Title: Benchmarking Open-ended Segmentation
Primary area: datasets and benchmarks
Keywords: Benchmarking, Open-ended Segmentation, Evaluation Protocol, Lexical Alignment

Abstract: Open-ended segmentation requires models capable of generating free-form descriptions of previously unseen concepts and regions. Despite advancements in model development, current evaluation protocols for open-ended segmentation tasks fail to capture the true semantic accuracy of the generated descriptions. We empirically demonstrate that embedding‐based similarity score mappings diverge significantly from human judgments. To address this issue, we introduce a novel mapping function that considers multiple lexical relationships between free‐form outputs and test‐vocabulary labels, yielding much closer alignment with human annotations. We integrate this mapping into a robust evaluation framework and re‐benchmark previous state‐of‐the‐art methods. Additionally, we present the first Multi-modal Large‐Language Model trained with a contrastive objective to jointly align visual regions and textual descriptions, achieving new state‐of‐the‐art results in open‐ended panoptic segmentation.