NeurIPS Conference 2025 Conference Paper
LangHOPS: Language Grounded Hierarchical Open-Vocabulary Part Segmentation
- Yang Miao
- Jan-Nico Zaech
- Xi Wang
- Fabien Despinoy
- Danda Pani Paudel
- Luc V Gool
We propose LangHOPS, the first Multimodal Large Language Model (MLLM)-based framework for open-vocabulary object–part instance segmentation. Given an image, LangHOPS can jointly detect and segment hierarchical object and part instances from open-vocabulary candidate categories. Unlike prior approaches that rely on heuristic or learnable visual grouping, our approach grounds object–part hierarchies in language space. It integrates the MLLM into the object-part parsing pipeline to leverage rich knowledge and reasoning capabilities, and link multi-granularity concepts within the hierarchies. We evaluate LangHOPS across multiple challenging scenarios, including in-domain and cross-dataset object-part instance segmentation, and zero-shot semantic segmentation. LangHOPS achieves state-of-the-art results, surpassing previous methods by 5. 5% Average Precision(AP) (in-domain) and 4. 8% (cross-dataset) on the PartImageNet dataset and by 2. 5% mIOU on unseen object parts in ADE20K (zero-shot). Ablation studies further validate the effectiveness of the language-grounded hierarchy and MLLM-driven part query refinement strategy.