VMV: Vision, Modeling, and Visualization

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https://diglib7.eg.org/handle/10.2312/1013

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3D Curve-Skeleton Extraction Algorithm Using a Pseudo-Normal Vector Field
(The Eurographics Association, 2010) Pantuwong, Natapon; Sugimoto, Masanori; Reinhard Koch and Andreas Kolb and Christof Rezk-Salama
A curve skeleton is a line representation of a 3D object. It is useful in many applications, such as animation, shape matching or scientific analysis. The method described in this paper extracts a curve skeleton from the vector field which is created inside the 3D object. The topology of the vector field is analyzed to obtain the curve skeleton. In contrast with previous methods, the vector field is calculated using a pseudo-normal vector. Furthermore, by using the proposed skeleton-growing method, the vector field topology need not be computed for every voxel. Therefore, the proposed approach requires significantly less computation compared with previous vector field-based approaches, while still capturing all important parts of 3D object. The proposed method is very useful for any applications, especially real-time applications such as quick animation production and prototyping of graphical systems.
3D Face Reconstruction with Silhouette Constraints
(The Eurographics Association, 2016) Hu, Qiyang; Zwicker, Matthias; Favaro, Paolo; Matthias Hullin and Marc Stamminger and Tino Weinkauf
In this paper we introduce silhouette constraints to improve the quality of unconstrained 3D face reconstruction. Previously, state of the art unconstrained 3D face reconstruction techniques relied solely on photometric consistency and matching sparse facial landmarks. We show that constraining the silhouettes of the 3D reconstruction to match silhouettes in the input images can further improve reconstruction quality. Our technique automatically detects silhouettes and iteratively matches silhouette points computed from the current 3D reconstruction with silhouettes in the input images. We demonstrate that our results improve on the previous state of the art in unconstrained 3D face reconstruction and that our additional constraints can easily be included in the iterative reconstruction at little additional cost.
3D Shape Cropping
(The Eurographics Association, 2013) Franco, Jean-Sebastien; Petit, Benjamin; Boyer, Edmond; Michael Bronstein and Jean Favre and Kai Hormann
We introduce shape cropping as the segmentation of a bounding geometry of an object as observed by sensors with different modalities. Segmenting a bounding volume is a preliminary step in many multi-view vision applications that consider or require the recovery of 3D information, in particular in multi-camera environments. Recent vision systems used to acquire such information often combine sensors of different types, usually color and depth sensors. Given depth and color images we present an efficient geometric algorithm to compute a polyhedral bounding surface that delimits the region in space where the object lies. The resulting cropped geometry eliminates unwanted space regions and enables the initialization of further processes including surface refinements. Our approach exploits the fact that such a region can be defined as the intersection of 3D regions identified as non empty in color or depth images. To this purpose, we propose a novel polyhedron combination algorithm that overcomes computational and robustness issues exhibited by traditional intersection tools in our context. We show the correction and effectiveness of the approach on various combination of inputs.
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.
Accurate Face Reconstruction through Anisotropic Fitting and Eye Correction
(The Eurographics Association, 2015) Achenbach, Jascha; Zell, Eduard; Botsch, Mario; David Bommes and Tobias Ritschel and Thomas Schultz
Fitting a facial template model to 3D-scanner data is a powerful technique for generating face avatars, in particular in the presence of noisy and incomplete measurements. Consequently, there are many approaches for the underlying non-rigid registration task, and these are typically composed from very similar algorithmic building blocks. By providing a thorough analysis of the different design choices, we derive a face matching technique tailored to high quality reconstructions from high resolution scanner data. We then extend this approach in two ways: An anisotropic bending model allows us to more accurately reconstruct facial details. A simultaneous constrained fitting of eyes and eye lids improves the reconstruction of the eye region considerably.
Adaptive Image-space Stereo View Synthesis
(The Eurographics Association, 2010) Didyk, Piotr; Ritschel, Tobias; Eisemann, Elmar; Myszkowski, Karol; Seidel, Hans-Peter; Reinhard Koch and Andreas Kolb and Christof Rezk-Salama
Stereo vision is becoming increasingly popular in feature films, visualization and interactive applications such as computer games. However, computation costs are doubled when rendering an individual image for each eye. In this work, we propose to only render a single image, together with a depth buffer and use image-based techniques to generate two individual images for the left and right eye. The resulting method computes a high-quality stereo pair for roughly half the cost of the traditional methods. We achieve this result via an adaptive-grid warping that also involves information from previous frames to avoid artifacts.
Adaptive Level-of-Precision for GPU-Rendering
(The Eurographics Association, 2011) Meyer, Quirin; Sussner, Gerd; Greiner, Günter; Stamminger, Marc; Peter Eisert and Joachim Hornegger and Konrad Polthier
Video memory is a valuable resource that has grown much slower than the rendering power of GPUs over the last years. Today, video memory is often the limiting factor in interactive high-quality rendering applications. The most often used solution to reduce memory consumption is to apply level-of-detail (LOD) methods: only a simplified version of the mesh with less vertices and triangles is kept in memory. In this paper we examine a simple orthogonal compression approach that is mostly neglected: adapting the level-of-precision (LOP) of vertex data. The main idea is to quantize vertex positions according to the current view distance, and adapt precision by adding or removing single bit planes. We provide an analysis of the resulting image error, and show that visual artifacts can be avoided by simply constraining the quantization for critical vertices. Our approach allows both random access on vertex data as well as quickly switching between LOP. In experiments we found that our approach compresses vertex positions by about 70percent on average without loss in rendering performance or image quality.
Adaptive Sampling for Geometry-aware Reconstruction Filters
(The Eurographics Association, 2011) Bauszat, Pablo; Eisemann, Martin; Magnor, Marcus; Peter Eisert and Joachim Hornegger and Konrad Polthier
We present an adaptive sampling scheme for Monte-Carlo-based renderers with the aim to support geometryaware filtering techniques for interactive computation of global illumination. While sophisticated filtering techniques for homogeneous areas can already produce high-quality results with as few as one sample per pixel, these approaches lack the ability to filter sufficiently in the vicinity of complex geometric structures. The result are visible artifacts in the final rendering result. Our sampling scheme distributes the samples for the indirect illumination in the image plane according to the necessity of a geometry-aware filtering. We show how to implement our scheme efficiently on current graphics hardware and how to combine it with a sophisticated filtering in order to achieve high-quality interactive frame rates for global illumination simulations. The resulting computational overhead is only in the range of a few milliseconds, making our approach suitable for real-time implementations.
Adaptive Surface Visualization of Vessels with Embedded Blood Flow Based on the Suggestive Contour Measure
(The Eurographics Association, 2013) Lawonn, Kai; Gasteiger, Rocco; Preim, Bernhard; Michael Bronstein and Jean Favre and Kai Hormann
The investigation of hemodynamic information for the assessment of cardiovascular diseases (CVD) has increased in recent years. Improved flow measuring modalities and computational fluid dynamics (CFD) simulations are suitable to provide domain experts with reliable blood flow information. For a visual exploration of the flow information domain experts are used to investigate the flow information combined with its enclosed vessel anatomy. Since the flow is spatially embedded in the surrounding vessel surface, occlusion problems have to be resolved that include a meaningful visual reduction of the vessel surface but still provide important anatomical features. We accomplish this by applying an adaptive surface visualization inspired by the suggestive contour measure. Our approach combines several visualization techniques to improve the perception of surface shape and depth. Thereby, we ensure appropriate visibility of the embedded flow information, which can be depicted with established or advanced flow visualization techniques. We apply our approach to cerebral aneurysms and aortas with simulated and measured blood flow. In an informal user feedback with nine domain experts, we confirm the advantages of our approach compared with existent methods, e.g., semi-transparent surface rendering.
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.
AFiT - Atrial Fibrillation Ablation Planning Tool
(The Eurographics Association, 2011) Brost, Alexander B.; Bourier, Felix; Kleinoeder, Andreas; Raab, Jens; Koch, Martin; Stamminger, Marc; Hornegger, Joachim; Strobel, Norbert; Kurzidim, Klaus; Peter Eisert and Joachim Hornegger and Konrad Polthier
The planning of cryo-balloon ablations for treatment of atrial fibrillation is a crucial task for a physician as he has to determine which size of the balloon catheter is required for isolation at each pulmonary vein. Today, the diameter of the pulmonary vein's ostium is measured in a pre-operative data set to determine which type of catheter is most appropriate. We present a novel tool that visualizes a cryo-balloon catheter model within a 3-D model representing a segmented left atrium. Using this approach, physicians are able to better assess the catheter fit. So far, measurement of the pulmonary vein diameters have been performed by evaluation of 2-D slices taken from pre-operative data sets. The first feedback obtained by physicians was very encouraging as this tool offers better insights for balloon catheter ablation procedures.
Alignment and Reassembly of Broken Specimens for Creep Ductility Measurements
(The Eurographics Association, 2022) Knauthe, Volker; Kraus, Maurice; Buelow, Max von; Wirth, Tristan; Rak, Arne; Merth, Laurenz; Erbe, Alexander; Kontermann, Christian; Guthe, Stefan; Kuijper, Arjan; Fellner, Dieter W.; Bender, Jan; Botsch, Mario; Keim, Daniel A.
Designing new types of heat-resistant steel components is an important and active research field in material science. It requires detailed knowledge of the inherent steel properties, especially concerning their creep ductility. Highly precise automatic stateof- the-art approaches for such measurements are very expensive and often times invasive. The alternative requires manual work from specialists and is time consuming and unrobust. In this paper, we present a novel approach that uses a photometric scanning system for capturing the geometry of steel specimens, making further measurement extractions possible. In our proposed system, we apply calibration for pan angles that occur during capturing and a robust reassembly for matching two broken specimen pieces to extract the specimen's geometry. We compare our results against µCT scans and found that it deviates by 0.057mm on average distributed over the whole specimen for a small amount of 36 captured images. Additionally, comparisons to manually measured values indicate that our system leads to more robust measurements.
Analysis of Structural Dependencies for the Automatic Visual Inspection of Wire Ropes
(The Eurographics Association, 2010) Haase, Daniel; Wacker, Esther-Sabrina; Schukat-Talamazzini, Ernst Günter; Denzler, Joachim; Reinhard Koch and Andreas Kolb and Christof Rezk-Salama
Automatic visual inspection is an arising field of research. Especially in security relevant applications, an automation of the inspection process would be a great benefit. For wire ropes, a first step is the acquisition of the curved surface with several cameras located all around the rope. Because most of the visible defects in such a rope are very inconspicuous, an automatic defect detection is a very challenging problem. As in general there is a lack of defective training data, most of the presented ideas for automatic rope inspection are embedded in a one-class classification framework. However, none of these methods makes use of the context information which results from the fact that all camera views image the same rope. In contrast to an individual analysis of each camera view, this work proposes the simultaneous analysis of all available camera views with the help of a vector autoregressive model. Moreover, various dependency analysis methods are used to give consideration to the regular rope structure and to deal with the high dimensionality of the problem. These dependencies are then used as constraints for the vector autoregressive model, which results in a sparse but powerful detection system. The proposed method is evaluated by using real wire rope data and the conducted experiments show that our approach clearly outperforms all previously presented methods.
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.
Appearance Bending: A Perceptual Editing Paradigm for Data-Driven Material Models
(The Eurographics Association, 2017) Mylo, Marlon; Giesel, Martin; Zaidi, Qasim; Hullin, Matthias; Klein, Reinhard; Matthias Hullin and Reinhard Klein and Thomas Schultz and Angela Yao
Data-driven representations of material appearance play an important role in a wide range of applications. Unlike with analytical models, however, the intuitive and efficient editing of tabulated reflectance data is still an open problem. In this work, we introduce appearance bending, a set of image-based manipulation operators, such as thicken, inflate, and roughen, that implement recent insights from perceptual studies. In particular, we exploit a link between certain perceived visual properties of a material, and specific bands in its spectrum of spatial frequencies or octaves of a wavelet decomposition. The result is an editing interface that produces plausible results at interactive rates, even for drastic manipulations. We present the effectiveness of our method on a database of bidirectional texture functions (BTFs) for a variety of material samples.
Application of Tensor Approximation to Multiscale Volume Feature Representations
(The Eurographics Association, 2010) Suter, Susanne K.; Zollikofer, Christoph P. E.; Pajarola, Renato; Reinhard Koch and Andreas Kolb and Christof Rezk-Salama
Advanced 3D microstructural analysis in natural sciences and engineering depends ever more on modern data acquisition and imaging technologies such as micro-computed or synchrotron tomography and interactive visualization. The acquired volume data sets are not only of high-resolution but in particular exhibit complex spatial structures at different levels of scale (e.g. variable spatial expression of multiscale periodic growth structures in tooth enamel). Such highly structured volume data sets represent a tough challenge to be analyzed and explored by means of interactive visualization due to the amount of raw volume data to be processed and filtered for the desired features. As an approach to address this bottleneck by multiscale feature preserving data reduction, we propose higher-order tensor approximations (TAs). We demonstrate the power of TA to represent, and highlight the structural features in volume data. We visually and quantitatively show that TA yields high data reduction and that TA preserves volume features at multiple scales.
Art-directable Stroke-based Rendering on Mobile Devices
(The Eurographics Association, 2023) Wagner, Ronja; Schulz, Sebastian; Reimann, Max; Semmo, Amir; Döllner, Jürgen; Trapp, Matthias; Guthe, Michael; Grosch, Thorsten
This paper introduces an art-directable stroke-based rendering technique for transforming photos into painterly renditions on mobile devices. Unlike previous approaches that rely on time-consuming iterative computations and explicit brush-stroke geometry, our method offers a interactive image-based implementation tailored to the capabilities of modern mobile devices. The technique places curved brush strokes in multiple passes, leveraging a texture bombing algorithm. To maintain and highlight essential details for stylization, we incorporate additional information such as image salience, depth, and facial landmarks as parameters. Our technique enables a user to control and manipulate using a wide range of parameters and masks during editing to adjust and refine the stylized image. The result is an interactive painterly stylization tool that supports high-resolution input images, providing users with an immersive and engaging artistic experience on their mobile devices.
Artistic Composition for Painterly Rendering
(The Eurographics Association, 2016) Lindemeier, Thomas; Spicker, Marc; Deussen, Oliver; Matthias Hullin and Marc Stamminger and Tino Weinkauf
We present a technique for painterly renderings that follows a decomposition of the canvas into a set of regions and layers (coarse to fine). The regions reflect the spatial arrangement of the composition and the order in which the painting is to be created (typically back to front), and are produced in a way that new strokes only minimally paint over existing ones. Layers reflect the application of tools and are optimized for certain brush sizes. The number of strokes and colors that are needed to represent an input image are minimized by this decomposition, which is good for software, but essential for hardware-based rendering. Our method allows us to apply different painting styles to different regions as well as layers, and to create painterly renderings with more artistic freedom. We demonstrate our decomposition technique on images that are processed using hierarchical segmentation techniques.
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.
Astray: A Performance-Portable Geodesic Ray Tracer
(The Eurographics Association, 2022) Demiralp, Ali Can; Krüger, Marcel; Chao, Chu; Kuhlen, Torsten W.; Gerrits, Tim; Bender, Jan; Botsch, Mario; Keim, Daniel A.
Geodesic ray tracing is the numerical method to compute the motion of matter and radiation in spacetime. It enables visualization of the geometry of spacetime and is an important tool to study the gravitational fields in the presence of astrophysical phenomena such as black holes. Although the method is largely established, solving the geodesic equation remains a computationally demanding task. In this work, we present Astray; a high-performance geodesic ray tracing library capable of running on a single or a cluster of computers equipped with compute or graphics processing units. The library is able to visualize any spacetime given its metric tensor and contains optimized implementations of a wide range of spacetimes, including commonly studied ones such as Schwarzschild and Kerr. The performance of the library is evaluated on standard consumer hardware as well as a compute cluster through strong and weak scaling benchmarks. The results indicate that the system is capable of reaching interactive frame rates with increasing use of high-performance computing resources. We further introduce a user interface capable of remote rendering on a cluster for interactive visualization of spacetimes.

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