MG²-RAG: Multi-Granularity Graph for Multimodal Retrieval-Augmented Generation

MULTIMODAL RETRIEVAL-AUGMENTED GENERATION

MG²-RAG

Multi-Granularity Graph for Multimodal Retrieval-Augmented Generation

A lightweight framework that preserves textual structure and fine-grained visual evidence in a unified multimodal graph, then retrieves across four semantic granularities with graph propagation.

Sijun Dai1,†Qiang Huang1,†Xiaoxing You2Jun Yu1,*

1 Harbin Institute of Technology (Shenzhen)   2 Hangzhou Dianzi University Equal contribution   * Corresponding author
43.3×average construction speedup

23.9×average cost reduction

Evaluated on retrieval, knowledge-based VQA, multimodal reasoning, and crisis classification.

Multi-Granularity Graph Case

Solid nodes form the PPR graph. Dashed sentence and object nodes visualize auxiliary retrieval pivots and their aggregation paths.

Drag nodes · scroll to zoom · drag canvas to pan

Graph Retrieval Example

Multimodal query signals activate the unified graph and rank the supporting chunk first.

QuestionQuery image of an impalaHow many days does the gestation of this animal take?
Generated answer180 days

PPR OUTPUT

Retrieved documents

Recall@1 = 1.0

RETRIEVED EVIDENCE

“Gestation lasts six to seven months, following which a single calf is born and immediately concealed in cover.”
Qwen3.6 generation1804 completion tokens · finish: stop

Framework Overview

Construction aligns text entities with visual regions. Retrieval activates evidence from chunks, sentences, images and objects before propagating relevance over the unified graph.

Complete MG2-RAG framework showing multimodal graph construction and retrieval

Knowledge-Based VQA Cases

Retrieved multimodal evidence supports entity recognition, factual grounding and cross-modal alignment.

VQA case studies covering a bridge, bird, lake, and edible plant
VQA case studies covering plant source, building location, bridge length, and building designer

Construction Efficiency

Lightweight textual structure extraction and entity-driven visual grounding reduce construction time and monetary cost.

Graph construction time and cost comparison across five multimodal datasets

Citation

If you find MG²-RAG useful in your research, please cite our paper.

@inproceedings{dai2026mg2rag,
  title={MG$^2$-RAG: Multi-Granularity Graph for Multimodal Retrieval-Augmented Generation},
  author={Sijun Dai and Qiang Huang and Xiaoxing You and Jun Yu},
  booktitle={Proceedings of the 19th European Conference on Computer Vision (ECCV)},
  year={2026},
}