Hugging Face Daily PapersYuheng Shi, Xiaohuan Pei, Minjing Dong1 min readpaperadvanced
Region-Level Policy Optimization for Fine-grained MLLM Perception
Summary
Vision‑RL2 trains a lightweight proposal network via region‑level reinforcement learning to select high‑resolution evidence for multimodal LLMs, allowing coarse‑resolution localization and fine‑resolution recognition. Across six fine‑grained vision benchmarks it reduces visual token count by ~4× while matching or surpassing full‑resolution accuracy.
- Localization tolerates 3–4× more token compression than recognition, enabling coarse‑view ROI detection.
- Vision‑RL2 uses a frozen MLLM to score region removals, training the proposal network without region annotations.
- Sparse encoding of selected regions amplifies evidence and discards background tokens, cutting memory and compute.
- Evaluated on six fine‑grained benchmarks and four MLLM backbones, achieving up to 4× fewer visual tokens with equal or higher accuracy.
MLLM engineers needing fine‑grained visual reasoning under token‑budget constraints should care.
8/10