This article describes the concept of knowledge integration in a 3D collaborative virtual environment. This concept characterizes collaborative design in terms of two models introduced in this article -an annotation model with a semantic metadata notion - and a knowledge model to capitalize and to manage annotations - MATRICS environment. We briefly describe this approach. Then we present the results of an empirical study in which subjects performed annotation tasks with the support of an ontology visualization 2D tool and through the navigation in the 3D annotations. This study shows that the knowledge model improves the quality of the understanding of design projects.

With the intensification and the expansion of collaboration modes between designers and engineers for better time and quality mastering, the communication efficiency between these two communities of practice have to be thought taking in to account both designers and engineer's representation systems. While designers participate to the concept research and deliver the product's scenario of use through images, sketches and renderings, the engineers participate to the physical definition and to the materialization of these concepts. There is a need for a common representation of the concepts and the product, i.e. explicit link between the subjective data coming from the designer and the objective data materializing the product. Nevertheless semantic product characterization have specific tools and methods usually found in 2D environments and 3D CAD systems do not answer to the needs of exchanges in a multi disciplinary design team. In this paper we introduce a virtual environment to integrate, capitalize and explore knowledge around the virtual mock up in order to facilitate subjective and objective product characterization for designers and engineers collaboration. This virtual environment (MATRICS) allows the user to post multi-media annotations on a virtual 3D mock up, to support intentions transferred from the designer to the engineer when communicating. Another aspect of this environment is to provide a shared visualization of knowledge connected to the model and users interaction with knowledge representation increasing the collaboration level while designing.

We address the problem of constructing a boundary model of an object when the input consists of a set of points that lie on its surface. We assume that the points are acquired using telemetric techniques. Such data constitute a discrete sampling of the surface: a "cloud" of points. Supplemental connectivity information between those points is necessary if one is to reconstruct an approximation to the underlying object. We use the implicit information provided by the acquisition procedure itself to achieve this goal.

Consideration is given to a world made up of a collection of objects which are all moving with respect to each other. The goal is to design a system capable of reporting predicting all possible object collisions, given that all relevant information is available in due time. Previous approaches are based on the notion of a distance function that reflects the closest distance between objects in the world at any given instant in time. Explicitly including time in the representation makes it possible to obtain an algorithm based on the shortest possible time before the next possible collision. The algorithm deals with all pairwise interactions between objects, sorts the pairs with respect to their predicted collision time, and maintains the most-likely-to-collide pairs at the top of a stack. A novel kind of hierarchy in the representation of the world is thus introduced. To find the shortest possible time before a collision, the trajectory of objects is constrained by imposing bounds on the object's acceleration and velocity. All interacting pairs are classified into buckets that reflect the imminence of the collision. The computing cost is kept constant by reclassifying only one pair from each bucket at each time sample.>

The authors consider the problem of aggregating the geometrical information provided by sensors such as range finders, and its applications to scene modeling. The information consists of collections of three-dimensional surface points that form a discrete subspace of the objects-to-free-space boundaries within the world to be modeled. The ultimate goal is to obtain a valid surface model which can in turn be transformed into an efficient volumetric representation for solid-interference-detection algorithms. This representation should achieve search efficiency, compactness, and parallelism. The authors first introduce such a volumetric representation which uses a tetrahedrization of space. Then they show that surface connectivity is a nontrivial and essential element of a valid representation. To that end, they introduce a formal graph-theoretic definition for model validity which they use to guide the process of aggregating the different views. Finally, the topological problems posed by objects nonhomeomorphic to spheres, such as multiholed tori, are introduced.>