VMV12

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

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Visualization of Scene Structure Uncertainty in a Multi-View Reconstruction Pipeline
(The Eurographics Association, 2012) Recker, Shawn; Hess-Flores, Mauricio; Duchaineau, Mark A.; Joy, Kenneth I.; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
This paper presents a novel, interactive visualization tool that allows for the analysis of scene structure uncer- tainty and its sensitivity to parameters in different multi-view scene reconstruction stages. Given a set of input cameras and feature tracks, the volume rendering-based approach first creates a scalar field from angular error measurements. The obtained statistical, visual, and isosurface information provides insight into the sensitivity of scene structure at the stages leading up to structure computation, such as frame decimation, feature tracking, and self-calibration. Furthermore, user interaction allows for such an analysis in ways that have traditionally been achieved mathematically, without any visual aid. Results are shown for different types of camera configurations, where it is discussed for example how over-decimation can be detected using the proposed technique, and how feature tracking inaccuracies have a stronger impact on scene structure than the camera's intrinsic parameters.
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.
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.
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.
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.
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.
Visualization and Exploration of Shape Variance for the Analysis of Cohort Study Data
(The Eurographics Association, 2012) Klemm, Paul; Oeltze, Steffen; Hegenscheid, Katrin; Völzke, Henry; Toennies, Klaus; Preim, Bernhard; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
In epidemiological studies, a group of people with common characteristics or experiences (a cohort) is studied including an analysis of socio-demographic as well as biological factors and correlations indicating per subject the absolute risk of getting a disease. Longitudinal studies are carried out over years or even decades comprising up to thousands of individuals. More recently, such studies include the acquisition of image data such as MRI to answer crucial epidemiological questions. For instance, how is the shape of an anatomical structure related to behavioral or clinical factors, e.g., liver shape related to drinking habits and obesity? We propose a pipeline for shape variance analysis in cohort study data which comprises the definition of groups of individuals and control groups based on socio-demographic and biological factors or attributes derived from the image data as well as the visualization of intra-group shape variance and inter-group shape difference. We employ different shape variance models and investigate the applicability of the pipeline for liver and spine related epidemiological research.
Single-Pass Rendering of Day and Night Sky Phenomena
(The Eurographics Association, 2012) Müller, Daniel; Engel, Juri; Döllner, Jürgen; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
This paper presents astronomical based rendering of skies as seen from low altitudes on earth, in respect to location, date, and time. The technique allows to compose an atmosphere with sun, multiple cloud layers, moon, bright stars, and Milky Way, into a holistic sky with unprecedented high level of detail and diversity. GPU generated, viewpoint-aligned billboards are used to render stars with approximated color, brightness, and scintillations. A similar approach is used to synthesize the moon considering lunar phase, earthshine, shading, and lunar eclipses. Atmosphere and clouds are rendered using existing methods adapted to our needs. Rendering is done in a single pass supporting interactive day-night cycles with low performance impact, and allows for easy integration in existing rendering systems.
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.
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 Preim
We 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.
Resolving Twisted Surfaces within an Iterative Refinement Surface Reconstruction Approach
(The Eurographics Association, 2012) Annuth, Hendrik; Bohn, Christian-A.; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
We present a method which resolves twisted surface regions within a surface reconstruction approach that uses local refinement operations to iteratively fit a surface into an unorganized point cloud. We show that this local operation can be integrated reliably and efficiently, although resolving twisted surfaces is not a local operation since it may cause modifications up to one half of the entire surface. We introduce a novel data structure called the minimal edge front that enables efficiently retrieving topological information from the surface under investigation. Equipped with this operation the algorithm is able to robustly handle huge point-clouds of complex closed and also not closed objects like landscapes.
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.
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 Preim
We 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.
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 Preim
The 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.
Segmentation of Vertebral Bodies in MR Images
(The Eurographics Association, 2012) Zukic, Dzenan; Vlasák, Ales; Dukatz, Thomas; Egger, Jan; Horínek, Daniel; Nimsky, Christopher; Kolb, Andreas; Michael Goesele and Thorsten Grosch and Holger Theisel and Klaus Toennies and Bernhard Preim
Segmentation of vertebral bodies is useful for diagnosis of certain spine pathologies, such as scoliosis, spondylolisthesis and vertebral fractures. In this paper, we present a fast and semi-automatic approach for spine segmentation in routine clinical MR images. Segmenting a single vertebra is based on multiple-feature boundary classification and mesh inflation, and starts with a simple point-in-vertebra initialization. The inflation retains a star-shape geometry to prevent selfintersections and uses a constrained subdivision hierarchy to control smoothness. Analyzing the shape of the first vertebra, the main spine direction is deduced and the locations of neighboring vertebral bodies are estimated for further segmentation. The method was tested on 11 routine lumbar datasets with 92 reference vertebrae resulting in a detection rate of 93%. The average Dice Similarity Coefficient (DSC) against manual reference segmentations was 78%, which is on par with state of the art. The main advantages of our method are high speed and a low amount of user interaction.
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 Preim
Using 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.
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.

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