Browsing by Author "Stork, André"

Now showing 1 - 7 of 7
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    Design of a Toolbox to Assist the Cartoon Production
    (The Eurographics Association, 2023) Madeira, Joaquim; Stork, André; F. Mário Martins; José João Almeida; Jorge Gustavo Rocha
    The production of 2D animation films (i.e. cartoons) using traditional techniques is a la- bor- and cost-intensive process. If some of its tasks could be efficiently suppoited by ap- propriate computer tools, production costs would certainly decre-ase. A set of tools to assist the painting and inbetweening stages of the traditional cartoon production is currently being developed. The reasoning behind the toolbox structure and the fundamental aspects of the developed assisted painting approach are presented.
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    Direct Limit Volumes: Constant-Time Limit Evaluation for Catmull-Clark Solids
    (The Eurographics Association, 2018) Altenhofen, Christian; Müller, Joel; Weber, Daniel; Stork, André; Fellner, Dieter W.; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    We present a novel approach for efficient limit volume evaluation on Catmull-Clark (CC) subdivision solids. Although several analogies exist between subdivision surfaces and subdivision volumes, extending Stam's limit evaluation technique from 2 to 3 dimensions is not straightforward, as irregularities and boundaries introduce new challenges in the volumetric case. We present new direct evaluation techniques for irregular volumetric topologies and boundary cells, which allow for calculating the limit of CC subdivision solids at arbitrary parameter values in constant time. Evaluation of limit points is a central aspect when using CC solids for applications such as simulation and multi-material additive manufacturing, or as a compact volumetric representation scheme for continuous scalar fields. We demonstrate that our approach is faster than existing evaluation techniques for every topological configuration or target parameter (u, v, w) that requires more than two local subdivision steps.
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    GPU-based Polynomial Finite Element Matrix Assembly for Simplex Meshes
    (The Eurographics Association and John Wiley & Sons Ltd., 2018) Mueller-Roemer, Johannes Sebastian; Stork, André; Fu, Hongbo and Ghosh, Abhijeet and Kopf, Johannes
    In this paper, we present a matrix assembly technique for arbitrary polynomial order finite element simulations on simplex meshes for graphics processing units (GPU). Compared to the current state of the art in GPU-based matrix assembly, we avoid the need for an intermediate sparse matrix and perform assembly directly into the final, GPU-optimized data structure. Thereby, we avoid the resulting 180% to 600% memory overhead, depending on polynomial order, and associated allocation time, while simplifying the assembly code and using a more compact mesh representation. We compare our method with existing algorithms and demonstrate significant speedups.
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    GPU-Parallel Constant-Time Limit Evaluation of Catmull-Clark Solids
    (The Eurographics Association, 2021) Besler, Sebastian; Altenhofen, Christian; Stork, André; Fellner, Dieter W.; Andres, Bjoern and Campen, Marcel and Sedlmair, Michael
    Subdivision solids, such as Catmull-Clark (CC) solids, are versatile volumetric representation schemes that can be employed for geometric modeling, physically based simulation, and multi-material additive manufacturing. With volumetric limit evaluation still being the performance bottleneck for these applications, we present a massively parallel approach to Altenhofen et al.'s constant-time limit evaluation method for CC solids. Our algorithm exploits the computational power of modern GPUs, while maintaining the mathematical concepts of Altenhofen et al.'s method. Distributing the computations for a single cell across multiple streaming multiprocessors (SMs) increases the utilization of the GPU's resources compared to straightforward parallelization. Specialized compute kernels for different topological configurations optimize shared memory usage and memory access. Our hybrid approach dynamically chooses the best kernel based on the topology and the evaluation parameters, resulting in speedups of between 5.75x and 61.58x compared to a CPU-parallel implementation of Altenhofen et al.'s method.
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    Joint Schedule and Layout Autotuning for Sparse Matrices with Compound Entries on GPUs
    (The Eurographics Association, 2019) Mueller-Roemer, Johannes Sebastian; Stork, André; Fellner, Dieter W.; Schulz, Hans-Jörg and Teschner, Matthias and Wimmer, Michael
    Large sparse matrices with compound entries, i.e., complex and quaternionic matrices as well as matrices with dense blocks, are a core component of many algorithms in geometry processing, physically based animation, and other areas of computer graphics. We generalize several matrix layouts and apply joint schedule and layout autotuning to improve the performance of the sparse matrix-vector product on massively parallel graphics processing units. Compared to schedule tuning without layout tuning, we achieve speedups of up to 5.5x. In comparison to cuSPARSE, we achieve speedups of up to 4.7x
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    Massively Parallel Adaptive Collapsing of Edges for Unstructured Tetrahedral Meshes
    (The Eurographics Association, 2023) Ströter, Daniel; Stork, André; Fellner, Dieter W.; Bikker, Jacco; Gribble, Christiaan
    Many tasks in computer graphics and engineering involve unstructured tetrahedral meshes. Numerical methods such as the finite element method (FEM) oftentimes use tetrahedral meshes to compute a solution for complex problems such as physicallybased simulation or shape deformation. As each tetrahedron costs computationally, coarsening tetrahedral meshes typically reduces the overhead of numerical methods, which is attractive for interactive applications. In order to enable reduction of the tetrahedron count, we present a quick adaptive coarsening method for unstructured tetrahedral meshes. Our method collapses edges using the massively parallel processing power of present day graphics processing units (GPU)s to achieve run times of up to one order of magnitude faster than sequential collapsing. For efficient exploitation of parallel processing power, we contribute a quick method for finding a compact set of conflict-free sub-meshes, which results in up to 59% fewer parallel collapsing iterations compared to the state of the art massively parallel conflict detection.
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    Principal Curvature-Driven Segmentation of Mesh Models: A Preliminary Assessment
    (The Eurographics Association, 2021) Madeira, Joaquim; Silva, Samuel; Stork, André; Serna, Sebastian Pena; Santos, Luís Paulo and Fonseca, Manuel João and Dias, Miguel and Jorge, Joaquim A. and Santos, Vítor
    Three methods for triangle mesh segmentation, based on precomputed principal curvature values and using a region growing algorithm to label the vertices defining distinct surface regions, were developed, aiming at supporting the later manipulation of mesh models. Examples are presented, using different models, to illustrate their behavior. Results are promising but, in some cases, there is a clear need for a further post-processing step to refine the boundaries between adjoining regions and eliminate segmentation artifacts.