6,169 research outputs found
Gap Processing for Adaptive Maximal Poisson-Disk Sampling
In this paper, we study the generation of maximal Poisson-disk sets with
varying radii. First, we present a geometric analysis of gaps in such disk
sets. This analysis is the basis for maximal and adaptive sampling in Euclidean
space and on manifolds. Second, we propose efficient algorithms and data
structures to detect gaps and update gaps when disks are inserted, deleted,
moved, or have their radius changed. We build on the concepts of the regular
triangulation and the power diagram. Third, we will show how our analysis can
make a contribution to the state-of-the-art in surface remeshing.Comment: 16 pages. ACM Transactions on Graphics, 201
Numerical and physical modelling in forming
An overview will be presented of recent developments concerning the application\ud
and development of computer codes for numerical simulation of forming processes. Special\ud
attention will be paid to the mathematical modeling of the material deformation and friction,\ud
and the effect of these models on the results of simulation
Error-Bounded and Feature Preserving Surface Remeshing with Minimal Angle Improvement
The typical goal of surface remeshing consists in finding a mesh that is (1)
geometrically faithful to the original geometry, (2) as coarse as possible to
obtain a low-complexity representation and (3) free of bad elements that would
hamper the desired application. In this paper, we design an algorithm to
address all three optimization goals simultaneously. The user specifies desired
bounds on approximation error {\delta}, minimal interior angle {\theta} and
maximum mesh complexity N (number of vertices). Since such a desired mesh might
not even exist, our optimization framework treats only the approximation error
bound {\delta} as a hard constraint and the other two criteria as optimization
goals. More specifically, we iteratively perform carefully prioritized local
operators, whenever they do not violate the approximation error bound and
improve the mesh otherwise. In this way our optimization framework greedily
searches for the coarsest mesh with minimal interior angle above {\theta} and
approximation error bounded by {\delta}. Fast runtime is enabled by a local
approximation error estimation, while implicit feature preservation is obtained
by specifically designed vertex relocation operators. Experiments show that our
approach delivers high-quality meshes with implicitly preserved features and
better balances between geometric fidelity, mesh complexity and element quality
than the state-of-the-art.Comment: 14 pages, 20 figures. Submitted to IEEE Transactions on Visualization
and Computer Graphic
SurfelMeshing: Online Surfel-Based Mesh Reconstruction
We address the problem of mesh reconstruction from live RGB-D video, assuming
a calibrated camera and poses provided externally (e.g., by a SLAM system). In
contrast to most existing approaches, we do not fuse depth measurements in a
volume but in a dense surfel cloud. We asynchronously (re)triangulate the
smoothed surfels to reconstruct a surface mesh. This novel approach enables to
maintain a dense surface representation of the scene during SLAM which can
quickly adapt to loop closures. This is possible by deforming the surfel cloud
and asynchronously remeshing the surface where necessary. The surfel-based
representation also naturally supports strongly varying scan resolution. In
particular, it reconstructs colors at the input camera's resolution. Moreover,
in contrast to many volumetric approaches, ours can reconstruct thin objects
since objects do not need to enclose a volume. We demonstrate our approach in a
number of experiments, showing that it produces reconstructions that are
competitive with the state-of-the-art, and we discuss its advantages and
limitations. The algorithm (excluding loop closure functionality) is available
as open source at https://github.com/puzzlepaint/surfelmeshing .Comment: Version accepted to IEEE Transactions on Pattern Analysis and Machine
Intelligenc
Improvements in FE-analysis of real-life sheet metal forming
An overview will be presented of recent developments concerning the application\ud
and development of computer codes for numerical simulation of sheet metal forming\ud
processes. In this paper attention is paid to some strategies which are followed to improve the\ud
accuracy and to reduce the computation time of a finite element simulation. Special attention\ud
will be paid to the mathematical modeling of the material deformation and friction, and the\ud
effect of these models on the results of simulations. An equivalent drawbead model is\ud
developed which avoids a drastic increase of computation time without significant loss of\ud
accuracy. The real geometry of the drawbead is replaced by a line on the tool surface. When\ud
an element of the sheet metal passes this drawbead line an additional drawbead restraining\ud
force, lift force and a plastic strain are added to that element. A commonly used yield\ud
criterion for anisotropic plastic deformation is the Hill yield criterion. This description is not\ud
always sufficient to accurately describe the material behavior. This is due to the\ud
determination of material parameters by uni-axial tests only. A new yield criterion is\ud
proposed, which directly uses the experimental results at multi-axial stress states. The yield\ud
criterion is based on the pure shear point, the uni-axial point, the plane strain point and the\ud
equi-biaxial point
Obtaining Potential Field Solution with Spherical Harmonics and Finite Differences
Potential magnetic field solutions can be obtained based on the synoptic
magnetograms of the Sun. Traditionally, a spherical harmonics decomposition of
the magnetogram is used to construct the current and divergence free magnetic
field solution. This method works reasonably well when the order of spherical
harmonics is limited to be small relative to the resolution of the magnetogram,
although some artifacts, such as ringing, can arise around sharp features. When
the number of spherical harmonics is increased, however, using the raw
magnetogram data given on a grid that is uniform in the sine of the latitude
coordinate can result in inaccurate and unreliable results, especially in the
polar regions close to the Sun.
We discuss here two approaches that can mitigate or completely avoid these
problems: i) Remeshing the magnetogram onto a grid with uniform resolution in
latitude, and limiting the highest order of the spherical harmonics to the
anti-alias limit; ii) Using an iterative finite difference algorithm to solve
for the potential field. The naive and the improved numerical solutions are
compared for actual magnetograms, and the differences are found to be rather
dramatic.
We made our new Finite Difference Iterative Potential-field Solver (FDIPS) a
publically available code, so that other researchers can also use it as an
alternative to the spherical harmonics approach.Comment: This paper describes the publicly available Finite Difference
Iterative Potential field Solver (FDIPS). The code can be obtained from
http://csem.engin.umich.edu/FDIP
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