8,345 research outputs found
A Novel Self-Intersection Penalty Term for Statistical Body Shape Models and Its Applications in 3D Pose Estimation
Statistical body shape models are widely used in 3D pose estimation due to
their low-dimensional parameters representation. However, it is difficult to
avoid self-intersection between body parts accurately. Motivated by this fact,
we proposed a novel self-intersection penalty term for statistical body shape
models applied in 3D pose estimation. To avoid the trouble of computing
self-intersection for complex surfaces like the body meshes, the gradient of
our proposed self-intersection penalty term is manually derived from the
perspective of geometry. First, the self-intersection penalty term is defined
as the volume of the self-intersection region. To calculate the partial
derivatives with respect to the coordinates of the vertices, we employed
detection rays to divide vertices of statistical body shape models into
different groups depending on whether the vertex is in the region of
self-intersection. Second, the partial derivatives could be easily derived by
the normal vectors of neighboring triangles of the vertices. Finally, this
penalty term could be applied in gradient-based optimization algorithms to
remove the self-intersection of triangular meshes without using any
approximation. Qualitative and quantitative evaluations were conducted to
demonstrate the effectiveness and generality of our proposed method compared
with previous approaches. The experimental results show that our proposed
penalty term can avoid self-intersection to exclude unreasonable predictions
and improves the accuracy of 3D pose estimation indirectly. Further more, the
proposed method could be employed universally in triangular mesh based 3D
reconstruction
Feature Lines for Illustrating Medical Surface Models: Mathematical Background and Survey
This paper provides a tutorial and survey for a specific kind of illustrative
visualization technique: feature lines. We examine different feature line
methods. For this, we provide the differential geometry behind these concepts
and adapt this mathematical field to the discrete differential geometry. All
discrete differential geometry terms are explained for triangulated surface
meshes. These utilities serve as basis for the feature line methods. We provide
the reader with all knowledge to re-implement every feature line method.
Furthermore, we summarize the methods and suggest a guideline for which kind of
surface which feature line algorithm is best suited. Our work is motivated by,
but not restricted to, medical and biological surface models.Comment: 33 page
Accurate and efficient surface reconstruction from volume fraction data on general meshes
Simulations involving free surfaces and fluid interfaces are important in
many areas of engineering. There is, however, still a need for improved
simulation methods. Recently, a new efficient geometric VOF method called
isoAdvector for general polyhedral meshes was published. We investigate the
interface reconstruction step of isoAdvector, and demonstrate that especially
for unstructured meshes the applied isosurface based approach can lead to noisy
interface orientations. We then introduce a novel computational interface
reconstruction scheme based on calculation of a reconstructed distance function
(RDF). By iterating over the RDF calculation and interface reconstruction, we
obtain second order convergence of both the interface normal and position
within cells even with a strict error norm. In 2D this is verified
with reconstruction of a circle on Cartesian meshes and on unstructured
triangular and polygonal prism meshes. In 3D the second order convergence is
verified with reconstruction of a sphere on Cartesian meshes and on
unstructured tetrahedral and polyhedral meshes. The new scheme is combined with
the interface advection step of the isoAdvector algorithm. Significantly
reduced absolute advection errors are obtained, and for CFL number 0.2 and
below we demonstrate second order convergence on all the mentioned mesh types
in 2D and 3D. The implementation of the proposed interface reconstruction
schemes is straightforward and the computational cost is significantly reduced
compared to contemporary methods. The schemes are implemented as an extension
to the Computational Fluid Dynamics (CFD) Open Source software package,
OpenFOAM. The extension module and all test cases presented in this paper are
released as open source
Meshed Up: Learnt Error Correction in 3D Reconstructions
Dense reconstructions often contain errors that prior work has so far
minimised using high quality sensors and regularising the output. Nevertheless,
errors still persist. This paper proposes a machine learning technique to
identify errors in three dimensional (3D) meshes. Beyond simply identifying
errors, our method quantifies both the magnitude and the direction of depth
estimate errors when viewing the scene. This enables us to improve the
reconstruction accuracy.
We train a suitably deep network architecture with two 3D meshes: a
high-quality laser reconstruction, and a lower quality stereo image
reconstruction. The network predicts the amount of error in the lower quality
reconstruction with respect to the high-quality one, having only view the
former through its input. We evaluate our approach by correcting
two-dimensional (2D) inverse-depth images extracted from the 3D model, and show
that our method improves the quality of these depth reconstructions by up to a
relative 10% RMSE.Comment: Accepted for the International Conference on Robotics and Automation
(ICRA) 201
A reliable and efficient implicit a posteriori error estimation technique for the time harmonic Maxwell equations
We analyze an implicit a posteriori error indicator for the time harmonic Maxwell equations and prove that it is both reliable and locally efficient. For the derivation, we generalize some recent results concerning explicit a posteriori error estimates. In particular, we relax the divergence free constraint for the source term. We also justify the complexity of the obtained estimator
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