Shape Animation with Combined Captured and Simulated Dynamics

We present a novel volumetric animation generation framework to create new types of animations from raw 3D surface or point cloud sequence of captured real performances. The framework considers as input time incoherent 3D observations of a moving shape, and is thus particularly suitable for the output of performance capture platforms. In our system, a suitable virtual representation of the actor is built from real captures that allows seamless combination and simulation with virtual external forces and objects, in which the original captured actor can be reshaped, disassembled or reassembled from user-specified virtual physics. Instead of using the dominant surface-based geometric representation of the capture, which is less suitable for volumetric effects, our pipeline exploits Centroidal Voronoi tessellation decompositions as unified volumetric representation of the real captured actor, which we show can be used seamlessly as a building block for all processing stages, from capture and tracking to virtual physic simulation. The representation makes no human specific assumption and can be used to capture and re-simulate the actor with props or other moving scenery elements. We demonstrate the potential of this pipeline for virtual reanimation of a real captured event with various unprecedented volumetric visual effects, such as volumetric distortion, erosion, morphing, gravity pull, or collisions

An Efficient Volumetric Framework for Shape Tracking

International audienceRecovering 3D shape motion using visual information is an important problem with many applications in computer vision and computer graphics, among other domains. Most existing approaches rely on surface-based strategies, where surface models are fit to visual surface observations. While numerically plausible, this paradigm ignores the fact that the observed surfaces often delimit volumetric shapes, for which deformations are constrained by the volume inside the shape. Consequently, surface-based strategies can fail when the observations define several feasible surfaces, whereas volumetric considerations are more restrictive with respect to the admissible solutions. In this work, we investigate a novel volumetric shape parametrization to track shapes over temporal sequences. In constrast to Eulerian grid discretizations of the observation space, such as voxels, we consider general shape tesselations yielding more convenient cell decompositions, in particular the Centroidal Voronoi Tesselation. With this shape representation, we devise a tracking method that exploits volumetric information, both for the data term evaluating observation conformity, and for expressing deformation constraints that enforce prior assumptions on motion. Experiments on several datasets demonstrate similar or improved precisions over state-of-the-art methods, as well as improved robustness, a critical issue when tracking sequentially over time frames

Shape Animation with Combined Captured and Simulated Dynamics

We present a novel volumetric animation generation framework to create new types of animations from raw 3D surface or point cloud sequence of captured real performances. The framework considers as input time incoherent 3D observations of a moving shape, and is thus particularly suitable for the output of performance capture platforms. In our system, a suitable virtual representation of the actor is built from real captures that allows seamless combination and simulation with virtual external forces and objects, in which the original captured actor can be reshaped, disassembled or reassembled from user-specified virtual physics. Instead of using the dominant surface-based geometric representation of the capture, which is less suitable for volumetric effects, our pipeline exploits Centroidal Voronoi tessellation decompositions as unified volumetric representation of the real captured actor, which we show can be used seamlessly as a building block for all processing stages, from capture and tracking to virtual physic simulation. The representation makes no human specific assumption and can be used to capture and re-simulate the actor with props or other moving scenery elements. We demonstrate the potential of this pipeline for virtual reanimation of a real captured event with various unprecedented volumetric visual effects, such as volumetric distortion, erosion, morphing, gravity pull, or collisions

Etude de la réorganisation macroscopique de la peau de souris lors d'une sollicitation bi-axiale

La peau est composée en majorité de collagène et présente une microstructure très hiérarchisée qui influe sur son comportement mécanique aux différentes échelles. Pour caractériser l'influence de la microstructure sur les propriétés mécaniques, un test de traction bi-axiale couplé à une mesure macroscopique (corrélation d'images numériques) et microscopique (génération de second harmonique) a été développé . A terme, ce travail permettra de corréler les propriétés macroscopiques à la microstructures. Cette étude présente les résultats de la mesure effectuée par corrélation d'images

Calcium and plasma membrane force-gated ion channels behind development

International audienceDuring development, tissues are submitted to high variation of compression and tension forces. The roles of the cell wall, the cytoskeleton, the turgor pressure and the cell geometry during this process have received due attention. In contrast, apart from its role in the establishment of turgor pressure, the involvement of the plasma membrane as a transducer of mechanical forces during development has been under studied. Force-gated (FG) or Mechanosensitive (MS) ion channels embedded in the bilayer represent 'per se' archetypal mechanosensor able to directly and instantaneously transduce membrane forces into electrical and calcium signals. We discuss here how their fine-tuning, combined with their ability to detect micro-curvature and local membrane tension, allows FG channels to transduce mechanical cues into developmental signals

Improving the experimental protocol for a more accurate identification of a given mechanical behavior in a single assay: application to skin

International audienceMechanical properties of the skin, the external organ of the human body, are important for many applications such as surgery or cosmetics. Due to the highly hierarchical structure of the tissue, it is interesting to develop microstructural models which have a better predictability and should reduce the consequences of the sample variability. However, these models generally include a quite large number of mechanical parameters. Therefore, complex assays are required to achieve a proper identification of the microstructural models. We investigated here the best experimental protocol to identify a non-linear, anisotropic, model of skin behavior, namely the Holzapfel's law, using displacement field and force measurements. This was done through a sensitivity analysis of the different parameters. We determined first the 1 optimal assay, which appears to be a biaxial test with an alternated loading: first a stretch in one direction, then in the perpendicular one, and so on. To further improve the quality of the assay, we also determined the optimal geometry. Interestingly, slightly asymmetric geometries are more adequate than symmetric ones, while being easier to realize

Factitious disorder imposed on self: A retrospective study of 2232 cases from health insurance databases

International audienceObjective: Patients with factitious disorder imposed on self (FDIS) seek medical care for deliberately falsified problems. Although a large amount of work has been published, the scientific literature lacks robust data on FDIS. The present study aimed to estimate the annual mean of in-hospital FDIS codings in France, describe the sociodemographic characteristics of subjects with FDIS, assess healthcare utilisation and medical nomadism, and describe the pathologies most frequently associated with FDIS.Method: Subjects with at least one coding of FDIS in French health insurance databases between January 1, 2009, and December 31, 2017 were included. Subjects younger than 18 years of age at the time of first coding were excluded from the study. Sociodemographic data of subjects and diagnoses associated with the first coding of FDIS were collected. Healthcare utilisation and medical nomadism were analysed descriptively from one year before to one year after the first FDIS coding.Results: 2232 subjects were included, representing an average of 248 new in-hospital FDIS codings per year. The subjects included were 58.2% female. The mean age at diagnosis was 48.5 years. In the year following the first coding of FDIS, 1268 subjects (56.8%) were re-hospitalised at least once, including 159 (7.1%) with at least one new coding for FDIS. From one year before to one year after the first coding of FDIS, 66% of the subjects included had received at least one prescription for benzodiazepines, 58.3% for antidepressants, and 42.6% for antipsychotics.Conclusions: Our findings bring new data working towards a better understanding of FDIS. The consumption of psychotropic drugs is particularly frequent in patients with FDIS

Effects of Q&P processing conditions on austenite carbon enrichment studied by in situ high-energy x-ray diffraction experiments

International audienceWe report the first ultra-fast time-resolved quantitative information on the quenching and partitioning process of conventional high-strength steel by an in situ high-energy X-ray diffraction (HEXRD) experiment. The time and temperature evolutions of phase fractions, their carbon content, and internal stresses were determined and discussed for different process parameters. It is shown that the austenite-to-martensite transformation below the martensite start temperature Ms is followed by a stage of fast carbon enrichment in austenite during isothermal holding at both 400 and 450 °C. The analysis proposed supports the concurrent bainite transformation and carbon diffusion from martensite to austenite as the main mechanisms of this enrichment. Furthermore, we give evidence that high hydrostatic tensile stresses in austenite are produced during the final quenching, and must be taken into account for the estimation of the carbon content in austenite. Finally, a large amount of carbon is shown to be trapped in the microstructure

Effects of Q&P processing conditions on austenite carbon enrichment studied by in situ high-energy x-ray diffraction experiments

We report the first ultra-fast time-resolved quantitative information on the quenching and partitioning process of conventional high-strength steel by an in situ high-energy X-ray diffraction (HEXRD) experiment. The time and temperature evolutions of phase fractions, their carbon content, and internal stresses were determined and discussed for different process parameters. It is shown that the austenite-to-martensite transformation below the martensite start temperature Ms is followed by a stage of fast carbon enrichment in austenite during isothermal holding at both 400 and 450 °C. The analysis proposed supports the concurrent bainite transformation and carbon diffusion from martensite to austenite as the main mechanisms of this enrichment. Furthermore, we give evidence that high hydrostatic tensile stresses in austenite are produced during the final quenching, and must be taken into account for the estimation of the carbon content in austenite. Finally, a large amount of carbon is shown to be trapped in the microstructure.Partition du carbone dans les phases ferritiques nanostructurées: cinétiques et microstructuresDesign des Alliages Métalliques pour Allègement des Structure

Corrélation des propriétés mécaniques et micro-structurelles de la peau de souris à partir d'une sollicitation bi-axiale

International audienceLe derme, composant principal de la peau, est composée en majorité de collagène et présente une micro-structure très hiérarchisée qui influe sur son comportement mécanique aux différentes échelles. La prédiction de son comportement nécessite de caractériser l’influence de la micro-structure sur les propriétés mécaniques. Aussi, un test de traction bi-axiale couplé indépendamment à une mesure macroscopique et à une mesure microscopique a été développé. Ce travail a finalement permis d’identifier les paramètres d’une loi hyper-élastique anisotrope et de tester l’hypothèse de transformation affine sous-jacent au comportement adopté