Virtual Environments for Training: From Individual Learning to Collaboration with Humanoids

The next generation of virtual environments for training is oriented towards collaborative aspects. Therefore, we have decided to enhance our platform for virtual training environments, adding collaboration opportunities and integrating humanoids. In this paper we put forward a model of humanoid that suits both virtual humans and representations of real users, according to collaborative training activities. We suggest adaptations to the scenario model of our platform making it possible to write collaborative procedures. We introduce a mechanism of action selection made up of a global repartition and an individual choice. These models are currently being integrated and validated in GVT, a virtual training tool for maintenance of military equipments, developed in collaboration with the French company NEXTER-Group

Fast Collision Culling in Large-Scale Environments Using GPU Mapping Function

International audienceThis paper presents a novel and efficient GPU-based parallel algorithm to cull non-colliding object pairs in very large-scale dynamic simulations. It allows to cull objects in less than 25ms with more than 100K objects. It is designed for many-core GPU and fully exploits multi-threaded capabilities and data-parallelism. In order to take advantage of the high number of cores, a new mapping function is defined that enables GPU threads to determine the objects pair to compute without any global memory access. These new optimized GPU kernel functions use the thread indexes and turn them into a unique pair of objects to test. A square root approximation technique is used based on Newton's estimation, enabling the threads to only perform a few atomic operations. A first characterization of the approximation errors is presented, enabling the fixing of incorrect computations. The I/O GPU streams are optimized using binary masks. The implementation and evaluation is made on largescale dynamic rigid body simulations. The increase in speed is highlighted over other recently proposed CPU and GPU-based techniques. The comparison shows that our system is, in most cases, faster than previous approaches

Ajout de détails dynamiques à une animation temps-réel de personnage

National audienceReal-time animation of characters often relies on a geometric technique called skinning which enables the skin and clothes to follow the skeleton motion. However, dynamic effects - non-rigid tissues vibrations, dynamic wrinkles of skin and clothes - can not be generated by it. However such deformations are of primary importance for the realism of the generated animation. In this paper, we propose two intuitive methods which address those specific problems with little increase in computational cost of the animation. Our tools can be combined together on an existing animation sequence to enhance its realism, with no need to change the original animation, no mechanics precomputation and no modification of the model. We illustrate our results with several characters and animals animations.L'animation temps-réel de personnages repose généralement sur une technique d'habillage, appelée skinning en anglais, permettant à la peau et aux vêtements de suivre les mouvements du squelette. Cette technique n'engendre malheureusement aucun des effets dynamiques - vibrations des tissus non-rigides, plissement variable de la peau et des vêtements - pourtant cruciaux pour le réalisme. Dans cet article, nous présentons deux techniques complémentaires pour ajouter ces effets de manière intuitive, tout en limitant au maximum les sur-coûts lors du calcul de l'animation. Combinables entre eux et rapides à mettre en place, nos outils améliorent le réalisme visuel du mouvement sans nécessiter de modification de la séquence d'animation de départ, de précalcul mécanique ni de modification des modèles. Nous illustrons nos résultats sur des animations variées de personnages et d'animaux

Internal 3D Printing of Intricate Structures

International audienceAdditive technologies are increasingly used in Cultural Heritage process , for example in order to reproduce, complete, study or exhibit artefacts. 3D copies are based on digitization techniques such as laser scan or photogramme-try. In this case, the 3d copy remains limited to the external surface of objects. Medical images based digitization such as MRI or CT scan are also increasingly used in CH as they provide information on the internal structure of archaeological material. Different previous works illustrated the interest of combining 3D printing and CT scan in order to extract concealed artefacts from larger archaeological material. The method was based on 3D segmentation techniques within volume data obtained by CT scan to isolate nested objects. This approach was useful to perform a digital extraction, but in some case it is also interesting to observe the internal spatial organization of an intricate object in order to understand its production process. We propose a method for the representation of a complex internal structure based on a combination of CT scan and emerging 3D printing techniques mixing colored and transparent parts. This method was successfully applied to visualize the interior of a funeral urn and is currently applied on a set of tools agglomerated in a gangue of corrosion

Preservative Approach to Study Encased Archaeological Artefacts

International audienceWe propose a workflow based on a combination of computed tomography, 3D images and 3D printing to analyse different archaeological material dating from the Iron Age, a weight axis, a helical piece, and a fibula. This workflow enables a preservative analysis of the artefacts that are unreachable because encased either in stone, corrosion or ashes. Computed tomography images together with 3D printing provide a rich toolbox for archaeologist work allowing to access a tangible representation of hidden artefacts. These technologies are combined in an efficient, affordable and accurate workflow compatible with Preventive archaeology constraints

A Software Toolbox to Carry-out Virtual Experiments on Human Motion

We present a simulation toolbox to carry-out virtual experiments on human motion. 3D visualization, automatic code generation and generic control design patterns bring dynamic simulation tools into the hands of biomechanicians and doctors

A Broad Phase Collision Detection Algorithm Adapted to Multi-cores Architectures

International audienceRecent years have seen the impressive evolution of graphics hardware and processors architecture from single core to multi and many-core architectures. Confronted to this evolution, new trends in collision detection optimisation consist in proposing a solution that maps on the runtime architecture. We present, in this paper, two contributions in the field of collision detection in large-scale environments. We present a first way to parallelise, on a multi-core architecture, the initial step of the collision detection pipeline: the broad-phase. Then, we describe a new formalism of the collision detection pipeline that takes into account runtime architecture. The well-known broadphase algorithm used is the ”Sweep and Prune” and it has been adapted to a multi-threading use. To handle one or more thread per core, critical writing sections and threads idling must be minimised. Our model is able to work on a n-core architecture reducing computation time to detect collision between 3D objects in a large-scale environment

FuRIA: A Novel Feature Extraction Algorithm for Brain-Computer Interfaces using Inverse Models and Fuzzy Regions of Interest

In this paper, we propose a new feature extraction algorithm for Brain-Computer Interfaces (BCIs). This algorithm is based on inverse models and uses the novel concept of fuzzy Region Of Interest (ROI). It can automatically identify the relevant ROIs and their reactive frequency bands. The activity in these ROIs can be used as features for any classifier. A first evaluation of the algorithm, using a Support Vector Machine (SVM) as classifier, is reported on data set IV from BCI competition 2003. Results are promising as we reached an accuracy on the test set ranging from 85% to 86% whereas the winner of the competition on this data set reached 84%

Ray-Traced Collision Detection : Interpenetration Control and Multi-GPU Performance

International audienceWe proposed [LGA13] an iterative ray-traced collision detection algorithm (IRTCD) that exploits spatial and temporal coherency and proved to be computationally efficient but at the price of some geometrical approximations that allow more interpenetration than needed. In this paper, we present two methods to efficiently control and reduce the interpenetration without noticeable computation overhead. The first method predicts the next potentially colliding vertices. These predictions are used to make our IRTCD algorithm more robust to the above-mentioned approximations, therefore reducing the errors up to 91%. We also present a ray re-projection algorithm that improves the physical response of ray-traced collision detection algorithm. This algorithm also reduces, up to 52%, the interpenetration between objects in a virtual environment. Our last contribution shows that our algorithm, when implemented on multi-GPUs architectures, is far faster

Toward an Enhanced Mutual Awareness in Asymmetric CVE

International audience—Collaborative Virtual Environments (CVEs) aim at providing several users with a consistent shared virtual world. In this work, we focus on the lack of mutual awareness that may appear in many situations and we evaluate different ways to present the distant user and his actions in the Virtual Environment (VE) in order to understand his perception and cognitive process. Indeed, an efficient collaboration involves not only the good perception of some objects but their meaning too. This second criterion introduces the concept of distant analysis that could be a great help in improving the understanding of distant activities. For this work, we focus on a common case consisting in estimating accurately the time at which a distant user analyzed the meaning of a remotely pointed object. Thus, we conduct some experiments to evaluate the concept and compare different techniques for implementing this new awareness feature in a CVE. Amongst others, results show that expertise of the users influences on how they estimate the distant activity and the type of applied strategies