A Vortex Method for Bi-phasic Fluids Interacting with Rigid Bodies

We present an accurate Lagrangian method based on vortex particles, level-sets, and immersed boundary methods, for animating the interplay between two fluids and rigid solids. We show that a vortex method is a good choice for simulating bi-phase flow, such as liquid and gas, with a good level of realism. Vortex particles are localized at the interfaces between the two fluids and within the regions of high turbulence. We gain local precision and efficiency from the stable advection permitted by the vorticity formulation. Moreover, our numerical method straightforwardly solves the two-way coupling problem between the fluids and animated rigid solids. This new approach is validated through numerical comparisons with reference experiments from the computational fluid community. We also show that the visually appealing results obtained in the CG community can be reproduced with increased efficiency and an easier implementation

Implicit FEM and Fluid Coupling on GPU for Interactive Multiphysics Simulation

International audienceWe present a method to implement on the GPU an implicit FEM solver which is fast and stable enough to handle interactions and collisions. We combine this method with GPU-based fluids and collision detection to achieve interactive multiphysics simulations entirely running on the GPU

Modularity for Large Virtual Reality Applications

International audienceThis paper focuses on the design of high performance VR applications. These applications usually involve various I/O devices and complex simulations. A parallel architecture or grid infrastructure is required to provide the necessary I/O and processing capabilities. Developing such applications faces several difficulties, two important ones being software engineering and performance issues. We argue that application modularity is a key concept to help the developer handle the complexity of these applications. We discuss how various approaches borrowed from other existing works can be combined to significantly improve the modularity of VR applications. This led to the development of the FlowVR middleware that associates a data-flow model with a hierarchical component model. Different case studies are presented to discuss the benefits of the approach proposed

A (Near) Real-Time Simulation Method of Aneurysm Coil Embolization

International audienceA (Near) Real-Time Simulation Method of Aneurysm Coil Embolizatio

Simulation de l'interaction entre film fluide et solides déformables

National audienceBody fluids are a major constituent of the human body as well by their volume as by their functions. Besides the blood and the lymphatic liquid, many other liquids are present in the body and they have important functions such as lubrication or shock absorption. In this work, we are more particularly interested in the fluids being in the interface between two anatomical structures. We present a method making it possible to simulate the phenomena of interaction between a fluid film and surfaces between which it is forced. The approach that we propose is based on a fluid model and its mechanical coupling with deformable surfaces. According to the pressure of the fluid and the stiffness of the deformable solids in contact with the fluid, various behaviours are expected. Our preliminary results show that it is possible to simulate the main features of these behaviours. Furthermore, the approaches chosen for the fluid model, the deformable model and the coupling between both, are compatible with real time simulations.Les liquides organiques sont un constituant essentiel du corps humain, aussi bien par leur volume que par leurs multiples fonctions. En dehors du sang et du liquide lymphatique, de nombreux autres fluides sont présents dans l'organisme et y ont des fonctions importantes, telles que lubrification ou d'absorption de chocs. Dans ce travail nous nous intéressons plus particulièrement aux fluides se trouvant à l'interface entre deux structures anato-miques. Nous présentons une méthode permettant de simuler les phénomènes d'interaction entre un film fluide et les surfaces entre lesquelles il est contraint. L'approche que nous proposons repose sur un modèle de fluide et son couplage mécanique avec des surfaces déformables. Selon la pression du fluide et la raideur des solides dé-formables en contact avec le fluide, différents comportements sont attendus. Nos résultats préliminaires montrent qu'il est possible de simuler les caractéristiques principales de ces comportements. De plus, les approches choi-sies pour le modèle de fluide, le modèle déformable, et le couplage entre les deux sont compatibles avec des simulations temps-réel

Asynchronous Preconditioners for Efficient Solving of Non-linear Deformations

International audienceIn this paper, we present a set of methods to improve numerical solvers, as used in real-time non-linear deformable models based on implicit integration schemes. The proposed approach is particularly beneficial to simulate nonhomogeneous objects or ill-conditioned problem at high frequency. The first contribution is to desynchronize the computation of a preconditioner from the simulation loop.We also exploit today's heterogeneous parallel architectures: the graphic processor performs the mechanical computations whereas the CPU produces efficient preconditioners for the simulation. Moreover, we propose to take advantage of a warping method to limit the divergence of the preconditioner over time. Finally, we validate our work with several preconditioners on different deformable models. In typical scenarios, our method improves significantly the performances of the perconditioned version of the conjugate gradient

Simulation of Lipofilling Reconstructive Surgery using coupled Eulerian Fluid and Deformable Solid Models

International audienceWe present a method to simulate the outcome of reconstructive facial surgery based on fat-filling. Facial anatomy is complex: the fat is constrained between layers of tissues which behave as walls along the face; in addition, connective tissues that are present between these different layers also influence the fat-filling procedure. To simulate the end result, we propose a method which couples a 2.5D Eulerian fluid model for the fat and a finite element model for the soft tissues. The two models are coupled using the computation of the mechanical compliance matrix. Two contributions are presented in this paper: a solver for fluids which couples properties of solid tissues and fluid pressure, and an application of this solver to fat-filling surgery procedure simulation.Nous présentons une méthode pour simuler le résultat obtenu par la chirurgie reconstructive basée fat-filling. L'anatomie du visage est complexe: la graisse est contrainte entre les couches de tissues qui se comportent comme des murs le long du visage. De plus, des tissus connectifs sont présents entre ces différentes couches, donc influence la opération de fat-filling. Pour simuler le résultat final, nous proposons une méthode qui couple un fluide eulerien 2.5D pour la graisse et un modèle à éléments finis pour les tissus mous. Les deux modèles sont couplés en utilisant le calcul de la matrice de compliance. Deux contributions sont présentées dans ce papier: un solver pour les fluides qui couple les propriétés des tissus solides et la pression du fluide, puis une application de ce solver pour la simulation de le l'opération chirurgicale du fat-filling

Toward Real-time Simulation of Blood-Coil Interaction during Aneurysm Embolization

International audienceOver the last decade, remarkable progress has been made in the field of endovascular treatment of aneurysms. Technological advances continue to enable a growing number of patients with cerebral aneurysms to be treated with a variety of endovascular strategies, essentially using detachable platinum coils. Yet, coil embolization remains a very complex medical procedure for which careful planning must be combined with advanced technical skills in order to be successful. In this paper we propose a method for computing the complex blood flow patterns that take place within the aneurysm, and for simulating the interaction of coils with this flow. This interaction is twofold, first involving the impact of the flow on the coil during the initial stages of its deployment, and second concerning the decrease of blood velocity within the aneurysm, as a consequence of coil packing. We also propose an ap- proach to achieve real-time computation of coil-flow bilateral influence, necessary for interactive simulation. This in turns allows to dynamically plan coil embolization for two key steps of the procedure: choice and placement of the first coils, and assessment of the number of coils neces- sary to reduce aneurysmal blood velocity and wall pressure

Grimage: markerless 3D interactions

International audienceGrimage glues multi-camera 3D modeling, physical simulation and parallel execution for a new immersive experience. Put your hands or any object into the interaction space. It is instantaneously modeled in 3D and injected into a virtual world populated with solid and soft objects. Push them, catch them and squeeze them

High Fidelity Haptic Rendering for Deformable Objects Undergoing Topology Changes

International audienceThe relevance of haptic feedback for minimally invasive surgery has been demonstrated at numerous counts. However, the proposed methods often prove inadequate to handle correct contact computation during the complex interactions or topological changes that can be found in surgical interventions. In this paper, we introduce an approach that allows for accurate computation of contact forces even in the presence of topological changes due to the simulation of soft tissue cutting. We illustrate this approach with a simulation of cataract surgery, a typical example of microsurgery