Resultados de la búsqueda21 resultados

Elevation Cable Modeling for Interactive Simulation of Cranes
García fernández, I.; Pla Castells, M.; Martínez Durá, R. J.
(2008). ArticleSCA '08: Proceedings of the 2008 ACM SIGGRAPH/Eurographics Symposium on Computer Animation 2008, 110 In this paper, the way to simulate hoisting cables in real time is addressed. We overcome instability in such simulation by considering a twolayered model: a model for the dynamics of a cable passing through a set of pulleys and an oscillation model based on the classical onedimensional wave equation. The ﬁrst layer considers the interaction between the cable and pulleys with the elevation equipment, while the second layer simulates cable oscillation. Numerical instability is avoided by suspending the oscillation layer when required. Due to the system properties, this can be carried out...
SCA '08: Proceedings of the 2008 ACM SIGGRAPH/Eurographics Symposium on Computer Animation 2008, 110 In this paper, the way to simulate hoisting cables in real time is addressed. We overcome instability in such simulation by considering a twolayered model: a model for the dynamics of a cable passing through a set of pulleys and an oscillation model based on the classical onedimensional wave equation. The ﬁrst layer considers the interaction between the cable and pulleys with the elevation equipment, while the second layer simulates cable oscillation. Numerical instability is avoided by suspending the oscillation layer when required. Due to the system properties, this can be carried out in such a way that does not cause signiﬁcant loss in the system quality. It considers the oscillation of the cable between every pair of pulleys, collision detection and the variation of the cable length very efﬁciently. Rendering issues are discussed, with remarks on how to prevent aliasing artifacts in the cable. Efﬁciency is analyzed, including performance tests which show that the model can be run very efﬁciently. The paper also covers how to integrate the model in a complex multibody simulation with a high degree of interactivity.
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PhysicallyBased Interactive Sand Simulation
Pla Castells, M.; García Fernández, I.; Martínez Durá, R. J.
(2008). ArticleEurographics 2008  Short Papers, 2124. 2008 The interactive simulation of 3D terrains has been approached from several perspectives. Due to the complexity of the system involved, most of the models proposed focus on a visually realistic animation of the scene, rather than on a physicallybased accurate simulation of a granular system. Those models lack generality when interacting with the environment; in most cases, no reaction forces are computed, considering only soil deformation. This limitation reduces their usability in applications such as driving simulators. We propose the use of a theoretical discrete model that considers normal forces for 3D realtime simulation of granular...
Eurographics 2008  Short Papers, 2124. 2008 The interactive simulation of 3D terrains has been approached from several perspectives. Due to the complexity of the system involved, most of the models proposed focus on a visually realistic animation of the scene, rather than on a physicallybased accurate simulation of a granular system. Those models lack generality when interacting with the environment; in most cases, no reaction forces are computed, considering only soil deformation. This limitation reduces their usability in applications such as driving simulators. We propose the use of a theoretical discrete model that considers normal forces for 3D realtime simulation of granular systems. We also extend this model to consider horizontal forces, allowing a wider range of interactions. Several numerical tests have been implemented and detailed results have been analyzed which show a good model performance.
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Analysis of cable model, considering mass and wave oscillations
García Fernández, I.; Pla Castells, M.; Martínez Durá, R. J.
(2007). ArticleInternational eConference on Computer Science. Proceedings of the IeCCS2007 2007 Theoretical cablepulley dynamics models usually lead to computationally expensive numerical models. For this reason, both mass and cable oscillation are usually neglected when efﬁciency is an issue. Recently a new model has been presented that allows the simulation of cable oscillation and catenary with low computational cost. In this paper, we present a preliminary analysis of the dynamics of the model, based on numerical tests. More precisely, we analyze the inﬂuence of the main parameters of the model over its dynamics, taking as a reference the massless models used so far.

A Mixed Model for RealTime, Interactive Simulation of a Cable Passing Through Several Pulleys
García Fernández, I.; Pla Castells, M.; Martínez Durá, R.J.
(2007). ArticleAIP Conference Proceedings, AIP 2007, 212215 A model of a cable and pulleys is presented that can be used in Real Time Computer Graphics applications. The model is formulated by the coupling of a damped spring and a variable coefﬁcient wave equation, and can be integrated in more complex mechanical models of lift systems, such as cranes, elevators, etc. with a high degree of interactivity.

Interactive Terrain Simulation and Force Distribution Models in Sand Piles
Pla Castells, M.; García Fernández, I.; Martínez Durá, R. J.
(2006). ArticleLecture Notes on Computer Science, 2006, 4173, 392401 This paper presents an application of Cellular Automata in the ﬁeld of dry Granular Systems modelling. While the study of granular systems is not a recent ﬁeld, no eﬃcient models exist, from a computational point of view, in classical methodologies. Some previous works showed that the use of Cellular Automata is suitable for the development of models that can be used in real time applications. This paper extends the existing Cellular Automata models in order to make them interactive. A model for the reaction to external forces and a pressure distribution model are presented and analyzed, with numerical examples and simulations.

Granular system models for real time simulation
Pla Castells, M.; García Fernández, I.; Martínez Durá, R. J.
(2004). ArticleProceedings of the Industrial Simulation Conference 2004, 8893 Granular systems appear in many industrial and agricultural disciplines, which has lead to a wide range of models for their simulation, both in engineering and applied physics. However, most of the current models are addressed to make a deep analysis of the properties of the system, and they are not suitable for their use in realtime simulations. Thus, despite of the efforts in computational ﬂuid dynamics and molecular dynamics, the application of granular systems in the ﬁeld of virtual reality and computer graphics lacks of a set of fast interactive models that allow their execution in realtime. In this paper we propose an...
Proceedings of the Industrial Simulation Conference 2004, 8893 Granular systems appear in many industrial and agricultural disciplines, which has lead to a wide range of models for their simulation, both in engineering and applied physics. However, most of the current models are addressed to make a deep analysis of the properties of the system, and they are not suitable for their use in realtime simulations. Thus, despite of the efforts in computational ﬂuid dynamics and molecular dynamics, the application of granular systems in the ﬁeld of virtual reality and computer graphics lacks of a set of fast interactive models that allow their execution in realtime. In this paper we propose an efﬁcient granular system model based on cellular automata, designed to be used in computer graphics applications. The model is provided with inertia which gives it more realistic physical properties. Also, several details for its implementation are given together with an analysis of its computational complexity.
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Approximation of Continuous Media Models for Granular Systems Using Cellular Automata
Pla Castells, M.; García Fernández I.; Martínez Durá, R. J.
(2004). ArticleLecture Notes in Computer Science, 2004, 230237 In this paper a new cellular automata model suitable for granular systems simulation is presented. The proposed model is shown to be equivalent to a particularization of the well known BCRE model of granular systems and a correspondence between the parameters of the presented model and the BCRE model is also set, allowing to ﬁt these parameters for a given system. The model has the advantage over other cellular automata models of being more realistic in the behavior of the surface of heaps and slopes. The dynamics of the CA is analyzed in order to conﬁrm that it also has one of the most important features of these systems, 1/f noise.

Continuous force reaction in animation of avatars
Rodríguez Cerro, A.; García Fernández, I.; Martínez Durá, R. J.
(2004). ArticleSCA '10: Proceedings of the 2010 ACM SIGGRAPH/Eurographics Symposium on Computer Animation 2010 Prerecorded animation is the best way to reproduce detailed and natural human movements. However, in interactive animations we need techniques to modify the avatar movement in a feasible way. This research combines prerecorded and physicsbased animation to simulate the movement of the body when it is perturbed by external forces. The main results of this work are the possibility of separately animating different parts of the body and to obtain the reaction to forces that last long intervals of time.

Visual Representation Of Enhanced Sand Pile Models
Pla Castells, M.; García Fernández, I.; Martínez Durá, R. J.
(2003). ArticleProceedings of the Industrial Simulation Conference 2003, 141146 This paper overviews some models based on the Chip Firing Game and propose a modification of the Abelian Sand Pile Model in a lattice in order to implement a realistic simulation of a pile of sand falling and finding an stable configuration. We have modified the update rule in the way that now is based on the comparision among neighbour nodes. We found that the simulations can be suitable for doing them in real time and propose as a future work a better solution to reduce the computational cost of the algorithms.

New Models for Fast Contact Force Computation
García Fernández, I.; Pla Castells, M.; martínez Durá, R. J.
(2003). ArticleProceedings of the Industrial Simulation Conference 2003, 401407 This work focuses on the subject of impact response modeling in Real Time rigid body simulation, and more precisely in those applications where a very high accuracy in the solution is not required. The problem of impact response has several aspects to overcome, such as the instantaneous nature of the forces that appear during the contact, the absence of a unique solution in the case of contacts with friction, of the stiffness of the resultant models. This makes the impact management to be one of the most problematic parts to resolve during the implementation of computational models for rigid body systems. We present a model...
Proceedings of the Industrial Simulation Conference 2003, 401407 This work focuses on the subject of impact response modeling in Real Time rigid body simulation, and more precisely in those applications where a very high accuracy in the solution is not required. The problem of impact response has several aspects to overcome, such as the instantaneous nature of the forces that appear during the contact, the absence of a unique solution in the case of contacts with friction, of the stiffness of the resultant models. This makes the impact management to be one of the most problematic parts to resolve during the implementation of computational models for rigid body systems. We present a model for contacts that is much simpler than the usual methods and that achieves an accuracy of the same order than the integration step size respect to the usual method. The model is valid both for frictional and nonfrictional contacts.
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