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  • Frontiers in Robotics and AI

     Andujar Gran, Carlos A.
    Collaboration in journals

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  • 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.

  • AdaptiveCave: A new high-resolution, multi-projector VR system

     Andujar Gran, Carlos A.; Brunet, Pere; Díaz, Jesús; Vico, Miguel Angel; Vinacua Pla, Alvaro
    Spanish Computer Graphics Conference
    p. 11-
    Presentation's date: 2014
    Presentation of work at congresses

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    In this paper, a novel four wall, passive stereo multi-projector CAVE architecture is presented. It is powered by 40 ¿possibly different¿ off the shelf DLP projectors controlled by 12 PCs. We have achieved high resolution while significantly reducing the overall cost, resulting on a high brigthness, 2000 x 2000 pixel resolution on each of the 4 walls. The AdaptiveCave VR System has an increased versatility both in terms of projectors and screen architecture. First, the system works with any mix of a wide range of projector models that can be substituted ¿one by one¿ at any moment, for more modern or cheaper ones. Second, the self-calibration software, which guarantees a uniform final image with concordance and continuity, can be adapted to many other wall and screen configurations. The AdaptiveCave project includes the set-up and all related software components: geometric and chromatic calibration, simultaneous rendering on 40 projected viewports, synchronization and interaction. The interaction is based on a cableless, kinect-based gesture interface with natural interaction paradigms.

  • A survey of 3D object selection techniques for virtual environments

     Argelaguet Sanz, Fernando; Andujar Gran, Carlos A.
    Computers & graphics
    Vol. 37, num. 3, p. 121-136
    DOI: 10.1016/j.cag.2012.12.003
    Date of publication: 2013-05
    Journal article

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  • NightLighting: a nocturnal urban illumination approach

     Muñoz Pandiella, Imanol; Andujar Gran, Carlos A.; Patow, Gustavo Ariel
    Eurographics Workshop on Urban Data Modelling and Visualisation
    p. 13-16
    DOI: 10.2312/UDMV/UDMV13/013-016
    Presentation of work at congresses

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    Real time rendering of cities with realistic global illumination is still an open problem. In this paper we propose a two-step algorithm to simulate the nocturnal illumination of a city. The first step computes an approximate aerial solution using simple textured quads for each street light. The second step uses photon mapping to locally compute the global illumination coming from light sources close to the viewer. Then, we transfer the local, highquality solution to the low resolution buffers used for aerial views, refining it with accurate information from the local simulation. Our approach achieves real time frame rates in commodity hardware.

  • Human-subject experiments in virtual reality and 3DUI

     Andujar Gran, Carlos A.
    Virtual Realities (Dagstuhl Seminar 13241)
    p. 42
    DOI: 10.4230/DagRep.3.6.38
    Presentation's date: 2013
    Presentation of work at congresses

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    This talk is about the major peculiarities and difficulties we encounter when trying to validate research results in fields such as virtual reality (VR) and 3D user interfaces (3DUI). We review the steps in the empirical method and discuss a number of challenges when conducting human-subject experiments. These challenges include the number of independent variables to control to get useful findings, the within-subjects or between-subjects dilemma, hard-to-collect data, experimenter effects, ethical issues, and the lack of background in the community for proper statistical analysis and interpretation of the results. We show that experiments involving human-subjects hinder the adoption of traditional experimental principles (comparison, repeatability, reproducibility, justification and explanation) and propose some ideas to improve the reliability of findings in VR and 3DUI disciplines.

  • 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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  • Adaptive compression of texture pyramids

     Andujar Gran, Carlos A.
    Computer graphics forum
    Vol. 31, num. 6, p. 1973-1983
    DOI: 10.1111/j.1467-8659.2012.03077.x
    Date of publication: 2012-09
    Journal article

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    High-quality texture minification techniques, including trilinear and anisotropic filtering, require texture data to be arranged into a collection of pre-filtered texture maps called mipmaps. In this paper, we present a compression scheme for mipmapped textures which achieves much higher quality than current native schemes by exploiting image coherence across mipmap levels. The basic idea is to use a high-quality native compressed format for the upper levels of the mipmap pyramid (to retain efficient minification filtering) together with a novel compact representation of the detail provided by the highest-resolution mipmap. Key elements of our approach include delta-encoding of the luminance signal, efficient encoding of coherent regions through texel runs following a Hilbert scan, a scheme for run encoding supporting fast random-access, and a predictive approach for encoding indices of variable-length blocks. We show that our scheme clearly outperforms native 6:1 compressed texture formats in terms of image quality while still providing real-time rendering of trilinearly filtered textures.

  • Efficient rendering of animated characters through optimized per-joint impostors

     Beacco Porres, Alejandro; Andujar Gran, Carlos A.; Pelechano Gomez, Nuria; Spanlang, Bernhard
    Computer animation and virtual worlds
    Vol. 23, num. 1, p. 33-47
    DOI: 10.1002/cav.1422
    Date of publication: 2012-02
    Journal article

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    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.

  • See-through techniques for referential awareness in collaborative virtual reality

     Argelaguet Sanz, Fernando; Kulik, Alexander; Kunert, André; Andujar Gran, Carlos A.; Froehlich, Bernd
    International journal of human-computer studies
    Vol. 69, num. 6, p. 387-400
    DOI: 10.1016/j.ijhcs.2011.01.003
    Date of publication: 2011
    Journal article

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    Multi-user virtual reality systems enable natural collaboration in share virtual worlds. Users can talk to each other, gesture and point into the virtual scenery as if it were real. As in reality, refer ring to objects by pointing results often in a situation whereon objects are occluded from the other users’ viewpoints. While in reality this problem can only be solved by adapting the viewing position, specialized individual views of the shared virtual scene enable various other solutions. As one such solution we propose show-through techniques to make sure that the objects one is pointing to can always be seen by others. We first study the impact of such augmented viewing techniques on the spatial understanding of the scene, the rapidity of mutual information exchange as well as the proxemic behavior of users. To this end we conducted a user study in a co-located stereoscopic multi-user setup. Our study revealed advantages for show- through techniques interms of comfort, user acceptance and compliance to social protocols while spatial understanding and mutual information exchange is retained. Motivated by these results we further analyze whether show-through techniques may also be beneficial in distributed virtual environments.We investigated a distributed setup for two users, each participant having its own display screen and a minimalist avatar representation for each participant. In such a configuration there is a lack of mutual awareness, which hinders the understanding of each other’s pointing gestures and decreases the relevance of social protocols interms of proxemic behavior. Nevertheless, we found that show-through techniques can improve collaborative interaction tasks even in such situations

  • A Flexible Approach for Output-Sensitive Rendering of Animated Characters

     Beacco Porres, Alejandro; Spanlang, Bernhard; Andujar Gran, Carlos A.; Pelechano Gomez, Nuria
    Computer graphics forum
    Vol. 30, num. 8, p. 2328-2340
    DOI: 10.1111/j.1467-8659.2011.02065.x
    Date of publication: 2011-12
    Journal article

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  • Mesh repair with user-friendly topology control

     Hétroy, Franck; Rey, Stéphanie; Andujar Gran, Carlos A.; Brunet Crosa, Pere; Vinacua Pla, Alvaro
    Computer Aided Design
    Vol. 43, num. 1, p. 101-113
    DOI: 10.1016/j.cad.2010.09.012
    Date of publication: 2011-01
    Journal article

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    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.

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    The ViRVIG institute  Open access

     Andujar Gran, Carlos A.; Navazo Alvaro, Isabel; Vazquez Alcocer, Pere Pau; Patow, Gustavo Ariel; Pueyo, Xavier
    SBC Journal on 3D interactive systems
    Vol. 2, num. 2, p. 2-5
    Date of publication: 2011-11-16
    Journal article

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    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.

  • 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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  • POINTING FACILITATION TECHNIQUES FOR 3D OBJECT SELECTION ON VIRTUAL ENVIRONMENTS  Open access

     Argelaguet Sanz, Fernando
    Department of Computer Science, Universitat Politècnica de Catalunya
    Theses

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    Les contribucions d’aquesta tesi s’emmarquen en la interacció home-computador en entorns de realitat virtual. Concretament, en la millora de tasques de selecció d’objectes tridimensionals. La selecció d’objectes és una tasca primordial en la interacció en entorns virtuals, doncs defineixen el curs de les accions de l’usuari envers l’entorn virtual. En aquesta tesi s’analitzen els factors que determinen l’eficiència de les tasques de selecció i es proposen millores en la seva usabilitat incrementant, tant la productivitat de l’usuari, com el seu confort. Al ser una tasca crítica, la seva millora és un factor prioritari. Les tasques de selecció en un entorn tridimensional requereixen la interacció mitjançant gestos, per exemple, agafar un objecte amb les mans o apuntar-lo amb el dit. L’efectivitat d’una tasca de selecció depèn de múltiples factors, com podria ser l’habilitat de l’usuari o en la percepció espacial de l’entorn. La tesi es centra en l’estudi de les limitacions de les tasques de selecció i de com els models d’interacció home-màquina existents, permeten el seu replantejament per a millorar la seva eficiència. Al llarg de la tesi es proposen diverses tècniques de selecció basades en la llei de Fitts, i s’analitza com evitar la dependència en la percepció espacial. Els anàlisis teòrics es complementen amb estudis d’usabilitat on s’avalua, tant l’efectivitat de les solucions proposades, com les ja existents. Encara que la major part de contribucions es centren en la selecció d’objectes tridimensionals, també s’estudia la selecció i manipulació d’interfícies gràfiques d’usuari 2D en entorns virtuals, i en la millora de la transferència d’informació entre usuaris en entorns col·laboratius. En aquests tipus d’entorns, és comú l’ús de la selecció per fer referència a determinats objectes o característiques del medi, a altres usuaris. No obstant, la impossibilitat de veure els objectes amb els què d’altres usuaris estan interactuant, dificulta l’intercanvi d’informació entre ells. S’ha fet un estudi de les eines utilitzades per a la gestió de l’oclusió i de com milloren l’intercanvi d’informació entre usuaris. Lloc i

  • High-quality compression of mipmapped textures

     Andujar Gran, Carlos A.
    Ibero-American Symposium in Computer Graphics
    p. 53-60
    Presentation's date: 2011-06
    Presentation of work at congresses

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    World-in-miniature interaction for complex virtual environments  Open access

     Trueba Hornero, Ramon; Andujar Gran, Carlos A.; Argelaguet Sanz, Fernando
    International journal of creative interfaces and computer graphics
    Vol. 1, num. 2, p. 1-14
    DOI: 10.4018/jcicg.2010070101
    Date of publication: 2010-12
    Journal article

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    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.

  • 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.

  • Computer graphics in Spain: A selection of papers from CEIG 2009

     Andujar Gran, Carlos A.; Lluch, Javier
    Computers & graphics
    Vol. 34, num. 6, p. 688
    DOI: 10.1016/j.cag.2010.08.005
    Date of publication: 2010-12
    Journal article

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    Topographic map visualization from adaptively compressed textures  Open access

     Andujar Gran, Carlos A.
    Computer graphics forum
    Vol. 29, num. 3, p. 1083-1092
    DOI: 10.1111/j.1467-8659.2009.01682.x
    Date of publication: 2010
    Journal article

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    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.

  • Hand-based disocclusion for the world-in-miniature metaphor

     Andujar Gran, Carlos A.; Argelaguet Sanz, Fernando; Trueba, Ramon
    Presence - Teleoperators and virtual environments
    Vol. 19, num. 6, p. 499-512
    DOI: 10.1162/pres_a_00018
    Date of publication: 2010-12
    Journal article

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  • Output-sensitive rendering of detailed animated characters for crowd simulation

     Spanlang, Bernhard; Andujar Gran, Carlos A.; Pelechano Gomez, Nuria; Beacco Porres, Alejandro
    Spanish Computer Graphics Conference
    p. 37-46
    Presentation's date: 2010-09
    Presentation of work at congresses

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  • Relief mapping on cubic cell complexes

     Apaza, Karl; Andujar Gran, Carlos A.
    International Conference on Computer Graphics Theory and Applications
    Presentation's date: 2010-05-19
    Presentation of work at congresses

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  • Space-optimized texture atlases for 3D scenes with per-polygon textures

     Martinez Bayona, Jonàs; Andujar Gran, Carlos A.
    Pacific Conference on Computer Graphics and Applications
    p. 14-23
    DOI: 10.1109/PacificGraphics.2010.10
    Presentation's date: 2010-09
    Presentation of work at congresses

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  • Automatic speed graph generation for predefined camera paths

     Argelaguet Sanz, Fernando; Andujar Gran, Carlos A.
    International Symposium on Smart Graphics
    p. 115-126
    DOI: 10.1007/978-3-642-13544-6
    Presentation's date: 2010
    Presentation of work at congresses

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    Predefined camera paths are a valuable tool for the exploration of complex virtual environments. The speed at which the virtual camera travels along different path segments is key for allowing users to perceive and understand the scene while maintaining their attention. Current tools for speed adjustment of camera motion along predefined paths, such as keyframing, interpolation types and speed curve editors provide the animators with a great deal of flexibility but offer little support for the animator to decide which speed is better for each point along the path. In this paper we address the problem of computing a suitable speed curve for a predefined camera path through an arbitrary scene. We strive at adapting speed along the path to provide non-fatiguing, informative, interestingness and concise animations. Key elements of our approach include a new metric based on optical flow for quantifying the amount of change between two consecutive frames, the use of perceptual metrics to disregard optical flow in areas with low image saliency, and the incorporation of habituation metrics to keep the user attention. We also present the results of a preliminary user-study comparing user response with alternative approaches for computing speed curves.

  • Best paper award Joint Virtual Reality Conference EGVE-ICAT-EURO VR 2009

     Trueba Hornero, Ramon; Andujar Gran, Carlos A.; Argelaguet Sanz, Fernando
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  • Efficient 3D Pointing Selection in Cluttered Virtual Environments

     Argelaguet Sanz, Fernando; Andujar Gran, Carlos A.
    IEEE computer graphics and applications
    Vol. 29, num. 6, p. 34-43
    DOI: 10.1109/MCG.2009.117
    Date of publication: 2009-12
    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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  • Complexity and occlusion management for the World-in-Miniature Metaphor

     Trueba Hornero, Ramon; Andujar Gran, Carlos A.; Argelaguet Sanz, Fernando
    International Symposium on Smart Graphics
    p. 155-166
    Presentation of work at congresses

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    he World in Miniature (WIM) metaphor allows users to interact and travel efficiently in virtual environments. In addition to the first-person perspective offered by typical VR applications, the WIM offers a second dynamic viewpoint through a hand-held miniature copy of the environment. In the original WIM paper the miniature was a scaled down replica of the whole scene, thus limiting its application to simple models being manipulated at a single level of scale. Several WIM extensions have been proposed where the replica shows only a part of the environment. In this paper we present a new approach to handle complexity and occlusion in the WIM. We discuss algorithms for selecting the region of the scene which will be covered by the miniature copy and for handling occlusion from an exocentric viewpoint. We also present the results of a user-study showing that our technique can greatly improve user performance on spatial tasks in densely-occluded scenes.

  • Dynamic Terrains: Cities and Real-Time Video on Gigantic Terrain Models

     Andujar Gran, Carlos A.; Brunet Crosa, Pere; Díaz Iriberri, José
    Geographical Information Processing and Visual Analytics for Environmental Security NATO - ADVANCED RESEARCH WORKSHOP
    p. 209-213
    Presentation of work at congresses

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  • Multi-scale manipulation in indoor scenes with the World in Miniature Metaphor

     Trueba Hornero, Ramon; Andujar Gran, Carlos A.; Argelaguet Sanz, Fernando
    Eurographics Symposium on Virtual Environments
    p. 93-100
    DOI: 10.2312/EGVE/JVRC09/093-100
    Presentation's date: 2009
    Presentation of work at congresses

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  • Locally-adaptive texture compression

     Andujar Gran, Carlos A.; Martinez Bayona, Jonas
    Spanish Computer Graphics Conference
    p. 105-114
    Presentation's date: 2009-09
    Presentation of work at congresses

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    Current schemes for texture compression fail to exploit spatial coherence in an adaptive manner due to the strict efficiency constraints imposed by GPU-based, fragment-level decompression. In this paper we present a texture compression framework for quasi-lossless, locally-adaptive compression of graphics data. Key elements include a Hilbert scan to maximize spatial coherence, efficient encoding of homogeneous image regions through arbitrarilysized texel runs, a cumulative run-length encoding supporting fast random-access, and a compression algorithm suitable for fixed-rate and variable-rate encoding. Our scheme can be easily integrated into the rasterization pipeline of current programmable graphics hardware allowing real-time GPU decompression. We show that our scheme clearly outperforms competing approaches such as S3TC DXT1 on a large class of images with some degree of spatial coherence. Unlike other proprietary formats, our scheme is suitable for compression of any graphics data including color maps, shadow maps and relief maps. We have observed compression rates of up to 12:1, with minimal or no loss in visual quality and a small impact on rendering time.

  • Visual feedback techniques for virtual pointing on stereoscopic displays  awarded activity

     Argelaguet Sanz, Fernando; Andujar Gran, Carlos A.
    ACM Symposium on Virtual Reality Software and Technology
    p. 163-170
    DOI: 10.1145/1643928.1643966
    Presentation's date: 2009
    Presentation of work at congresses

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    The act of pointing to graphical elements is one of the fundamental tasks in Human-Computer Interaction. In this paper we analyze visual feedback techniques for accurate pointing on stereoscopic displays. Virtual feedback techniques must provide precise information about the pointing tool and its spatial relationship with potential targets. We show both analytically and empirically that current approaches provide poor feedback on stereoscopic displays, resulting in low user performance when accurate pointing is required. We propose a new feedback technique following a camera viewfinder metaphor. The key idea is to locally flatten the scene objects around the pointing direction to facilitate their selection. We present the results of a user study comparing cursor-based and ray-based visual feedback techniques with our approach. Our user studies indicate that our viewfinder metaphor clearly outperforms competing techniques in terms of user performance and binocular fusion.

  • Best Short Paper Award, ACM Symposium on Virtual Reality Software and Technology 2008

     Argelaguet Sanz, Fernando; Andujar Gran, Carlos A.
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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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  • Improving 3D selection in immersive environments through expanding targets

     Andujar Gran, Carlos A.
    Dagstuhl Seminar Virtual Realities
    p. 9
    Presentation's date: 2008
    Presentation of work at congresses

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  • Overcoming Eye-Hand Visibility Mismatch in 3D Pointing Selection

     Argelaguet Sanz, Fernando; Andujar Gran, Carlos A.; Trueba Hornero, Ramon
    ACM Symposium on Virtual Reality Software and Technology
    p. 43-46
    DOI: /doi.acm.org/10.1145/1450579.1450588
    Presentation of work at congresses

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    Dynamic worlds in miniature  Open access

     Trueba Hornero, Ramon; Andujar Gran, Carlos A.
    Jornadas sobre Realidad Virtual y Entornos Virtuales
    p. 1-10
    Presentation of work at congresses

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    The World in Miniature (WIM) metaphor allows users to interact and travel efficiently in virtual environments. In addition to the first-person perspective offered by typical VR applications, the WIM offers a second dynamic viewpoint through a hand-held miniature copy of the virtual environment. In the original WIM paper the miniature was a scaled down replica of the whole environment, thus limiting the technique to simple models being manipulated at a single level of scale. Several WIM extensions have been proposed where the replica shows only a part of the virtual environment. In this paper we present an improved visualization of WIM that supports arbitrarily-complex, densely-occluded scenes. In particular, we discuss algorithms for selecting the region of the virtual environment which will be covered by the miniature copy and efficient algorithms for handling 3D occlusion from an exocentric viewpoint.

    Postprint (author’s final draft)

  • Improving 3D selection in VEs through expanding targets and forced disocclusion

     Argelaguet Sanz, Fernando; Andujar Gran, Carlos A.
    International Symposium on Smart Graphics
    p. 45-57
    DOI: 10.1007/978-3-540-85412-8_5
    Presentation of work at congresses

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    In this paper we explore the extension of 2D pointing facilitation techniques to 3D object selection. We discuss what problems must be faced when adapting such techniques to 3D interaction on VR applications, and we propose two strategies to adapt the expanding targets approach to the 3D realm, either by dynamically scaling potential targets or by using depth-sorting to guarantee that potential targets appear completely unoccluded. We also present three experiments to evaluate both strategies in 3D selection tasks with multiple targets at varying densities. Our user studies show promising results of 3D expanding targets in terms of error rates and, most importantly, user acceptance.

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    Relief impostor selection for large scale urban rendering  Open access

     Andujar Gran, Carlos A.; Díaz Iriberri, José; Brunet Crosa, Pere
    IEEE Virtual Reality Workshop on Virtual Cityscapes: Key Research Issues in Modeling Large-Scale Immersive Urban Environments
    Presentation's date: 2008-03-08
    Presentation of work at congresses

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    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.

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    Anisomorphic ray-casting manipulation for interacting with 2D GUIs  Open access

     Andujar Gran, Carlos A.; Argelaguet Sanz, Fernando
    Computers & graphics
    Vol. 31, num. 1, p. 15-25
    DOI: 10.1016/j.cag.2006.09.003
    Date of publication: 2007-01
    Journal article

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    The accommodation of conventional 2D GUIs with virtual environments (VEs) can greatly enhance the possibilities of many VE applications. In this paper we present a variation of the well-known ray-casting technique for fast and accurate selection of 2D widgets over a virtual window immersed into a 3D world. The main idea is to provide a new interaction mode where hand rotations are scaled down so that the ray is constrained to intersect the active virtual window. This is accomplished by changing the control¿display ratio between the orientation of the user¿s hand and the ray used for selection. Our technique uses a curved representation of the ray providing visual feedback of the orientation of both the input device and the selection ray. We have implemented this technique and evaluated its effectiveness in terms of performance and user preference. Our experiments on a four-sided CAVE indicate that the proposed technique can increase the speed and accuracy of component selection in 2D GUIs immersed into 3D worlds.

    The accommodation of conventional 2D GUIs with virtual environments (VEs) can greatly enhance the possibilities of many VE applications. In this paper we present a variation of the well-known ray-casting technique for fast and accurate selection of 2D widgets over a virtual window immersed into a 3D world. The main idea is to provide a new interaction mode where hand rotations are scaled down so that the ray is constrained to intersect the active virtual window. This is accomplished by changing the control–display ratio between the orientation of the user’s hand and the ray used for selection. Our technique uses a curved representation of the ray providing visual feedback of the orientation of both the input device and the selection ray. We have implemented this technique and evaluated its effectiveness in terms of performance and user preference. Our experiments on a four-sided CAVE indicate that the proposed technique can increase the speed and accuracy of component selection in 2D GUIs immersed into 3D worlds.

  • Omni-directional relief impostors

     Andujar Gran, Carlos A.; Boo, J; Brunet Crosa, Pere; Fairen Gonzalez, Marta; Navazo Alvaro, Isabel; Vazquez Alcocer, Pere Pau; Vinacua Pla, Alvaro
    Computer graphics forum
    Vol. 26, num. 3, p. 553-560
    DOI: 10.1111/j.1467-8659.2007.01078.x
    Date of publication: 2007-07
    Journal article

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  • Dynamic worlds in miniature

     Trueba Hornero, Ramon; Andujar Gran, Carlos A.
    PRESENCCIA PhD Symposium
    Presentation of work at congresses

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  • Virtual Pads: Decoupling Motor Space and Visual Space for Flexible Manipulation of 2D Windows within VEs

     Andujar Gran, Carlos A.; Argelaguet Sanz, Fernando
    IEEE Symposium on 3D User Interfaces
    p. 99-106
    DOI: /doi.ieeecomputersociety.org/10.1109/3DUI.2007.340781
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  • Tessellation-Independent Best View Selection

     Vazquez Alcocer, Pere Pau; Andujar Gran, Carlos A.
    International Conference on Computer Graphics and Artificial Intelligence
    p. 109-119
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    A topological comparison of surface extraction algorithms  Open access

     Andujar Gran, Carlos A.; Brunet Crosa, Pere; Fairen Gonzalez, Marta; Navazo Alvaro, Isabel; Vinacua Pla, Alvaro
    Date: 2006-01
    Report

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    In many application areas, it is useful to convert the discrete information stored in the nodes of a regular grid into a continuous boundary model. Isosurface extraction algorithms di er on how the discrete information in the grid is generated, on what information does the grid store and on the properties of the output surface.

  • Pressing: Smooth Isosurfaces with Flats from Binary Grids

     Andujar Gran, Carlos A.; Brunet Crosa, Pere; Navazo Alvaro, Isabel; Vinacua Pla, Alvaro
    Date: 2006-02
    Report

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  • IST-027731 PRESENCCIA coordinació

     Slater, Melvyn; Navazo Alvaro, Isabel; Brunet Crosa, Pere; Vinacua Pla, Alvaro; Andujar Gran, Carlos A.
    Competitive project

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  • A cost-effective approach for developing application-control GUIs for virtual environments

     Andujar Gran, Carlos A.; Fairen Gonzalez, Marta; Argelaguet Sanz, Fernando
    IEEE Symposium on 3D User Interfaces
    p. 45-52
    Presentation of work at congresses

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