Enhancing Physical Plausibility in Video Generation by Reasoning the Implausibility

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Main Authors: Hao, Yutong, Chen, Chen, Mian, Ajmal Saeed, Xu, Chang, Liu, Daochang
Format: Preprint
Published: 2025
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author Hao, Yutong
Chen, Chen
Mian, Ajmal Saeed
Xu, Chang
Liu, Daochang
author_facet Hao, Yutong
Chen, Chen
Mian, Ajmal Saeed
Xu, Chang
Liu, Daochang
contents Diffusion models can generate realistic videos, but existing methods rely on implicitly learning physical reasoning from large-scale text-video datasets, which is costly, difficult to scale, and still prone to producing implausible motions that violate fundamental physical laws. We introduce a training-free framework that improves physical plausibility at inference time by explicitly reasoning about implausibility and guiding the generation away from it. Specifically, we employ a lightweight physics-aware reasoning pipeline to construct counterfactual prompts that deliberately encode physics-violating behaviors. Then, we propose a novel Synchronized Decoupled Guidance (SDG) strategy, which leverages these prompts through synchronized directional normalization to counteract lagged suppression and trajectory-decoupled denoising to mitigate cumulative trajectory bias, ensuring that implausible content is suppressed immediately and consistently throughout denoising. Experiments across different physical domains show that our approach substantially enhances physical fidelity while maintaining photorealism, despite requiring no additional training. Ablation studies confirm the complementary effectiveness of both the physics-aware reasoning component and SDG. In particular, the aforementioned two designs of SDG are also individually validated to contribute critically to the suppression of implausible content and the overall gains in physical plausibility. This establishes a new and plug-and-play physics-aware paradigm for video generation.
format Preprint
id arxiv_https___arxiv_org_abs_2509_24702
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Enhancing Physical Plausibility in Video Generation by Reasoning the Implausibility
Hao, Yutong
Chen, Chen
Mian, Ajmal Saeed
Xu, Chang
Liu, Daochang
Computer Vision and Pattern Recognition
Diffusion models can generate realistic videos, but existing methods rely on implicitly learning physical reasoning from large-scale text-video datasets, which is costly, difficult to scale, and still prone to producing implausible motions that violate fundamental physical laws. We introduce a training-free framework that improves physical plausibility at inference time by explicitly reasoning about implausibility and guiding the generation away from it. Specifically, we employ a lightweight physics-aware reasoning pipeline to construct counterfactual prompts that deliberately encode physics-violating behaviors. Then, we propose a novel Synchronized Decoupled Guidance (SDG) strategy, which leverages these prompts through synchronized directional normalization to counteract lagged suppression and trajectory-decoupled denoising to mitigate cumulative trajectory bias, ensuring that implausible content is suppressed immediately and consistently throughout denoising. Experiments across different physical domains show that our approach substantially enhances physical fidelity while maintaining photorealism, despite requiring no additional training. Ablation studies confirm the complementary effectiveness of both the physics-aware reasoning component and SDG. In particular, the aforementioned two designs of SDG are also individually validated to contribute critically to the suppression of implausible content and the overall gains in physical plausibility. This establishes a new and plug-and-play physics-aware paradigm for video generation.
title Enhancing Physical Plausibility in Video Generation by Reasoning the Implausibility
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2509.24702