VMV12
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Item 3D Shape Matching based on Geodesic Distance Distributions(The Eurographics Association, 2012) Martinek, Michael; Ferstl, Matthias; Grosso, Roberto; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimIn this work, we present a signature for 3D shapes which is based on the distribution of geodesic distances. Our shape descriptor is invariant with respect to rotation and scaling as well as articulations of the object. It consists of shape histograms which reflect the geodesic distance distribution of randomly chosen pairs of surface points as well as the distribution of geodesic eccentricity and centricity. We show, that a combination of these shape histograms provides good discriminative power to find similar objects in 3D databases even if they are differently articulated. In order to improve the efficiency of the feature extraction, we employ a fast voxelization method and compute the geodesic distances on a boundary voxel representation of the objects.Item Adaptive Treelet Meshes for Efficient Streak-Surface Visualization on the GPU(The Eurographics Association, 2012) Fuchs, Raphael; Schindler, Benjamin; Carnecky, Robert; Waser, Jürgen; Yang, Yun; Peikert, Ronny; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimWe describe a novel adaptive mesh representation for streak-surfaces. The surface is represented as a mesh of small trees of initial depth zero (treelets). This mesh representation allows for efficient integration, refinement, coarsening and appending of surface patches utilizing the computational capacities of modern GPUs. Integration, refinement, and rendering are strictly separated into effectively parallelizable substeps of the streak-surface integration algorithm. We also describe a sampler framework which unifies the handling of different vector field representations.Item Analysis of Vortex Merge Graphs(The Eurographics Association, 2012) Kasten, Jens; Zoufahl, Andre; Hege, Hans-Christian; Hotz, Ingrid; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimWe propose an analysis framework to investigate different flow quantities such as vorticity, λ<sub>2</sub> or the acceleration magnitude along vortex merge graphs and within their regions of influence. The explicit extraction of vortex merge graphs enables the application of statistical tools to investigate the vortex core lines themselves. The analysis tool provides common plots as scatter plots and parallel coordinates to explore the correlation of different quantities. An abstract representation of the vortex merge graph highlights birth, death and merges of vortices. Interactive picking of substructures supports a closer insepection of single vortices and their evolution. A further step integrates the regions of influence into the statistical analysis. Minima, maxima, median, mean and other percentiles of the measures along the vortex merge graph and its regions are visualized. The usability of the framework is demonstrated using a simulated flow data set of a mixing layer and a jet.Item Automatic Detection and Recognition of Engineered Nanoparticles in SEM Images(The Eurographics Association, 2012) Kockentiedt, Stephen; Toennies, Klaus; Gierke, Erhardt; Dziurowitz, Nico; Thim, Carmen; Plitzko, Sabine; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimEngineered nanoparticles have gained importance in recent years and will do so in the future, but their potential toxicity remains an open question. To better understand their effects on the human body, it is necessary to determine their concentration in ambient air. We propose a method to automatically detect nanoparticles in SEM images and differentiate engineered particles from other particles common in ambient air. The method reached Gmeans of 0.985, 0.779 and 0.820 for the classification against non-engineered particles of silver, titanium dioxide and zinc oxide respectively. This is comparable to manual classification.Item Cyclic Numerical Time Integration in Variational Non-Rigid Image Registration based on Quadratic Regularisation(The Eurographics Association, 2012) Mang, Andreas; Schuetz, Tina Anne; Becker, Stefan; Toma, Alina; Buzug, Thorsten M.; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimIn the present work, a novel computational framework for variational non-rigid image registration is discussed. The fundamental aim is to provide an alternative to approximate approaches based on successive convolution, which have gained great popularity in recent years, due to their linear complexity and ease of implementation. An optimise-then-discretise framework is considered. The corresponding Euler-Lagrange equations (ELEs), which arise from calculus of variation, constitute a necessary condition for a minimiser of the variational optimisation problem. The conventional, semi-implicit (SI) time integration for the solution of the ELEs is replaced by an explicit approach rendering the implementation straightforward. Since explicit methods are subject to a restrictive stability requirement on the maximal admissible time step size, they are in general inefficient and prone to get stuck in local minima. As a remedy, we take advantage of methods based on cyclic explicit numerical time integration. With this the strong stability requirement on each individual time step can be replaced by a relaxed stability requirement. This in turn results in an unconditionally stable method, which is as efficient as SI approaches. As a basis of comparison, SI methods are considered. Generalisability is demonstrated within a generic variational framework based on quadratic regularisation. Qualitative and quantitative analysis of numerical experiments based on synthetic test data demonstrates accuracy and efficiency.Item Design and Fabrication of Faceted Mirror Arrays for Light Field Capture(The Eurographics Association, 2012) Fuchs, Martin; Kächele, Markus; Rusinkiewicz, Szymon; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimThe high resolution of digital cameras has made single-shot, single-sensor acquisition of light fields feasible, though considerable design effort is still necessary in order to construct the necessary collection of optical elements for particular acquisition scenarios. This article explores a pipeline for designing, fabricating, and utilizing faceted mirror arrays which simplifies this task. The foundation of the pipeline is an interactive tool that automatically optimizes for mirror designs while exposing to the user a set of intuitive parameters for light field quality and manufacturing constraints. We investigate two manufacturing processes for automatic fabrication of the resulting designs: one is based on CNC milling, polishing, and plating of one solid work piece, while the other involves assembly of precision cut mirror facets. We demonstrate results for refocusing in a macro photography scenario.Item An Efficient Trim Structure for Rendering Large B-Rep Models(The Eurographics Association, 2012) Claux, Frédéric; Vanderhaeghe, David; Barthe, Loïc; Paulin, Mathias; Jessel, Jean-Pierre; Croenne, David; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimWe present a multiresolution trim structure for fast and accurate B-Rep model visualization. To get a good tradeoff between performance and visual accuracy, we propose to use a vectorial but approximated representation of the model that allows efficient, real-time GPU exploitation. Our structure, based on a quadtree, enables us to do shallow lookups for distant fragments. For closeups, we leverage hardware tessellation. We get interactive frame rates for models that consists of hundreds of thousands of B-Rep faces, regardless of the zoom level.Item Fast Accurate Soft Shadows with Adaptive Light Source Sampling(The Eurographics Association, 2012) Schwärzler, Michael; Mattausch, Oliver; Scherzer, Daniel; Wimmer, Michael; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimPhysically accurate soft shadows in 3D applications can be simulated by taking multiple samples from all over the area light source and accumulating them. Due to the unpredictability of the size of the penumbra regions, the required sampling density has to be high in order to guarantee smooth shadow transitions in all cases. Hence, several hundreds of shadow maps have to be evaluated in any scene configuration, making the process computationally expensive. Thus, we suggest an adaptive light source subdivision approach to select the sampling points adaptively. The main idea is to start with a few samples on the area light, evaluating there differences using hardware occlusion queries, and adding more sampling points if necessary. Our method is capable of selecting and rendering only the samples which contribute to an improved shadow quality, and hence generate shadows of comparable quality and accuracy. Even though additional calculation time is needed for the comparison step, this method saves valuable rendering time and achieves interactive to real-time frame rates in many cases where a brute force sampling method does not.Item Fast and Robust Landmark Tracking in X-ray Locomotion Sequences Containing Severe Occlusions(The Eurographics Association, 2012) Amthor, Manuel; Haase, Daniel; Denzler, Joachim; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimRecent advances in the understanding of animal locomotion have proven it to be a key element of many fields in biology, motion science, and robotics. For the analysis of walking animals, high-speed x-ray videography is employed. For a biological evaluation of these x-ray sequences, anatomical landmarks have to be located in each frame. However, due to the motion of the animals, severe occlusions complicate this task and standard tracking methods can not be applied. We present a robust tracking approach which is based on the idea of dividing a template into sub-templates to overcome occlusions. The difference to other sub-template approaches is that we allow soft decisions for the fusion of the single hypotheses, which greatly benefits tracking stability. Also, we show how anatomical knowledge can be included into the tracking process to further improve the performance. Experiments on real datasets show that our method achieves results superior to those of existing robust approaches.Item Generating Smooth High-Quality Isosurfaces for Interactive Modeling and Visualization of Complex Terrains(The Eurographics Association, 2012) Löffler, Falko; Schumann, Heidrun; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimIn modeling and rendering of complex procedural terrains the extraction of isosurfaces is an important part. In this paper we introduce an approach to generate high-quality isosurfaces from regular grids at interactive frame rates. The surface extraction is a variation of Dual Marching Cubes and designed as a set of well-balanced parallel computation kernels. In contrast to a straightforward parallelization we generate a quadrilateral mesh with full connectivity information and 1-ring vertex neighborhood. We use this information to smooth the extracted mesh and to approximate the smooth subdivision surface for detail tessellation. Both improve the visual fidelity when modeling procedural terrains interactively. Moreover, our extraction approach is generally applicable, for example in the field of volume visualization.Item GPU-accelerated Interactive Material Aging(The Eurographics Association, 2012) Günther, Tobias; Rohmer, Kai; Grosch, Thorsten; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimA photorealistic appearance of a 3D scene is required in many applications today. Thereby, one vital aspect is the usage of realistic materials, for which a broad variety of reflectance models is available. When directly employing those models, surfaces always look new, which contrasts strongly the real objects surrounding us as they have undergone diverse kinds of aging processes. The literature already proposes a set of viable methods to simulate different aging phenomena, but all of them are computationally expensive and can thus only be computed off-line. Therefore, this paper presents the first interactive, GPU-accelerated method to simulate material aging in a given scene. Thereby, our approach allows artists to precisely control the course of the aging process. Our particlebased method is capable to reproduce the most common deterioration phenomena in a few seconds, including plausible dirt bleeding, flow effects, corrosion and patina.Item The Great Wall of Space-Time(The Eurographics Association, 2012) Tominski, Christian; Schulz, Hans-Joerg; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimUnderstanding how data evolves in space and time is an essential task in many application domains. Despite the numerous visual methods that have been proposed to facilitate this task (e.g., showing the data on a map or plotting a time graph), the exploration of data with references to space and time still remains challenging. In this work, we present a novel concept for visualizing spatio-temporal data that refer to 2D geographical space and 1D linear time. The idea is to construct a non-planar slice - called the Great Wall of Space-Time - through the 3D (2D+1D) space-time continuum. Different visual representations can be projected onto the wall in order to display the data. We illustrate data visualizations based on color-coding and parallel coordinates. Compared to existing approaches, the wall has the advantage that it shows a closed path through space with no gaps between the information-bearing pixels on the screen. Hence, our novel visualization has the potential to be a useful addition to the user's toolbox of techniques for exploring the spatial and temporal evolution of data.Item Hybrid Sample-based Surface Rendering(The Eurographics Association, 2012) Reichl, Florian; Chajdas, Matthäus G.; Bürger, Kai; Westermann, Rüdiger; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimThe performance of rasterization-based rendering on current GPUs strongly depends on the abilities to avoid overdraw and to prevent rendering triangles smaller than the pixel size. Otherwise, the rates at which highresolution polygon models can be displayed are affected significantly. Instead of trying to build these abilities into the rasterization-based rendering pipeline, we propose an alternative rendering pipeline implementation that uses rasterization and ray-casting in every frame simultaneously to determine eye-ray intersections. To make ray-casting competitive with rasterization, we introduce a memory-efficient sample-based data structure which gives rise to an efficient ray traversal procedure. In combination with a regular model subdivision, the most optimal rendering technique can be selected at run-time for each part. For very large triangle meshes our method can outperform pure rasterization and requires a considerably smaller memory budget on the GPU. Since the proposed data structure can be constructed from any renderable surface representation, it can also be used to efficiently render isosurfaces in scalar volume fields. The compactness of the data structure allows rendering from GPU memory when alternative techniques already require exhaustive paging.Item Illumination-Driven Opacity Modulation for Expressive Volume Rendering(The Eurographics Association, 2012) Csébfalvi, Balázs; Tóth, Balázs; Bruckner, Stefan; Gröller, Eduard; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimUsing classical volume visualization, typically a couple of isosurface layers are rendered semi-transparently to show the internal structures contained in the data. However, the opacity transfer function is often difficult to specify such that all the isosurfaces are of high contrast and sufficiently perceivable. In this paper, we propose a volumerendering technique which ensures that the different layers contribute to fairly different regions of the image space. Since the overlapping between the effected regions is reduced, an outer translucent isosurface does not decrease significantly the contrast of a partially hidden inner isosurface. Therefore, the layers of the data become visually well separated. Traditional transfer functions assign color and opacity values to the voxels depending on the density and the gradient. In contrast, we assign also different illumination directions to different materials, and modulate the opacities view-dependently based on the surface normals and the directions of the light sources, which are fixed to the viewing angle. We will demonstrate that this model allows an expressive visualization of volumetric data.Item Implicit Integral Surfaces(The Eurographics Association, 2012) Stöter, Torsten; Weinkauf, Tino; Seidel, Hans-Peter; Theisel, Holger; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimWe present an implicit method for globally computing all four classic types of integral surfaces - stream, path, streak, and time surfaces - in 3D time-dependent vector fields. Our novel formulation is based on the representation of a time surface as implicit isosurface of a 3D scalar function advected by the flow field. The evolution of a time surface is then given as an isovolume in 4D space-time spanned by a series of advected scalar functions. Based on this, the other three integral surfaces are described as the intersection of two isovolumes derived from different scalar functions. Our method uses a dense flow integration to compute integral surfaces globally in the entire domain. This allows to change the seeding structure efficiently by simply defining new isovalues. We propose two rendering methods that exploit the implicit nature of our integral surfaces: 4D raycasting, and projection into a 3D volume. Furthermore, we present a marching cubes inspired surface extraction method to convert the implicit surface representation to an explicit triangle mesh. In contrast to previous approaches for implicit stream surfaces, our method allows for multiple voxel intersections, covers all regions of the flow field, and provides full control over the seeding line within the entire domain.Item Interactive Geometry-Aware Segmentation for the Decomposition of Kaleidoscopic Images(The Eurographics Association, 2012) Klehm, Oliver; Reshetouski, Ilya; Eisemann, Elmar; Seidel, Hans-Peter; Ihrke, Ivo; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimMirror systems have recently emerged as an alternative low-cost multi-view imaging solution. The use of these systems critically depends on the ability to compute the background of a multiply mirrored object. The images taken in such systems show a fractured, patterned view, making edge-guided segmentation difficult. Further, global illumination and light attenuation due to the mirrors make standard segmentation techniques fail. We therefore propose a system that allows a user to do the segmentation manually. We provide convenient tools that enable an interactive segmentation of kaleidoscopic images containing three-dimensional objects. Hereby, we explore suitable interaction and visualization schemes to guide the user. To achieve interactivity, we employ the GPU in all stages of the application, such as 2D/3D rendering as well as segmentation.Item Juggling Increases Interhemispheric Brain Connectivity: A Visual and Quantitative dMRI Study(The Eurographics Association, 2012) Schultz, Thomas; Gerber, Peter; Schmidt-Wilcke, Tobias; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimWe use visualization to help analyze a diffusion magnetic resonance imaging study that has investigated the effects of learning how to juggle on nerve fiber microstructure in the human brain. Building on a standard voxel-wise statistical analysis, we perform a more elaborate visual analysis of the affected fiber bundles. Based on the visualization, we hypothesize that brain image data allows us to distinguish learners from controls with better-thanrandom accuracy; we test this hypothesis with a machine learning technique. We believe that our results exemplify the value of more tightly integrating statistical with visual analysis and machine learning in brain imaging studies, in order to complement the group-wise view of traditional analysis with insights about specific individuals.Item Kinematic ICP for Articulated Template Fitting(The Eurographics Association, 2012) Fechteler, Philipp; Hilsmann, Anna; Eisert, Peter; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimIn this paper, we present an efficient optimization method to adapt an articulated 3D template model to a full or partial 3D mesh. The well-known ICP algorithm is enhanced to fit a generic template to a target mesh. Each iteration jointly refines the parameters for global rigid alignment, uniform scale as well as the rotation parameters of all joint angles. The articulated 3D template model is based on the publicly available SCAPE data set, enhanced with automatically learned rotation centers of the joints and Linear Blend Skinning weights for each vertex. In two example applications we demonstrate the effectiveness of this computationally efficient approach: pose recovery from full meshes and pose tracking from partial depth maps.Item Markov Chain Driven Multi-Dimensional Visual Pattern Analysis with Parallel Coordinates(The Eurographics Association, 2012) Geng, Zhao; Walker, James; Laramee, Robert S.; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimParallel coordinates is a widely used visualization technique for presenting, analyzing and exploring multidimensional data. However, like many other visualizations, it can suffer from an overplotting problem when rendering large data sets. Until now, quite a few methods are proposed to discover and illustrate the major data trends in cluttered parallel coordinates. Among them, frequency-based approaches using binning and histograms are widely adopted. The traditional binning method, which records line-segment frequency, only considers data in a two-dimensional subspace, as a result, the multi-dimensional features are not taken into account for trend and outlier analysis. Obtaining a coherent binned representation in higher dimensions is challenging because multidimensional binning can suffer from the curse of dimensionality. In this paper, we utilize the Markov Chain model to compute an n-dimensional joint probability for each data tuple based on a two-dimensional binning method. This probability value can be utilized to guide the user for selection and brushing. We provide various interaction techniques for the user to control the parameters during the brushing process. Filtered data with a high probability measure often explicitly illustrates major data trends. In order to scale to large data sets, we also propose a more precise angular representation for angular histograms to depict the density of the brushed data trends. We demonstrate our methods and evaluate the results on a wide variety of data sets, including real-world, high-dimensional biological data.Item A Mixed Shape Space for Fast Interpolation of Articulated Shapes(The Eurographics Association, 2012) Marras, Stefano; Cashman, Thomas J.; Hormann, Kai; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard PreimInterpolation between compatible triangle meshes that represent different poses of some object is a fundamental operation in geometry processing. A common approach is to consider the static input shapes as points in a suitable shape space and then use simple linear interpolation in this space to find an interpolated shape. In this paper, we present a new interpolation technique that is particularly tailored for meshes that represent articulated shapes. It is up to an order of magnitude faster than state-of-the-art methods and gives very similar results. To achieve this, our approach introduces a novel space shape that takes advantage of the underlying structure of articulated shapes and distinguishes between rigid parts and non-rigid joints. This allows us to use fast vertex interpolation on the rigid parts and resort to comparatively slow edge-based interpolation only for the joints.