VMV11

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https://diglib.eg.org/handle/10.2312/1015

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Markerless Motion Capture using multiple Color-Depth Sensors
(The Eurographics Association, 2011) Berger, Kai; Ruhl, Kai; Schroeder, Yannic; Bruemmer, Christian; Scholz, Alexander; Magnor, Marcus; Peter Eisert and Joachim Hornegger and Konrad Polthier
With the advent of the Microsoft Kinect, renewed focus has been put on monocular depth-based motion capturing. However, this approach is limited in that an actor has to move facing the camera. Due to the active light nature of the sensor, no more than one device has been used for motion capturing so far. In effect, any pose estimation must fail for poses occluded to the depth camera. Our work investigates on reducing or mitigating the detrimental effects of multiple active light emitters, thereby allowing motion capture from all angles. We systematically evaluate the concurrent use of one to four Kinects, including calibration, error measures and analysis, and present a time-multiplexing approach.
Partial Symmetry Detection in Volume Data
(The Eurographics Association, 2011) Kerber, Jens; Wand, Michael; Krüger, Jens; Seidel, Hans-Peter; Peter Eisert and Joachim Hornegger and Konrad Polthier
In this paper, we present an algorithm for detecting partial Euclidean symmetries in volume data. Our algorithm finds subsets in voxel data that map to each other approximately under translations, rotations, and reflections. We implement the search for partial symmetries efficiently and robustly using a feature-based approach: We first reduce the volume to salient line features and then create transformation candidates from matching only local configurations of these line networks. Afterwards, only a shortlist of transformation candidates need to be verified using expensive dense volume matching. We apply our technique on both synthetic test scenes as well as real CT scans and show that we can recover a large amount of partial symmetries for complexly structured volume data sets.
Pose Correction by Space-Time Integration
(The Eurographics Association, 2011) Esturo, Janick Martinez; Rössl, Christian; Fröhlich, Stefan; Botsch, Mario; Theisel, Holger; Peter Eisert and Joachim Hornegger and Konrad Polthier
The deformation of a given model into different poses is an important problem in computer graphics and computer animation. In a typical workflow, a carefully designed reference surface is deformed into a couple of poses, which can then act as a basis for interpolating arbitrarily intermediate poses. To this end the input poses should be free of geometric artifacts like self-intersections, since these degeneracies will be reproduced or even amplified by the interpolation. Not only are the resulting artifacts visually disturbing, they typically cause severe numerical problems for further downstream applications. In this paper we present an automatic approach for removing these geometric artifacts from a given set of mesh poses, while maintaining the original mesh connectivity. The deformation from the rest pose to a target pose is faithfully reproduced by integration of a smooth space-time vector field, which by construction guarantees the absence of self-intersections in the repaired target pose. Our approach is computationally efficient, and its effectiveness is demonstrated on a range of typical animation examples.
FreeCam: A Hybrid Camera System for Interactive Free-Viewpoint Video
(The Eurographics Association, 2011) Kuster, Claudia; Popa, Tiberiu; Zach, Christopher; Gotsman, Craig; Gross, Markus; Peter Eisert and Joachim Hornegger and Konrad Polthier
We describe FreeCam - a system capable of generating live free-viewpoint video by simulating the output of a virtual camera moving through a dynamic scene. The FreeCam sensing hardware consists of a small number of static color video cameras and state-of-the-art Kinect depth sensors, and the FreeCam software uses a number of advanced GPU processing and rendering techniques to seamlessly merge the input streams, providing a pleasant user experience. A system such as FreeCam is critical for applications such as telepresence, 3D video-conferencing and interactive 3D TV. FreeCam may also be used to produce multi-view video, which is critical to drive newgeneration autostereoscopic lenticular 3D displays.
Interactive Exploration of Polymer-Solvent Interactions
(The Eurographics Association, 2011) Thomaß, Bertram; Walter, Jonathan; Krone, Michael; Hasse, Hans; Ertl, Thomas; Peter Eisert and Joachim Hornegger and Konrad Polthier
The interaction of three-dimensional linked hydrophilic polymers with surrounding solvents in time-dependent data sets is of great interest for domain experts and current research in molecular dynamics. These polymers are called hydrogels, and their most characteristic property is their swelling in aqueous solutions by absorbing the solvent. Their conformation transition can be studied by investigations of the interaction of the single polymer strand and the solvent directly around the polymer at an atomistic level. We present new visualization techniques to interactively study time-dependent data sets from molecular dynamics simulations-with special regard to polymer-solvent interactions like local concentrations and hydrogen bonds-as well as filtering methods to facilitate analysis. Such methods that visualize polymer-solvent interactions on a hydration shell around a polymer are not available in current tools and can greatly facilitate the visual analysis, which helps domain experts to extract additional information about hydrogel characteristics and gain new insights from the simulation results. While our visual analysis methods presented in this paper clearly facilitate the analysis of hydrogels and lead to new insight, the presented concepts are applicable to other domains like proteins or polymers in general that interact with solvents.
A View-Dependent and Inter-Frame Coherent Visualization of Integral Lines using Screen Contribution
(The Eurographics Association, 2011) Günther, Tobias; Bürger, Kai; Westermann, Rüdiger; Theisel, Holger; Peter Eisert and Joachim Hornegger and Konrad Polthier
In vector field visualization, integral lines like stream, path, or streak lines are often used to examine the behavior of steady and unsteady flows. In 3D, however, visualizing integral lines is problematic since the resulting geometric structures cause occlusions, often hiding relevant features in the data. For this reason one important goal is to find a minimum number of lines which can represent all relevant features in the vector field. In this paper we propose a novel approach that reduces the number of displayed lines, and occlusions thereof, by smoothly fading out lines based on their contribution to the viewport. In order to reduce visual clutter that is introduced by rendering multiple line contribution into one pixel, the blending equation is slightly modified. In addition, an interactive brushing is applied to further support exploration. Our approach attains a view-dependent visualization of integral lines that is inter-frame coherent and achieves real-time frame rates. To demonstrate the effectiveness and efficiency of our approach, we pursued a number of tests using real-world steady and unsteady vector fields.
Koiter's Thin Shells on Catmull-Clark Limit Surfaces
(The Eurographics Association, 2011) Wawrzinek, Anna; Hildebrandt, Klaus; Polthier, Konrad; Peter Eisert and Joachim Hornegger and Konrad Polthier
We present a discretization of Koiter's model of elastic thin shells based on a finite element that employs limit surfaces of Catmull Clark's subdivision scheme. The discretization can directly be applied to control grids of Catmull Clark subdivision surfaces, and, therefore, integrates modeling of Catmull Clark subdivision surfaces with analysis and optimization of elastic thin shells. To test the discretization, we apply it to standard examples for physical simulation of thin shells and compute free vibration modes of thin shells. Furthermore, we use the discrete shell model to set up a deformation-based modeling system for Catmull Clark subdivision surfaces. This system integrates modeling of subdivision surfaces with deformation-based modeling and allows to switch back and forth between the two different approaches to modeling.
Effective Back-Patch Culling for Hardware Tessellation
(The Eurographics Association, 2011) Loop, Charles; Nießner, Matthias; Eisenacher, Christian; Peter Eisert and Joachim Hornegger and Konrad Polthier
When rendering objects with hardware tessellation, back-facing patches should be culled as early as possible to avoid unnecessary surface evaluations, and setup costs for the tessellator and rasterizer. For dynamic objects the popular cone-of-normals approach is usually approximated using tangent and bitangent cones. This is faster to compute, but less effective. We present a novel approach using the Bézier convex hull of the parametric tangent plane. It is much more accurate, and by operating in clip space we are able to reduce the computational cost significantly. As our algorithm vectorizes well, we observe comparable test times with increased cull-rates.
Data-Driven Visualization of Functional Brain Regions from Resting State fMRI Data
(The Eurographics Association, 2011) Crippa, Alessandro; Roerdink, Jos B.T.M.; Peter Eisert and Joachim Hornegger and Konrad Polthier
Functional parcellation of the human cortex plays an important role in the understanding of brain functions. Tradi- tionally, functional areas are defined according to anatomical landmarks. Recently, new techniques were proposed that do not require a priori segmentation of the cortex. Such methods allow functional parcellation by functional information alone. We propose here a data-driven approach for the exploration of functional connectivity of the cortex. The method extends a known parcellation method, used in multichannel EEG analysis, to define and extract functional units (FUs), i.e., spatially connected brain regions that record highly correlated fMRI signals. We apply the method to the study of fMRI data and provide a visualization, inspired by the EEG case, that uses linked views to facilitate the understanding of both the location and the functional similarity of brain regions. Initial feedback on our approach was received from four domain experts, researchers in the field of neuroscience.
Extracting Flow Structures Using Sparse Particles
(The Eurographics Association, 2011) Agranovsky, Alexy; Garth, Christoph; Joy, Kenneth I.; Peter Eisert and Joachim Hornegger and Konrad Polthier
In recent years, Lagrangian Coherent Structures (LCS) have been characterized using the Finite-Time Lyapunov Exponent, following the advection of a dense set of particles into a corresponding flow field. The large amount of particles needed to sufficiently map a flow field has been a non-trivial computational burden in the application of LCS. By seeding a minimal amount of particles into the flow field, Moving Least Squares, combined with FTLE, will extrapolate the important feature locations at which further refinement is desired. Following the refinement procedure, MLS produces a continuous function reconstruction allowing the characterization of Lagrangian Coherent Structures with a lower number of particles. Through multiple data sets, we show that given a sparse and refined sampling, MLS will reproduce FTLE fields exhibiting a nominal error while maintaining a performance increase when compared to the standard, dense finite difference approach.
Probabilistic Inverse Dynamics for Blood Pattern Reconstruction
(The Eurographics Association, 2011) Cecchetto, Benjamin T.; Heidrich, Wolfgang; Peter Eisert and Joachim Hornegger and Konrad Polthier
We present a method of reconstructing the region of origin and trajectories for particles given impact directions and positions. This method works for nonlinear trajectories, such as parabolic motion or motion with drag if given drag parameters. Our method works if given the impact speeds as well, or they can be estimated using a similar total initial energy prior. We apply our algorithm to the case of forensic blood pattern reconstruction, by automatically estimating impact velocities directly form the blood patterns. We validate our method in physically accurate simulated experiments, a feasibility study varying the impact angle and speed to estimate the impact speed from blood drop densities, as well as a forensic experiment using blood to reconstruct the region of origin.
Assessment of Time-of-Flight Cameras for Short Camera-Object Distances
(The Eurographics Association, 2011) Stürmer, Michael; Becker, Guido; Hornegger, Joachim; Peter Eisert and Joachim Hornegger and Konrad Polthier
In this paper we have compared Time-of-Flight cameras of different vendors at object-camera distances of 500 mm, 1500 mm and 2500 mm. The aim was to find the highest possible precision at the distance of 500 mm, to estimate the change of the accuracy depending on scene-reflectivity and working distance and to investigate the possibility to use the cameras as per-pixel sub-centimeter accurate measuring devices. To this end, we have evaluated the variation of the distance measurement noise over several distances as well as the minimum noise we could achieve with each camera. As the amplitude-dependent distance error may become significantly large, we also tried to quantify it in order to estimate if it can be reduced to fulfill given accuracy requirements. We compared a Camcube3 from PMD Technologies, a Swissranger4000 from MESA Imaging and a C70E from Fotonic. All cameras showed different behaviors in terms of temporal noise, variation of noise and amplitude dependency. The Camcube showed the strongest amplitude dependent effects. The minimum standard deviations at 500 mm distance were at 4.8 mm for the Camcube, 1.6 mm for the Swissranger and 0.9 mm for the C70E.
A Framework for Interactive Visualization and Classification of Dynamical Processes at the Water Surface
(The Eurographics Association, 2011) Wanner, Sven; Sommer, Christoph; Rocholz, Roland; Jung, Michael; Hamprecht, Fred; Jähne, Bernd; Peter Eisert and Joachim Hornegger and Konrad Polthier
A framework for the visualization and classification of multi-channel spatio-temporal data from water wave imaging is presented. Our interactive visualization tool, WaveVis, allows a detailed study of the water surface shape in reference to additional data streams, like thermographic images or classification results. This facilitates an intuitive and effective inspection of huge amounts of data. WaveVis was used to select representative training examples of events for a supervised learning approach and to evaluate the results of the classification. The interactive classification and segmentation software ilastik was used to train a Random Forest classifier. The benefit of the combination of both programs is demonstrated for two applications, the estimation of the rain rate from the segmentation of impact craters, and the detection of small scale breaking waves. The classification of the impact crater of raindrops on the water surface worked very well, whereas the detection of the breaking waves was satisfactory only under certain experimental conditions. Nevertheless, the combination of WaveVis and ilastik proved to be valuable in both cases.
Landmark-constrained 3-D Histological Imaging: A Morphology-preserving Approach
(The Eurographics Association, 2011) Gaffling, Simone; Daum, Volker; Hornegger, Joachim; Peter Eisert and Joachim Hornegger and Konrad Polthier
The inspection of histological image sequences to gain knowledge about the original three-dimensional (3-D) morphological structure is a standard method in medical research. Its main advantage is that light microscopes feature high resolution enhanced visibility due to staining. In many cases this imaging technology could immensely profit from 3-D reconstructions of the slice images. For volumetric stacking, however, the tissue deformations due to slice preparation require an unwarping strategy to restore the original morphology. The challenge is to reverse the artificial deformations while preserving the natural morphological changes. In particular, unintentional straightening of curved structures across multiple slices has to be avoided. In this article, we propose a novel way to incorporate landmarks representing the morphological progression. They are used as additional regularization for intensity based non-rigid registration which is capable to exactly match the landmarks. Our approach is tested on synthetical and histological data sets. We show that it delivers smooth contours while preserving the morphological structure, and is a promising addition to existing methods.
Surface Reconstruction from Multi-resolution Sample Points
(The Eurographics Association, 2011) Mücke, Patrick; Klowsky, Ronny; Goesele, Michael; Peter Eisert and Joachim Hornegger and Konrad Polthier
Robust surface reconstruction from sample points is a challenging problem, especially for real-world input data. We significantly improve on a recent method by Hornung and Kobbelt [HK06b] by implementing three major extensions. First, we exploit the footprint information inherent to each sample point, that describes the underlying surface region represented by that sample. We interpret each sample as a vote for a region in space where the size of the region depends on the footprint size. In our method, sample points with large footprints do not destroy the fine detail captured by sample points with small footprints. Second, we propose a new crust computation making the method applicable to a substantially broader range of input data. This includes data from objects that were only partially sampled, a common case for data generated by multi-view stereo applied to Internet images. Third, we adapt the volumetric resolution locally to the footprint size of the sample points which allows to extract fine detail even in large-scale scenes. The effectiveness of our extensions is shown on challenging outdoor data sets as well as on a standard benchmark.
Direct Visualization of Particle-Partition of Unity Data
(The Eurographics Association, 2011) Üffinger, Markus; Schweitzer, Marc Alexander; Sadlo, Filip; Ertl, Thomas; Peter Eisert and Joachim Hornegger and Konrad Polthier
Direct visualization of higher-order data provides manifold advantages over the traditional approach, which is based on resampling and subsequent visualization by interpolation-based techniques. Most important, it avoids excessive computation and consumption of memory, and prevents artifacts by pixel-accurate visualization at interactive rates. This work addresses particle-partition of unity simulation data, where fields are modeled both using cell-based analytic representations together with enrichment functions centered at individual points. This combination of bases allows for superior simulation convergence rates and is able to capture high field variations with comparably small sets of basis functions. In this paper we propose direct visualization of such data from 2D simulations, providing accurate insight. We additionally visualize solver performance, allowing for more directed simulation design, and exemplify our technique using a GPU-based prototype on crack simulation examples.
Monocular Pose Reconstruction for an Augmented Reality Clothing System
(The Eurographics Association, 2011) Rogge, Lorenz; Neumann, Thomas; Wacker, Markus; Magnor, Marcus; Peter Eisert and Joachim Hornegger and Konrad Polthier
In this paper, we present an approach for realizing an augmented reality system for try-on of apparel. The core component of our system is a quick human pose estimation algorithm based on a single camera view only. Due to monocular input data, pose reconstruction may be ambiguous. We solve this problem by using a markered suit, though not relying on any specific marker layout. To recover 3D joint angles of the person using the system we use Relevance Vector Machine regression with image descriptors that include neighborhood configurations of visible colored markers and image gradient orientations. This novel combination of image descriptors results in a measurable improvement in reconstruction quality. We initialize and evaluate our algorithm with pose data acquired using a motion capture system. As the final step, we simulate a cloth draped around a virtual character adopting the estimated pose. Composing the original view and the rendered cloth creates the illusion of the user wearing virtual garments.
Particle-Based Anisotropic Sampling for Two-Dimensional Tensor Field Visualization
(The Eurographics Association, 2011) Kratz, Andrea; Kettlitz, Nino; Hotz, Ingrid; Peter Eisert and Joachim Hornegger and Konrad Polthier
We present a particle-based approach to generate unstructured distributions of elliptical samples. Size and shape of the samples are determined by a local metric that is derived from a two-dimensional tensor field. In contrast to previous methods, we propose the use of an anisotropic Delaunay triangulation of particle positions. It guarantees exact neighbor computations and provides a good means for an explicit and automatic control of prominent holes and overlaps, which otherwise would result in unpleasant visualizations. We use the final distribution to compute a generalized Voronoi diagram, which represents a novel and flexible visualization technique for two-dimensional tensor fields. Via texturing of Voronoi regions, many possibilities arise to design the final image.
Near-Regular Texture Synthesis by Random Sampling and Gap Filling
(The Eurographics Association, 2011) Recas, Diego Lopez; Hilsmann, Anna; Eisert, Peter; Peter Eisert and Joachim Hornegger and Konrad Polthier
This paper addresses the synthesis of near-regular textures, i.e. textures that consist of a regular global structure plus subtle yet very characteristic stochastic irregularities. Such textures are difficult to synthesize due to the complementary characteristics of these structures. In this paper, we propose a method which we call Random Sampling and Gap Filling (RSGF) to synthesize near-regular textures. The synthesis approach is guided by a lattice of the global structure estimated from a generalized normalized autocorrelation of the sample image. This lattice constrains a random sampling process to maintain the global regular structure yet ensuring the characteristic randomness of the irregular structures. Results presented in this paper show that our method does not only produce convincing results for regular or near-regular textures but also for irregular textures.
A Clustering-based Visualization Technique to Emphasize Meaningful Regions of Vector Fields
(The Eurographics Association, 2011) Kuhn, Alexander; Lehmann, Dirk J.; Gaststeiger, Rocco; Neugebauer, Matthias; Preim, Bernhard; Theisel, Holger; Peter Eisert and Joachim Hornegger and Konrad Polthier
This paper proposes a vector field visualization approach that extracts and visualizes grouped regions of static 3D vector fields of similar curvature behavior. These regions are argued to ease the recognition of regions of potential interest and accelerate the general exploration process of vector fields. Our approach detects regions of similar geometric stream properties such as integral curvature and visualizes them by means of compact cluster boundaries. To supplement existing approaches our method combines information on relevant scales to extract meaningful semantical aspects of the overall field structure. For proof of concept we illustrate our results based on real and synthetic data sets.

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