Examinando por Autor "Congote, J."
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Ítem Adaptative cubical grid forisosurface extraction(2009-01-01) Congote, J.; Moreno, A.; Barandiaran, I.; Barandiaran, J.; Ruiz, O.E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis work proposes a variation on the Marching Cubes algorithm, where the goal is to represent implicit functions with higher resolution and better graphical qualiry using the same grid size. The proposed algorithm displaces the vertices of the cubes iteratively until the stop condition is achieved. After each iteration, the difference betvveen the implicit and the explicit representations are reduced, and when the algorithm finishes, the implicit surface representation using the modified cubical grid is more detailed, as the results shall confirm. The proposed algorithm corrects some topological problems that may appear in the discretisation process using the original grid.Ítem Evaluation of interest point detectors for image information extraction(IOS PRESS, 2012-01-01) Barandiaran, I.; Congote, J.; Goenetxea, J.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEInterest points extraction and matching is a common task in many computer vision based application, which are used in different domains, such as 3D reconstruction, object recognition, or tracking. We present an evaluation of current state of the art about interest point extraction algorithms to measure several parameters, such as detection quality, invariance to rotation and scale transformation, and computational efficiency. © 2012 The authors and IOS Press. All rights reserved.Ítem Extending marching cubes with adaptative methods to obtain more accurate iso-surfaces(Springer Verlag, 2010-01-01) Congote, J.; Moreno, A.; Barandiaran, I.; Barandiaran, J.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis work proposes an extension of the Marching Cubes algorithm, where the goal is to represent implicit functions with higher accuracy using the same grid size. The proposed algorithm displaces the vertices of the cubes iteratively until the stop condition is achieved. After each iteration, the difference between the implicit and the explicit representations is reduced, and when the algorithm finishes, the implicit surface representation using the modified cubical grid is more accurate, as the results shall confirm. The proposed algorithm corrects some topological problems that may appear in the discretization process using the original grid. © 2010 Springer-Verlag Berlin Heidelberg.Ítem Face reconstruction with structured light(INSTICC-INST SYST TECHNOLOGIES INFORMATION CONTROL & COMMUNICATION, 2011-01-01) Congote, J.; Barandiaran, I.; Barandiaran, J.; Nieto, M.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis article presents a methodology for reconstruction of 3D faces which is based on stereoscopic images of the scene using active and passive surface reconstruction. A sequence of Gray patterns is generated, which are projected onto the scene and their projection recorded by a pair of stereo cameras. The images are rectified to make coincident their epipolar planes and so to generate a stereo map of the scene. An algorithm for stereo matching is applied, whose result is a bijective mapping between subsets of the pixels of the images. A particular connected subset of the images (e.g. the face) is selected by a segmentation algorithm. The stereo mapping is applied to such a subset and enables the triangulation of the two image readings therefore rendering the (x,y,z) points of the face, which in turn allow the reconstruction of the triangular mesh of the face. Since the surface might have holes, bilateral filters are applied to have the holes filled. The algorithms are tested in real conditions and we evaluate their performance with virtual datasets. Our results show a good reconstruction of the faces and an improvement of the results of passive systems.Ítem Hardware-accelerated web visualization of vector fields: Case study in oceanic currents(2012-01-01) Aristizabal, M.; Congote, J.; Segura, A.; Moreno, A.; Arregui, H.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEVisualization of vector fields plays an important role in research activities nowadays. Increasing web applications allow a fast, multi-platform and multi-device access to data. As a result, web applications must be optimized in order to be performed heterogeneously as well as on high-performance as on low capacity devices. This paper presents a hardware-accelerated scheme for integration-based flow visualization techniques, based on a hierarchical integration procedure which reduces the computational effort of the algorithm from linear to logarithmic, compared to serial integration methodologies. The contribution relies on the fact that the optimization is only implemented using the graphics application programming interface (API), instead of requiring additional APIs or plug-ins. This is achieved by using images as data storing elements instead of graphical information matrices. A case study in oceanic currents is implemented.Ítem Interactive visualization of volumetric data with WebGL in real-time(2011-01-01) Congote, J.; Segura, A.; Kabongo, L.; Moreno, A.; Posada, J.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis article presents and discusses the implementation of a direct volume rendering system for the Web, which articulates a large portion of the rendering task in the client machine. By placing the rendering emphasis in the local client, our system takes advantage of its power, while at the same time eliminates processing from unreliable bottlenecks (e.g. network). The system developed articulates in efficient manner the capabilities of the recently released WebGL standard, which makes available the accelerated graphic pipeline (formerly unusable). The dependency on specially customized hardware is eliminated, and yet efficient rendering rates are achieved. The Web increasingly competes against desktop applications in many scenarios, but the graphical demands of some of the applications (e.g. interactive scientific visualization by volume rendering), have impeded their successful settlement in Web scenarios. Performance, scalability, accuracy, security are some of the many challenges that must be solved before visual Web applications popularize. In this publication we discuss both performance and scalability of the volume rendering by WebGL ray-casting in two different but challenging application domains: medical imaging and radar meteorology. © 2011 ACM.Ítem Marching cubes in an unsigned distance field for surface reconstruction from unorganized point sets(INSTICC-INST SYST TECHNOLOGIES INFORMATION CONTROL & COMMUNICATION, 2010-01-01) Congote, J.; Moreno, A.; Barandiaran, I.; Barandiaran, J.; Posada, J.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAESurface reconstruction from unorganized point set is a common problem in computer graphics. Generation of the signed distance field from the point set is a common methodology for the surface reconstruction. The reconstruction of implicit surfaces is made with the algorithm of marching cubes, but the distance field of a point set can not be processed with marching cubes because the unsigned nature of the distance. We propose an extension to the marching cubes algorithm allowing the reconstruction of 0-level iso-surfaces in an unsigned distance field. We calculate more information inside each cell of the marching cubes lattice and then we extract the intersection points of the surface within the cell then we identify the marching cubes case for the triangulation. Our algorithm generates good surfaces but the presence of ambiguities in the case selection generates some topological mistakes.Ítem Real-time depth map generation architecture for 3D videoconferencing(2010-01-01) Congote, J.; Barandiaran, I.; Barandiaran, J.; Montserrat, T.; Quelen, J.; Ferran, C.; Mindan, P.J.; Mur, O.; Tarres, F.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn this paper we present a reliable depth estimation system which works in real-time with commodity hardware. The system is specially intended for 3D visualization using autostereoscopic displays. The core of this work is an implementation of a modified version of the adaptive support-weight algorithm that includes highly optimized algorithms for GPU, allowing accurate and stable depth map generation. Our approach overcomes typical problems of live depth estimation systems such as depth noise and flickering. Proposed approach is integrated within the versatile GStreamer multimedia software platform. Accurate depth map estimation together with real-time performance make proposed approach suitable for 3D videoconferencing. © 2010 IEEE.Ítem Real-time volume rendering and tractography visualization on the web(Vaclav Skala, 2012-01-01) Congote, J.; Novo, E.; Kabongo, L.; Ginsburg, D.; Gerhard, S.; Pienaar, R.; Ruiz, O.E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEIn the field of computer graphics, Volume Rendering techniques allow the visualization of 3D datasets, and specifically, Volume Ray-Casting renders images from volumetric datasets, typically used in some scientific areas, such as medical imaging. This article aims to describe the development of a combined visualization of tractography and volume rendering of brain T1 MRI images in an integrated way. An innovative web viewer for interactive visualization of neuro-imaging data has been developed based on WebGL. This recently developed standard enables the clients to use the web viewer on a wide range of devices, with the only requirement of a compliant web-browser. As the majority of the rendering tasks take place in the client machine, the effect of bottlenecks and server overloading are minimized. The web application presented is able to compete with desktop tools, even supporting high graphical demands and facing challenges regarding performance and scalability. The developed software modules are available as open source code and include MRI volume data and tractography generated by the Diffusion Toolkit, and connectivity data from the Connectome Mapping Toolkit. Our contribution for the Volume Web Viewer implements early ray termination step according to the tractography depthmap, combining volume images and estimated white matter fibers. Furthermore, the depthmap system extension can be used for visualization of other types of data, where geometric and volume elements are displayed simultaneously.Ítem ReWeb3D - Enabling desktop 3D applications to run in the web(2013-01-01) Glander, T.; Moreno, A.; Aristizabal, M.; Congote, J.; Posada, J.; Garcia-Alonso, A.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAECurrently, 3D rendering is accessible within Web browsers through open standards such as WebGL, X3D, and X3DOM. At the same time, there is wealth of mature desktop software which comprises algorithms, data structures, user interfaces, databases, etc. It is a challenge to reuse such desktop software using the Web visualization resources. In response to this challenge, this article presents a novel framework, called ReWeb3D, which minimizes the redevelopment for migration of existing 3D applications to the Web. The redeployed application runs on a Web server. ReWeb3D captures low-level graphic calls including geometry, texture, and shader programs. The captured content is then served as a WebGL-enabled web page that conveys full interactivity to the client. By splitting the graphics pipeline between client and server, the workload can be balanced, and high-level implementation details and 3D content are hidden. The feasibility of ReWeb3D has been tested with applications which use OpenSceneGraph as rendering platform. The approach shows good results for applications with large data sets (e.g. geodata), but is less suited for applications intensive in animations (e.g. games). Copyright © ACM 978-1-4503-2133-4/13/06 $15.00.Ítem Visualization of flow fields in the web platform(Vaclav Skala, 2012-01-01) Aristizabal, M.; Congote, J.; Segura, A.; Moreno, A.; Arregui, H.; Ruiz, O.E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEVisualization of vector fields plays an important role in research activities nowadays. Web applications allow a fast, multi-platform and multi-device access to data, which results in the need of optimized applications to be implemented in both high and low-performance devices. The computation of trajectories usually repeats calculations due to the fact that several points might lie over the same trajectory. This paper presents a new methodology to calculate point trajectories over a highly-dense and uniformly-distributed grid of points in which the trajectories are forced to lie over the points in the grid. Its advantages rely on a highly parallel computing implementation and in the reduction of the computational effort to calculate the stream paths since unnecessary calculations are avoided by reusing data through iterations. As case study, the visualization of oceanic streams in the web platform is presented and analyzed, using WebGL as the parallel computing architecture and the rendering engine.Ítem Volume Visual Attention Maps (VVAM) in ray-casting rendering(IOS Press, 2012-01-01) Beristain, A.; Congote, J.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis paper presents an extension visual attention maps for volume data visualization, where eye fixation points become rays in the 3D space, and the visual attention map becomes a volume. This Volume Visual Attention Map (VVAM) is used to interactively enhance a ray-casting based direct volume rendering (DVR) visualization. The practical application of this idea into the biomedical image visualization field is explored for interactive visualization. © 2012 The authors and IOS Press. All rights reserved.Ítem Web based hybrid volumetric visualisation of urban GIS data: Integration of 4D Temperature and Wind Fields with LoD-2 CityGML models(EDP Sciences, 2012) Congote, J.; Moreno, A.; Kabongo, L.; Pérez, J.-L.; San-José, R.; Ruíz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAECity models visualisation, buildings, structures and volumetric information, is an important task in Computer Graphics and Urban Planning -- The different formats and data sources involved in the visualisation make the development of applications a big challenge -- We present a homogeneous web visualisation framework using X3DOM and MEDX3DOM for the visualisation of these urban objects -- We present an integration of different declarative data sources, enabling the utilization of advanced visualisation algorithms to render the models -- It has been tested with a city model composed of buildings from the Madrid University Campus, some volumetric datasets coming from Air Quality Models and 2D layers wind datasets -- Results show that the visualisation of all the urban models can be performed in real time on the Web -- An HTML5 web interface is presented to the users, enabling real time modifications of visualisation parameters