http://hdl.handle.net/2117/3565 Sat, 25 May 2013 04:14:43 GMT 2013-05-25T04:14:43Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no 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. Thu, 28 Feb 2013 11:07:58 GMT http://hdl.handle.net/2117/18016 2013-02-28T11:07:58Z Andújar Gran, Carlos Antonio; Navazo Álvaro, Isabel; Vázquez Alcocer, Pere Pau; Patow, Gustavo; Pueyo, Xavier no ViRVIG Institute, 3D user Interfaces 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. 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. Tue, 13 Nov 2012 10:51:14 GMT http://hdl.handle.net/2117/16905 2012-11-13T10:51:14Z Pelechano Gómez, Núria; Spanlang, Bernhard; Beacco Porres, Alejandro no Crowd animation, Foot sliding 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. 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. Mon, 27 Aug 2012 16:35:45 GMT http://hdl.handle.net/2117/16390 2012-08-27T16:35:45Z Beacco Porres, Alejandro; Andújar Gran, Carlos Antonio; Pelechano Gómez, Núria; Spanlang, Bernhard no crowd rendering, image-based rendering, impostors, level of detail 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. 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. Wed, 20 Jun 2012 10:05:42 GMT http://hdl.handle.net/2117/16104 2012-06-20T10:05:42Z Theoktisto, Víctor; Fairén González, Marta; Navazo Álvaro, Isabel no Haptic Rendering, Mesostructure, Displacement mapping 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. 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. Tue, 29 May 2012 10:08:08 GMT http://hdl.handle.net/2117/15934 2012-05-29T10:08:08Z Trueba Hornero, Ramón; Andújar Gran, Carlos Antonio; Argelaguet Sanz, Fernando no 3D selection and manipulation, 3D user interfaces, Occlusion management, Virtual environments, World-In-Miniature 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. 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. Thu, 17 May 2012 10:31:11 GMT http://hdl.handle.net/2117/15887 2012-05-17T10:31:11Z Andújar Gran, Carlos Antonio; Brunet Crosa, Pere; Chica Calaf, Antonio; Navazo Álvaro, Isabel no Urban rendering, Relief mapping, Large city visualization 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. 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. Thu, 17 May 2012 10:11:40 GMT http://hdl.handle.net/2117/15886 2012-05-17T10:11:40Z Hétroy, Franck; Rey, Stéphanie; Andújar Gran, Carlos Antonio; Brunet Crosa, Pere; Vinacua Pla, Álvaro no Topology, Morphology, Opening, Closing, 2-manifold 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. http://hdl.handle.net/2117/15705 Title: Topographic map visualization from adaptively compressed textures Authors: Andújar Gran, Carlos Antonio Abstract: Raster-based topographic maps are commonly used in geoinformation systems to overlay geographic entities on top of digital terrain models. Using compressed texture formats for encoding topographic maps allows reducing latency times while visualizing large geographic datasets. Topographic maps encompass high-frequency content with large uniform regions, making current compressed texture formats inappropriate for encoding them. In this paper we present a method for locally-adaptive compression of topographic maps. Key elements include a Hilbert scan to maximize spatial coherence, efficient encoding of homogeneous image regions through arbitrarily-sized texel runs, a cumulative run-length encoding supporting fast random-access, and a compression algorithm supporting lossless and lossy compression. Our scheme can be easily implemented on current programmable graphics hardware allowing real-time GPU decompression and rendering of bilinear-filtered topographic maps. Wed, 04 Apr 2012 10:40:25 GMT http://hdl.handle.net/2117/15705 2012-04-04T10:40:25Z Andújar Gran, Carlos Antonio no 3D Graphics and realism, Texture Raster-based topographic maps are commonly used in geoinformation systems to overlay geographic entities on top of digital terrain models. Using compressed texture formats for encoding topographic maps allows reducing latency times while visualizing large geographic datasets. Topographic maps encompass high-frequency content with large uniform regions, making current compressed texture formats inappropriate for encoding them. In this paper we present a method for locally-adaptive compression of topographic maps. Key elements include a Hilbert scan to maximize spatial coherence, efficient encoding of homogeneous image regions through arbitrarily-sized texel runs, a cumulative run-length encoding supporting fast random-access, and a compression algorithm supporting lossless and lossy compression. Our scheme can be easily implemented on current programmable graphics hardware allowing real-time GPU decompression and rendering of bilinear-filtered topographic maps. http://hdl.handle.net/2117/14334 Title: Simulation and study of the geometric parameters in the inguinal area and the genesis of inguinal hernias Authors: Fortuny Anguera, Gerard; López Cano, Manuel; Susín Sánchez, Antonio; Herrera, Blas Abstract: We are interested in studying the genesis of a very common pathology: the human inguinal hernia. How the human inguinal hernia appears is not definitively clear, but it is accepted that it is caused by a combination of mechanical and biochemical alterations, and that muscular simulation plays an important role in this. This study proposes a model to explain how some physical parameters affect the ability to simulate the region dynamically and how these parameters are involved in generating inguinal hernias. We are particularly interested in understanding the mechanical alterations in the inguinal region because little is known about them or how they behave dynamically. Our model corroborates the most important theories regarding the generation of inguinal hernias and is an initial approach to numerically evaluating this affection. Wed, 28 Dec 2011 11:12:49 GMT http://hdl.handle.net/2117/14334 2011-12-28T11:12:49Z Fortuny Anguera, Gerard; López Cano, Manuel; Susín Sánchez, Antonio; Herrera, Blas no finite element method, simulation, inguinal hernia, muscular contraction We are interested in studying the genesis of a very common pathology: the human inguinal hernia. How the human inguinal hernia appears is not definitively clear, but it is accepted that it is caused by a combination of mechanical and biochemical alterations, and that muscular simulation plays an important role in this. This study proposes a model to explain how some physical parameters affect the ability to simulate the region dynamically and how these parameters are involved in generating inguinal hernias. We are particularly interested in understanding the mechanical alterations in the inguinal region because little is known about them or how they behave dynamically. Our model corroborates the most important theories regarding the generation of inguinal hernias and is an initial approach to numerically evaluating this affection. http://hdl.handle.net/2117/13069 Title: Reflector design from radiance distributions Authors: Patow, Gustavo; Pueyo, Xavier; Vinacua Pla, Álvaro Abstract: This paper proposes a technique for the design of reflector shapes from prescribed optical properties (far field radiance distribution) and geometrical constraints, which is of high importance in the field of Lighting Engineering, more specifically for Luminaire Design. The reflector shape to be found is just a part of a set of pieces of what is known in lighting engineering as an optical set, and is composed of a lamp (light source), a reflector, a holding case and a glass that protects the system from dust and other environmental phenomena. Thus, we aim at the design and development of a system capable of generating a reflector shape in a way such that the optical set emits a given, user defined, far field radiance distribution. This problem can be put in the mathematical context of inverse problems, which refer to all the problems where, contrary to what happens with traditional direct problems, several aspects of the scene are unknown. Then, the algorithm is allowed to work backwards to establish the missing parameters. In order to do so, light propagation inside and outside the optical set must be computed and the resulting radiance distribution compared to the desired one. Finally, constraints on the shape imposed by industry needs must be taken into account, bounding the set of possible shape definitions. The general approach taken is based on a minimization procedure on the space of possible reflector shapes. The algorithm moves towards minimizing the distance, in the I2 metric, between the resulting illumination far from the reflector and a prescribed, ideal optical radiance distribution specified at the far field by the user. Thu, 28 Jul 2011 09:19:00 GMT http://hdl.handle.net/2117/13069 2011-07-28T09:19:00Z Patow, Gustavo; Pueyo, Xavier; Vinacua Pla, Álvaro no Reflector design, Inverse problems, Inverse rendering This paper proposes a technique for the design of reflector shapes from prescribed optical properties (far field radiance distribution) and geometrical constraints, which is of high importance in the field of Lighting Engineering, more specifically for Luminaire Design. The reflector shape to be found is just a part of a set of pieces of what is known in lighting engineering as an optical set, and is composed of a lamp (light source), a reflector, a holding case and a glass that protects the system from dust and other environmental phenomena. Thus, we aim at the design and development of a system capable of generating a reflector shape in a way such that the optical set emits a given, user defined, far field radiance distribution. This problem can be put in the mathematical context of inverse problems, which refer to all the problems where, contrary to what happens with traditional direct problems, several aspects of the scene are unknown. Then, the algorithm is allowed to work backwards to establish the missing parameters. In order to do so, light propagation inside and outside the optical set must be computed and the resulting radiance distribution compared to the desired one. Finally, constraints on the shape imposed by industry needs must be taken into account, bounding the set of possible shape definitions. The general approach taken is based on a minimization procedure on the space of possible reflector shapes. The algorithm moves towards minimizing the distance, in the I2 metric, between the resulting illumination far from the reflector and a prescribed, ideal optical radiance distribution specified at the far field by the user. http://hdl.handle.net/2117/13066 Title: Enhancing collaboration in virtual reality applications Authors: Theoktisto, Víctor; Fairén González, Marta Abstract: We derive a complete component framework for transforming standalone virtual reality (VR) applications into fullfledged multithreaded collaborative virtual reality environments (CVREs), after characterizing existing implementations into a feature-rich superset. Our main contribution is placing over the existing VR tool a very concise and extensible class framework as an add-on component that provides emerging collaboration features. The enhancements include: a scalable arbitrated peer-to-peer topology for scene sharing; multi-threaded components for graphics rendering, user interaction and network communications; a streaming message protocol for client communications; a collaborative user interface model for session handling; and interchangeable user roles with multicamera perspectives, avatar awareness and shared 3D annotations. We validate the framework by converting the existing ALICE VR Navigator into complete CVRE, with experimental results showing good performance in the collaborative inspection and manipulation of complex models. Wed, 27 Jul 2011 11:54:17 GMT http://hdl.handle.net/2117/13066 2011-07-27T11:54:17Z Theoktisto, Víctor; Fairén González, Marta no We derive a complete component framework for transforming standalone virtual reality (VR) applications into fullfledged multithreaded collaborative virtual reality environments (CVREs), after characterizing existing implementations into a feature-rich superset. Our main contribution is placing over the existing VR tool a very concise and extensible class framework as an add-on component that provides emerging collaboration features. The enhancements include: a scalable arbitrated peer-to-peer topology for scene sharing; multi-threaded components for graphics rendering, user interaction and network communications; a streaming message protocol for client communications; a collaborative user interface model for session handling; and interchangeable user roles with multicamera perspectives, avatar awareness and shared 3D annotations. We validate the framework by converting the existing ALICE VR Navigator into complete CVRE, with experimental results showing good performance in the collaborative inspection and manipulation of complex models. http://hdl.handle.net/2117/13064 Title: Space efficient connectivity test for n-dimensional images Authors: Andújar Gran, Carlos Antonio Abstract: An image is a discrete array whose elements, called points, represent some property. Images are broadly used in computer graphics. In 2D graphics applications, color, depth and other image properties are frequently used. In 3D graphics, a solid may be represented by a 3D binary image whose elements have value 0 or 1 indicating absence or presence of solid. Similarly, many volume applications use non-binary 3D images to represent some spatial function. Here we propose an algorithm to solve the connectivity problem, which can be stated as follows: given an n-dimensional image I, an m-adjacency A and a predicate P which segments the property values into black and white points, check if the black points of I are m-connected, that is, if I has a single m-connected black component. Wed, 27 Jul 2011 11:38:48 GMT http://hdl.handle.net/2117/13064 2011-07-27T11:38:48Z Andújar Gran, Carlos Antonio no An image is a discrete array whose elements, called points, represent some property. Images are broadly used in computer graphics. In 2D graphics applications, color, depth and other image properties are frequently used. In 3D graphics, a solid may be represented by a 3D binary image whose elements have value 0 or 1 indicating absence or presence of solid. Similarly, many volume applications use non-binary 3D images to represent some spatial function. Here we propose an algorithm to solve the connectivity problem, which can be stated as follows: given an n-dimensional image I, an m-adjacency A and a predicate P which segments the property values into black and white points, check if the black points of I are m-connected, that is, if I has a single m-connected black component. http://hdl.handle.net/2117/13061 Title: Way-finder: guided tours through complex walkthrough models Authors: Andújar Gran, Carlos Antonio; Vázquez Alcocer, Pere Pau; Fairén González, Marta Abstract: The exploration of complex walkthrough models is often a difficult task due to the presence of densely occluded regions which pose a serious challenge to online navigation. In this paper we address the problem of algorithmic generation of exploration paths for complex walkthrough models. We present a characterization of suitable properties for camera paths and we discuss an efficient algorithm for computing them with little or no user intervention. Our approach is based on identifying the free-space structure of the scene (represented by a cell and portal graph) and an entropy-based measure of the relevance of a view-point. This metric is key for deciding which cells have to be visited and for computing critical way-points inside each cell. Several results on different model categories are presented and discussed. Wed, 27 Jul 2011 10:22:05 GMT http://hdl.handle.net/2117/13061 2011-07-27T10:22:05Z Andújar Gran, Carlos Antonio; Vázquez Alcocer, Pere Pau; Fairén González, Marta no The exploration of complex walkthrough models is often a difficult task due to the presence of densely occluded regions which pose a serious challenge to online navigation. In this paper we address the problem of algorithmic generation of exploration paths for complex walkthrough models. We present a characterization of suitable properties for camera paths and we discuss an efficient algorithm for computing them with little or no user intervention. Our approach is based on identifying the free-space structure of the scene (represented by a cell and portal graph) and an entropy-based measure of the relevance of a view-point. This metric is key for deciding which cells have to be visited and for computing critical way-points inside each cell. Several results on different model categories are presented and discussed. http://hdl.handle.net/2117/13048 Title: Automatic keyframe selection for high-quality image-based walkthrough animation using viewpoint entropy Authors: Vázquez Alcocer, Pere Pau; Sbert Cassasayas, Mateu Abstract: The computation of high quality animation sequences is expensive. Generation time for each frame can take a few hours Recently, Image-Based Rendering methods have been proposed to solve this problem. As these techniques obtain new arbitrary views from precomputed ones at low cost, walkthroughs may be computed faster. Consequently, the selection of the precomputed images is a very important step. The initial set of keyframes should fulfill two requirements, it must be small but provide as much information as possible on the scene. In this paper we review several keyframe selection strategies and then we propose a new method based on entropy that achieve similar, and in some cases better, results. Tue, 26 Jul 2011 12:13:20 GMT http://hdl.handle.net/2117/13048 2011-07-26T12:13:20Z Vázquez Alcocer, Pere Pau; Sbert Cassasayas, Mateu no High-quality walkthrough, Image-based rendering, Keyframe selection, Entropy The computation of high quality animation sequences is expensive. Generation time for each frame can take a few hours Recently, Image-Based Rendering methods have been proposed to solve this problem. As these techniques obtain new arbitrary views from precomputed ones at low cost, walkthroughs may be computed faster. Consequently, the selection of the precomputed images is a very important step. The initial set of keyframes should fulfill two requirements, it must be small but provide as much information as possible on the scene. In this paper we review several keyframe selection strategies and then we propose a new method based on entropy that achieve similar, and in some cases better, results. http://hdl.handle.net/2117/13047 Title: An interactive 3D framework for anatomical education Authors: Vázquez Alcocer, Pere Pau; Götzelmann, Timo; Hartmann, Knut; Nürnberger, Andreas Abstract: Object: This paper presents a 3D framework for Anatomy teaching. We are mainly concerned with the proper understanding of human anatomical 3D structures. Materials and methods: The main idea of our approach is taking an electronic book such as Henry Gray’s Anatomy of the human body, and a set of 3D models properly labeled, and constructing the correct linking that allows users to perform mutual searches between both media. Results: We implemented a system where learners can interactively explore textual descriptions and 3D visualizations. Conclusion: Our approach allows easily performing two search tasks: first, the user may select a text region and get a view showing the objects that contain the selected structures, and second, using the interactive exploration of a 3D model the user may automatically search for the textual description of the structures visible in the current view. Tue, 26 Jul 2011 11:40:50 GMT http://hdl.handle.net/2117/13047 2011-07-26T11:40:50Z Vázquez Alcocer, Pere Pau; Götzelmann, Timo; Hartmann, Knut; Nürnberger, Andreas no Computer-assisted instruction, Medical educational materials, Computer graphics Object: This paper presents a 3D framework for Anatomy teaching. We are mainly concerned with the proper understanding of human anatomical 3D structures. Materials and methods: The main idea of our approach is taking an electronic book such as Henry Gray’s Anatomy of the human body, and a set of 3D models properly labeled, and constructing the correct linking that allows users to perform mutual searches between both media. Results: We implemented a system where learners can interactively explore textual descriptions and 3D visualizations. Conclusion: Our approach allows easily performing two search tasks: first, the user may select a text region and get a view showing the objects that contain the selected structures, and second, using the interactive exploration of a 3D model the user may automatically search for the textual description of the structures visible in the current view.