AbstractÐThis paper introduces a refined general definition of a skeleton that is based on a penalized-distance function and cannot create any of the degenerate cases of the earlier CEASAR and TEASAR algorithms. Additionally, we provide an algorithm that finds the skeleton accurately and rapidly. Our solution is fully automatic, which frees the user from having to engage in manual data preprocessing. We present the accurate skeletons computed on a number of test datasets. The algorithm is very efficient as demonstrated by the running times which were all below seven minutes. Index TermsÐSkeleton, centerline, medial axis, automatic preprocessing, modeling. 1

This thesis describes an online search engine for 3D models, focusing on query interfaces and their corresponding model/query representations and matching methods. A large number of 3D models has already been created, many of which are freely available on the web. Because of the time and e#ort involved in creating a highquality 3D model, considerable resources could be saved if these models could be reused. However, finding the model you need is not easy, since most online models are scattered across the web, on repository sites, project sites, and personal homepages. To make these models more accessible, we have developed a prototype 3D model search engine. This project serves as a test bed for new methods in web crawling, query interfaces, and matching of 3D models. This thesis focuses on query interfaces and their accompanying matching methods. We investigated query interfaces based on text keywords, 3D shape, 2D shape, and some combinations.

. Methods of direct or indirect volume rendering are well established and helpful tools for the interactive visual exploration of volumetric datasets. However, the usual display is oriented on surface information, such as the surface of volumetric objects. The actual volumetric information is difficult to interpret intuitively with solely visual methods. In this paper, we add a haptic cue to improve the intuitive interpretation of volumetric data. Based on segmented volume datasets, we generate several distance fields. One distance field encodes the distance from each voxel -- which belongs to the segmentation -- to the specified surface of the dataset. Another distance field encodes the gradient from a specified starting point to a target point, which is also specified. A local gradient is computed for both distance fields, employing central differences and trilinear interpolation. These gradients are evaluated by a potential field function at the current position. We inte...

Virtual endoscopy is among the most active topics in virtual medicine and medical imaging. It is mostly motivated by recent studies in medicine that suggest that early screening examinations may significantly reduce the risk of serious illnesses (ie., cancer). Some of these examinations require the endoscopic inspection of organs like the colon. While the patients compliance of these uncomfortable procedures is very low, virtual endoscopy methods promise a significantly less unpleasant examination. Other indications for virtual endoscopy are the planning, intra-operative navigation, and training for increasingly difficult minimally-invasive procedures. In this tutorial, the attendees learn about medical imaging and computer-science techniques leveraged for virtual endoscopy, its advantages to traditional methods, but lean also about its specific and inherent limitations. For updates and additional information, see