EG UK Theory and Practice of Computer Graphics 2012

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https://diglib.eg.org/handle/10.2312/907

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Browsing EG UK Theory and Practice of Computer Graphics 2012 by Subject "and object representations"

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    Computing Curve Skeletons from Medial Surfaces of 3D Shapes
    (The Eurographics Association, 2012) Telea, Alexandru; Jalba, Andrei C.; Hamish Carr and Silvester Czanner
    Skeletons are powerful shape descriptors with many applications in shape processing, reconstruction and matching. In this paper we show that in 3D, curve skeletons can be extracted from surface skeletons in the same manner as surface skeletons can be computed from 3D object representations. Thus, the curve skeleton is conceptually the result of a recursion applied twice to a given 3D shape. To compute them, we propose an explicit advection of the surface skeleton in the implicitly-computed gradient of its distance-transform field. Through this process, surface skeleton points collapse into the sought curve skeleton. As a side result, we show how to reconstruct accurate and smooth surface skeletons from point-cloud representations thereof. Finally, we compare our method to existing state-of-the-art approaches.
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    Visualizing a Spherical Geological Discrete Element Model of Fault Evolution
    (The Eurographics Association, 2012) Longshaw, Stephen M.; Turner, Martin J.; Finch, Emma; Hamish Carr and Silvester Czanner
    Discrete Element Modelling (DEM) is a numerical technique that uses a system of interacting discrete bodies to simulate the movement of material being exposed to external forces. This technique is often used to simulate granular systems; however by adding further elements that inter-connect the bodies, it can be used to simulate the deformation of a large volume of material. This method has precedent for use in the Earth Sciences and recently, with the increase of available computing power, it has been put to good use simulating the evolution of extensional faults in large scale crustal experiments that involve over half a million individual spherical bodies. An interactive environment that provides high quality rendering is presented, showing that interactivity is key in allowing the intelligent application of visualization methods such as colour-mapping and visibility thresholds in order to extract fault information from a geological DEM. It is also shown that glyph representation alone is not sufficient to provide full insight into the complex three dimensional geometries of the faults found within the model. To overcome this, a novel use of the MetaBall method is described, which results in implicit surface representations of sphere sub-sets. The surfaces produced are shown to provide greater insight into the faults found within the data but also raise questions as to their meaning.