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We investigated whether observation of actions reproduced in three-dimensional virtual reality would engage perceptual and visuomotor brain processes different from those induced by the observation of real hand actions. Participants were asked to passively observe grasping actions of geometrical objects made by a real hand or by hand reconstructions of(More)
An approximating neural model, called hierarchical radial basis function (HRBF) network, is presented here. This is a self-organizing (by growing) multiscale version of a radial basis function (RBF) network. It is constituted of hierarchical layers, each containing a Gaussian grid at a decreasing scale. The grids are not completely filled, but units are(More)
Social virtual worlds such as Second Life (SL) are digital representations of the real world where human-controlled avatars evolve and interact through social activities. Understanding the characteristics of virtual worlds can be extremely valuable in order to optimize their design. In this paper, we perform an extensive analysis of SL. We exploit standard(More)
—A procedure for the real-time construction of three-dimensional (3-D) multiscale meshes from not evenly sampled 3-D points is described and discussed in this paper. The process is based on the connectionist model named hierarchical radial basis functions network (HRBF), which has been proved effective in the reconstruction of smooth surfaces from sparse(More)
—A portable and flexible system for three-dimensional (3-D) scanning is here presented. It is constituted of four main modules. The first module is devoted to the acquisition of a set of 3-D points over the surface through laser scanning (digitization). The second module reconstructs a continuous 3-D surface, filtering the measurement noise. Whenever(More)
The method presented here is aimed to a direct fast setting of the parameters of a RBF network for function approximation. It is based on a hierarchical gridding of the input space; additional layers of Gaussians at lower scales are added where the residual error is higher. The number of the Gaussians of each layer and their variance are computed from(More)
In this paper, a novel real-time online network model is presented. It is derived from the hierarchical radial basis function (HRBF) model and it grows by automatically adding units at smaller scales, where the surface details are located, while data points are being collected. Real-time operation is achieved by exploiting the quasi-local nature of the(More)
—Hierarchical radial basis functions (HRBFs) networks have been recently introduced as a tool for adaptive multiscale image reconstruction from range data. These are based on local operation on the data and are able to give a sparse approximation. In this paper, HRBFs are reframed for the regular sampling case, and they are compared with wavelet(More)
Second Life (SL) is currently the most popular social virtual world, i.e., a digitalization of the real world where avatars can meet, socialize and trade. SL is managed through a Client/Server (C/S) architecture with a very high cost and limited scalability. A scalable and cheap alternative to C/S is to use a Peer-to-Peer (P2P) approach, where SL users rely(More)