131 research outputs found
A global approach to the refinement of manifold data
A refinement of manifold data is a computational process, which produces a
denser set of discrete data from a given one. Such refinements are closely
related to multiresolution representations of manifold data by pyramid
transforms, and approximation of manifold-valued functions by repeated
refinements schemes. Most refinement methods compute each refined element
separately, independently of the computations of the other elements. Here we
propose a global method which computes all the refined elements simultaneously,
using geodesic averages. We analyse repeated refinements schemes based on this
global approach, and derive conditions guaranteeing strong convergence.Comment: arXiv admin note: text overlap with arXiv:1407.836
Spline Subdivision Schemes for Compact Sets. A Survey
Dedicated to the memory of our colleague Vasil Popov January 14, 1942 β May 31, 1990
* Partially supported by ISF-Center of Excellence, and by The Hermann Minkowski Center for Geometry at Tel Aviv University, IsraelAttempts at extending spline subdivision schemes to operate
on compact sets are reviewed. The aim is to develop a procedure for
approximating a set-valued function with compact images from a finite set of
its samples. This is motivated by the problem of reconstructing a 3D object
from a finite set of its parallel cross sections. The first attempt is limited to
the case of convex sets, where the Minkowski sum of sets is successfully applied
to replace addition of scalars. Since for nonconvex sets the Minkowski
sum is too big and there is no approximation result as in the case of convex
sets, a binary operation, called metric average, is used instead. With the
metric average, spline subdivision schemes constitute approximating operators
for set-valued functions which are Lipschitz continuous in the Hausdorff
metric. Yet this result is not completely satisfactory, since 3D objects are
not continuous in the Hausdorff metric near points of change of topology,
and a special treatment near such points has yet to be designed
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