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Item ACM/EG Symposium on Computer Animation 2004(The Eurographics Association and Blackwell Publishing Ltd., 2004) Boulic, Ronan; Pai, Dinesh K.; Badler, Norman; Desbrun, Mathieu; Reveret, LionelItem Interactive Motion Deformation with Prioritized Constraints(The Eurographics Association, 2004) Callennec, Benoît Le; Boulic, Ronan; R. Boulic and D. K. PaiIn this paper, we present an interactive motion deformation method to modify animations so that they satisfy a set of prioritized constraints. Our approach successfully handles the problem of retargetting, adjusting a motion, as well as adding significant changes to preexisting animations. We introduce the concept of prioritized constraints to avoid tweaking issues for competing constraints. Each frame is individually and smoothly adjusted to enforce a set of prioritized constraints. The iterative construction of the solution channels the convergence through intermediate solutions, enforcing the highest prioritized constraints first. In addition, we propose a new, simple formulation to control the position of the center of mass so that the resulting motions are physically plausible. Finally, we demonstrate that our method can address a wide range of motion editing problems.Item A Generic Method for Geometric Contraints Detection(Eurographics Association, 2004) Salvati, Marc; Lecallennec, Benoît; Boulic, Ronan; M. Alexa and E. GalinIn this paper, we present a generic method to automatically detect geometric constraints on motion capture animations. At each frame, elementary geometric constraints are computed with respect to a reference which can either be the world coordinate system or any moving object in the scene. We then use constraint-related concepts of union and intersection to merge the elementary constraints together and/or to generate new ones. Finally, our algorithm provides an exhaustive list of geometric constraints with an accurate evaluation of their duration. The detected constraints can characterize virtual human motion (e.g. footprints) as well as interactions with moving objects of the scene (e.g. a hand touching a ball). While our approach also detects sliding geometric constraints, we focus our discussion on detecting positional geometric constraints.Item Multi-Finger Haptic Rendering of Deformable Objects(The Eurographics Association, 2004) Maciel, Anderson; Sarni, Sofiane; Buchwalder, Olivier; Boulic, Ronan; Thalmann, Daniel; Sabine Coquillart and Martin GoebelThe present paper describes the integration of a multi-finger haptic device with deformable objects in an interactive environment. Repulsive forces are synthesized and rendered independently for each finger of a user wearing a Cybergrasp force-feedback glove. Deformation and contact models are based on mass-spring systems, and the issue of the user independence is dealt with through a geometric calibration phase. Motivated by the knowledge that human hand plays a very important role in the somatosensory system, we focused on the potential of the Cybergrasp device to improve perception in Virtual Reality worlds. We especially explored whether it is possible to distinguish objects with different elasticities. Results of performance and perception tests are encouraging despite current technical and computational limitations.