cal and global feature learning awareness. To remedy this,
introducing a more diverse set of filters in different band-
passes and hybridization with spatial-based models can be
a promising solution.
In this study, we propose a hybrid model (Figure 1) that
incorporates the merits of both spatial and spectral-based
approaches to overcome the limitations mentioned above.
Our model learns in an end-to-end setting, starting with a
point cloud U-Net block to learn geometric features and
feed them to a spectral-based graph convolutional network
to learn robust and discriminative features. To overcome
the over-smoothing nature of graph convolutional networks,
we adopt graph wavelet kernel as diverse filters to capture
intrinsic information from different band-pass lenses. To
make our filters even more diverse, we also propose to use
the anisotropic LBO to make our kernels directionally sen-
sitive. Finally, as the last layer of our network, we creatively
use a layer to perturb the feature map to force the network
to learn more discriminative features. As a result, it signifi-
cantly improves our system performance.
Overall, our contributions are summarized as follows:
(1) To our knowledge, it is the first geometric deep learning
framework that learns both spatial-based (via U-net) and
spectral-based (via anisotropic wavelet graph convolution
network) geometric features in a data-driven fashion. The
learned features are sensitive to subtle geometric changes
and robust to 3D discretization differences.
(2) We employ anisotropic wavelet filters to address the
common over-smoothing drawback of conventional graph
convolutional networks. Instead of only low-pass filter-
ing, we design graph wavelet functions with different band-
passes. Our work achieves a diverse set of filters sensitive
to various directions and band-passes and effectively learns
rich intrinsic geometric features.
(3) We creatively apply a simple feature perturbation func-
tion in our last layer. It significantly boosts our model’s per-
formance in both average geodesic errors and convergence
speed. The remarkable result may enrich our understand-
ing of geometric learning strategy designs and inspire new
architectures in the geometric deep learning field.
Our extensive experimental results verify the effective-
ness of our method. We hope this work contributes to shape
correspondence research and sheds new light on general ge-
ometric deep learning mechanisms to maximize their learn-
ing power.
2. Related Works
Shape correspondence computation methods generally
fall into three main categories: (1) traditional hand-crafted
descriptors defined in spatial and spectral domains, (2)
optimization-based methods rooted in the spectrum of
shapes with functional maps being the pillar, and (3), more
recent geometric deep learning techniques, notably graph
neural networks.
Starting with hand-crafted descriptors, they mainly fall
into spatial and spectral methods. The spatial-based de-
scriptors are usually based on statistics of locally defined
features [27]. These methods, mostly, suffer from gener-
alizability regarding changes in surface discretization and
capturing global information of the shape [32]. This behav-
ior is similar to spatial-based graph neural network frame-
works that rely on learning small receptive fields around
each vertex, making feature learning less globally aware.
Spectral-based methods heavily rely on the LBO spec-
trum. Importantly, these intrinsic descriptors are isometry-
invariant, making them robust to arbitrary spatial transfor-
mations. The methods proposed in [3, 8, 10] belong to
the spectral-based category. Most recently, wavelet-based
spectral-based descriptors have been proposed in [32, 21],
exploiting a multi-scale setting to diversify the set of learned
filters. However, our study does not rely on hand-crafted
features as they are sub-optimal in learning-based models.
The second category of shape correspondence tech-
niques is based on optimizing a dense map between shapes.
Particularly, the vanguard of such methods is the success-
ful functional map framework [26]. More recently, the au-
thors in [13, 12, 23] proposed unsupervised and supervised
learning schemes on top of the functional map for a more
robust and accurate correspondence. In [13], authors pro-
posed a U-Net structure to learn point-wise features to cir-
cumvent the pre-computation of hand-crafted features re-
sulting in geometrically meaningful features independent of
meshing structure. In [23], authors used a deep residual
network model to enhance the functional maps in creating
a soft correspondence map. One of the most recent works
on using a functional map based on learned features is the
work in [36]. They employed a continuous geodesic convo-
lution in an end-to-end fashion. In another study [12] with
functional map setting, authors introduced an unsupervised
framework for learning orientation-preserving features for
functional map computation, which is also robust to dis-
cretization changes in the mesh. The last category belongs
to the state-of-the-art methods rooted in geometric deep
learning, a new realm of deep learning in unstructured data
like point clouds and meshes. In [5], authors proposed win-
dowed Fourier transform in a supervised-learning setting to
learn local shape descriptors for shape matching problems
Later, they used anisotropic LBO to learn multi-kernel fil-
ters to further improve the accuracy and diversity of learned
features [21]. Though mainly used for node and graph clas-
sification settings, graph neural network models have also
been used for 3D dense shape correspondence. Frame-
works in [16, 25, 6] are among methods that hold state-of-
the-art performance in graph classification, 3D shape seg-
mentation, and shape matching. Another model based on
anisotropic LBO is proposed in [22] and their experiment