Implicit Preference Alignment for Human Image Animation

Hugging Face Daily Papers Papers

Summary

This paper introduces Implicit Preference Alignment (IPA), a data-efficient post-training framework that improves hand motion generation in human image animation without requiring paired preference data. It utilizes implicit reward maximization and hand-aware local optimization to enhance generation quality while reducing data curation costs.

Human image animation has witnessed significant advancements, yet generating high-fidelity hand motions remains a persistent challenge due to their high degrees of freedom and motion complexity. While reinforcement learning from human feedback, particularly direct preference optimization, offers a potential solution, it necessitates the construction of strict preference pairs. However, curating such pairs for dynamic hand regions is prohibitively expensive and often impractical due to frame-wise inconsistencies. In this paper, we propose Implicit Preference Alignment (IPA), a data-efficient post-training framework that eliminates the need for paired preference data. Theoretically grounded in implicit reward maximization, IPA aligns the model by maximizing the likelihood of self-generated high-quality samples while penalizing deviations from the pretrained prior. Furthermore, we introduce a Hand-Aware Local Optimization mechanism to explicitly steer the alignment process toward hand regions. Experiments demonstrate that our method achieves effective preference optimization to enhance hand generation quality, while significantly lowering the barrier for constructing preference data. Codes are released at https://github.com/mdswyz/IPA
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Paper page - Implicit Preference Alignment for Human Image Animation

Source: https://huggingface.co/papers/2605.07545

Abstract

Implicit Preference Alignment (IPA) addresses hand motion generation challenges through data-efficient post-training that eliminates need for paired preference data while using hand-aware local optimization for improved quality.

Human image animation has witnessed significant advancements, yet generating high-fidelity hand motions remains a persistent challenge due to their high degrees of freedom and motion complexity. Whilereinforcement learning from human feedback, particularlydirect preference optimization, offers a potential solution, it necessitates the construction of strictpreference pairs. However, curating such pairs for dynamic hand regions is prohibitively expensive and often impractical due to frame-wise inconsistencies. In this paper, we proposeImplicit Preference Alignment(IPA), a data-efficientpost-training frameworkthat eliminates the need for paired preference data. Theoretically grounded inimplicit reward maximization, IPA aligns the model by maximizing the likelihood of self-generated high-quality samples while penalizing deviations from the pretrained prior. Furthermore, we introduce aHand-Aware Local Optimizationmechanism to explicitly steer the alignment process toward hand regions. Experiments demonstrate that our method achieves effective preference optimization to enhance hand generation quality, while significantly lowering the barrier for constructing preference data. Codes are released at https://github.com/mdswyz/IPA

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