifold or pseudomanifold. The algorithms we develop reconstruct not only the polygons of the boundaries but also the hole-face inclusion relationship. Our algorithms have a simple input so they can be used to convert many different kinds of models to B-Rep. In the 2D case, the input is the set of vertices, and in the 3D case, some small additional information must be supplied for every vertex. All proposed algorithms run in View the MathML source time and use O(n) space, where n is the number of vertices of the input. Moreover, we explain how to use our proposal to extract the boundary from the well-known voxel and octree models as well as from three vertex-based models found in the related literature: the neighbourhood, the EVM, and the weighted vertex list models. 2012-04-16T08:15:20Z http://hdl.handle.net/2117/14703 Title: Animation of 3D Avatars for Rehabilitation of the Upper Limbs Authors: Moya, Sergio; Grau Carrion, Sergi; Tost Pardell, Daniela; Campeny, Ricard; Ruiz, Marcel Abstract: The paper presents a 3D Virtual Environment (VE) for neurorehabilitation of the upper limb. Patients move one of their arms trying to simulate concrete daily actions, such as grasping a bottle, opening a door or putting a book on a shelve. They wear a special garment that integrates four inertial sensors providing in real time information on the orientation of the patient’s shoulder, elbow and wrist. The VE is a complete scenario integrating all the objects needed to perform virtually the actions simulated by the patients. In the VE, patients are represented by 3D avatars that, using the data provided by the inertial sensors, reproduce in real time their arm movements. Since only the arm movement is monitorized, but neither the hand nor the trunk and the neck, the system must combine real movements with baked animations in order to show a realistic behavior of the 3D avatar. Moreover, it must take into account collisions between the 3D avatar and the virtual objects. Finally, it must detect when the patient is about to simulate an interaction with an object in order to realize it virtually. We describe the strategies that we have designed to provide these functionalities. 2012-01-20T12:27:40Z http://hdl.handle.net/2117/14322 Title: A connected-component-labeling-based approach to virtual porosimetry Authors: Rodríguez, Jorge Ernesto; Cruz, Irving; Vergés Garcia, Eduard; Ayala Vallespí, M. Dolors Abstract: Analyzing the pore-size distribution of porous materials, made up of an aggregation of interconnected pores, is a demanding task. Mercury intrusion porosimetry (MIP) is a physical method that intrudes mercury into a sample at increasing pressures to obtain a poresize histogram. This method has been simulated in-silice with several approaches requiring prior computation of a skeleton. We present a new approach to simulate MIP that does not require skeleton computation. Our method is an iterative process that considers the diameters corresponding to pressures. At each iteration, geometric tests detect throats for the corresponding diameter and a CCL process collects the region invaded by the mercury. Additionally, a new decomposition model called CUDB, is used. This is suitable for computing the throats and performs better with the CCL algorithm than a voxel model. Our approach obtains the pore-size distribution of the porous medium, and the corresponding pore graph. 2011-12-27T10:59:00Z http://hdl.handle.net/2117/14127 Title: Videojuegos como un entorno de aprendizaje: el Caso de "Monturiol el joc"" Authors: Eguía Gómez, Jose Luis; Contreras Espinosa, Ruth S.; Solano Albajés, Lluís 2011-12-01T08:31:16Z http://hdl.handle.net/2117/13418 Title: Skeleton computation of orthogonal polyhedra Authors: Martínez Bayona, Jonás; Vigo Anglada, Marc; Pla García, Núria Abstract: Skeletons are powerful geometric abstractions that provide useful representations for a number of geometric operations. The straight skeleton has a lower combinatorial complexity compared with the medial axis. Moreover, while the medial axis of a polyhedron is composed of quadric surfaces the straight skeleton just consist of planar faces. Although there exist several methods to compute the straight skeleton of a polygon, the straight skeleton of polyhedra has been paid much less attention. We require to compute the skeleton of very large datasets storing orthogonal polyhedra. Furthermore, we need to treat geometric degeneracies that usually arise when dealing with orthogonal polyhedra. We present a new approach so as to robustly compute the straight skeleton of orthogonal polyhedra. We follow a geometric technique that works directly with the boundary of an orthogonal polyhedron. Our approach is output sensitive with respect to the number of vertices of the skeleton and solves geometric degeneracies. Unlike the existing straight skeleton algorithms that shrink the object boundary to obtain the skeleton, our algorithm relies on the plane sweep paradigm. The resulting skeleton is only composed of axis-aligned and 45 rotated planar faces and edges. 2011-10-04T14:00:51Z http://hdl.handle.net/2117/13384 Title: Navigating large terrains using commodity mobile devices Authors: Noguera, José María; Segura, Rafael; Ogáyar, Carlos; Joan Arinyo, Robert 2011-09-28T16:34:59Z http://hdl.handle.net/2117/12989 Title: Parameter tunning of PBIL and CHC evolutionary algorithms applied to solve the Root Identification Problem Authors: Joan Arinyo, Robert; Luzón, M.V.; Yeguas Bolívar, Enrique Abstract: Evolutionary algorithms are among the most successful approaches for solving a number of problems where systematic searches in huge domains must be performed. One problem of practical interest that falls into this category is known as The Root Identification Problem in Geometric Constraint Solving, where one solution to the geometric problem must be selected among a number of possible solutions bounded by an exponential number. In previous works we have shown that applying genetic algorithms, a category of evolutionary algorithms, to solve the Root Identification Problem is both feasible and effective. In this work, we report on an empirical statistical study conducted to establish the influence of the driving parameters in the PBIL and CHC evolutionary algorithms when they are used to solve the Root Identification Problem. We identify a set of values that optimize algorithms performance. The driving parameters considered for the PBIL algorithm are population size, mutation probability, mutation shift and learning rate. For the CHC algorithm we studied population size, divergence rate, differential threshold and the set of best individuals. In both cases we applied unifactorial and multifactorial analysis, post hoc tests and best parameter level selection. Experimental results show that CHC outperforms PBIL when applied to solve the Root Identification Problem. 2011-07-18T08:46:48Z http://hdl.handle.net/2117/12066 Title: Computer graphics at the Universitat Politècnica de Catalunya Authors: Brunet Crosa, Pere; Joan Arinyo, Robert; Navazo Álvaro, Isabel; Tost Pardell, Daniela; Vila, S Abstract: This paper describes the authors experience in the organization and teaching of courses of Computer Graphics for both undergraduate and graduate students. Curriculum contents and teaching methodologies are discussed, taking into account practical constraints related to the facilities available at laboratories and curriculum structures. 2011-03-25T12:18:28Z http://hdl.handle.net/2117/11065 Title: Topology-reducing surface simplification using a discrete solid representation Authors: Andújar Gran, Carlos Antonio; Brunet Crosa, Pere; Ayala Vallespí, M. Dolors Abstract: This paper presents a new approach for generating coarse-level approximations of topologically complex models. Dramatic topology reduction is achieved by converting a 3D model to and from a volumetric representation. Our approach produces valid, error-bounded models and supports the creation of approximations that do not interpenetrate the original model, either being completely contained in the input solid or bounding it. Several simple to implement versions of our approach are presented and discussed. We show that these methods perform significantly better than other surface-based approaches when simplifying topologically-rich models such as scene parts and complex mechanical assemblies. 2011-01-17T11:49:20Z http://hdl.handle.net/2117/10860 Title: Analysis of methods for generating octree models of objects from their silhouettes Authors: Franquesa Niubó, Marta; Brunet Crosa, Pere Abstract: Reconstructing 3D models from their projection images has been an interesting research topic in computer vision and geometric modeling. In this paper, we review several methods that generate octree models of objects from their silhouettes in images. The complexity analysis of the algorithms is developed and presented. It is concluded that the performance of the algorithms depents mostly on the number of starting images and the object shapes through their number of faces and concavities. 2010-12-31T09:27:40Z