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Scalable surface reconstruction from point clouds with extreme scale and density diversity

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arXiv 2017年

作者： Mostegel, Christian Prettenthaler, Rudolf Fraundorfer, Friedrich Bischof, Horst Institute for Computer Graphics and Vision Graz University of Technology

In this paper we present a scalable approach for robustly computing a 3D surface mesh from multi-scale multi-view stereo point clouds that can handle extreme jumps of point density (in our experiments three orders of magnitude). The backbone of our approach is a combination of octree data partitioning, local Delaunay tetrahedralization and graph cut optimization. Graph cut optimization is used twice, once to extract surface hypotheses from local Delaunay tetrahedralizations and once to merge overlapping surface hypotheses even when the local tetrahedralizations do not share the same topology. This formulation allows us to obtain a constant memory consumption per sub-problem while at the same time retaining the density independent interpolation properties of the Delaunay-based optimization. On multiple public datasets, we demonstrate that our approach is highly competitive with the state-of-the-art in terms of accuracy, completeness and outlier resilience. Further, we demonstrate the multi-scale potential of our approach by processing a newly recorded dataset with 2 billion points and a point density variation of more than four orders of magnitude-requiring less than 9GB of RAM per process. Copyright © 2017, The Authors. All rights reserved.

关键词： Random access storage

Real-time panoramic tracking for event cameras

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Real-time panoramic tracking for event cameras

IEEE International Conference on Computational Photography (ICCP)

作者： Christian Reinbacher Gottfried Munda Thomas Pock Institute for Computer Graphics and Vision Graz University of Technology

ISBN: (纸本)9781509057467

Event cameras are a paradigm shift in camera technology. Instead of full frames, the sensor captures a sparse set of events caused by intensity changes. Since only the changes are transferred, those cameras are able to capture quick movements of objects in the scene or of the camera itself. In this work we propose a novel method to perform camera tracking of event cameras in a panoramic setting with three degrees of freedom. We propose a direct camera tracking formulation, similar to state-of-the-art in visual odometry. We show that the minimal information needed for simultaneous tracking and mapping is the spatial position of events, without using the appearance of the imaged scene point. We verify the robustness to fast camera movements and dynamic objects in the scene on a recently proposed dataset [18] and self-recorded sequences.

关键词： Cameras Tracking Robot vision systems Two dimensional displays computer vision Simultaneous localization and mapping Image reconstruction

Interactive planning of miniplates

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Interactive planning of miniplates

SPIE Medical Imaging 2017

作者： Gall, Markus Reinbacher, Knut Wallner, Jürgen Stanzel, Jan Chen, Xiaojun Schwenzer-Zimmerer, Katja Schmalstieg, Dieter Egger, Jan Graz University of Technology Institute for Computer Graphics and Vision Graz AustriaBioTechMed-Graz Graz Austria Medical University of Graz Department of Maxillofacial Surgery Graz AustriaMedArtis AG Basel Switzerland Shanghai Jiao Tong University School of Mechanical Engineering Shanghai China

In this contribution, a novel method for computer aided surgery planning of facial defects by using models of purchasable MedArtis Modus 2.0 miniplates is proposed. Implants of this kind, which belong to the osteosynthetic material, are commonly used for treating defects in the facial area. By placing them perpendicular on the defect, the miniplates are fixed on the healthy bone, bent with respect to the surface, to stabilize the defective area (Figure 1). Our software is able to fit a selection of the most common implant models to the surgeon's desired position in a 3D computer model. The fitting respects the local surface curvature and adjusts direction and position in any desired way. © 2017 SPIE.

关键词： Curve fitting

Interaction concepts for collaborative visual analysis of scatterplots on large vertically-mounted high-resolution multi-touch displays 10

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Interaction concepts for collaborative visual analysis of sc...

10th Forum Media technology, FMT 2017 and 3rd All Around Audio Symposium

作者： Chegini, Mohammad Shao, Lin Lehmann, Dirk J. Andrews, Keith Schreck, Tobias Institute of Computer Graphics and Knowledge Visualisation Graz University of Technology Austria University of Magdeburg Germany Institute of Interactive Systems and Data Science Graz University of Technology Austria

Large vertically-mounted high-resolution multitouch displays are becoming increasingly available for interactive data visualisation. Such devices are well-suited to small-team collaborative visual analysis. In particular, the visual analysis of large high-dimensional datasets can benefit from high-resolution displays capable of showing multiple coordinated views. This paper identifies some of the advantages of using large, high-resolution displays for visual analytics in general, and introduces a set of interactions to explore high-dimensional datasets on large vertically-mounted high-resolution multi-touch displays using scatterplots. A set of touch interactions for collaborative visual analysis of scatterplots have been implemented and are presented. Finally, three perception-based level of detail techniques are introduced for such displays as a concept for further implementation.

关键词： Data visualization

Real-time panoramic tracking for event cameras

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arXiv 2017年

作者： Reinbacher, Christian Munda, Gottfried Pock, Thomas Institute for Computer Graphics and Vision Graz University of Technology Austria

关键词： Cameras

Clinical evaluation of semi-automatic opensource algorithmic software segmentation of the mandibular bone: Practical feasibility and assessment of a new course of action

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arXiv 2018年

作者： Wallner, Jürgen Hochegger, Kerstin Chen, Xiaojun Mischak, Irene Reinbacher, Knut Pau, Mauro Zrnc, Tomislav Schwenzer-Zimmerer, Katja Zemann, Wolfgang Schmalstieg, Dieter Egger, Jan Department of Oral & Maxillofacial Surgery Medical University of Graz Auenbruggerplatz 5/1 Graz Austria Laboratory Graz Austria Institute for Computer Graphics and Vision Graz University of Technology Inffeldgasse 16c/II Graz Austria School of Mechanical Engineering Shanghai Jiao Tong University Shanghai China Department of Dental Medicine and Oral Health Medical University of Graz Billrothgasse 4 Graz Austria BioTechMed-Graz Krenngasse 37/1 Graz Austria

Introduction: computer assisted technologies based on algorithmic software segmentation are an increasing topic of interest in complex surgical cases. However-due to functional instability, time consuming software processes, personnel resources or licensed-based financial costs many segmentation processes are often outsourced from clinical centers to third parties and the industry. Therefore, the aim of this trial was to assess the practical feasibility of an easy available, functional stable and licensed-free segmentation approach to be used in the clinical practice. Material and methods: In this retrospective, randomized, controlled trail the accuracy and accordance of the opensource based segmentation algorithm GrowCut was assessed through the comparison to the manually generated ground truth of the same anatomy using 10 CT lower jaw data-sets from the clinical routine. Assessment parameters were the segmentation time, the volume, the voxel number, the Dice Score and the Hausdorff distance. Results: Overall semi-automatic GrowCut segmentation times were about one minute. Mean Dice Score values of over 85% and Hausdorff Distances below 33.5 voxel could be achieved between the algorithmic GrowCut-based segmentations and the manual generated ground truth schemes. Statistical differences between the assessment parameters were not significant (p0.94) for any of the comparison made between the two groups. Discussion: Complete functional stable and time saving segmentations with high accuracy and high positive correlation could be performed by the presented interactive open-source based approach. In the cranio-maxillofacial complex the used method could represent an algorithmic alternative for image-based segmentation in the clinical practice for e.g. surgical treatment planning or visualization of postoperative results and offers several advantages. Due to an open-source basis the used method could be further developed by other groups or specialists. Systematic compari

关键词： Geometry

Unified models for second-order TV-type regularisation in imaging: A new perspective based on vector operators

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arXiv 2018年

作者： Brinkmann, Eva-Maria Burger, Martin Grah, Joana Sarah Applied Mathematics: Institute for Analysis and Numerics Westfälische Wilhelms-Universität Münster Germany Department Mathematik Friedrich-Alexander Universität Erlangen-Nürnberg Germany Institute for Computer Graphics and Vision Graz University of Technology Austria

We introduce a novel regulariser based on the natural vector field operations gradient, divergence, curl and shear. For suitable choices of the weighting parameters contained in our model it generalises well-known firstand second-order TV-type regularisation methods including TV, ICTV and TGV2 and enables interpolation between them. To better understand the influence of each parameter, we characterise the nullspaces of the respective regularisation functionals. Analysing the continuous model, we conclude that it is not sufficient to combine penalisation of the divergence and the curl to achieve high-quality results, but interestingly it seems crucial that the penalty functional includes at least one component of the shear or suitable boundary conditions. We investigate which requirements regarding the choice of weighting parameters yield a rotational invariant approach. To guarantee physically meaningful reconstructions, implying that conservation laws for vectorial differential operators remain valid, we need a careful discretisation that we therefore discuss in detail. Copyright © 2018, The Authors. All rights reserved.

关键词： Mathematical operators

Visual odometry using a homography formulation with decoupled rotation and translation estimation using minimal solutions

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Visual odometry using a homography formulation with decouple...

IEEE International Conference on Robotics and Automation

作者： Banglei Guan Pascal Vasseur Cedric Demonceaux Friedrich Fraundorfer College of Aerospace Science and Engineering National University of Defense Technology China LITIS Université de Rouen France Le2i Université Bourgogne Franche-Comté France Institute of Computer Graphics and Vision TU Graz Austria and with the Remote Sensing Technology Institute Germany

In this paper we present minimal solutions for two-view relative motion estimation based on a homography formulation. By assuming a known vertical direction (e.g. from an IMU) and assuming a dominant ground plane we demonstrate that rotation and translation estimation can be decoupled. This result allows us to reduce the number of point matches needed to compute a motion hypothesis. We then derive different algorithms based on this decoupling that allow an efficient estimation. We also demonstrate how these algorithms can be used efficiently to compute an optimal inlier set using exhaustive search or histogram voting instead of a traditional RANSAC step. Our methods are evaluated on synthetic data and on the KITTI data set, demonstrating that our methods are well suited for visual odometry in road driving scenarios.

关键词： Estimation Visual odometry Mathematical model Cameras Histograms Gravity Motion estimation

Integration of the HTC vive into the medical platform MeVisLab

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Integration of the HTC vive into the medical platform MeVisL...

SPIE Medical Imaging 2017

作者： Egger, Jan Gall, Markus Wallner, Jürgen Boechat, Pedro Hann, Alexander Li, Xing Chen, Xiaojun Dieter Schmalstieg Graz University of Technology Institute for Computer Graphics and Vision Graz AustriaBioTechMed-Graz Graz Austria Medical University of Graz Department of Maxillofacial Surgery Graz Austria Ulm University Department of Internal Medicine I Ulm Germany Shanghai Jiao Tong University School of Mechanical Engineering Shanghai China