807866
Surface reconstruction with triangular B-splines
This paper presents a modeling technique for reconstructing a triangular B-spline surface from a set of scanned 3D points. Unlike existing surface reconstruction methods based on tensor-product B-splines which primarily generate a network of patches and then enforce certain continuity (usually, G/sup 1/ or C/sup 1/) between adjacent patches, our algorithm can avoid the complicated procedures of surface trimming and patching. In our framework, the user simply specifies the degree n of the triangular B-spline surface and fitting error tolerance /spl epsi/. The surface reconstruction procedure generates a single triangular B-spline patch that has C/sup n-1/ continuity over smooth regions and C/sup 0/ on sharp features. More importantly, all the knots and control points are determined by minimizing a linear combination of interpolation and fairness functionals. Examples are presented which demonstrate the effectiveness of the technique for real data sets.
8614411
Manifold T-Spline
This paper develops the manifold T-splines, which naturally extend the concept and the currently available algorithms/techniques of the popular planar tensor-product NURBS and T-splines to arbitrary manifold domain of any topological type. The key idea is the global conformal parameterization that intuitively induces a tensor-product structure with a finite number of zero points, and hence offering a natural mechanism for generalizing the tensor-product splines throughout the entire manifold. In our shape modeling framework, the manifold T-splines are globally well-defined except at a finite number of extraordinary points, without the need of any tedious trimming and patching work. We present an efficient algorithm to convert triangular meshes to manifold T-splines. Because of the natural, built-in hierarchy of T-splines, we can easily reconstruct a manifold T-spline surface of high-quality with LOD control and hierarchical structure.
290365
Spline Thin-Shell Simulation of Manifold Surfaces
It has been technically challenging to effectively model and simulate elastic deformation of spline-based, thin-shell objects of complicated topology. This is primarily because traditional FEM are typically defined upon planar domain, therefore incapable of constructing complicated, smooth spline surfaces without patching/trimming. Moreover, at least C1 continuity is required for the convergence of FEM solutions in thin-shell simulation. In this paper, we develop a new paradigm which elegantly integrates the thin-shell FEM simulation with geometric design of arbitrary manifold spline surfaces. In particular, we systematically extend the triangular B-spline FEM from planar domains to manifold domains. The deformation is represented as a linear combination of triangular B-splines over shell surfaces, then the dynamics of thin-shell simulation is computed through the minimization of Kirchhoff-Love energy. The advantages given by our paradigm are: FEM simulation of arbitrary manifold without meshing and data conversion, and the integrated approach for geometric design and dynamic simulation/analysis. Our system also provides a level-of-detail sculpting tool to manipulate the overall shapes of thin-shell surfaces for effective design. The proposed framework has been evaluated on a set of spline models of various topologies, and the results demonstrate its efficacy in physics-based modeling, interactive shape design and finite-element simulation.
5843308
A C1 Globally Interpolatory Spline of Arbitrary Topology
Converting point samples and/or triangular meshes to a more compact spline representation for arbitrarily topology is both desirable and necessary for computer vision and computer graphics. This paper presents a C1 manifold interpolatory spline that can exactly pass through all the vertices and interpolate their normals for data input of complicated topological type. Starting from the Powell-Sabin spline as a building block, we integrate the concepts of global parametrization, affine atlas, and splines defined over local, open domains to arrive at an elegant, easy-to-use spline solution for complicated datasets. The proposed global spline scheme enables the rapid surface reconstruction and facilitates the shape editing and analysis functionality.
483980
Rational spherical splines for genus zero shape modeling
Traditional approaches for modeling a closed manifold surface with either regular tensor-product or triangular splines (defined over an open planar domain) require decomposing the acquired geometric data into a group of charts, mapping each chart to a planar parametric domain, fitting an open surface patch of certain degree to each chart, and finally, trimming the patches (if necessary) and stitching all of them together to form a closed manifold. In this paper, we develop a novel modeling method which does not need any cutting or patching operations for genus zero surfaces. Our new approach is founded upon the concept of spherical splines proposed by Pfeifle and Seidel. Our work is strongly inspired by the fact that, for genus zero surfaces, it is both intuitive and necessary to employ spheres as their natural domains. Using this framework, we can convert genus zero mesh to a single rational spherical spline whose maximal error deviated from the original data is less than a user-specified tolerance. With the rational spherical splines, we can model sharp features and edit both the global shape and the local details with ease. Furthermore, we can accurately compute the differential quantities without resorting to any numerical approximations. We conduct several experiments in order to demonstrate the efficacy of our approach for reverse engineering, shape modeling, and interactive graphics.
45341657
3-D Reconstruction of Macroscopic Optical Brain Slice Images
We present a method for reconstruction of macroscopic optical images of post-mortem brain slices to form a 3-D volume. This forms a key part of a series of procedures to allow post mortem findings to be accurately registered with MR images, and more generally provides a method for 3-D mapping of the distribution of pathological changes throughout the brain. In this preliminary work, four brains from a study of Creutzfeldt-Jakob disease were examined. After brain fixation, the pathologist cut coronal slices several mm thick through the brain. The anterior and posterior faces of each slice were photographed. We show that the 2-D co-registration of each such pair of images was most effectively obtained if the slice was placed in a jig before photographing. Fiducials on the jig were detected automatically and point-based rigid registration computed. For co-registration between slices, i.e., across a single cut, an intensity-based method for 2-D non-rigid registration is used which provided satisfactory results. By propagating the 2-D registrations through the volume and using the known slice thickness, the 3-D volume was reconstructed.
1259633
An autonomic routing framework for sensor networks
Current routing services for sensor networks are often designed for specific applications and network conditions, thus have difficulty in adapting to application and network dynamics. This paper proposes an autonomic framework to promote the adaptivity of routing services in sensor networks. The key idea of this framework is to maintain some feature functions that are decoupled from originally-integrated routing services. This separation enables significant service changes to be done by only tuning these functions. Measures including parameterization are taken to save the energy for changing these functions. Further, this framework includes a monitoring module to support a policy-based collaborative adaptation. This paper shows an example autonomic routing service conforming to this framework.
1033072
Gathercast with active networks
Small packets constitute a large fraction of packets in the Internet. Gathercast is a network layer service that combines small packets going to the same destination into a single packet, reducing the number of packets in the network and saving computations at intermediate routers. We propose a new model for gathercast using active network techniques. With this model, gathercast is built throughout the network with low overhead, service parameters can be dynamically adjusted and end-user applications obtain benefits from gathercast without knowing its existence. We also present an implementation of the active gathercast.
2201352
On Mitigating Network Partitioning in Peer-to-Peer Massively Multiplayer Games
Recently, peer-to-peer infrastructure has been proposed to support massively multiplayer games in the literature. However, when underlying network partitions due to network outages, the game world will partition into several parallel game worlds and it is difficult and costly to merge them when the network partitions disappear. Existing approaches resort to a centralized server to arbitrate. Aiming at mitigating the effects brought by network partitions, we propose a fully distributed algorithm based on state-stack matching. Our theoretical analysis and numerical results show that our approach can resolve the merging issue at the least loss of game states with high probability.
28965598
A semantic matchmaker service on the grid
A fundamental task on the Grid is to decide what jobs to run on what computing resources based on job or application requirements. Our previous work on ontology-based matchmaking discusses a resource matchmaking mechanism using Semantic Web technologies. We extend our previous work to provide dynamic access to such matchmaking capability by building a persistent online matchmaking service. Our implementation uses the Globus Toolkit for the Grid service development, and exploits the monitoring and discovery service in the Grid infrastructure to dynamically discover and update resource information. We describe the architecture of our semantic matchmaker service in the poster.