Title
On The Continuity Of Rotation Representations In Neural Networks
Abstract
In neural networks, it is often desirable to work with various representations of the same space. For example, 3D rotations can be represented with quaternions or Euler angles. In this paper,we advance a definition of a continuous representation,which can be helpful for training deep neural networks. We relate this to topological concepts such as homeomorphism and embedding. We then investigate what are continuous and discontinuous representations for 2D, 3D, and n-dimensional rotations. We demonstrate that for 3D rotations, all representations are discontinuous in the real Euclidean spaces of four or fewer dimensions. Thus, widely used representations such as quaternions and Euler angles are discontinuous and difficult for neural networks to learn. We show that the 3D rotations have continuous representations in 5D and 6D, which are more suitable for learning. We also present continuous representations for the general case of the n-dimensional rotation group SO(n). While our main focus is on rotations,we also show that our constructions apply to other groups such as the orthogonal group and similarity transforms. We finally present empirical results, which show that our continuous rotation representations outperform discontinuous ones for several practical problems in graphics and vision, including a simple autoencoder sanity test, a rotation estimator for 3D point clouds, and an inverse kinematics solver for 3D human poses.
Year
DOI
Venue
2018
10.1109/CVPR.2019.00589
2019 IEEE/CVF CONFERENCE ON COMPUTER VISION AND PATTERN RECOGNITION (CVPR 2019)
Field
DocType
Volume
Mathematical optimization,Autoencoder,Algebra,Quaternion,Euler angles,Euclidean space,Orthogonal group,Solver,Artificial neural network,Rotation group SO,Mathematics
Journal
abs/1812.07035
ISSN
Citations 
PageRank 
1063-6919
11
0.46
References 
Authors
9
5
Name
Order
Citations
PageRank
Yi Zhou123032.97
Connelly Barnes2172959.07
Jingwan Lu321817.00
Jimei Yang4108340.68
Hao Li552018.80