OP3DSG: Open-vocabulary Part-aware 3D Scene Graph Generation for Real-world Environments

3D scene graphs (3DSGs) provide a compact and structuredabstraction of 3D environments. Although advances in foundation modelshave enabled open-vocabulary 3DSG generation, existing approaches re-main object-centric and encode limited relational information—restrictingtheir applicability in real-world scenarios that require fine-grained under-standing. We propose OP3DSG, an open-vocabulary part-aware 3DSGgeneration framework that constructs unified graphs that jointly modelobjects, interactive parts, spatial relations, functional relations, and af-fordances. OP3DSG integrates object-part knowledge-guided detectionwith part-aware 3D fusion to preserve small and interaction-relevantcomponents, and employs a geometry-initialized prior graph with LLM-based refinement to reduce spurious relational predictions while enablingefficient graph construction. To systematically evaluate unified 3D scenegraph construction, we introduce UniGraph3D, a benchmark designedfor part-aware perception and multi-level relational reasoning. Experi-mental results show that OP3DSG achieves state-of-the-art performanceand demonstrates its effectiveness as a perception backbone in diversereal-world robotics tasks.