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Berndt, René; Tuemmler, Carl; Kehl, Christian; Aehnelt, Mario; Grasser, Tim; Franek, Andreas; Ullrich, Torsten

Open Problems in 3D Model and Data Management

2020

Proceedings of the 15th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications

International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications (VISIGRAPP) <15, 2020, Valetta, Malta>

In interdisciplinary, cooperative projects that involve different representations of 3D models (such as CAD data and simulation data), a version problem can occur: different representations and parts have to be merged to form a holistic view of all relevant aspects. The individual partial models may be exported by and modified in different software environments. These modifications are a recurring activity and may be carried out again and again during the progress of the project. This position paper investigates the version problem; furthermore, this contribution is intended to stimulate discussion on how the problem can be solved.

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Weber, Daniel; Grasser, Tim; Stork, André

Rapid Interactive Structural Analysis

2020

2020 NAFEMS DACH Regionalkonferenz

NAFEMS DACH Regionalkonferenz <5, 2020, Online>

Auf dem Weg zu einem hocheffizienten Produktentwicklungsprozess, der aus Design, Simulation, Analyse und Iterationen besteht, liegen noch einige ungenutzte Potenziale. Bei der Analyse des Prozesses wird häufig die Integration verschiedener Software-Werkzeuge entlang der Prozesskette als eine der Schwachstellen identifiziert. Hierbei sind Interoperabilität und die Standardisierung von Austauschformaten insbesondere für die Kombination von Software verschiedener Hersteller von zentraler Bedeutung. Jedoch hat die Dauer der Simulation ebenfalls einen maßgeblichen Einfluss auf die Effizienz, um schlussendlich Produkte schneller auf den Markt zu bringen oder eine höhere Qualität zu erzielen. Wenn die Ergebnisse von Simulationen praktisch direkt nach ihrem Start zur Verfügung stehen würden, so könnten einzelne Iterationsschleifen drastisch verkürzt und dasmit eine Vielzahl von Design-Variationen exploriert werden. Auch die rechnergestützte Formoptimierung, bei der Hunderte von Simulationsrechnungen automatisiert durchgeführt werden, würde von solch kurzen Simulationszeiten stark profitieren. Im Projekt Rapid Interactive Structural Analysis wurde eine schnelle, interaktive Simulationslösung mit direkter Visualisierung auf Basis finiter Elemente entwickelt. Durch Nutzung der zur Verfügung stehen-den, immensen Rechenpower von Graphikkarten (GPUs) können Simulationen, wie beispielsweise strukturmechanische Analysen, signifikant beschleunigt werden. Der Lösungsansatz basiert auf massiv-parallelen Algorithmen und beschleunigt dadurch linear-elastische Struktursimulationen um einen Fak-tor von bis zu 80. Mit dieser schnellen Simulationstechnologie werden neuartige Anwendungen möglich, wie beispielsweise die direkte Identifikation von Korrelationen zwischen geometrischen Änderungen und Spannungsverteilung oder die signifikante Beschleunigung von Form- oder Topologieoptimierungen. Die Genauigkeit und Geschwindigkeit des vorgestellten Ansatzes zu herkömmlichen Simulationen auf Basis der Finite-Elemente-Methode (FEM) wird verglichen.

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Altenhofen, Christian; Luu, Thu Huong; Grasser, Tim; Dennstädt, Marco; Mueller-Roemer, Johannes; Weber, Daniel; Stork, André

Continuous Property Gradation for Multi-material 3D-printed Objects

2018

Solid Freeform Fabrication 2018: Proceedings of the 29th Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference

Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference <29, 2018, Austin, TX, USA>

Modern AM processes allow for printing multiple materials. The resulting objects can be stiff/dense in some areas and soft/porous in others, resulting in distinct physical properties. However, modeling material gradients is still tedious with current approaches, especially when smooth transitions are required. Current approaches can be distinguished into a) NURBS-BReps-based and b) voxel-based. In case of NURBS-BReps, discrete material distributions can be modeled by manually introducing separate shells inside the object; smooth gradation can only be approximated in discrete steps. For voxel representations, gradation is discrete by design and comes along with an approximation error. In addition, interacting on a per-voxel basis is tedious for the designer/engineer. We present a novel approach for representing material gradients in volumetric models using subdivision schemes, supporting continuity and providing elegant ways for interactive modeling of locally varying properties. Additionally, the continuous volumetric representation allows for on-demand sampling at any resolution required by the 3D printer.

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Altenhofen, Christian; Loosmann, Felix; Mueller-Roemer, Johannes; Grasser, Tim; Luu, Thu Huong; Stork, André

Integrating Interactive Design and Simulation for Mass Customized 3D-Printed Objects - A Cup Holder Example

2017

Solid Freeform Fabrication 2017: Proceedings of the 28th Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference

Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference <28, 2017, Austin, USA>

We present an approach for integrating interactive design and simulation for customizing parameterized 3D models. Instead of manipulating the mesh directly, a simplified interface for casual users allows for adapting intuitive parameters, such as handle diameter or height of our example object - a cup holder. The transition between modeling and simulation is performed with a volumetric subdivision representation, allowing direct adaption of the simulation mesh without re-meshing. Our GPU-based FEM solver calculates deformation and stresses for the current parameter configuration within seconds with a pre-defined load case. If the physical constraints are met, our system allows the user to 3D print the object. Otherwise, it provides guidance which parameters to change to optimize stability while adding as little material as possible based on a finite differences optimization approach. The speed of our GPU-solver and the fluent transition between design and simulation renders the system interactive, requiring no pre-computation.

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Grasser, Tim; Stork, André [Supervisor]; Weber, Daniel [Advisor]

Energy-Preserving Integrators for Fluid Animation with Discrete Exterior Calculus on Two-Dimensional Meshes

2012

Darmstadt, TU, Bachelor Thesis, 2012

In the last decades a lot of approaches have been developed for implementing computational fluid dynamics (CFD) in the computer graphics community. One of the new approaches in fluid simulations is the discrete exterior calculus (DEC). DEC uses well-centered meshes to describe its integration space. Mullen et al. [MCP+09] introduced 2009 a new integration scheme based on DEC and the Navier-Stokes equations that preserves mass by definition of DEC. His discrete formulation of the Navier-Stokes equations provides full control about viscosity and moreover an almost perfect preservation of kinetic energy. We translate Mullens discretization into two dimensions and extend it to regular girds. We will discuss how to manage non-trivial boundary conditions. Finally we will analyze the results of Mullens approach, and analyze alternative methods to further improve those results.