11,550 research outputs found
Data-Driven Shape Analysis and Processing
Data-driven methods play an increasingly important role in discovering
geometric, structural, and semantic relationships between 3D shapes in
collections, and applying this analysis to support intelligent modeling,
editing, and visualization of geometric data. In contrast to traditional
approaches, a key feature of data-driven approaches is that they aggregate
information from a collection of shapes to improve the analysis and processing
of individual shapes. In addition, they are able to learn models that reason
about properties and relationships of shapes without relying on hard-coded
rules or explicitly programmed instructions. We provide an overview of the main
concepts and components of these techniques, and discuss their application to
shape classification, segmentation, matching, reconstruction, modeling and
exploration, as well as scene analysis and synthesis, through reviewing the
literature and relating the existing works with both qualitative and numerical
comparisons. We conclude our report with ideas that can inspire future research
in data-driven shape analysis and processing.Comment: 10 pages, 19 figure
A Survey of the Trends in Facial and Expression Recognition Databases and Methods
Automated facial identification and facial expression recognition have been
topics of active research over the past few decades. Facial and expression
recognition find applications in human-computer interfaces, subject tracking,
real-time security surveillance systems and social networking. Several holistic
and geometric methods have been developed to identify faces and expressions
using public and local facial image databases. In this work we present the
evolution in facial image data sets and the methodologies for facial
identification and recognition of expressions such as anger, sadness,
happiness, disgust, fear and surprise. We observe that most of the earlier
methods for facial and expression recognition aimed at improving the
recognition rates for facial feature-based methods using static images.
However, the recent methodologies have shifted focus towards robust
implementation of facial/expression recognition from large image databases that
vary with space (gathered from the internet) and time (video recordings). The
evolution trends in databases and methodologies for facial and expression
recognition can be useful for assessing the next-generation topics that may
have applications in security systems or personal identification systems that
involve "Quantitative face" assessments.Comment: 16 pages, 4 figures, 3 tables, International Journal of Computer
Science and Engineering Survey, October, 201
FutureMapping: The Computational Structure of Spatial AI Systems
We discuss and predict the evolution of Simultaneous Localisation and Mapping
(SLAM) into a general geometric and semantic `Spatial AI' perception capability
for intelligent embodied devices. A big gap remains between the visual
perception performance that devices such as augmented reality eyewear or
comsumer robots will require and what is possible within the constraints
imposed by real products. Co-design of algorithms, processors and sensors will
be needed. We explore the computational structure of current and future Spatial
AI algorithms and consider this within the landscape of ongoing hardware
developments
An Extended Beta-Elliptic Model and Fuzzy Elementary Perceptual Codes for Online Multilingual Writer Identification using Deep Neural Network
Actually, the ability to identify the documents authors provides more chances
for using these documents for various purposes. In this paper, we present a new
effective biometric writer identification system from online handwriting. The
system consists of the preprocessing and the segmentation of online handwriting
into a sequence of Beta strokes in a first step. Then, from each stroke, we
extract a set of static and dynamic features from new proposed model that we
called Extended Beta-Elliptic model and from the Fuzzy Elementary Perceptual
Codes. Next, all the segments which are composed of N consecutive strokes are
categorized into groups and subgroups according to their position and their
geometric characteristics. Finally, Deep Neural Network is used as classifier.
Experimental results reveal that the proposed system achieves interesting
results as compared to those of the existing writer identification systems on
Latin and Arabic scripts
A Stable Cardinality Distance for Topological Classification
This work incorporates topological features via persistence diagrams to
classify point cloud data arising from materials science. Persistence diagrams
are multisets summarizing the connectedness and holes of given data. A new
distance on the space of persistence diagrams generates relevant input features
for a classification algorithm for materials science data. This distance
measures the similarity of persistence diagrams using the cost of matching
points and a regularization term corresponding to cardinality differences
between diagrams. Establishing stability properties of this distance provides
theoretical justification for the use of the distance in comparisons of such
diagrams. The classification scheme succeeds in determining the crystal
structure of materials on noisy and sparse data retrieved from synthetic atom
probe tomography experiments.Comment: 15 pages, 8 figure
Machine Learning Techniques and Applications For Ground-based Image Analysis
Ground-based whole sky cameras have opened up new opportunities for
monitoring the earth's atmosphere. These cameras are an important complement to
satellite images by providing geoscientists with cheaper, faster, and more
localized data. The images captured by whole sky imagers can have high spatial
and temporal resolution, which is an important pre-requisite for applications
such as solar energy modeling, cloud attenuation analysis, local weather
prediction, etc.
Extracting valuable information from the huge amount of image data by
detecting and analyzing the various entities in these images is challenging.
However, powerful machine learning techniques have become available to aid with
the image analysis. This article provides a detailed walk-through of recent
developments in these techniques and their applications in ground-based
imaging. We aim to bridge the gap between computer vision and remote sensing
with the help of illustrative examples. We demonstrate the advantages of using
machine learning techniques in ground-based image analysis via three primary
applications -- segmentation, classification, and denoising
Shape Recognition by Bag of Skeleton-associated Contour Parts
Contour and skeleton are two complementary representations for shape
recognition. However combining them in a principal way is nontrivial, as they
are generally abstracted by different structures (closed string vs graph),
respectively. This paper aims at addressing the shape recognition problem by
combining contour and skeleton according to the correspondence between them.
The correspondence provides a straightforward way to associate skeletal
information with a shape contour. More specifically, we propose a new shape
descriptor. named Skeleton-associated Shape Context (SSC), which captures the
features of a contour fragment associated with skeletal information. Benefited
from the association, the proposed shape descriptor provides the complementary
geometric information from both contour and skeleton parts, including the
spatial distribution and the thickness change along the shape part. To form a
meaningful shape feature vector for an overall shape, the Bag of Features
framework is applied to the SSC descriptors extracted from it. Finally, the
shape feature vector is fed into a linear SVM classifier to recognize the
shape. The encouraging experimental results demonstrate that the proposed way
to combine contour and skeleton is effective for shape recognition, which
achieves the state-of-the-art performances on several standard shape
benchmarks.Comment: 10 pages. Has been Accepted by Pattern Recognition Letters 201
A Novel Space-Time Representation on the Positive Semidefinite Con for Facial Expression Recognition
In this paper, we study the problem of facial expression recognition using a
novel space-time geometric representation. We describe the temporal evolution
of facial landmarks as parametrized trajectories on the Riemannian manifold of
positive semidefinite matrices of fixed-rank. Our representation has the
advantage to bring naturally a second desirable quantity when comparing shapes
-- the spatial covariance -- in addition to the conventional affine-shape
representation. We derive then geometric and computational tools for
rate-invariant analysis and adaptive re-sampling of trajectories, grounding on
the Riemannian geometry of the manifold. Specifically, our approach involves
three steps: 1) facial landmarks are first mapped into the Riemannian manifold
of positive semidefinite matrices of rank 2, to build time-parameterized
trajectories; 2) a temporal alignment is performed on the trajectories,
providing a geometry-aware (dis-)similarity measure between them; 3) finally,
pairwise proximity function SVM (ppfSVM) is used to classify them,
incorporating the latter (dis-)similarity measure into the kernel function. We
show the effectiveness of the proposed approach on four publicly available
benchmarks (CK+, MMI, Oulu-CASIA, and AFEW). The results of the proposed
approach are comparable to or better than the state-of-the-art methods when
involving only facial landmarks.Comment: To be appeared at ICCV 201
A state of the art of urban reconstruction: street, street network, vegetation, urban feature
World population is raising, especially the part of people living in cities.
With increased population and complex roles regarding their inhabitants and
their surroundings, cities concentrate difficulties for design, planning and
analysis. These tasks require a way to reconstruct/model a city. Traditionally,
much attention has been given to buildings reconstruction, yet an essential
part of city were neglected: streets. Streets reconstruction has been seldom
researched. Streets are also complex compositions of urban features, and have a
unique role for transportation (as they comprise roads). We aim at completing
the recent state of the art for building reconstruction (Musialski2012) by
considering all other aspect of urban reconstruction. We introduce the need for
city models. Because reconstruction always necessitates data, we first analyse
which data are available. We then expose a state of the art of street
reconstruction, street network reconstruction, urban features
reconstruction/modelling, vegetation , and urban objects
reconstruction/modelling.
Although reconstruction strategies vary widely, we can order them by the role
the model plays, from data driven approach, to model-based approach, to inverse
procedural modelling and model catalogue matching. The main challenges seems to
come from the complex nature of urban environment and from the limitations of
the available data. Urban features have strong relationships, between them, and
to their surrounding, as well as in hierarchical relations. Procedural
modelling has the power to express these relations, and could be applied to the
reconstruction of urban features via the Inverse Procedural Modelling paradigm.Comment: Extracted from PhD (chap1
AMAT: Medial Axis Transform for Natural Images
We introduce Appearance-MAT (AMAT), a generalization of the medial axis
transform for natural images, that is framed as a weighted geometric set cover
problem. We make the following contributions: i) we extend previous medial
point detection methods for color images, by associating each medial point with
a local scale; ii) inspired by the invertibility property of the binary MAT, we
also associate each medial point with a local encoding that allows us to invert
the AMAT, reconstructing the input image; iii) we describe a clustering scheme
that takes advantage of the additional scale and appearance information to
group individual points into medial branches, providing a shape decomposition
of the underlying image regions. In our experiments, we show state-of-the-art
performance in medial point detection on Berkeley Medial AXes (BMAX500), a new
dataset of medial axes based on the BSDS500 database, and good generalization
on the SK506 and WH-SYMMAX datasets. We also measure the quality of
reconstructed images from BMAX500, obtained by inverting their computed AMAT.
Our approach delivers significantly better reconstruction quality with respect
to three baselines, using just 10% of the image pixels. Our code and
annotations are available at https://github.com/tsogkas/amat .Comment: 10 pages (including references), 5 figures, accepted at ICCV 201
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