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Shape Modeling and Applications, 2005 International Conference

Date 13-17 June 2005

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Displaying Results 1 - 25 of 52
  • International Conference on Shape Modeling and Applications [Front cover]

    Page(s): c1
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  • Proceedings: International Conference on Shape Modeling and Applications - SMI'05 [front matter]

    Page(s): i - iv
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  • Table of Contents: International Conference on Shape Modeling and Applications - SMI 2005

    Page(s): v - viii
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  • Preface

    Page(s): ix
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  • Conference Committee

    Page(s): x
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  • Program Committee

    Page(s): xi
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  • External reviewers

    Page(s): xii
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  • What's in a Mesh? A Survey of 3D Mesh Representation Schemes

    Page(s): 2
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    Geometric meshes consist of a set of points in 3D space connected in a (typically manifold) graph structure. As such a vector of 3n real values may represent them, where n is the number of vertices in the mesh. Unfortunately, although straightforward, this is not a very useful representation of the mesh, as it is difficult to naturally manipulate the mesh data using this representation. A better representation would capture the spatial correlation between vertices, be invariant to a class of natural transformations, not be too redundant, and be efficiently invertible. Recent years have seen the development of a variety of mesh representation schemes, intended primarily for mesh editing applications. The author surveys some of these representation schemes, discuss the pros and cons, and demonstrate how the may be used to edit, animate and morph mesh datasets. View full abstract»

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  • Reconstructing B-spline Curves from Point Clouds--A Tangential Flow Approach Using Least Squares Minimization

    Page(s): 4 - 12
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (233 KB) |  | HTML iconHTML  

    We present a novel algorithm based on least-squares minimization to approximate point cloud data in 2D plane with a smooth B-spline curve. The point cloud data may represent an open curve with self intersection and sharp corner. Unlike other existing methods, such as the moving least-squares method and the principle curve method, our algorithm does not need a thinning process. The idea of our algorithm is intuitive and simple - we make a B-spline curve grow along the tangential directions at its two end-points following local geometry of point clouds. Our algorithm generates appropriate control points of the fitting B-spline curve in the least squares sense. Although presented for the 2D case, our method can be extended in a straightforward manner to fitting data points by a B-spline curve in higher dimensions View full abstract»

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  • Smooth adaptive fitting of 3D models using hierarchical triangular splines

    Page(s): 13 - 22
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1176 KB) |  | HTML iconHTML  

    The recent ability to measure quickly and inexpensively dense sets of points on physical objects has deeply influenced the way engineers represent shapes in CAD systems, animation software or in the game industry. Many researchers advocated to completely bypass smooth surface representations, and to stick to a dense mesh model throughout the design process. Yet smooth analytic representations are still required in standard CAD systems and animation software, for reasons of compactness, control, appearance and manufacturability. In this paper we present a new method for fitting a smooth adoptively refinable triangular spline surface of arbitrary topology to an arbitrary dense triangular mesh. The key ingredient in our solution is that adaptive fitting is achieved by 4-splitting triangular surface patches locally therefore no particular attention has to be paid the validity of an underlying subdivided mesh. Furthermore, the final surface is composed of low-degree polynomial patches that always join with Gl-continuity. The ability to adoptively refine the model allows to achieve a given approximation error with a minimal number of patches. View full abstract»

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  • Visualization of point-based surfaces with locally reconstructed subdivision surfaces

    Page(s): 23 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB) |  | HTML iconHTML  

    Point-based surfaces (i.e. surfaces represented by discrete point sets which are either directly obtained by current 3D acquisition devices or converted from other surface representations) are well designed for multiresolution storage and transmission of complex objects. Unfortunately, visualization of point-based surfaces requires to develop specific rendering techniques (e.g. splatting) as point sets are not well adapted to existing graphics hardware which are optimized for polygonal meshes. In this paper, we propose an efficient reconstruction and visualization technique of point-based surfaces that takes full benefit from the whole optimized pipeline implemented in graphics hardware. The basic idea is to generate a set of independent meshes using a local 2D Delaunay triangulation of the point set. These meshes are then glued together to get a " visual continuity" by using a subdivision process. View full abstract»

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  • Convection-driven dynamic surface reconstruction

    Page(s): 33 - 42
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1048 KB) |  | HTML iconHTML  

    In this paper, we introduce a flexible framework for the reconstruction of a surface from an unorganized point set, extending the geometric convection approach introduced by Chaine. Given a dense input point cloud, we first extract a triangulated surface that interpolates a subset of the initial data. We compute this surface in an output sensitive manner by decimating the input point set on-the-fly during the reconstruction process. Our simplification procedure relies on a simple criterion that locally detects and reduces oversampling. If needed, we then operate in a dynamic fashion for local refinement or further simplification of the reconstructed surface. Our method allows to locally update the reconstructed surface by inserting or removing sample points without restarting the convection process from scratch. This iterative correction process can be controlled interactively by the user or automatized given some specific local sampling constraints. View full abstract»

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  • Remeshing Schemes for semi-regular tilings

    Page(s): 44 - 50
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1376 KB) |  | HTML iconHTML  

    Most frequently used subdivision schemes such as Catmull-Clark create regular regions after several applications. This paper shows that all semi-regular regions can be created by subdivision schemes and each semi-regular region type can be created with one application of a particular subdivision scheme to a particular regular region. Using this property of subdivision schemes it is easy to cover any given surface with semi-regular tiles by applying one semi-regularity creating subdivision after several applications of a regularity creating subdivision. View full abstract»

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  • An accurate error measure for adaptive subdivision surfaces

    Page(s): 51 - 56
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    A tight estimate on the maximum distance between a subdivision surface and its linear approximation is introduced to guide adaptive subdivision with guaranteed accuracy. View full abstract»

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  • Designing with distance fields

    Page(s): 58 - 59
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (920 KB) |  | HTML iconHTML  

    Creating 3D computer models is a difficult, time consuming task. Existing systems capable of providing detailed, expressive models of sufficient quality for Hollywood or CAD can be labor intensive and complex, thus limiting creativity and the availability of good 3D models. During the past few years, several systems have been presented that address some of these limitations by using distance fields to represent and create models. The author presents the latest advancements to the Kizamu system and several new design paradigms that can make use of distance fields for creating and editing 3D geometry. View full abstract»

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  • Mesh editing with an embedded network of curves

    Page(s): 62 - 71
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1632 KB) |  | HTML iconHTML  

    We propose a new topological data structure for representing a set of polygonal curves embedded in a meshed surface. In this embedding, the vertices of the curve do not necessarily correspond to the vertices of the surface. The partition of the surface yielded by the intersecting curves is efficiently represented as a "cut-graph". The cut-graph stores combinatorial information of the network of curves. In our approach, the combinatorial form of information is systematically preferred to geometrical information since it improves both robustness and efficiency. Thanks to the topological data structure and algorithms, the cut-graph can be sketched through iterations of designing and erasing curves on the mesh surface in a "nondestructive" way, i.e. without modifying the mesh until the cutting operation is committed. We also demonstrate several prototype curve design tools inspired by 2D vector and bitmap graphics paradigms. We show how to sketch the cut-graph and how these tools can be mixedly used. View full abstract»

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  • Minimal-cut model composition

    Page(s): 72 - 81
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1872 KB) |  | HTML iconHTML  

    Constructing new, complex models is often done by reusing parts of existing models, typically by applying a sequence of segmentation, alignment and composition operations. Segmentation, either manual or automatic, is rarely adequate for this task, since it is applied to each model independently, leaving it to the user to trim the models and determine where to connect them. In this paper we propose a new composition tool. Our tool obtains as input two models, aligned either manually or automatically, and a small set of constraints indicating which portions of the two models should be preserved in the final output. It then automatically negotiates the best location to connect the models, trimming and stitching them as required to produce a seamless result. We offer a method based on the graph theoretic minimal cut as a means of implementing this new tool. We describe a system intended for both expert and novice users, allowing easy and flexible control over the composition result. In addition, we show our method to be well suited for a variety of model processing applications such as model repair, hole filling, and piecewise rigid deformations. View full abstract»

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  • Rational spherical splines for genus zero shape modeling

    Page(s): 82 - 91
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2808 KB) |  | HTML iconHTML  

    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. View full abstract»

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  • Anisotropic meshing of implicit surfaces

    Page(s): 94 - 103
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1264 KB) |  | HTML iconHTML  

    This paper proposes a new grid-based method for adaptive anisotropic meshing of implicit surfaces. Grid-based methods are considered the major technique for implicit surface meshing, mainly due to their efficiency and simplicity. However, these methods suffer from a number of inherent drawbacks, resulting from the fact that the imposed Cartesian grid is generally not well adapted to the iso-surface, either in size or in orientation. To overcome the above obstacles, we propose a new implicit surface meshing method. The main idea of this method is first to construct a geometric field which is induced by the shape of the surface. This geometric field represents the natural directions and grid cell size for each point in R3. Then, the imposed volumetric grid is deformed toward the object's shape according to the produced geometric field. The iso-surface meshes can be extracted from the resulting adaptive grid by any conventional grid-based contouring technique, since the topology of the grid is not modified during the adaptation process. These meshes provide better approximation of the unknown surface and exhibit anisotropy, which is present in this surface. View full abstract»

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  • Interactive implicit modeling with hierarchical spatial caching

    Page(s): 104 - 113
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB) |  | HTML iconHTML  

    Complex implicit CSG models can be represented hierarchically as a tree of nodes (the BlobTree) . However, current methods cannot be used to visualize changes made to these models at interactive rates due to the large number of potential field evaluations required. A hierarchical spatial caching technique is presented which accelerates evaluations of the potential function. This method introduces the concept of a caching node inserted into the implicit model tree. Caching nodes store exact potential field values at the vertices of a voxel grid and rely on tri-linear and tri-quadratic reconstruction filters to locally approximate the potential field of a sub-tree. A lazy evaluation scheme is used to avoid expensive pre-computation. Polygonization timings with and without caching are compared for a complex model undergoing manipulation in an interactive modeling tool. An order-of-magnitude improvement in visualization time is achieved for complex implicit models containing thousands of primitives. View full abstract»

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  • A programmable particle system framework for shape modeling

    Page(s): 114 - 123
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB) |  | HTML iconHTML  

    Particle systems are an effective tool for visualizing information in a variety of contexts. This paper focuses on the use of surface-constrained particles to visualize information about the surface. We have designed a particle system programming framework consisting of behaviors, attributes and shaders that allows users to rapidly create, debug, and deploy particle systems for sensing and extracting specific surface information and displaying this information in an visually effective manner. We also introduce a simple particle system "little language" to facilitate the articulation of these particle programs. We demonstrate the flexibility and power of this framework for surface visualization with the applications of singularity detection and display, non-photorealistic surface illustration, and surface mesh algorithm visualization. View full abstract»

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  • Robust particle systems for curvature dependent sampling of implicit surfaces

    Page(s): 124 - 133
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1200 KB) |  | HTML iconHTML  

    Recent research on point-based surface representations suggests that point sets may be a viable alternative to parametric surface representations in applications where the topological constraints of a parameterization are unwieldy or inefficient. Particle systems offer a mechanism for controlling point samples and distributing them according to needs of the application. Furthermore, particle systems can serve as a surface representation in their own right, or to augment implicit functions, allowing for both efficient rendering and control of implicit function parameters. The state of the art in surface sampling particle systems, however, presents some shortcomings. First, most of these systems have many parameters that interact with some complexity, making it difficult for users to tune the system to meet specific requirements. Furthermore, these systems do not lend themselves to spatially adaptive sampling schemes, which are essential for efficient, accurate representations of complex surfaces. In this paper we present a new class of energy functions for distributing particles on implicit surfaces and a corresponding set of numerical techniques. These techniques provide stable, scalable, efficient, and controllable mechanisms for distributing particles that sample implicit surfaces within a locally adaptive framework. View full abstract»

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  • Subdomain aware contour trees and contour evolution in time-dependent scalar fields

    Page(s): 136 - 144
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    For time-dependent scalar fields, one is often interested in topology changes of contours in time. In this paper, we focus on describing how contours split and merge over a certain time interval. Rather than attempting to describe all individual contour splitting and merging events, we focus on the simpler and therefore more tractable in practice problem: describing and querying the cumulative effect of the splitting and merging events over a user-specified time interval. Using our system one can, for example, find all contours at time t0 that continue to two contours at time t1 without hitting the boundary of the domain. For any such contour, there has to be a bifurcation happening to it somewhere between the two times, but, in addition to that, many other events may possibly happen without changing the cumulative outcome (e.g. merging with several contours born after t0 or splitting off several contours that disappear before t1). Our approach is flexible enough to enable other types of queries, if they can be cast as counting queries for numbers of connected components of intersections of contours with certain simply connected domains. Examples of such queries include finding contours with large life spans, contours avoiding certain subset of the domain over a given time interval or contours that continue to two at a later time and then merge back to one some time later. Experimental results show that our method can handle large 3D (2 space dimensions plus time) and 4D (3D+time) datasets. Both preprocessing and query algorithms can easily be parallelized. View full abstract»

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  • Design and manipulation of polygonal models in a haptic, stereoscopic virtual environment

    Page(s): 145 - 154
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1080 KB) |  | HTML iconHTML  

    This paper presents a flexible, scalable framework for interactive hands-on shape design in a haptic, stereoscopic virtual environment. The framework is founded upon the concept of PDE-based geometric surface flow. Given an input polygonal mesh, a user can interactively define implicit functions around regions of interest of the mesh model, and the locally or globally affected regions of the model will automatically deform according to the underlying partial differential equations and reconstruct the implicitly defined shape. During the model deformation process, the model can always maintain its regularity and can properly modify its topology when collisions between different parts of the model occur. With augmented haptics functionality and stereoscopic display, our system provides a more intuitive interface, which allows users to directly manipulate 3D polygonal objects with hands. View full abstract»

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  • Predicting AE attenuation in structures by geometric analysis

    Page(s): 155 - 162
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (912 KB) |  | HTML iconHTML  

    This paper investigates the feasibility of predicting the attenuation of AE signals travelling within a complex solid body. Such AE can occur due to external stimulation (e.g. impact) or internal events (i.e. crack propagation). The attenuation of these signals is affected not only by material properties but also by the geometry of the object. For example, wave propagation on a typical engine block is complex because of its intricate shape with variations and discontinuities in thickness and surface curvature. In contrast to much of the reported work in computer graphics (CG) literature that models the transmission of sound in rooms and buildings, this paper reports the development of a ray firing procedure to model the transmission of rays both across the surface and through the interior of a complex mechanical solid. The attenuation rate is proportional to the AE path length so the challenge of modelling the physical phenomena involves calculating the path lengths between the sensor and the source. The results of the computational simulation are compared with those obtained by experiment and found to be in good agreement. View full abstract»

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