Solid Modeling 04

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https://diglib.eg.org/handle/10.2312/1000

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Automatic Building of Structured Geological Models
(The Eurographics Association, 2004) Brandel, S.; Schneider, S.; Perrin, M.; Guiard, N.; Rainaud, J. F.; Lienhardt, P.; Bertrand, Y.; Gershon Elber and Nicholas Patrikalakis and Pere Brunet
The present article proposes a method to signi cantly improve the construction and updating of 3D geological models used for oil and gas exploration. The proposed method takes advantage of the speci c structures which characterize geological objects. We present a prototype of a geological pilot which enables monitoring the automatic building of a 3D model topologically and geologically consistent, starting from a set of unsegmented surfaces. The geological pilot uses a Geological Evolution Scheme (GES) which records all the interpretation elements that the exploration geologist, who is the end user, wishes to introduce into the model. The model building is performed by reading instructions deduced from the GES. Topology is dealt with step by step by using a 3D Generalized Maps (3-G-Maps) data model enriched to enable the manipulation of objects having speci c geological attributes. The result is a correct 3D model on which geological links between objects can easily be visualized. This model can automatically be revised in case of changes in the geometric data or in the interpretation. In its nal version, the created modular tool will be plugged in 3D modelers currently used in exploration geology in order to improve their performance.
Efficient and Robust Computation of an Approximated Medial Axis
(The Eurographics Association, 2004) Yang, Y.; Brock, O.; Moll, R. N.; Gershon Elber and Nicholas Patrikalakis and Pere Brunet
The medial axis can be viewed as a compact representation for an arbitrary model; it is an essential geometric structure in many applications. A number of practical algorithms for its computation have been aimed at speeding up its computation and at addressing its instabilities. In this paper we propose a new algorithm to compute the medial axis with arbitrary precision. It exhibits several desirable properties not previously combined in a practical and ef cient algorithm. First, it allows for a tradeoff between computation time and accuracy, making it well-suited for applications in which an approximation of the medial axis suf ces, but computational ef ciency is of particular concern. Second, it is output sensitive: the computation complexity of the algorithm does not depend on the size of the representation of a model, but on the size of the representation of the resulting medial axis. Third, the densities of the approximated medial axis points in different areas are adaptive to local free space volumes, based on the assumption that a coarser approximation in wide open area can still suf ce the requirements of the applications. We present theoretical results, bounding the error introduced by the approximation process. The algorithm has been implemented and experimental results are presented that illustrate its computational ef ciency and robustness.
A Framework for Multiresolution Adaptive Solid Objects
(The Eurographics Association, 2004) Chang, Y.- S.; Qin, H.; Gershon Elber and Nicholas Patrikalakis and Pere Brunet
Despite the growing interest in subdivision surfaces within the computer graphics and geometric processing communities, subdivision approaches have been receiving much less attention in solid modeling. This paper presents a powerful new framework for a subdivision scheme that is defined over a simplicial complex in any n-D space. We first present a series of definitions to facilitate topological inquiries during the subdivision process. The scheme is derived from the double (k+1)-directional box splines over k-simplicial domains. Thus, it guarantees a certain level of smoothness in the limit on a regular mesh. The subdivision rules are modified by spatial averaging to guarantee C1 smoothness near extraordinary cases. Within a single framework, we combine the subdivision rules that can produce 1-, 2-, and 3-manifold in arbitrary n-D space. Possible solutions for non-manifold regions between the manifolds with different dimensions are suggested as a form of selective subdivision rules according to user preference. We briefly describe the subdivision matrix analysis to ensure a reasonable smoothness across extraordinary topologies, and empirical results support our assumption. In addition, through modifications, we show that the scheme can easily represent objects with singularities, such as cusps, creases, or corners. We further develop local adaptive refinement rules that can achieve level-of-detail control for hierarchical modeling. Our implementation is based on the topological properties of a simplicial domain. Therefore, it is flexible and extendable. We also develop a solid modeling system founded on our theoretical framework to show potential benefits of our work in industrial design, geometric processing, and other applications.
Multiresolution Heterogeneous Solid Modeling and Visualization Using Trivariate Simplex Splines
(The Eurographics Association, 2004) Hua, J.; He, Y.; Qin, H.; Gershon Elber and Nicholas Patrikalakis and Pere Brunet
This paper presents a new and powerful heterogeneous solid modeling paradigm for representing, modeling, and rendering of multi-dimensional, physical attributes across any volumetric objects. The modeled solid can be of complicated geometry and arbitrary topology. It is formulated using a trivariate simplex spline defined over a tetrahedral decomposition of any 3D domain. Heterogeneous material attributes associated with solid geometry can be modeled and edited by manipulating the control vectors and/or associated knots of trivariate simplex splines easily. The multiresolution capability is achieved by interactively subdividing any regions of interest and allocating more knots and control vectors accordingly. We also develop a feature-sensitive fitting algorithm that can reconstruct a more compact, continuous trivariate simplex spline from structured or unstructured volumetric grids. This multiresolution representation results from the adaptive and progressive tetrahedralization of the 3D domain. In addition, based on the simplex spline theory, we derive several theoretical formula and propose a fast direct rendering algorithm for interactive data analysis and visualization of the simplex spline volumes. Our experiments demonstrate that the proposed paradigm augments the current modeling and visualization techniques with the new and unique advantages.
Shortest Circuits with Given Homotopy in a Constellation
(The Eurographics Association, 2004) Michelucci, D.; Neveu, M.; Gershon Elber and Nicholas Patrikalakis and Pere Brunet
Abstract A polynomial method is described for computing the shortest circuit with a prescribed homotopy on a surface. The surface is not described by a mesh but by a constellation: a set of sampling points. Points close enough (their distance is less than a prescribed threshold) are linked with an edge: the induced graph is not a triangulation but still permits to compute homologic and homotopic properties. Advantages of constellations over meshes are their simplicity and robustness.
Update Operations on 3D Simplicial Decompositions of Non-manifold Objects
(The Eurographics Association, 2004) Floriani, L. De; Hui, A.; Gershon Elber and Nicholas Patrikalakis and Pere Brunet
We address the problem of updating non-manifold mixed-dimensional objects, described by three-dimensional simplicial complexes embedded in 3D Euclidean space. We consider two local update operations, edge collapse and vertex split, which are the most common operations performed for simplifying a simplicial complex. We examine the effect of such operations on a 3D simplicial complex, and we describe algorithms for edge collapse and vertex split on a compact representation of a 3D simplicial complex, that we call the Non-Manifold Indexed data structure with Adjacencies (NMIA). We also discuss how to encode the information needed for performing a vertex split and an edge collapse on a 3D simplicial complex. The encoding of such information together with the algorithms for updating the NMIA data structure form the basis for de ning progressive as well as multi-resolution representations for objects described by 3D simplicial complexes and for extracting variable-resolution object descriptions.
Using Cayley Menger Determinants
(The Eurographics Association, 2004) Michelucci, D.; Foufou, S.; Gershon Elber and Nicholas Patrikalakis and Pere Brunet
We use Cayley-Menger Determinants (CMDs) to obtain an intrinsic formulation of geometric constraints. First, we show that classical CMDs are very convenient to solve the Stewart platform problem. Second, issues like distances between points, distances between spheres, cocyclicity and cosphericity of points are also addressed. Third, we extend CMDs to deal with asymmetric problems. In 2D, the following configurations are considered: 3 points and a line; 2 points and 2 lines; 3 lines. In 3D, we consider: 4 points and a plane; 2 points and 3 planes; 4 planes.

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Browsing Solid Modeling 04 by Subject "Computational Geometry and Object Modeling"

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