Capture de mouvement

Résumé

La capture de mouvement (motion capture en anglais, parfois abrégé en mocap) est une technique permettant d'enregistrer les positions et rotations d'objets ou de membres d'êtres vivants, pour en contrôler une contrepartie virtuelle sur ordinateur (caméra, modèle 3D, ou avatar). Une restitution visuelle de ces mouvements en temps réel est faite via le moteur de rendu 3D de l'application interfacée avec le matériel utilisé qui peut les stocker dans un fichier d'animation de type BVH pour être traités ultérieurement dans un logiciel 3D classique (Maya, 3dsMax, XSI, Cinema4d, etc.) ; ou bien, via un plugin vers MotionBuilder, logiciel spécialisé dans le traitement, l'édition, le filtrage ou l'exportation de ces animations. Histoire Les lointaines origines de cette technique peuvent être retrouvées chez Étienne-Jules Marey sous le nom de chronophotographie qu'il a initialement développée dans un cadre médical pour analyser ce qu'il appelle poétiquement la machine animale, mais

Source officielle

https://fr.wikipedia.org/wiki/Capture_de_mouvement

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (100)

Publications associées

Chargement

Personnes associées (49)

Personnes associées

Chargement

Unités associées (25)

Afficher plus

Unités associées

Chargement

Concepts associés (35)

Concepts associés

Chargement

Cours associés (27)

Cours associés

Chargement

Séances de cours associées (41)

Séances de cours associées

Chargement

In motion capture applications whose aim is to recover human body postures from various input, the high dimensionality of the problem makes it desirable to reduce the size of the search-space by eliminating a priori impossible configurations. This can be carried out by constraining the posture recovery process in various ways. Most recent work in this area has focused on applying camera viewpoint-related constraints to eliminate erroneous solutions. When camera calibration parameters are available, they provide an extremely efficient tool for disambiguating not only posture estimation, but also 3D reconstruction and data segmentation. Increased robustness is indeed to be gained from enforcing such constraints, which we prove in the context of an optical motion capture framework. Our contribution in this respect resides in having applied such constraints consistently to each main step involved in a motion capture process, namely marker reconstruction and segmentation, followed by posture recovery. These steps are made inter-dependent, where each one constrains the other. A more application-independent approach is to encode constraints directly within the human body model, such as limits on the rotational joints. This being an almost unexplored research subject, our efforts were mainly directed at determining a new method for measuring, representing and applying such joint limits. To the present day, the few existing range of motion boundary representations present severe drawbacks that call for an alternative formulation. The joint limits paradigm we propose not only overcomes these drawbacks, but also allows to capture intra- and inter-joint rotation dependencies, these being essential to realistic joint motion representation. The range of motion boundary is defined by an implicit surface, its analytical expression enabling us to readily establish whether a given joint rotation is valid or not. Furthermore, its continuous and differentiable nature provides us with a means of elegantly incorporating such a constraint within an optimisation process for posture recovery. Applying constrained optimisation to our body model and stereo data extracted from video sequence, we demonstrate the clearly resulting decrease in posture estimation errors. As a bonus, we have integrated our joint limits representation in character animation packages to show how motion can be naturally constrained in this manner.

EPFL2004

Chargement

Machine Learning for Musculoskeletal Modeling of Upper Extremity

Rahul Sharma

We propose a novel machine learning (ML)-driven methodology to estimate biomechanical variables of interest traditionally obtained from upper-extremity musculoskeletal (MSK) modeling. MSK models facilitate personalized modeling, perform "what-if" analyses, and potentially enhance clinical decision-making. In certain settings, MSK models are driven by inertial motion capture (IMC) data. IMC systems are portable, user-friendly, and relatively affordable as well as provide additional biomechanical information. However, MSK models can be computationally expensive, often require extensive data, and can be prohibitively slow in making real-time predictions. Our ML method- involving a rigorous hyperparameters search-predicts kinematic and kinetic biomechanical information associated with human upper-extremity movements solely using IMC input data, thereby bypassing MSK models. The scaled cadaver-based MSK model was based on the Dutch Shoulder Model and the spine model implemented in the AnyBody Managed Model Repository. We employ neural networks (NNs), which are trained on IMC data obtained from five nondisabled subjects in subject- exposed (SE) settings (at least a trial from all subjects is used in training) and subject- naive (SN) settings (no information from test subjects is used in training). We compare the predictions of our ML model with that of an MSK model and find an excellent agreement in SE settings (average Pearson's r = 0.96, normalized RMSE (NRMSE) = 0.23) and strong correspondence in SN settings (average r = 0.89, NRMSE = 0.45). The linear model performed poorly for SN settings, which motivated a more complex ML model. Our findings suggest that an ML-based approach is highly viable for estimating upper-extremity biomechanical information solely from IMC data.

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2022

Chargement

A Primer on Motion Capture with Deep Learning: Principles, Pitfalls, and Perspectives

Jessy Lauer, Mackenzie Mathis, Alexander Mathis, Steffen Schneider

Extracting behavioral measurements non-invasively from video is stymied by the fact that it is a hard computational problem. Recent advances in deep learning have tremendously advanced our ability to predict posture directly from videos, which has quickly impacted neuroscience and biology more broadly. In this primer, we review the budding field of motion capture with deep learning. In particular, we will discuss the principles of those novel algorithms, highlight their potential as well as pitfalls for experimentalists, and provide a glimpse into the future.

2020

Chargement

EPFL2004