AbstractShape analysis is a mathematical approach to problems of pattern and object recognition and has developed considerably in the last decade. The use of shapes is natural in applications where it is interesting to compare curves or surfaces independently of their parametrisation. Considering a smooth setting where the parametrized curves or surfaces belong to an infinite dimensional Riemannian manifold, one defines the corresponding shapes to be equivalence classes of curves differing only by their parametrization. Under appropriate assumptions, the Riemannian metric can be used to obtain a meaningful measure of distance on the space of shapes. One computationally efficient approach to shape analysis is based on the Square Root Velocity Transform, and we have proposed a generalisation of this approach to shapes on Lie groups and homogeneous manifolds. The Lie group approach can be effective when dealing with skeletal animation data coming for example from human motion.
A demanding task when approximating shape distances is finding the optimal reparametrization. The problem can be phrased as an optimisation problem on the infinite dimensional group of orientation preserving diffeomorphisms Diff+(Ω), where Ω is the domain where the curves or surfaces are defined. In the case of curves, one robust approach to compute optimal reparametrizations is based on dynamic programming, [10], but this method seems difficult to generalize to surfaces.
We consider here a method where the approximations are obtained composing in succession a number of elementary diffeomorphism and optimising simultaneously over a larger number of parameters. This approach is reminiscent of deep learning with ResNets and the optimal control interpretation of deep learning.
If time permits I will discuss connection to structure preserving numerical discretization of differential equations, structure preserving deep learning andequivariant neural networks. This talk is built on material taken from [5, 6, 7, 11, 1, 3, 2].
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