One-shot Feature-Preserving Point Cloud Simplification with Gaussian Processes on Riemannian Manifolds

The processing, storage and transmission of large-scale point clouds is an ongoing challenge in the computer vision community which hinders progress in the application of 3D models to real-world settings, such as autonomous driving, virtual reality and remote sensing. We propose a novel, one-shot point cloud simplification method which preserves both the salient structural features and the overall shape of a point cloud without any prior surface reconstruction step. Our method employs Gaussian processes with kernels defined on Riemannian manifolds, allowing us to model the surface variation function across any given point cloud. A simplified version of the original cloud is obtained by sequentially selecting points using a greedy sparsification scheme. The selection criterion used for this scheme ensures that the simplified cloud best represents the surface variation of the original point cloud. We evaluate our method on several benchmark datasets, compare it to a range of existing methods and show that our method is competitive both in terms of empirical performance and computational efficiency.Comment: 10 pages, 5 figure

Tyre Design and Optimization by Dedicated CAD Tyre Model

Structural optimization by Finite Elements (FE) is proved very effective in tyre design. For that purpose, major tyre manufacturers use in-house applications. An alternative solution, involving dedicated CAD tyre model (DCTM), is here proposed. DCTM concept permits to easily change the FE tyre models, concerning shape and structure, by moving a part of pre-processing from FE analysis to CAD. No special skills regarding CAD or FEA are required. For every new tyre design, only a new DCTM and a corresponding FE model must be built. All subsequent model changes are automatically performed by mapping and translation routines. To test this concept, DTCM models of an existing tyre were created and used within a pilot design study

Composition and Manufacturing Effects on Electrical Properties of Li/FeS2 Thermal Battery Cathodes

Li/FeS2 thermal batteries provide a stable, robust, and reliable power source capable of long-term electrical energy storage without performance degradation. These systems rely on a eutectic salt that melts at elevated temperature, activating the cell. When the electrolyte melts, the cathode becomes a suspension, with cathode particles suspended in a molten salt. The suspension experiences mechanical deformation, or slumping.\u27 This slump changes the mechanical compression of the cell, as well as the tortuosity and electronic and ionic conductivity of the cell as the cathode mesostructure is reordered in response to the external compressive stress. The combined effect of deformation, component composition, and manufacturing conditions on electrical conductivity has not been studied, yet the cathode electrical properties are critically important to battery performance. This thesis presents simulation results from a computer model in combination with experiments to elucidate the effects of electrical conductivity in FeS2 cathode pellets when composition and manufacturing parameters are varied. Experiments applied impedance spectroscopy measurements of pressed-powder cathode pellets before and after slumping. Pellets were manufactured with variations in pellet density, FeS2 particle size distribution, and FeS2 content. The results showed that prior to slumping, the electrical conductivity increased with pellet density and FeS2 content. After slumping, pellets exhibited greater electrical conductivity, but the effects of processing parameters appear to have been erased, at least within the ranges tested. The conformal decomposition finite element method (CDFEM) was applied to surface-meshed geometric representations of cathode microstructures generated from microcomputed tomography reconstructions. Results from the SIERRA/Aria finite element code indicate that the selected processing and composition parameters do not provide a clear trend on the preslumped electrical conductivity, but density slightly affected the postslumped conductivity. These results indicate that the simulations lacked fidelity compared to experiments. However, the simulations combined with experimental data provide a fundamental look at the effects of processing and composition on thermal battery microstructure and electrical conductivity. The understanding of manufacturing effects on battery performance is not well developed, and this effort represents a step forward in correlated and predicting performance of cells based upon observed manufacturing trends.\u2

Subdivision Surface based One-Piece Representation

Subdivision surfaces are capable of modeling and representing complex shapes of arbi-trary topology. However, methods on how to build the control mesh of a complex surfaceare not studied much. Currently, most meshes of complicated objects come from trian-gulation and simplification of raster scanned data points, like the Stanford 3D ScanningRepository. This approach is costly and leads to very dense meshes.Subdivision surface based one-piece representation means to represent the final objectin a design process with only one subdivision surface, no matter how complicated theobject\u27s topology or shape. Hence the number of parts in the final representation isalways one.In this dissertation we present necessary mathematical theories and geometric algo-rithms to support subdivision surface based one-piece representation. First, an explicitparametrization method is presented for exact evaluation of Catmull-Clark subdivisionsurfaces. Based on it, two approaches are proposed for constructing the one-piece rep-resentation of a given object with arbitrary topology. One approach is to construct theone-piece representation by using the interpolation technique. Interpolation is a naturalway to build models, but the fairness of the interpolating surface is a big concern inprevious methods. With similarity based interpolation technique, we can obtain bet-ter modeling results with less undesired artifacts and undulations. Another approachis through performing Boolean operations. Up to this point, accurate Boolean oper-ations over subdivision surfaces are not approached yet in the literature. We presenta robust and error controllable Boolean operation method which results in a one-piecerepresentation. Because one-piece representations resulting from the above two methodsare usually dense, error controllable simplification of one-piece representations is needed.Two methods are presented for this purpose: adaptive tessellation and multiresolutionanalysis. Both methods can significantly reduce the complexity of a one-piece represen-tation and while having accurate error estimation.A system that performs subdivision surface based one-piece representation was im-plemented and a lot of examples have been tested. All the examples show that our ap-proaches can obtain very good subdivision based one-piece representation results. Eventhough our methods are based on Catmull-Clark subdivision scheme, we believe they canbe adapted to other subdivision schemes as well with small modifications

A new 3-D mesh simplificatión algorithm

To simplify the 3D color head mesh ,it is more important to keep the boundary and quality of the head’s sense organs including eyes, eyebrows, nose and mouth. In this paper, we present a novel mesh simplification algorithm based on region segmentation. The algorithm can be divided into two stages: segmentation and simplification. After the automatic segmentation of 3D color head mesh into different head parts, vertices are classed into region-boundary vertices and region-inner vertices. Using iterative edge collapse and region-weighted error metric, the algorithm generates continuous levels of detail (LOD). Results of several experiments are shown, demonstrating the validity and efficiency of our method.Keywords: mesh simplification, level of detail, image segmentation, multi-resolution mode

Web-based visualization for 3D data in archaeology : The ADS 3D viewer

The solid geometry of archaeological deposits is fundamental to the interpretation of their chronological sequence. However, such stratigraphic sequences are generally viewed as static two-dimensional diagrammatic representations which are difficult to manipulate or to relate to real layers. The ADS 3D Viewer is a web-based resource for the management and analysis of archaeological data. The viewer was developed to take advantage of recent developments in web technology, namely the adoption of WebGL (Web Graphics Library) by current web browsers. The ADS 3D Viewer combines the potential of the 3D Heritage Online Presenter (3DHOP), a software package for the web-based visualization of 3D geometries, with the infrastructure of the Archaeology Data Service (ADS) repository, in the attempt to create a platform for the visualization and analysis of 3D data archived by the ADS. Two versions of the viewer have been developed to answer the needs of different users. The first version, the Object Level 3D Viewer, was implemented to extend the browsing capability of ADS project archives by enabling the visualization of single 3D models. The second version, the Stratigraphy 3D Viewer, is an extension which allows the exploration of a specific kind of aggregated data: the multiple layers of an archaeological stratigraphic sequence. This allows those unable to participate directly in the fieldwork to access, analyse and re-interpret the archaeological context remotely. This has the potential to transform the discipline, allowing inter-disciplinary, cross-border and ‘at-distance’ collaborative workflows, and enabling easier access to and analysis of archaeological data