Understanding the Impact of Geometric Foundation Models on Vision-Language-Action Models
For researchers building robotic manipulation systems, this work provides a rigorous analysis and practical guidance on integrating 3D geometric understanding into VLAs, though it is incremental as it focuses on a specific VLA (GR00T-N1.5) and GFM (VGGT).
The paper investigates whether vision-language-action models (VLAs) lack geometric understanding, quantifies this 'geometric gap' via linear probing, and compares three architectures for integrating geometric foundation models (GFMs) into VLAs, finding that the best architecture improves task success by 15% over the baseline VLA.
Recent work explores new opportunities at the intersection of vision-language-action models (VLAs) and geometric foundation models (GFMs) for 3D reconstruction, such as VGGT. While the resulting geometric VLAs often show improved performance, it remains unclear (i) if modern VLAs already have sufficient geometric understanding to start with, (ii) what is the best architecture to inject geometric understanding into a VLA, and (iii) what is the effect of other design choices that affect geometric VLAs. In this paper we provide a rigorous experimental analysis to shed light on these questions, for a specific choice of VLA (GR00T-N1.5) and GFM (VGGT). Our first contribution is to formalize prior work's intuition that current VLAs lack geometric understanding, by providing a rigorous analysis based on linear probing. The analysis quantifies, for the first time, the "geometric gap" between VLAs and GFMs. Our second contribution is to identify and compare different strategies to bridge GFMs with VLAs. We implement three different architectures, which differ in the way they inject geometry in the VLA, while keeping low-level implementation details as similar as possible, to ensure a fair comparison. Finally, we analyze the impact of non-architectural choices (e.g., training data, number of cameras, reconstruction quality) on the performance of the geometric VLAs.