417 research outputs found
3D Shape Descriptor-Based Facial Landmark Detection: A Machine Learning Approach
Facial landmark detection on 3D human faces has had numerous applications in the literature
such as establishing point-to-point correspondence between 3D face models which is itself a
key step for a wide range of applications like 3D face detection and authentication, matching,
reconstruction, and retrieval, to name a few.
Two groups of approaches, namely knowledge-driven and data-driven approaches, have been
employed for facial landmarking in the literature. Knowledge-driven techniques are the
traditional approaches that have been widely used to locate landmarks on human faces. In
these approaches, a user with sucient knowledge and experience usually denes features to
be extracted as the landmarks. Data-driven techniques, on the other hand, take advantage
of machine learning algorithms to detect prominent features on 3D face models. Besides
the key advantages, each category of these techniques has limitations that prevent it from
generating the most reliable results.
In this work we propose to combine the strengths of the two approaches to detect facial
landmarks in a more ecient and precise way. The suggested approach consists of two phases.
First, some salient features of the faces are extracted using expert systems. Afterwards,
these points are used as the initial control points in the well-known Thin Plate Spline (TPS)
technique to deform the input face towards a reference face model. Second, by exploring and
utilizing multiple machine learning algorithms another group of landmarks are extracted.
The data-driven landmark detection step is performed in a supervised manner providing an
information-rich set of training data in which a set of local descriptors are computed and used
to train the algorithm. We then, use the detected landmarks for establishing point-to-point
correspondence between the 3D human faces mainly using an improved version of Iterative
Closest Point (ICP) algorithms. Furthermore, we propose to use the detected landmarks for
3D face matching applications
Deep Shape Representations for 3D Object Recognition
Deep learning is a rapidly growing discipline that models high-level features in data as multilayered
neural networks. The recent trend toward deep neural networks has been driven, in large part, by
a combination of affordable computing hardware, open source software, and the availability of
pre-trained networks on large-scale datasets.
In this thesis, we propose deep learning approaches to 3D shape recognition using a multilevel
feature learning paradigm. We start by comprehensively reviewing recent shape descriptors,
including hand-crafted descriptors that are mostly developed in the spectral geometry setting and
also the ones obtained via learning-based methods. Then, we introduce novel multi-level feature
learning approaches using spectral graph wavelets, bag-of-features and deep learning. Low-level
features are first extracted from a 3D shape using spectral graph wavelets. Mid-level features are
then generated via the bag-of-features model by employing locality-constrained linear coding as a
feature coding method, in conjunction with the biharmonic distance and intrinsic spatial pyramid
matching in a bid to effectively measure the spatial relationship between each pair of the bag-offeature
descriptors.
For the task of 3D shape retrieval, high-level shape features are learned via a deep auto-encoder
on mid-level features. Then, we compare the deep learned descriptor of a query shape to the
descriptors of all shapes in the dataset using a dissimilarity measure for 3D shape retrieval. For the
task of 3D shape classification, mid-level features are represented as 2D images in order to be fed
into a pre-trained convolutional neural network to learn high-level features from the penultimate
fully-connected layer of the network. Finally, a multiclass support vector machine classifier is
trained on these deep learned descriptors, and the classification accuracy is subsequently computed.
The proposed 3D shape retrieval and classification approaches are evaluated on three standard 3D
shape benchmarks through extensive experiments, and the results show compelling superiority of
our approaches over state-of-the-art methods
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