VMV12

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https://diglib.eg.org/handle/10.2312/1016

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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 Preim
Interpolation 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.
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 Preim
Mirror 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.
Optimized Canonical Coordinate Frames for 3D Object Normalization
(The Eurographics Association, 2012) Martinek, Michael; Grosso, Roberto; Greiner, Günther; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
In this paper, we describe a method to optimize an orthogonal system of axes for 3D objects in order to perform normalization with respect to orientation and scale. An energy function evaluates the quality of a system by considering symmetry, rectilinearity and the origin of the system within the current axis aligned bounding box. Starting with the PCA-axes as initial system, we find a canonical coordinate frame by minimizing the energy in an efficient and elaborate optimization process. We provide a fully automatic normalization pipeline with the possibility to manually set various intuitive parameters in order to influence the outcome. The symmetry part of our energy function uses a combination of plane reflective and rotational symmetries. In this context, we introduce a novel continuous symmetry measure which is entirely implemented on the GPU. The high efficiency of the implementation enables us to find an optimal alignment for 3D objects interactively, making our method suitable even for large 3D databases. We also demonstrate the applicability of our framework for 3D shape matching by approximating the Hausdorff distance for 3D models.
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 Preim
In 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.
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 Preim
The 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.
Spectral Analysis of Higher-Order and BFECC Texture Advection
(The Eurographics Association, 2012) Netzel, Rudolf; Ament, Marco; Burch, Michael; Weiskopf, Daniel; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
We present a spectral analysis of higher-order texture advection in combination with Back and Forth Error Compensation and Correction (BFECC). Semi-Lagrangian texture advection techniques exhibit high numerical diffusion, which acts as a low-pass filter and tends to smooth out high frequencies. In the spatial domain, numerical diffusion leads to a loss of details and causes a blurred image. To reduce this effect, higher-order interpolation methods or BFECC can be employed separately. In this paper, we combine both approaches and analyze the quality of different compositions of higher-order interpolation schemes with and without BFECC. We employ radial power spectrum diagrams for different advection times and input textures to evaluate the conservation of the spectrum up to fifth-order polynomials. Our evaluation shows that third-order backward advection delivers a good compromise between quality and computational costs.
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 Preim
We 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.
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 Preim
In 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.
Registration of Temporal Ultrasonic Image Sequences Using Markov Random Fields
(The Eurographics Association, 2012) Schäfer, Sebastian; Toennies, Klaus; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
Ultrasound perfusion imaging is a rapid and inexpensive technique which enables observation of a dynamic process with high temporal resolution. The image acquisition is disturbed by various motion influences due to the acquisition procedure and patient motion. To extract valid information about perfusion for quantification and diagnostic purposes this influence must be compensated. In this work an approach to account for non-linear motion using a markov random field (MRF) based optimization scheme for registration is presented. Optimal transformation parameters are found all at once in a single optimization framework. Spatial and temporal constraints ensure continuity of a displacement field which is used for image transformation. Simulated datasets with known transformation fields are used to evaluate the presented method and demonstrate the potential of the system. Experiments with patient datasets show that superior results could be achieved compared to a pairwise image registration approach. Furthermore, it is shown that the method is suited to include prior knowledge about the data as the MRF system is able to model dependencies between the parameters of the optimization process.
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 Preim
Understanding 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.
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 Preim
We 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.
Visualizing Solar Dynamics Data
(The Eurographics Association, 2012) Machado, Gustavo M.; Sadlo, Filip; Müller, Thomas; Müller, Daniel; Ertl, Thomas; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
Solar dynamics data, particularly those from the Solar Dynamics Observatory, are now available in a sheer volume that is hard to investigate with traditional visualization tools, which mainly display 2D images. While the challenge of data access and browsing has been solved by web-based interfaces and efforts like the Helioviewer project, the approaches so far only provide 2D visualizations. We introduce the visualization of such data in the full 3D context, providing appropriate coordinate systems and projection techniques. We also apply and extend methods from volume rendering and flow visualization to 3D magnetic fields, which we derive from the sensor data in an interactive process, and introduce space-time visualization of photospheric data. Here, we concentrate on two solar phenomena: the structure and dynamics of coronal loops, and the development of the plasma convection in close vicinity of sunspots over time. Our approach avoids the time-coherence issue inherent in traditional magnetic field line placement, providing insight in the magnetic field and the structure of the coronal plasma. We are convinced that the presented techniques are applicable in many other fields such as the terrestrial magnetospheric physics, or magnetohydrodynamics simulations.
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 Preim
A 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.
Visualizing Dynamic Call Graphs
(The Eurographics Association, 2012) Burch, Michael; Müller, Christoph; Reina, Guido; Schmauder, Hansjoerg; Greis, Miriam; Weiskopf, Daniel; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
Visualizing time-varying call graphs is challenging due to vast amounts of data at many dimensions to be displayed: Hierarchically organized vertices with attributes, directed or undirected edges with weights, and time. In this paper, we introduce a novel overview representation that shows dynamic graphs as a timeline- and pixelbased aggregated view targeting the preservation of a viewer's mental map by encoding the time-varying data into a static diagram. This view allows comparisons of dynamic call graphs on different levels of hierarchical granularity. Our data extraction and visualization system uses this overview as a starting point for further investigations by applying existing dynamic graph visualization techniques that show the graph structures and properties more clearly. These more task-specific visualizations show the dynamic graph data from different perspectives such as curved node-link diagrams or glyph-based representations combined by linking and brushing. Intermediate analysis steps can be stored and rebuilt at any time by using corresponding thumbnail representations.
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 Preim
Parallel 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.
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 Preim
We 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.
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 Preim
In 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.
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 Preim
In 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.
Screen Space Spherical Harmonic Occlusion
(The Eurographics Association, 2012) Herholz, Sebastian; Schairer, Timo; Schilling, Andreas; Straßer, Wolfgang; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
In this paper we present a new algorithm for real-time directional occlusion sampling. We combine the real-time capabilities of Screen Space Ambient Occlusion (SSAO) with the Spherical Harmonics (SH) representation of local directional occlusion. SH are well established and used in modern off-line rendering implementations such as PantaRay [PFHA10]. Through our combination we are able to transfer a method for realistic local directional occlusion effects from offline rendering to dynamic real-time applications. These local occlusion effects react to the environmental lighting situation and lead to dynamic and colored local occlusion shadows while only generating a small computational overhead compared to SSAO. Unlike other real-time directional occlusion algorithms such as Screen Space Direction Occlusion (SSDO) [RGS09] our occlusion sampling is separated from the actual lighting process and therefore can be easily integrated in existing SH lighting methods such as Irradiance Volumes [GSHG98]. We furthermore extend our algorithm to include first bounce indirect illumination effects.
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 Preim
Recent 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.

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