Struct2D: A Perception-Guided Framework for Spatial Reasoning in MLLMs

Fuente: arXiv
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Main Authors: Zhu, Fangrui, Wang, Hanhui, Xie, Yiming, Gu, Jing, Ding, Tianye, Yang, Jianwei, Jiang, Huaizu
Format: Preprint
Published: 2025
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author Zhu, Fangrui
Wang, Hanhui
Xie, Yiming
Gu, Jing
Ding, Tianye
Yang, Jianwei
Jiang, Huaizu
author_facet Zhu, Fangrui
Wang, Hanhui
Xie, Yiming
Gu, Jing
Ding, Tianye
Yang, Jianwei
Jiang, Huaizu
contents Unlocking spatial reasoning in Multimodal Large Language Models (MLLMs) is crucial for enabling intelligent interaction with 3D environments. While prior efforts often rely on explicit 3D inputs or specialized model architectures, we ask: can MLLMs reason about 3D space using only structured 2D representations derived from perception? We introduce Struct2D, a perception-guided prompting framework that combines bird's-eye-view (BEV) images with object marks and object-centric metadata, optionally incorporating egocentric keyframes when needed. Using Struct2D, we conduct an in-depth zero-shot analysis of closed-source MLLMs (e.g., GPT-o3) and find that they exhibit surprisingly strong spatial reasoning abilities when provided with structured 2D inputs, effectively handling tasks such as relative direction estimation and route planning. Building on these insights, we construct Struct2D-Set, a large-scale instruction tuning dataset with 200K fine-grained QA pairs across eight spatial reasoning categories, generated automatically from 3D indoor scenes. We fine-tune an open-source MLLM (Qwen2.5VL) on Struct2D-Set, achieving competitive performance on multiple benchmarks, including 3D question answering, dense captioning, and object grounding. Our approach demonstrates that structured 2D inputs can effectively bridge perception and language reasoning in MLLMs-without requiring explicit 3D representations as input. We will release both our code and dataset to support future research.
format Preprint
id arxiv_https___arxiv_org_abs_2506_04220
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Struct2D: A Perception-Guided Framework for Spatial Reasoning in MLLMs
Zhu, Fangrui
Wang, Hanhui
Xie, Yiming
Gu, Jing
Ding, Tianye
Yang, Jianwei
Jiang, Huaizu
Computer Vision and Pattern Recognition
Unlocking spatial reasoning in Multimodal Large Language Models (MLLMs) is crucial for enabling intelligent interaction with 3D environments. While prior efforts often rely on explicit 3D inputs or specialized model architectures, we ask: can MLLMs reason about 3D space using only structured 2D representations derived from perception? We introduce Struct2D, a perception-guided prompting framework that combines bird's-eye-view (BEV) images with object marks and object-centric metadata, optionally incorporating egocentric keyframes when needed. Using Struct2D, we conduct an in-depth zero-shot analysis of closed-source MLLMs (e.g., GPT-o3) and find that they exhibit surprisingly strong spatial reasoning abilities when provided with structured 2D inputs, effectively handling tasks such as relative direction estimation and route planning. Building on these insights, we construct Struct2D-Set, a large-scale instruction tuning dataset with 200K fine-grained QA pairs across eight spatial reasoning categories, generated automatically from 3D indoor scenes. We fine-tune an open-source MLLM (Qwen2.5VL) on Struct2D-Set, achieving competitive performance on multiple benchmarks, including 3D question answering, dense captioning, and object grounding. Our approach demonstrates that structured 2D inputs can effectively bridge perception and language reasoning in MLLMs-without requiring explicit 3D representations as input. We will release both our code and dataset to support future research.
title Struct2D: A Perception-Guided Framework for Spatial Reasoning in MLLMs
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2506.04220