Issue 2

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https://diglib.eg.org/handle/10.2312/100

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    A Novel Approach for Delaunay 3D Reconstruction with a Comparative Analysis in the Light of Applications
    (Blackwell Publishers Ltd and the Eurographics Association, 2001) Nonato, L.; Minghim, R.; Oliveira, M. C. F.; Tavares, G.
    This paper presents a novel algorithm for volumetric reconstruction of objects from planar sections using Delaunay triangulation, which solves the main problems posed to models defined by reconstruction, particularly from the viewpoint of producing meshes that are suitable for interaction and simulation tasks. The requirements for these applications are discussed here and the results of the method are presented. Additionally, it is compared to another commonly used reconstruction algorithm based on Delaunay triangulation, showing the advantages of the reconstructions obtained by our technique.
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    Adaptive Implicit Surface Polygonization Using Marching Triangles
    (Blackwell Publishers Ltd and the Eurographics Association, 2001) Akkouche, Samir; Galin, Eric
    This paper presents several improvements to the marching triangles algorithm for general implicit surfaces. The original method generates equilateral triangles of constant size almost everywhere on the surface. We present several modifications to adapt the size of the triangles to the curvature of the surface. As cracks may arise in the resulting polygonization, we propose a specific crack-closing method invoked at the end of the mesh growing step. Eventually, we show that the marching triangles can be used as an incremental meshing technique in an interactive modeling environment. In contrast to existing incremental techniques based on spatial subdvision, no extra data-structure is needed to incrementally edit skeletal implicit surfaces, which saves both memory and computation time.
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    Fast and Controllable Simulation of the Shattering of Brittle Objects
    (Blackwell Publishers Ltd and the Eurographics Association, 2001) Smith, Jeffrey; Witkin, Andrew; Baraff, David
    We present a method for the rapid and controllable simulation of the shattering of brittle objects under impact. An object is represented as a set of point masses connected by distance-preserving linear constraints. This use of constraints, rather than stiff springs, gains us a significant advantage in speed while still retaining fine control over the fracturing behavior. The forces exerted by these constraints during impact are computed using Lagrange multipliers. These constraint forces are then used to determine when and where the object will break, and to calculate the velocities of the newly created fragments. We present the details of our technique together with examples illustrating its use.An earlier version of this paper was presented at Graphics Interface 2000, held in Montreal, Canada.
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    Recent Advances in Volume Visualization
    (Blackwell Publishers Ltd and the Eurographics Association, 2001) Brodlie, Ken; Wood, Jason
    In the past few years, there have been key advances in the three main approaches to the visualization of volumetric data: isosurfacing, slicing and volume rendering, which together make up the field of volume visualization.In this survey paper we set the scene by describing the fundamental techniques for each of these approaches, using this to motivate the range of advances which have evolved over the past few years.In isosurfacing, we see how the original marching cubes algorithm has matured, with improvements in robustness, topological consistency, accuracy and performance. In the performance area, we look in detail at pre-processing steps which help identify data which contributes to the particular isosurface required. In slicing too, there are performance gains from identifying active cells quickly.In volume rendering, we describe the two main approaches of ray casting and projection. Both approaches have evolved technically over the past decade, and the holy grail of real-time volume rendering has arguably been reached.The aim of this review paper is to pull these developments together in a coherent review of recent advances in volume visualization.
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    Constrained Fairing for Meshes
    (Blackwell Publishers Ltd and the Eurographics Association, 2001) Liu, Xinguo; Bao, Hujun; Heng, PhengAnn; Wong, TienTsin; Peng, Qunsheng
    In this paper, we present a novel fairing algorithm for the removal of noise from uniform triangular meshes without shrinkage and serious distortion. The key feature of this algorithm is to keep all triangle centers invariant at each smoothing step by including some constraints in the energy minimization functional. The constrained functional is then minimized efficiently using an iterative method. Further, we apply this smoothing technique to a multiresolution representation to remove arbitrary levels of detail. A volume-preserving decimation algorithm is presented to generate the multiresolution representation. The experimental results demonstrate the combined algorithm's stability and efficiency.
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    Triangle Strip Compression
    (Blackwell Publishers Ltd and the Eurographics Association, 2001) Isenburg, Martin
    In this paper we introduce a simple and efficient scheme for encoding the connectivity and the stripification of a triangle mesh. Since generating a good set of triangle strips is a hard problem, it is desirable to do this just once and store the computed strips with the triangle mesh. However, no previously reported mesh encoding scheme is designed to include triangle strip information into the compressed representation. Our algorithm encodes the stripification and the connectivity in an interwoven fashion, that exploits the correlation existing between the two.
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    Editorial
    (Blackwell Publishers Ltd and the Eurographics Association, 2001)
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    Eurographics
    (Blackwell Publishers Ltd and the Eurographics Association., 2001)
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    Smoothing Normal Vectors on Discrete Surfaces While Preserving Slope Discontinuities
    (Blackwell Publishers Ltd and the Eurographics Association, 2001) Thurmer, Grit
    A new method is proposed which smoothes normal vectors over a discrete surface, preserving slope discontinuities and small details. Assume an estimate of the normal vector at each surface point is known and these estimates are computed from small neighbourhoods such that slope discontinuities and small details are still reflected by these normals. To smooth these normals, the normal vectors at points in a certain neighbourhood are averaged. The size of the neighbourhood considered for the smoothing at a point is adapted according the local surface configuration. The adaptation is performed, depending on the tangent plane at the point considered as well as the angles between the normals at neighbouring points and the normal at the point in question.
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    Adaptive Representation of Specular Light
    (Blackwell Publishers Ltd and the Eurographics Association, 2001) Briere, Normand; Poulin, Pierre
    Caustics produce beautiful and intriguing illumination patterns. However, their complex behavior makes them difficult to simulate accurately in all but the simplest configurations. To capture their appearance, we present an adaptive approach based upon light beams. Exploiting the coherence between the light rays forming a beam greatly reduces the number of samples required for precise illumination reconstruction. The beams characterize the light distribution due to interactions with specular surfaces in 3D space. They thus allow for the treatment of illumination within single-scattering participating media. A hierarchical structure enclosing the light beams possesses inherent properties to detect efficiently all beams reaching any 3D point, to adapt itself according to illumination effects in the final image, and to reduce memory consumption via caching.