Annie Luciani

A Physical Model Of Turbulent Fluids

Turbulent phenomena are a subject of great interest for the computer graphics community as well as for the physics community. In computer graphics, current models of turbulent flow are mostly kinematic and stochastic models. The models presented in this paper are all physically-based and totally deterministic. They were achieved using the Cordis-Anima physical modeller-simulator, which is based upon point physics connected by physical interactions. In order to obtain physically and visually fine phenomena, while using a rather low number of particles, we resort to multi-scale modelling: the turbulent phenomena are modelled by a medium-scale physical model, whereas the refinement is achieved by a small-scale linear physical model. The final simulation is achieved by coupling these models. The resulting simulations present various phenomena inherent in turbulent fluids (curls, vortices, dissipation, diffusion). We also succeeded in reproducing several specific observed phenomena such as Kelvin-Helmholtz and Von Karman turbulences.

An Unified View of Multitude Behavior, Flexibility, Plasticity and Fractures Balls, Bubbles and Agglomerates

The work presented here, is a part of a “modeler-simulator”, capable of representing and simulating a large variety of physical objects: The Cordis-Anima system.

PRESENCE: the sense of believability of inaccessible worlds

With the development of communication methods and devices, it became possible to perform actions more and more distant from the task spaces. These new tools raise today the question of Presence of distant spaces with a growing accuracy. In a first part, we show that the distance between the manipulation space and the task space, in a teleoperation activity, points to different meanings. However, the same need for a strong Presence of the task space raises, whatever the distance between these spaces is. We then discuss the notion of Presence as a cross-point between technological and scientific disciplines, and propose some general idea that may reinforce it. In a second part, we illustrate the previous ideas with the example of manipulation of nano-objects. We show how it is possible to enhance dramatically the feeling of Presence of the nano-objects to be perceived and manipulated, by adding haptic bi-directional transducers to the visual and acoustical sensors used today. By the end, we defend the idea that the feeling of Being there is deeply dependent on multisensoriality.

Ergotic Sounds : A New Way to Improve Playability, Believability and Presence of Virtual Musical Instruments

Abstract We explore how an ‘ergotic gesture-sound situation’ is a genuine way to improve the playability, believability and presence of virtual musical instruments. An ergotic gesture-sound situation is a situation where the instrumental gesture and the sound produced are intimately energetically linked. We perform two sets of experiments: the first aims at identifying the respective role of haptic and auditory perceptions in recognition of a virtual object, here a virtual bowed string; the second aims at evaluating the role of haptic and auditory perceptions with respect to action, in the achievement of a difficult musical task. The musical goal consists in maintaining the continuity of sound when changing bow direction. The first experiments are subjective experiments. They show that the feeling of presence of the bowed string is strongly reinforced when sounds and gestural friction are intimately linked, as is the case when the vibrations of the string are returned to the fingers. The second are subjec...

Predicting the dynamic behaviour of a planetary vehicle using physical modeling

This paper addresses the motion prediction problem of a planetary vehicle under the following hypotheses: the vehicle must be able to move on both, natural and hostile terrains, it must have the ability of selecting and applying several navigation strategies depending on the characteristics of the terrain, and it must be capable of showing complex behaviors derived by both, its sophisticated mechanical structure and the vehicle/terrain physical interactions. An original method to simulate the dynamic behavior of the vehicle (i.e., vehicle/terrain interactions, sliding or gripping effects...) when executing motions having the previous characteristics is presented. This method is based on the concept of physical modeling which has been initially developed in the field of computer graphics and man/machine communication. The basic idea is to consider that motions and/or deformations of physical objects result from the application of physical laws involving a set of forces whose application points depend on the intrinsic structure of the interacting objects.

Animation of Interacting Objects with Collisions and Prolonged Contacts

In this paper, we present the development of an interaction simulation model between deformable objects which deal with both collisions and prolonged contacts. The model involves reaction forces (in the normal direction) and friction forces (in the tangential direction). Friction forces are classified as either kinetic friction when the objects are slipping on each other, and static friction when the objects are stuck. This model is developed in the framework of a modular system for dynamic simulations: The CordisAnima system.

Educational tool for nanophysics using multisensory rendering

The presentation and the evaluation of an educational tool based on a haptic interface used to teach physical phenomena at a nanometer scale are the central objectives of the present work. This haptic interface has also allowed characterising non-conventional samples illustrated through an experience when students shake the Drosophilae leg.

Integrating tactile and force feedback for highly dynamic tasks: Technological, experimental and epistemological aspects

For hand-object interaction in real situations the interplay between the local tactile interaction and force interaction seems to be very important. In current haptic interfaces, however, two different trends are present: force feedback devices which offer a permanent invariable grip and a resultant force, and tactile devices, which offer variable local patterns, often used for texture rendering. The purpose of the present work is to combine the two types of devices in a coherent manner. In the new device presented here, the tactile stimulation is obtained from strictly the same interaction loop, and obeys to the same physical model, as the force feedback, providing the information on the spatial distribution of forces circulating between the object and the fingertip. An experiment on following sharp edges of virtual object comparing the force feedback alone and different tactile augmentations is presented and discussed, alone with some open epistemological issues.

Global and local path planning in natural environment by physical modeling

In the field of robotics, some autonomous vehicles work in natural sites. One problem for the autonomous system is to plan a path to the goal. A usual method uses potential fields to find a global path. With this method, obstacles must be clearly defined. But this is not the case in such natural environments. A new physically based potential method is introduced to find paths such as, for instance, a winding path to a pass. Moreover, locally, vehicles have to cope with a geometrically unstable environment and thus have a complex dynamic behavior. Thus it is necessary to elaborate a physical model of the robot-environment system. Generally, the two plannings, global and local, are independent. The introduced potential method resorts to the simulations of the vehicles to find a feasible path.

Physical simulation of land vehicles with obstacle avoidance and various terrain interactions

Programming the motions of an autonomous planetary robot moving in an hostile and hazardous environment is a complex task which requires both the construction of nominal motion plans and the anticipation as far as possible of the effects of the interactions existing between the vehicle and the terrain. In this paper we show how physical models and dynamic simulation tools can be used for amending and completing a nominal motion plan provided by a classical geometrical path planner. The purpose of our physical modeller-simulator is to anticipate the dynamic behaviour of the vehicle while executing the nominal motion plan. Then the obtained simulation results can be used to assess and optimize the nominal motion plan. In the first part, we outline the physical models that have been used for modelling the different types of vehicle, of terrain and of vehicle-surface interactions. Then we formulate the motion planning problem through the definition of two basic abstract constructions derived from physical model: the concept of generalized obstacle and the concept of physical target. We show with various examples how it is possible, when using this method, to solve the locomotion problem and the obstacle avoidance problem simultaneously and, furthermore, to provide the human operator with a true force feedback gestural control over the simulated robot.