🤖 AI Summary
This work addresses the limitations of existing visual preference optimization methods, which rely on coarse-grained feedback or off-policy perturbations and struggle to support fine-grained visual reasoning. The authors propose rDPO, a novel framework that introduces, for the first time, an instance-level scoring rubric mechanism. This mechanism defines core and auxiliary criteria for each image-instruction pair, enabling the construction of an offline rubric pool subsequently used for online policy data generation and response scoring. By integrating rubric-guided prompt engineering and rubric-based response filtering, rDPO significantly enhances the quality and task relevance of preference data. Experimental results demonstrate that rDPO achieves performance close to GPT-5.4 on established reward modeling benchmarks, with a downstream macro-average score of 82.69 and a composite scalability score of 61.01, both surpassing current state-of-the-art baselines.
📝 Abstract
The effectiveness of Direct Preference Optimization (DPO) depends on preference data that reflect the quality differences that matter in multimodal tasks. Existing pipelines often rely on off-policy perturbations or coarse outcome-based signals, which are not well suited to fine-grained visual reasoning. We propose rDPO, a preference optimization framework based on instance-specific rubrics. For each image-instruction pair, we create a checklist-style rubric of essential and additional criteria to score responses from any possible policies. The instruction-rubric pool is built offline and reused during the construction of on-policy data. On public reward modeling benchmarks, rubric-based prompting massively improves a 30B-A3B judge and brings it close to GPT-5.4. On public downstream benchmarks, rubric-based filtering raises the macro average to 82.69, whereas outcome-based filtering drops it to 75.82 from 81.14. When evaluating scalability on a comprehensive benchmark, rDPO achieves 61.01, markedly outperforming the style-constrained baseline (52.36) and surpassing the 59.48 base model. Together, these results show that visual preference optimization benefits from combining on-policy data construction with instance-specific criterion-level feedback.