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Hauptverfasser: Ashutosh, Kumar, Wang, XuDong, Yin, Xi, Grauman, Kristen, Polyak, Adam, Misra, Ishan, Girdhar, Rohit
Format: Preprint
Veröffentlicht: 2026
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Online-Zugang:https://arxiv.org/abs/2601.14037
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author Ashutosh, Kumar
Wang, XuDong
Yin, Xi
Grauman, Kristen
Polyak, Adam
Misra, Ishan
Girdhar, Rohit
author_facet Ashutosh, Kumar
Wang, XuDong
Yin, Xi
Grauman, Kristen
Polyak, Adam
Misra, Ishan
Girdhar, Rohit
contents Video generation models have recently achieved impressive visual fidelity and temporal coherence. Yet, they continue to struggle with complex, non-rigid motions, especially when synthesizing humans performing dynamic actions such as sports, dance, etc. Generated videos often exhibit missing or extra limbs, distorted poses, or physically implausible actions. In this work, we propose a remarkably simple reward model, HuDA, to quantify and improve the human motion in generated videos. HuDA integrates human detection confidence for appearance quality, and a temporal prompt alignment score to capture motion realism. We show this simple reward function that leverages off-the-shelf models without any additional training, outperforms specialized models finetuned with manually annotated data. Using HuDA for Group Reward Policy Optimization (GRPO) post-training of video models, we significantly enhance video generation, especially when generating complex human motions, outperforming state-of-the-art models like Wan 2.1, with win-rate of 73%. Finally, we demonstrate that HuDA improves generation quality beyond just humans, for instance, significantly improving generation of animal videos and human-object interactions.
format Preprint
id arxiv_https___arxiv_org_abs_2601_14037
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Human detectors are surprisingly powerful reward models
Ashutosh, Kumar
Wang, XuDong
Yin, Xi
Grauman, Kristen
Polyak, Adam
Misra, Ishan
Girdhar, Rohit
Computer Vision and Pattern Recognition
Video generation models have recently achieved impressive visual fidelity and temporal coherence. Yet, they continue to struggle with complex, non-rigid motions, especially when synthesizing humans performing dynamic actions such as sports, dance, etc. Generated videos often exhibit missing or extra limbs, distorted poses, or physically implausible actions. In this work, we propose a remarkably simple reward model, HuDA, to quantify and improve the human motion in generated videos. HuDA integrates human detection confidence for appearance quality, and a temporal prompt alignment score to capture motion realism. We show this simple reward function that leverages off-the-shelf models without any additional training, outperforms specialized models finetuned with manually annotated data. Using HuDA for Group Reward Policy Optimization (GRPO) post-training of video models, we significantly enhance video generation, especially when generating complex human motions, outperforming state-of-the-art models like Wan 2.1, with win-rate of 73%. Finally, we demonstrate that HuDA improves generation quality beyond just humans, for instance, significantly improving generation of animal videos and human-object interactions.
title Human detectors are surprisingly powerful reward models
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2601.14037