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Item 3D Scene Comparison using Topological Graphs(The Eurographics Association, 2007) Paraboschi, L.; Biasotti, S.; Falcidieno, B.; Raffaele De Amicis and Giuseppe ContiNew technologies for shape acquisition and rendering of digital shapes have simplified the process of creating virtual scenes; nonetheless, shape annotation, recognition and manipulation of both the complete virtual scenes and even of subparts of them are still open problems. In this paper we deal with the problem of comparing two (or more) object sets, where each model is represented by an attributed graph. We will define a new distance to estimate the possible similarities among the sets of graphs and will validate our work using the shape graph [BGSF06].Item Volume Deformation via Scattered Data Interpolation(The Eurographics Association, 2007) Correa, Carlos D.; Silver, Deborah; Chen, Min; H.-C. Hege and R. Machiraju and T. Moeller and M. SramekWith the advent of contemporary GPUs, it has been possible to perform volume deformation at interactive rates. In particular, it has been shown that deformation can be important for the purposes of illustration. In such cases, rather than being the result of a physically-based simulation, volume deformation is often goal-oriented and user-guided. For this purpose, it is important to provide the user with tools for directly specifying a deformation interactively and refine it based on constraints or user intention. In many cases, deformation is obtained based on a reference object or image. In this paper, we present a method for deforming volumetric objects based on user guided scattered data interpolation. A GPU-based implementation enables real-time manipulation of 2D images and volumes. We show how this approach can have applications in scientific illustration, volume exploration and visualization, generation of animations and special effects, among others.Item The Aesthetics of Graph Visualization(The Eurographics Association, 2007) Bennett, Chris; Ryall, Jody; Spalteholz, Leo; Gooch, Amy; Douglas W. Cunningham and Gary Meyer and Laszlo NeumannThe discipline of graph visualization produces pictorial representations of node link structures. Much effort has been directed toward making such diagrams visually pleasing. A variety of aesthetic heuristics have been proposed, with the assumption that these will improve readability and understanding. We look at a perceptual basis for these heuristics, including Gestalt principles and Norman s emotional design framework. Next, we review the work to date on aesthetic heuristics and examine what has been done to evaluate these heuristics. We summarize this in a framework that outlines graph drawing heuristics, their perceptual basis, and evaluation status.Item GPU-assisted Positive Mean Value Coordinates for Mesh Deformations(The Eurographics Association, 2007) Lipman, Yaron; Kopf, Johannes; Cohen-Or, Daniel; Levin, David; Alexander Belyaev and Michael GarlandIn this paper we introduce positive mean value coordinates (PMVC) for mesh deformation. Following the observations of Joshi et al. [JMD*07] we show the advantage of having positive coordinates. The control points of the deformation are the vertices of a "cage" enclosing the deformed mesh. To define positive mean value coordinates for a given vertex, the visible portion of the cage is integrated over a sphere. Unlike MVC [JSW05], PMVC are computed numerically. We show how the PMVC integral can be efficiently computed with graphics hardware. While the properties of PMVC are similar to those of Harmonic coordinates [JMD*07], the setup time of the PMVC is only of a few seconds for typical meshes with 30K vertices. This speed-up renders the new coordinates practical and easy to use.Item Bringing the Semantics into Digital Shapes: the AIM@SHAPE Approach(The Eurographics Association, 2007) Falcidieno, Bianca; Raffaele De Amicis and Giuseppe ContiThis presentation describes the main objectives and achievements of the European Network of Excellence AIM@SHAPE. This NoE is aimed to advance research in the direction of semantic-based shape representations and tools able to acquire, build, transmit and process shapes with their associated knowledge. Acting on a multi-disciplinary research field, AIM@SHAPE deeply integrates geometry processing, computer graphics and vision with knowledge technologies. The core of the integration resides in the homogenisation of the approach to modelling shapes and their associated semantics using knowledge formalisation mechanisms: metadata and ontology. A main objective is also to develop an innovative e-science platform for modelling, processing and sharing digital shapes, called the Digital Shape Workbench (DSW). Through the definition of general and specific shape ontologies, the DSW is a framework able to store shapes, tools, and publications along with the knowledge related to them.Item Bayesian Surface Reconstruction via Iterative Scan Alignment to an Optimized Prototype(The Eurographics Association, 2007) Huang, Qi-Xing; Adams, Bart; Wand, Michael; Alexander Belyaev and Michael GarlandThis paper introduces a novel technique for joint surface reconstruction and registration. Given a set of roughly aligned noisy point clouds, it outputs a noise-free and watertight solid model. The basic idea of the new technique is to reconstruct a prototype surface at increasing resolution levels, according to the registration accuracy obtained so far, and to register all parts with this surface. We derive a non-linear optimization problem from a Bayesian formulation of the joint estimation problem. The prototype surface is represented as a partition of unity implicit surface, which is constructed from piecewise quadratic functions defined on octree cells and blended together using B-spline basis functions, allowing the representation of objects with arbitrary topology with high accuracy. We apply the new technique to a set of standard data sets as well as especially challenging real-world cases. In practice, the novel prototype surface based joint reconstruction-registration algorithm avoids typical convergence problems in registering noisy range scans and substantially improves the accuracy of the final output.Item An Immersive Granular Material Visualization System with Haptic Feedback(The Eurographics Association, 2007) Dorjgotov, Enkhtuvshin; Benes, Bedrich; Madhavan, Krishna; Ik Soo Lim and David DuceRecent advances in distributed virtual reality systems and haptic technologies provide new opportunities to augment human sense of touch into highly complex and immersive visual simulations. Haptic feedback further enhances human immersion into virtual environments. We present techniques for portable and distributed rendering of real-time active and passive stereo views of virtual granular material that allow real-time haptic interaction and visualization. The main goal of the research was to develop highly portable and immersive virtual reality system that provides intuitive haptic interactions between a user and the granular material in several VR configurations. We developed real-time haptic enabled virtual sand rendering system for high-end VR systems, a FLEX (CAVETM-like display from Fakespace Systems), a high resolution tiled-wall display, comparatively low cost portable VR system that consists of two projectors with two horizontally and vertically polarizing filters, and the Disney projection screen. Our system has a distributed rendering architecture where a server computer is dedicated to haptic interaction force rendering and client computers are dedicated to a visual rendering of granular surface. Interconnection between the haptic and visual rendering programs is realized through a stream based TCP/IP communication. We report the architecture and implementation details of this highly portable and haptic force feedback enabled virtual reality system for interactive granular surface manipulation in this paper.Item Priority Streamlines: A context-based Visualization of Flow Fields(The Eurographics Association, 2007) Schlemmer, Michael; Hotz, Ingrid; Hamann, Bernd; Morr, Florian; Hagen, Hans; K. Museth and T. Moeller and A. YnnermanFlow vector fields contain a wealth of information that needs to be visualized. As an extension of the well-known streamline technique, we have developed a context-based method for visualizing steady flow vector fields in two and three dimensions. We call our method "Priority Streamlines". In our approach, the density of the streamlines is controlled by a scalar function that can be user-defined, or be given by additional information (e.g., temperature, pressure, vorticity, velocity) considering the underlying flow vector field. In regions, which are interesting the streamlines are drawn with increased density, while less interesting regions are drawn sparsely. Since streamlines in the most important regions are drawn first, we can use thresholding to obtain a streamline representation highlighting essential features. Color-mapping and transparency can be used for visualizing other information hidden in the flow vector field.Item Stipple Placement using Distance in a Weighted Graph(The Eurographics Association, 2007) Mould, David; Douglas W. Cunningham and Gary Meyer and Laszlo NeumannWe present a stipple placement method which provides extra emphasis to image features, especially edges. Our algorithm transforms an image into a regular graph, with edge weights given by the local gradient magnitude of the input image. Then, a variant of Disjkstra s algorithm is used to place stipples: new stipples are placed along the frontier, which tends to be aligned with image edges. The resulting stipple distribution approximates a blue noise distribution, but emphasizes edges from the input image. We also show how irregular mosaics can be organized and the mosaic tiles shaped using the same underlying mechanism.