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Andrei Sharf email: asharf “at” gmail.com |
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I am currently a Visiting Associate Professor at the Shenzhen
Institute of Advanced Technology (SIAT) Chinese Academy of Sciences,
Shenzhen, China. I did my PostDoc with Prof. Nina Amenta at the Visualization and Graphics Research
Group, University of California at Davis. My research is in the realm of
Computer Graphics; I concentrate on 3D shape modeling, interactive
techniques, geometry processing and topology. A major part of my research is
focused on various techniques and algorithms for reconstruction and filtering
of imperfect data. Recently I have been exploring parallel data structures on
the GPU and large scale 3D urban modeling. Here are links to my Curriculum Vitae, Research
statement and Teaching statement. |
Research:
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Consensus Skeleton for Non-rigid Space-time Registration Qian Zheng, Andrei Sharf, Andrea Tagliasacchi, Baoquan
Chen, Hao Zhang, Alla Sheffer, Daniel Cohen-Or Eurographics 2010 We introduce the notion of consensus skeletons for
non-rigid space-time registration of a deforming shape. Instead of basing the
registration on point features, which are local and sensitive to noise, we
adopt the curve skeleton of the shape as a global and descriptive feature for
the task. Our method uses no template and only assumes that the skeletal
structure of the captured shape remains largely consistent over time… |
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L1-sparse
Reconstruction of Sharp Point Set Surfaces Haim Avron, Andrei Sharf, Chen Greif, Daniel
Cohen-Or ACM TOG 2009
(referred to) We introduce an L1-sparse method for
the reconstruction of a piecewise smooth point set surface. The assumption
underlying our work is that common objects, even geometrically complex ones,
can typically be characterized by a rather small number of features. The
sparse reconstruction principle gives rise to a reconstructed point set
surface that consists mainly of smooth modes, with the residual of the
objective function strongly concentrated near sharp features… |
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Real-Time Parallel
Hashing on the GPU Dan A. Alcantara, Andrei Sharf, Fatemeh Abbasinejad, Shubho Sengupta, Michael Mitzenmacher, John Owens, Nina Amenta ACM SIGGRAPH ASIA 2009 We consider two parallel algorithms
for real-time hash table construction, a classical sparse perfect hashing
approach and cuckoo hashing, a scheme which packs elements densely by allowing
an element to be stored in one of multiple possible locations. Our
construction is a hybrid approach that uses both algorithms. We show how our
hashing method can be applied to two graphics applications, geometric hashing
and 3D surface intersection… |
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Rotating Scans for Systematic
Error Removal Fatemeh Abbasinejad, Yong J. Kil, Andrei Sharf, Nina Amenta Eurographics Symposium on Geometry
Processing 2009 2nd Best Paper Award Optical triangulation laser scanners produce errors
at surface discontinuities and sharp features. We examine the causes of these
errors theoretically, and we study the correlation of systematic error with edge
size and orientation experimentally. We then present a novel processing
method for removing systematic errors, by combining scans taken at several
different orientations... |
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Feature-driven Deformation for
Dense Correspondence Deboshmita Ghosh, Andrei Sharf, Nina Amenta Proceeding
of SPIE Medical Imaging 2009 We present a method for matching a template to a collection
of possibly target meshes. Our method uses a very small number of user-placed
landmarks, which we augment with automatically detected feature
correspondences, found using spin images. We deform the template onto the
data using an ICP-like framework, smoothing the noisy correspondences at each
step so as to produce an averaged motion… |
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Space-time
Surface Reconstruction Using Incompressible Flow
Andrei Sharf, Dan A. Alcantara, Thomas Lewiner, Chen
Greif, Alla Sheffer, Nina Amenta, Daniel Cohen-Or ACM SIGGRAPH ASIA
2008 We introduce a volumetric space-time technique for
the reconstruction of moving and deforming objects from point data. The
output of our method is a four-dimensional generalized cylinder in
space-time, made up of spatial slices, each of which is a three-dimensional
solid bounded by a watertight manifold. The motion of the object is described
as an incompressible flow of material through time … |
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On-the-fly
Curve-skeleton Computation for 3D Shapes Andrei Sharf, Thomas Lewiner, Ariel Shamir and Leif
Kobbelt Eurographics 2007 The
curve-skeleton of a 3D object is an abstract geometrical and topological
representation of its 3D shape. It maps the spatial relation of geometrically
meaningful parts to a graph structure. We present an algorithm to extract
such a skeleton on-the-fly, both from point clouds and polygonal meshes. The
algorithm is based on a deformable model evolution that captures the object’s
volumetric shape… |
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Interactive
Topology-aware Surface Reconstruction (Patent pending) Andrei Sharf, Thomas Lewiner, Gil Shklarski, Sivan ACM
SIGGRAPH 2007 The reconstruction of a
complete watertight model from scan data is still a difficult process. In
particular, since scanned data is often incomplete, the reconstruction of the
expected shape is an illposed problem. The method that we introduce in this
paper is topology-aware: it uses minimal user input to make correct decisions
at regions where the topology of the model cannot be automatically induced
with a reasonable degree of confidence... |
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SnapPaste:
An Interactive Technique for Easy Mesh Composition Andrei Sharf, Marina Blumenkrants, Ariel Shamir, and
Daniel Cohen–Or Editing and manipulation of existing
3D geometric objects are means to extend their repertoire and promote their
availability. Traditionally, tools to compose or manipulate objects defined
by 3D meshes are in the realm of artists and experts. In this paper, we
introduce a simple and effective user interface for easy composition of 3D
mesh-parts for non-professionals… |
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Competing Fronts for Coarse–to–Fine
Surface Reconstruction Andrei Sharf, Thomas Lewiner, Ariel Shamir, Leif
Kobbelt and Daniel Cohen–Or Eurographics 2006 We present a deformable model to
reconstruct a surface from a point cloud. The model is based on an explicit
mesh representation composed of multiple competing evolving fronts. These
fronts adapt to the local feature size of the target shape in a
coarse–to–fine manner. Hence, they approach towards the finer (local)
features of the target shape only after the reconstruction of the coarse
(global) features has been completed. This conservative approach leads to a
better control and interpretation of the reconstructed topology. |
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Context-based Surface Completion Andrei Sharf, Marc Alexa and Daniel Cohen-Or ACM
SIGGRAPH 2004 Sampling
complex, real-world geometry with range scanning devices almost always yields
imperfect surface samplings. These ’holes’ in the surface are commonly filled
with a smooth patch that conforms with the boundary. We introduce a
context-based method: the characteristics of the given surface are analyzed,
and the hole is iteratively filled by copying patches from valid regions of
the given surface. |
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Feature-sensitive 3D Shape
Matching Andrei Sharf and Ariel Shamir Computer Graphics International 2004 In this
paper we present a new framework for shape matching. We call our approach
“feature-sensitive” since it extends the usual geometry-based matching by
adding sensitivity to the shape topology, various local shape features (sharp
angles, chemical attributes) and their relative positioning on the shape. Our
method can be used in conjecture with other geometric matching methods as a
pre or post-processing filtering stage, or it can be used as a stand-alone
feature-sensitive matching. |
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Enhanced
Hierarchical Shape Matching for Shape Transformation International Journal for Shape Modeling 2003 In
this paper we present a new framework for matching shapes, represented by
union of spheres hierarchies. Our approach is “feature-sensitive” since it
extends the usual geometry-based matching by adding sensitivity to shape
topology, shape features (sharp angles, chemical attributes) and their
relative positioning on the shape. Our method can be used in conjecture with
other geometric matching methods as a pre or post-processing filtering stage,
or it can be used as a stand-alone feature-sensitive matching. |
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This
is a project that I presented and guided in a CG workshop. It is an interactive
file browser that provides focus and context using a non-linear metric space.
The project has won the 2nd place at the TAU Computer Science
(2005-2006) workshops projects competition. |
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The
installation creates a novel up to date dialogue between two domains: the
sculpture-museum space and the digital 3D space. The sculpture is positioned
in its original place in the museum while above, on a digital screen its same
3D scanned shape. These are two observation modes that combined together
create a complete and novel experience… |
