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DeepPhase: Periodic Autoencoders for Learning Motion Phase Manifolds

Sebastian Starke, Ian Mason, Taku Komura

SIGGRAPHAcademic93 cites2 descendantsMotion Synthesis

Periodic Autoencoder extracts unsupervised spatial-temporal phase features from large unstructured motion datasets, winning SIGGRAPH 2022 Best Paper.

Abstract

Learning the spatial-temporal structure of body movements is a fundamental problem for character motion synthesis. In this work, we propose a novel neural network architecture called the Periodic Autoencoder that can learn periodic features from large unstructured motion datasets in an unsupervised manner. The character movements are decomposed into multiple latent channels that capture the non-linear periodicity of different body segments while progressing forward in time. Our method extracts a multi-dimensional phase space from full-body motion data, which effectively clusters animations and produces a manifold in which computed feature distances provide a better similarity measure than in the original motion space to achieve better temporal and spatial alignment. We demonstrate that the learned periodic embedding can significantly help to improve neural motion synthesis in a number of tasks, including diverse locomotion skills, style-based movements, dance motion synthesis from music, synthesis of dribbling motions in football, and motion query for matching poses within large animation databases.

How to read this

Category
Method: neural architecture for unsupervised motion phase manifolds
Contributions
  • A Periodic Autoencoder that learns periodic motion features from large unstructured datasets in an unsupervised manner
  • Decomposition of movement into multiple latent channels capturing non-linear periodicity of body segments over time, yielding a multi-dimensional phase space
  • A learned phase embedding whose feature distances give a better similarity measure than raw motion space, improving temporal/spatial alignment across synthesis tasks
Context
Advances the authors' phase-based motion line, from the Neural State Machine (Starke et al. 2019) and Local Motion Phases (Starke et al. 2020), toward fully unsupervised, learned phase extraction.Builds on: Neural State Machine for Character-Scene Interactions · Local Motion Phases for Learning Multi-Contact Character Movements
Correctness
Key idea is that an unsupervised periodic embedding aligns and clusters motion better than the original space; demonstrated to help several synthesis tasks (locomotion, style, dance-from-music, dribbling, pose matching), with the reader caveat that gains depend on dataset richness and the chosen number of phase channels.
Clarity
Well written and influential (noted as SIGGRAPH 2022 Best Paper); the concept lands on a first pass while the periodic encoder formulation rewards a second.
How to read it
First pass for the phase-manifold idea and why phase distance beats motion-space distance; second pass on the Periodic Autoencoder formulation if you intend to use phases as features in your own synthesis pipeline.

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