vriphys: Workshop in Virtual Reality Interactions and Physical Simulations

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Browsing vriphys: Workshop in Virtual Reality Interactions and Physical Simulations by Subject "and object representations"

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    Efficient Breast Deformation Simulation
    (The Eurographics Association, 2012) Harz, Markus T.; Georgii, Joachim; Wang, Lei; Schilling, Kathy; Peitgen, Heinz-Otto; Jan Bender and Arjan Kuijper and Dieter W. Fellner and Eric Guerin
    Breast surgery might benefit from image guidance, if position and extend of the disease could be visualized in the same breast deformation as the surgery is performed. Such visualizations, however, are challenging to obtain, since the positioning for image acquisition in MRI is prone, while the patient lies supine for surgical procedures, causing a considerable deformation of the breasts between the two states. In our contribution, we outline a set of novel algorithms and methods to improve an efficient simulation of breast deformation between the prone image and the supine surgery positioning. In particular, we propose several extensions to a highly efficient dynamic corotated finite element method (FEM), namely non-linear material properties, the sliding of the breast tissue on the chest wall, and a fine-tuning step to align the breast model to a measured surface. All extensions are carefully designed to keep the efficiency and stability of the approach, and thus to allow their application in clinical routine. We explore all novel techniques using synthetic and volunteer prone and supine breast MRI data and assess their feasibility towards accurate, yet efficient simulation of large breast deformations.
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    Implicit Mesh Generation using Volumetric Subdivision
    (The Eurographics Association, 2017) Altenhofen, Christian; Schuwirth, Felix; Stork, André; Fellner, Dieter W.; Fabrice Jaillet and Florence Zara
    In this paper, we present a novel approach for a tighter integration of 3D modeling and physically-based simulation. Instead of modeling 3D objects as surface models, we use a volumetric subdivision representation. Volumetric modeling operations allow designing 3D objects in similar ways as with surface-based modeling tools. Encoding the volumetric information already in the design mesh drastically simplifies and speeds up the mesh generation process for simulation. The transition between design, simulation and back to design is consistent and computationally cheap. Since the subdivision and mesh generation can be expressed as a precomputable matrix-vector multiplication, iteration times can be greatly reduced compared to common modeling and simulation setups. Therefore, this approach is especially well suited for early-stage modeling or optimization use cases, where many geometric changes are made in a short time and their physical effect on the model has to be evaluated frequently. To test our approach, we created, simulated and adapted several 3D models. Additionally, we measured and evaluated the timings for generating and applying the matrices for different subdivision levels. For comparison, we also measured the tetrahedral meshing functionality offered by CGAL for similar numbers of elements. For changing topology, our implicit meshing approach proves to be up to 70 times faster than creating the tetrahedral mesh only based on the outer surface. Without changing the topology and by precomputing the matrices, we achieve a speed-up of up to 2800.