@inproceedings{16410, abstract = {{Gathering n mobile robots in one single point in the Euclidean plane is a widely studied problem from the area of robot formation problems. Classically, the robots are assumed to have no physical extent, and they are able to share a position with other robots. We drop these assumptions and investigate a similar problem for robots with (a spherical) extent: the goal is to gather the robots as close together as possible. More exactly, we want the robots to form a sphere with minimum radius around a predefined point. We propose an algorithm for this problem which synchronously moves the robots towards the center of the sphere unless they block each other. In this case, if possible, the robots spin around the center of the sphere. We analyze this algorithm experimentally in the plane. If R is the distance of the farthest robot to the center of the sphere, the simulations indicate a runtime which is linear in n and R. Additionally, we prove a theoretic upper bound for the runtime of O(nR) for a discrete version of the problem. Simulations also suggest a runtime of O(n + R) for the discrete version.}}, author = {{Cord-Landwehr, Andreas and Degener, Bastian and Fischer, Matthias and Hüllmann, Martina and Kempkes, Barbara and Klaas, Alexander and Kling, Peter and Kurras, Sven and Märtens, Marcus and Meyer auf der Heide, Friedhelm and Raupach, Christoph and Swierkot, Kamil and Warner, Daniel and Weddemann, Christoph and Wonisch, Daniel}}, booktitle = {{37th International Conference on Current Trends in Theory and Practice of Computer Science (SOFSEM 2011)}}, isbn = {{9783642183805}}, issn = {{0302-9743}}, number = {{6543}}, pages = {{178--189}}, publisher = {{Springer}}, title = {{{Collisionless Gathering of Robots with an Extent}}}, doi = {{10.1007/978-3-642-18381-2_15}}, year = {{2011}}, } @inbook{16409, abstract = {{Given a set of n mobile robots in the d-dimensional Euclidean space, the goal is to let them converge to a single not predefined point. The challenge is that the robots are limited in their capabilities. Robots can, upon activation, compute the positions of all other robots using an individual affine coordinate system. The robots are indistinguishable, oblivious and may have different affine coordinate systems. A very general discrete time model assumes that robots are activated in arbitrary order. Further, the computation of a new target point may happen much earlier than the movement, so that the movement is based on outdated information about other robot's positions. Time is measured as the number of rounds, where a round ends as soon as each robot has moved at least once. In [Cohen, Peleg: Convergence properties of gravitational algorithms in asynchronous robot systems], the Center of Gravity is considered as target function, convergence was proven, and the number of rounds needed for halving the diameter of the convex hull of the robot's positions was shown to be O(n^2) and Omega(n). We present an easy-to-check property of target functions that guarantee convergence and yields upper time bounds. This property intuitively says that when a robot computes a new target point, this point is significantly within the current axes aligned minimal box containing all robots. This property holds, e.g., for the above-mentioned target function, and improves the above O(n^2) to an asymptotically optimal O(n) upper bound. Our technique also yields a constant time bound for a target function that requires all robots having identical coordinate axes. }}, author = {{Cord-Landwehr, Andreas and Degener, Bastian and Fischer, Matthias and Hüllmann, Martina and Kempkes, Barbara and Klaas, Alexander and Kling, Peter and Kurras, Sven and Märtens, Marcus and Meyer auf der Heide, Friedhelm and Raupach, Christoph and Swierkot, Kamil and Warner, Daniel and Weddemann, Christoph and Wonisch, Daniel}}, booktitle = {{Automata, Languages and Programming}}, isbn = {{9783642220111}}, issn = {{0302-9743}}, title = {{{A New Approach for Analyzing Convergence Algorithms for Mobile Robots}}}, doi = {{10.1007/978-3-642-22012-8_52}}, year = {{2011}}, } @inproceedings{26384, author = {{Renken, Hendrik and Laroque, Christoph and Fischer, Matthias}}, booktitle = {{Proceedings of The 25th European Simulation and Modelling Conference - ESM’2011}}, title = {{{An Easy Extendable Modeling Framework for Discrete Event Simulation Models and their Visualization}}}, year = {{2011}}, } @inproceedings{26387, author = {{Klaas, Alexander and Laroque, Christoph and Fischer, Matthias and Dangelmaier, Wilhelm}}, booktitle = {{Proceedings of the 2011 Winter Simulation Conference}}, title = {{{Simulation Aided, Knowledge Based Routing for AGVs in a Distribution Warehouse}}}, year = {{2011}}, } @inproceedings{17422, abstract = {{Commercial software of material flow simulations has the ability to layout the simulated models. Arranged equipment, such as conveyors or machines, includes the need to model and determine motion paths for moving objects like forklifts or automatically guided vehicles, so that the simulation framework is able to navigate all vehicles across those motion paths. After analyzing first scenarios, the user often carries out layout changes in the simulation model, e.g. moving, adding or deleting equipment. However, those changes cause time consuming, additional modeling of the motion paths for the user. Our motion planning algorithm reduces these changes by automatically determining the motion paths for moving objects, depending on an actual model layout without colliding with other objects. The algorithm works on the basis of the virtual scene’s 3D-data used for the simulation model’s visualization. We demonstrate the technique with a multi-floor building example.}}, author = {{Fischer, Matthias and Renken, Hendrik and Laroque, Christoph and Schaumann, Guido and Dangelmaier, Wilhelm}}, booktitle = {{Proceedings of the 2010 Winter Simulation Conference}}, isbn = {{9781424498666}}, title = {{{Automated 3D-motion planning for ramps and stairs in intra-logistics material flow simulations}}}, doi = {{10.1109/wsc.2010.5678906}}, year = {{2010}}, } @inproceedings{18136, abstract = {{We present a parallel algorithm for the rendering of complex three-dimensional scenes. The algorithm runs across heterogeneous architectures of PC-clusters consisting of a visualization-node, equipped with a powerful graphics adapter, and cluster nodes requiring weaker graphics capabilities only. The visualization-node renders a mixture of scene objects and simplified meshes (Reliefboards). The cluster nodes assist the visualization-node by asynchronous computing of Reliefboards, which are used to replace and render distant parts of the scene. Our algorithm is capable of gaining significant speedups if the cluster's nodes provide weak graphics adapters only. We trade the number of cluster nodes off the scene objects' image quality.}}, author = {{Fischer, Matthias and Jähn, Claudius and Suess, Tim}}, booktitle = {{Eurographics Symposium on Parallel Graphics and Visualization (EGPGV)}}, pages = {{43--51}}, publisher = {{The Eurographics Association}}, title = {{{Asynchronous Parallel Reliefboard Computation for Scene Object Approximation}}}, doi = {{10.2312/EGPGV/EGPGV10/043-051}}, year = {{2010}}, } @inproceedings{18289, abstract = {{Many professional cluster systems consist of nodes with different hardware configurations. Such heterogeneous environments require different load-balancing techniques than homogenous environments. The c-load-collision-protocol is able to achieve good results for data-management purposes. Using this protocol, we propose a way for load-balancing in interactive rendering environments. For this work, we implemented a parallel rendering system and took different picking strategies into account to compare the results. The advantage of our approach compared to other approaches is that we group the available nodes of a cluster into two different categories, based on the hardware abilities. Some nodes are used solely for rendering, while others serve as secondary storage and to assist the former ones by performing auxiliary calculations.}}, author = {{Suess, Tim and Wiesemann, Timo and Fischer, Matthias}}, booktitle = {{2010 IEEE Fifth International Conference on Networking, Architecture, and Storage}}, isbn = {{9781424481330}}, pages = {{448 -- 456}}, title = {{{Evaluation of a c-Load-Collision-Protocol for Load-Balancing in Interactive Environments}}}, doi = {{10.1109/nas.2010.52}}, year = {{2010}}, } @inbook{18290, abstract = {{Typischerweise sind die Knoten eines PC-Clusters nicht mit leistungsfähigen Grafikkarten ausgestattet. Dennoch bieten Cluster-Betreiber einige wenige Rechenknoten an, die mit Highend-Grafikkarten ausgestattet sind, um beispielsweise eine PowerWall zu betreiben. Wenn zwischen diesen unterschiedlichen Knotentypen ein schnelles Netzwerk existiert, kann die Bilderzeugung durch die Knoten mit schwacher Grafikkarte beschleunigt werden. Dabei können die unterschiedlichen Knotentypen unterschiedliche Aufgabe bearbeiten. In einem solchen heterogenen System, müssen die unterschiedlichen entstehenden Lasten auf andere Weise verteilt werden, als in einem System, bei dem alle Knoten gleich ausgestattet sind. Wir präsentieren in dieser Arbeit Lastbalancierungsmechanismen, die in einem parallelen Out-of-Core-Renderingsystem für heterogene PC-Cluster eingesetzt werden. }}, author = {{Suess, Tim and Wiesemann, Timo and Fischer, Matthias}}, booktitle = {{Augmented & Virtual Reality in der Produktentstehung}}, pages = {{39--52}}, title = {{{Gewichtetes c-Collision-Protokoll zur Balancierung eines parallelen Out-of-Core-Renderingsystems}}}, year = {{2010}}, } @inbook{16505, abstract = {{We present an approach for real-time rendering of complex 3D scenes consisting of millions of polygons on limited graphics hardware. In a preprocessing step, powerful hardware is used to gain fine granular global visibility information of a scene using an adaptive sampling algorithm. Additively the visual influence of each object on the eventual rendered image is estimated. This influence is used to select the most important objects to display in our approximative culling algorithm. After the visibility data is compressed to meet the storage capabilities of small devices, we achieve an interactive walkthrough of the Power Plant scene on a standard netbook with an integrated graphics chipset.}}, author = {{Eikel, Benjamin and Jähn, Claudius and Fischer, Matthias}}, booktitle = {{Advances in Visual Computing}}, isbn = {{9783642172885}}, issn = {{0302-9743}}, title = {{{Preprocessed Global Visibility for Real-Time Rendering on Low-End Hardware}}}, doi = {{10.1007/978-3-642-17289-2_60}}, year = {{2010}}, } @inproceedings{18138, abstract = {{Modern companies are nowadays confronted with an increasing demand of multiple products, where they need to perform more flexible every day. Cost-intensive decisions are to be confirmed in short times, in order to minimize risks and secure efficient production programs as well as material flows. Tools for this digital planning via simulation methods are one well established possibility to receive decision support. Nevertheless, the creation of the necessary simulation models is a complicated and error-prone process, where complexity of modeling, validation and verification depends on the used tool and its functionalities. This paper presents implemented concepts for an innovative user support in his tasks of verification and validation of simulation models during the execution of a simulation run. Time-intensive procedures like stopping simulation, parameterization and restarting within the problem analysis are simplified. So the user is able to focus on the real problem solving task.}}, author = {{Laroque, Christoph and Fischer, Matthias and Dangelmaier, Wilhelm}}, booktitle = {{European Simulation and Modelling Conference (ESM 2009)}}, publisher = {{EUROSIS-ETI}}, title = {{{Concepts for Model Verification and Validation during Simulation Runtime}}}, year = {{2009}}, } @inbook{18291, author = {{Suess, Tim and Fischer, Matthias and Huber, Daniel and Laroque, Christoph and Dangelmaier, Wilhelm}}, booktitle = {{Augmented & Virtual Reality in der Produktentstehung}}, pages = {{111----126}}, publisher = {{Verlagsschriftenreihe des Heinz Nixdorf Instituts, Paderborn}}, title = {{{Ein System zur aggregierten Visualisierung verteilter Materialflusssimulationen}}}, volume = {{252}}, year = {{2009}}, } @inproceedings{18346, abstract = {{For a fixed virtual scene (=collection of simplices) S and given observer position p, how many elements of S are weakly visible (i.e. not fully occluded by others) from p? The present work explores the trade-off between query time and preprocessing space for these quantities in 2D: exactly, in the approximate deterministic, and in the probabilistic sense. We deduce the EXISTENCE of an O(m^2/n^2) space data structure for S that, given p and time O(log n), allows to approximate the ratio of occluded segments up to arbitrary constant absolute error; here m denotes the size of the Visibility Graph--which may be quadratic, but typically is just linear in the size n of the scene S. On the other hand, we present a data structure CONSTRUCTIBLE in O(n*log(n)+m^2*polylog(n)/k) preprocessing time and space with similar approximation properties and query time O(k*polylog n), where k