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1 to 18 of 18 results
  • Inexpensive reconstruction and rendering of realistic roadside landscapes

     Andujar Gran, Carlos A.; Chica Calaf, Antonio; Vico, Miguel Angel; Moya, S.; Brunet, Pere
    Computer graphics forum
    Vol. 33, num. 6, p. 101-117
    DOI: 10.1111/cgf.12281
    Date of publication: 2014-09-01
    Journal article

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    In this paper, we present an inexpensive approach to create highly detailed reconstructions of the landscape surrounding a road. Our method is based on a space-efficient semi-procedural representation of the terrain and vegetation supporting high-quality real-time rendering not only for aerial views but also at road level. We can integrate photographs along selected road stretches. We merge the point clouds extracted from these photographs with a low-resolution digital terrain model through a novel algorithm which is robust against noise and missing data. We pre-compute plausible locations for trees through an algorithm which takes into account perceptual cues. At runtime we render the reconstructed terrain along with plants generated procedurally according to pre-computed parameters. Our rendering algorithm ensures visual consistency with aerial imagery and thus it can be integrated seamlessly with current virtual globes.

  • Example-guided segmentation

     Chica Calaf, Antonio; Monclús Lahoya, Eva; Brunet Crosa, Pere; Navazo Alvaro, Isabel; Vinacua Pla, Alvaro
    Graphical models
    Vol. 74, num. 6, p. 302-310
    DOI: 10.1016/j.gmod.2012.03.002
    Date of publication: 2012-11
    Journal article

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  • Distance learning in computer graphics

     Chica Calaf, Antonio; Fairen Gonzalez, Marta; Pelechano Gomez, Nuria
    Annual Conference of the European Association for Computer Graphics
    p. 65-72
    DOI: 10.2312/conf/EG2012/education/065-072
    Presentation's date: 2012-05-17
    Presentation of work at congresses

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  • User-interface design for the Ripoll Monastery exhibition at the National Art Museum of Catalonia

     Andujar Gran, Carlos A.; Chica Calaf, Antonio; Brunet, Pere
    Computers & graphics
    Vol. 36, num. 1, p. 28-37
    DOI: 10.1016/j.cag.2011.10.005
    Date of publication: 2012
    Journal article

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  • Multiscale acquisition and presentation of very large artifacts: The case of portalada

     Callieri, Marco; Chica Calaf, Antonio; Dellepiane, Matteo; Besora, Isaac; Corsini, Massimiliano; Moyés, Jordi; Ranzuglia, Guido; Scopigno, Roberto; Brunet, Pere
    ACM journal on computing and cultural heritage
    Vol. 3, num. 4, p. 14:1-14:20
    DOI: 10.1145/1957825.1957827
    Date of publication: 2011-04
    Journal article

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    The dichotomy between full detail representation and the efficient management of data digitization is still a big issue in the context of the acquisition and visualization of 3D objects, especially in the field of the cultural heritage. Modern scanning devices enable very detailed geometry to be acquired, but it is usually quite hard to apply these technologies to large artifacts. In this article we present a project aimed at virtually reconstructing the impressive (7 × 11 m.) portal of the Ripoll Monastery, Spain. The monument was acquired using triangulation laser scanning technology, producing a dataset of 2212 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 dissemination to the public. We show how time-of-flight laser scanning data can be used to speed-up the alignment process. In addition we show how, after creating a model and repairing imperfections, an interactive and immersive setup enables the public to navigate and display a fully detailed representation of the portal. This article shows that, after careful planning and with the aid of state-of-the-art algorithms, it is now possible to preserve and visualize highly detailed information, even for very large surfaces.

  • Avances en realidad virtual para aplicaciones punteras

     Fairen Gonzalez, Marta; Lligadas Rodriguez, Xavier; Campoalegre Vera, Lazaro; Ojeda Contreras, Jesus; Cervero Abello, Maria Angels; Chica Calaf, Antonio; Díaz Iriberri, José; Pelechano Gomez, Nuria; Argelaguet Sanz, Fernando; Vinacua Pla, Alvaro; Brunet Crosa, Pere; Susin Sanchez, Antonio; Vazquez Alcocer, Pere Pau; Monclús Lahoya, Eva; Andujar Gran, Carlos A.; Beacco Porres, Alejandro; Navazo Alvaro, Isabel
    Competitive project

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  • A volume approach to model repair and smoothing

     Brunet, Pere; Chica Calaf, Antonio; Monclús Lahoya, Eva; Navazo Alvaro, Isabel; Vinacua Pla, Alvaro
    Geometric Modeling (Dagstuhl Seminar 11211)
    p. 89-90
    DOI: 10.4230/DagRep.1.5.84
    Presentation's date: 2011
    Presentation of work at congresses

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  • Visualization of large-scale urban models through multi-level relief impostors

     Andujar Gran, Carlos A.; Brunet Crosa, Pere; Chica Calaf, Antonio; Navazo Alvaro, Isabel
    Computer graphics forum
    Vol. 29, num. 8, p. 2456-2468
    DOI: 10.1111/j.1467-8659.2010.01757.x
    Date of publication: 2010-12
    Journal article

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    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.

  • Massive mesh hole repair minimizing user intervention

     Brunet Crosa, Pere; Chica Calaf, Antonio; Navazo Alvaro, Isabel; Vinacua Pla, Alvaro
    Computing
    Vol. 86, num. 2-3, p. 101-115
    DOI: 10.1007/s00607-009-0052-9
    Date of publication: 2009-10
    Journal article

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  • GRUP DE RECERCA EN VISUALITZACIO, REALITAT VIRTUAL I INTERACCIO GRAFICA (VIRVIG)

     Vinacua Pla, Alvaro; Ojeda Contreras, Jesus; Cervero Abello, Maria Angels; Fairen Gonzalez, Marta; Susin Sanchez, Antonio; Andujar Gran, Carlos A.; Vazquez Alcocer, Pere Pau; Pelechano Gomez, Nuria; Argelaguet Sanz, Fernando; Lligadas Rodriguez, Xavier; Chica Calaf, Antonio; Monclús Lahoya, Eva; Díaz Iriberri, José; Campoalegre Vera, Lazaro; Navazo Alvaro, Isabel; Brunet Crosa, Pere
    Competitive project

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  • Pressing: Smooth Isosurfaces with Flats from Binary Grids

     Chica Calaf, Antonio; Williams, J; Andujar Gran, Carlos A.; Brunet Crosa, Pere; Navazo Alvaro, Isabel; Rossignac, J; Vinacua Pla, Alvaro
    Computer graphics forum
    Vol. 27, num. 1, p. 36-46
    Date of publication: 2008-01
    Journal article

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  • Real-time exploration of the virtual reconstruction of the entrance of the Ripoll Monastery

     Besora, Isaac; Brunet Crosa, Pere; Chica Calaf, Antonio; Morales, Daniel; Moyés, Jordi
    Congreso Español de Informática Gráfica
    p. 219-224
    Presentation's date: 2008
    Presentation of work at congresses

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  • Visibility-based feature extraction from discrete models

     Chica Calaf, Antonio
    ACM Symposium on Solid Modeling Foundations and CAD/CAM Applications
    p. 347-352
    Presentation of work at congresses

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    In this paper, we present a new visibility-based feature extraction algorithm from discrete models as dense point clouds resulting from laser scans. Based on the observation that one can characterize local properties of the surface by what can be seen by an imaginary creature on the surface, we propose algorithms that extract features using an intermediate representation of the model as a discrete volume for computational efficiency. We describe an efficient algorithm for computing the visibility map among voxels, based on the properties of a discrete erosion. The visibility information obtained in this first step is then used to extract the model components (faces, edges and vertices) —which may be curved— and to compute the topological connectivity graph in a very efficient and robust way. The results are discussed through several examples.

  • Portalada: a virtual reconstruction of the entrance of the Ripoll Monastery

     Besora, Isaac; Brunet Crosa, Pere; Callieri, Marco; Chica Calaf, Antonio; Corsini, Massimiliano; Dellepiane, Matteo; Morales, Daniel; Moyés, Jordi; Ranzuglia, Guido; Scopigno, Roberto
    International Symposium on 3D Data Processing, Visualization and Transmission
    p. 89-96
    Presentation's date: 2008
    Presentation of work at congresses

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    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.

  • Extracting Shapes from Binary Grids

     Chica Calaf, Antonio
    Universitat Politècnica de Catalunya
    Theses

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    Optimizing the topological and combinatorial complexity of isosurfaces  Open access

     Andujar Gran, Carlos A.; Brunet Crosa, Pere; Chica Calaf, Antonio; Navazo Alvaro, Isabel; Rossignac, Jarek; Vinacua Pla, Alvaro
    Computer Aided Design
    Vol. 37, num. 8, p. 847-857
    DOI: 10.1016/j.cad.2004.09.013
    Date of publication: 2005-07
    Journal article

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    Since the publication of the original Marching Cubes algorithm, numerous variations have been proposed for guaranteeing water-tight constructions of triangulated approximations of isosurfaces. Most approaches divide the 3D space into cubes that each occupy the space between eight neighboring samples of a regular lattice. The portion of the isosurface inside a cube may be computed independently of what happens in the other cubes, provided that the constructions for each pair of neighboring cubes agree along their common face. The portion of the isosurface associated with a cube may consist of one or more connected components, which we call sheets. The topology and combinatorial complexity of the isosurface is influenced by three types of decisions made during its construction: (1) how to connect the four intersection points on each ambiguous face, (2) how to form interpolating sheets for cubes with more than one loop, and (3) how to triangulate each sheet. To determine topological properties, it is only relevant whether the samples are inside or outside the object, and not their precise value, if there is one. Previously reported techniques make these decisions based on local —per cube— criteria, often using precomputed look-up tables or simple construction rules. Instead, we propose global strategies for optimizing several topological and combinatorial measures of the isosurfaces: triangle count, genus, and number of shells. We describe efficient implementations of these optimizations and the auxiliary data structures developed to support them.

  • Computing maximal tiles and application to impostor-based simplification

     Andujar Gran, Carlos A.; Brunet Crosa, Pere; Chica Calaf, Antonio; Navazo Alvaro, Isabel; Rossignac, J; Vinacua Pla, Alvaro
    Computer graphics forum
    Vol. 23, num. 3, p. 401-410
    DOI: 10.1111/j.1467-8659.2004.00771.x
    Date of publication: 2004-08
    Journal article

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    The computation of the largest planar region approximating a 3D object is an important problem with wide applications in modeling and rendering. Given a voxelization of the 3D object, we propose an efficient algorithm to solve a discrete version of this problem. The input of the algorithm is the set of grid edges connecting the interior and the exterior of the object (called sticks). Using a voting-based approach, we compute the plane that slices the largest number of sticks and is orientation-compatible with these sticks. The robustness and efficiency of our approach rests on the use of two different parameterizations of the planes with suitable properties. The first of these is exact and is used to retrieve precomputed local solutions of the problem. The second one is discrete and is used in a hierarchical voting scheme to compute the global maximum. This problem has diverse applications that range from finding object signatures to generating simplified models. Here we demonstrate the merits of the algorithm for efficiently computing an optimized set of textured impostors for a given polygonal model.

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    Optimal iso-surfaces  Open access

     Andujar Gran, Carlos A.; Brunet Crosa, Pere; Chica Calaf, Antonio; Navazo Alvaro, Isabel; Rossignac, Jarek; Vinacua Pla, Alvaro
    Computer-aided design and applications
    Vol. 1, num. 1-4, p. 503-511
    DOI: 10.3722/cadaps.2004.503-511
    Date of publication: 2004-05
    Journal article

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    Since the publication of the original Marching Cubes algorithm, numerous variations have been proposed for guaranteeing water-tight constructions of triangulated approximations of iso-surfaces. Most approaches divide the 3D space into cubes that each occupies the space between eight neighboring samples of a regular lattice. The portion of the iso-surface inside a cube may be computed independently of what happens in the other cubes, provided that the constructions for each pair of neighboring cubes agree along their common face. The portion of the iso-surface associated with a cube may consist of one or more connected components, which we call sheets. We distinguish three types of decisions in the construction of the iso-surface connectivity: (1) how to split the X-faces, which have alternating in/out samples, (2) how many sheets to use in a cube, and (3) how to triangulate each sheet. Previously reported techniques make these decisions based on local criteria, often using pre-computed look-up tables or simple construction rules. Instead, we propose global strategies for optimizing several topological and combinatorial measures of the isosurfaces: triangle count, genus, and number of shells. We describe efficient implementations of these optimizations and the auxiliary data structures developed to support them.