Zachmann, Gabriel
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Zachmann, Gabriel
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Zachmann, Gabriel
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Zachmann, G.
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Item-typ:Veröffentlichung, Geometric Proximity GraphsThis chapter focuses on geometric proximity graphs which can serve as a powerful tool to capture the structure or shape of otherwise unstructured point sets. These graphs have numerous applications in areas such as computer graphics, computer vision, geography, information retrieval, routing in ad-hoc networks, and computational biology, among many others. The chapter presents a small number of neighborhood graphs (other than polygonal meshes) and a few applications in computer graphics, where they can help to detect structure in point clouds. There are other geometric graphs that are more or less closely related to proximity graphs, such as the minimum spanning tree (MST) and the Delaunay graph (DG). The MST spans (i.e., connects) all points by a tree of minimal length. The DG is the dual of the Voronoi diagram.Wissenschaftlicher Artikel124 245 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, kDet: Parallel Constant Time Collision Detection for Polygonal ObjectsWe define a novel geometric predicate and a class of objects that enables us to prove a linear bound on the number of intersecting polygon pairs for colliding 3D objects in that class. Our predicate is relevant both in theory and in practice: it is easy to check and it needs to consider only the geometric properties of the individual objects – it does not depend on the configuration of a given pair of objects. In addition, it characterizes a practically relevant class of objects: we checked our predicate on a large database of real-world 3D objects and the results show that it holds for all but the most pathological ones. Our proof is constructive in that it is the basis for a novel collision detection algorithm that realizes this linear complexity also in practice. Additionally, we present a parallelization of this algorithm with a worst-case running time that is independent of the number of polygons. Our algorithm is very well suited not only for rigid but also for deformable and even topology-changing objects, because it does not require any complex data structures or pre-processing. We have implemented our algorithm on the GPU and the results show that it is able to find in real-time all colliding polygons for pairs of deformable objects consisting of more than 200k triangles, including self-collisions.Wissenschaftlicher Artikel129 130 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Adaptive Bitonic SortingAdaptive bitonic sorting is a sorting algorithm suitable for implementation on EREW parallel architectures. Similar to bitonic sorting, it is based on merging, which is recursively applied to obtain a sorted sequence. In contrast to bitonic sorting, it is data dependent. Adaptive bitonic merging can be performed in O(n/p) parallel time, p being the number of processors, and executes only O(n) operations in total. Consequently, adaptive bitonic sorting can be performed in O(n log n/p) time, which is optimal. So, one of its advantages is that it executes a factor of O(log n) less operations than bitonic sorting. Another advantage is that it can be implemented efficiently on modern GPUs.Wissenschaftlicher Artikel124 113 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Hand Pose Recognition — Overview and Current Research(2015); Vision-based markerless hand tracking has many applications, for instance in virtual prototyping, navigation in virtual environments, tele- and robot-surgery and video games. It is a very challenging task, due to the real-time requirements, 26 degrees-of-freedom, high appearance variability, and frequent self-occlusions. Because of that, and because of the many desirable applications, it has received increasing attention in the computer vision community of the past years. A lot of approaches have been proposed to (partially) solve the problem, but no system has been presented yet that can solve the full-DOF hand pose estimation problem robustly in real-time. The purpose of this article is to present an overview of the approaches that have been presented so far and where future research of hand tracking probably will go. First, we will explain the challenges in more detail. Second, we will classify the approaches; third, we will describe the most important approaches, and finally we will show the future directions and give a short overview of our current work.Wissenschaftlicher Artikel96 89 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Robustness of Eye Movement Biometrics Against Varying Stimuli and Varying Trajectory LengthRecent results suggest that biometric identification based on human's eye movement characteristics can be used for authentication. In this paper, we present three new methods and benchmark them against the state-of-the-art. The best of our new methods improves the state-of-the-art performance by 5.2 percentage points. Furthermore, we investigate some of the factors that affect the robustness of the recognition rate of different classifiers on gaze trajectories, such as the type of stimulus and the tracking trajectory length. We find that the state-of-the-art method only works well when using the same stimulus for testing that was used for training. By contrast, our novel method more than doubles the identification accuracy for these transfer cases. Furthermore, we find that with only 90 seconds of eye tracking data, 86.7% accuracy can be achieved.Konferenzbeitrag103 115 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, SIMDop: SIMD optimized Bounding Volume Hierarchies for Collision Detection(2019); ; We present a novel data structure for SIMD optimized simultaneous bounding volume hierarchy (BVH) traversals like they appear for instance in collision detection tasks. In contrast to all previous approaches, we consider both the traversal algorithm and the construction of the BVH. The main idea is to increase the branching factor of the BVH according to the available SIMD registers and parallelize the simultaneous BVH traversal using SIMD operations. This requires a novel BVH construction method because traditional BVHs for collision detection usually are simple binary trees. To do that, we present a new BVH construction method based on a clustering algorithm, Batch Neural Gas, that is able to build efficient n-ary tree structures along with SIMD optimized simultaneous BVH traversal. Our results show that our new data structure outperforms binary trees significantly.Konferenzbeitrag140 140 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Virtual Reality for User-Centered Design and Evaluation of Touch-free Interaction Techniques for Navigating Medical Images in the Operating Room(2017-05-06); ; ; ; Computer-assisted surgery has pervaded the operating room (OR). While display and imaging technologies advance rapidly, keyboard and mouse are still the dominant input devices, even though they cause sterility problems. We present an interactive virtual operating room (IVOR), intended as a tool to develop and study interaction methods for the OR, and two novel touch-free interaction techniques using hand and foot gestures. All was developed and evaluated with 20 surgeons. The results show that our techniques can be used with minimal learning time and no significant differences regarding completion time and usability compared to the control condition relying on verbal instruction of an assistant. Furthermore, IVOR as a tool was well received by the surgeons, although they had no prior experience with virtual reality. This confirms IVOR is an effective tool for user-centered design and evaluation, providing a portable, yet realistic substitution for a real OR for early evaluations.Konferenzbeitrag123 191 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, ProtoSphere: A GPU-Assisted Prototype Guided Sphere Packing Algorithm for Arbitrary Objects(2010); Filling objects densely with sets of non overlapping spheres has been investigated for centuries. Once started as a pure intellectual challenge, today, sphere packings have diverse applications in a wide spectrum of scientific and engineering disciplines, for example in automated radiosurgical treatment planning, investigation of processes such as sedimentation, compaction and sintering, in powder metallurgy for three-dimensional laser cutting, in cutting different natural crystals, the discrete element method is based on them, and so forth.Konferenzbeitrag93 127 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, GDS: Gradient based Density Spline Surfaces for Multiobjective Optimization in Arbitrary Simulations(2017); ; We present a novel approach for approximating objective functions in arbitrary deterministic and stochastic multi-objective blackbox simulations. Usually, simulated-based optimization approaches require pre-defined objective functions for optimization techniques in order to find a local or global minimum of the specified simulation objectives and multi-objective constraints. Due to the increasing complexity of state-of-the-art simulations, such objective functions are not always available, leading to so-called blackbox simulations. In contrast to existing approaches, we approximate the objective functions and design space for deterministic and stochastic blackbox simulations, even for convex and concave Pareto fronts, thus enabling optimization for arbitrary simulations. Additionally, Pareto gradient information can be obtained from our design space approximation. Our approach gains its efficiency from a novel gradient-based sampling of the parameter space in combination with a density-based clustering of sampled objective function values, resulting in a B-spline surface approximation of the feasible design space. We have applied our new method to several benchmarks and the results show that our approach is able to efficiently approximate arbitrary objective functions. Additionally, the computed multi-objective solutions in our evaluation studies are close to the Pareto front.Konferenzbeitrag120 82