This paper presents a new formalism for simulating highly deformable bodies with a particle system. Smoothed particles represent sample points that enable the approximation of the values and derivatives of local physical quantities inside a medium. They ensure valid and stable simulation of state equations that describe the physical behavior of the material. We extend the initial formalism, first introduced for simulating cosmological fluids, to the animation of inelastic bodies with a wide range of stiffness and viscosity. We show that the smoothed particles paradigm leads to a coherent definition of the object's surface as an iso-surface of the mass density function. Implementation issues are discussed, including an efficient integration scheme using individually adapted time steps to integrate particle motion. Animation requires a linear complexity in the number of particles, offering reasonable time and memory use.

This paper presents a hybrid model for animation of soft inelastic substance which undergo topological changes, e.g. separation and fusion and which fit with the objects they are in contact with. The model uses a particle system coated with a smooth iso-surface that is used for performing collision detection, precise contact modeling and integration of response forces. The animation technique solves three problems inherent in implicit modeling. Firstly, local volume controllers are defined to insure constant volume deformation, even during highly inelastic processes such as splitting or fusion. Secondly, we avoid unwanted distance blending between disconnected pieces of the same substance. Finally, we simulate both collisions and progressive merging under compression between implicit surfaces that do not blend together. Parameter tuning is facilitated by the layered model and animation is generated at interactive rates.

Published under the name Marie-Paule GascuelInternational audienceThis paper presents an implicit deformable model, based on isosurfaces of potential fields generated by skeletons, that provides elegant and unified formulations for both geometric parameters such as shape or deformation and physical properties such as rigidity. The model is especially designed to improve collision and contact processing for non-rigid objects. In particular, it generates and maintains exact contact surfaces during interactions

PublishedInternational audienceThis paper presents an integrated set of methods for the automatic construction and interactive animation of solid systems that satisfy specified geometric constraints. Displacement contraints enable the user to design articulated bodies with various degrees of freedom in rotation or in translation at highes and to restrict the scope of the movement at will. The graph of constrained objects may contain closed loops. The animation is achieved by decoupling the free motion of each solid component from the action of the constraints. We do this with iterative tunings in displacements. The method is currently implemented in a dynamically based animation system and takes the physical parameters into account while reestablishing the constraints. In particular, first-order momenta are preserved during this process. The approach would be easy to extend to modeling systems or animation modules without a physical model just by allowing the user to control more parameters. (source Springer

This paper presents a new method that combines a medial axis and implicit surfaces in order to reconstruct a 3D solid from an unstructured set of points scattered on the object's surface. The representation produced is based on iso‐surfaces generated by skeletons, and is a particularly compact way of defining a smooth free‐form solid. The method is based on the minimisation of an energy representing a “distance” between the set of data points and the iso‐surface, resembling previous reserach19. Initialisation, however, is more robust and efficient since there is computation of the medial axis of the set of points. Instead of subdividing existing skeletons in order to refine the object's surface, a new reconstruction algorithm progressively selects skeleton‐points from the pre‐ computed medial axis using an heuristic principle based on a “local energy” criterion. This drastically speeds up the reconstruction process. Moreover, using the medial axis allows reconstruction of objects with complex topology and geometry, like objects that have holes and branches or that are composed of several connected components. This process is fully automatic. The method has been successfully applied to both synthetic and real data.