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

Sonic interaction with a virtual orchestra of factory machinery

This paper presents an immersive application where users receive sound and visual feedbacks on their interactions with a virtual environment. In this application, the users play the part of conductors of an orchestra of factory machines since each of their actions on interaction devices triggers a pair of visual and audio responses. Audio stimuli were spatialized around the listener. The application was exhibited during the 2013 Science and Music day and designed to be used in a large immersive system with head tracking, shutter glasses and a 10.2 loudspeaker configuration.Comment: Sonic Interaction for Virtual Environments, Minneapolis : United States (2014

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

Experiencing the past in virtual reality A virtual reality event for the French National Days of Archaeology

International audienceThis document reports a public exhibition organized during the French National Days of Archaeology, that is the result of an interdisciplinary collaboration between archaeologists and computer scientists, centered on the immersive virtual reality platform Immersia, a node of the European Visionair project. This public exhibition had three main goals: (i) presentating our interdisciplinary collaboration, (ii) communicating on the scientific results of this collaboration, and (iii) offering an immersive experience in the past for visitors. This paper presents the scientific context of the event, its organization, and a discussion on feedbacks

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

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

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

Virtual reality tools for the West Digital Conservatory of Archaeological Heritage

International audienceIn the continuation of the 3D data production work made by the WDCAH, the use of virtual reality tools allows archaeologists to carry out analysis and understanding research about their sites. In this paper, we focus on the virtual reality services proposed to archaeologists in the WDCAH, through the example of two archaeological sites, the Temple de Mars in Corseul and the Cairn of Carn Island

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

The West Digital Conservatory of Archaelogical Heritage Project

International audienceThe West Digital Conservatory of Archaeological Heritage project, a.k.a. WDCAH, is a new French research organization whose aim is to both ensure the preservation of digital archaeological data, and deliver expertise in production, analysis, visualization and virtual reality exploration techniques. This project is an interdisciplinary project composed of engineers and researchers in archaeology, computer science, virtual reality and 3D interaction with virtual environments. The major objectives of this conservatory project are: (i) sustainable and centralized safeguarding and archiving of 2D/3D data produced by the archaeological community; (ii) free access to metadata; (iii) secure access to data for the different actors involved in scientific projects and (iv) the support and advice for these actors in the 3D data production and exploration through the latest digital technologies, modeling tools and virtual reality systems. Today the first activities of the WDCAH mainly concern digital models production using photogrammetry, 3D laser scans, and 3D computer graphics software. We are currently working on the reconstitution of six archaeological sites located in the west of France ranging from prehistory to the Middle Ages: the Cairn of Carn Island, the covered pathway of Roh Coh Coet, the Goh Min Ru megalithic site, the gallo-roman mansion of Vanesia, the keep of the Château de Sainte-Suzanne, the Porte des Champs of the Château d'Angers. Other proposals are currently under study