A 2B vision-language model with a geometry head cut robot trajectory error over 60 percent and beat autoregressive decoding at 3.8 times the throughput
AspireAI community · arXiv (WACV 2027)
Predicting where to grasp and how to move is a geometry problem, but vision-language models tokenize spatial coordinates into text and decode them autoregressively, which ignores spatial structure and truncates continuous precision. This work shows compact 0.5-2B off-the-shelf VLMs already encode rich spatial information in intermediate hidden states, and exposes it with a lightweight geometry-compatible head attached to a frozen backbone: it reads an intermediate layer, conditions a learned query on the task instruction and regresses affordance boxes and trajectory waypoints directly as continuous values. On ShareRobot-Bench and AGD20K the 2B variant cuts trajectory error by over 60 percent and improves affordance mAP 85 percent against the autoregressive baseline, approaching RoboBrain on trajectory prediction (0.251 vs 0.191 DFD) at 3.8 times higher throughput. Continuous regression from the final representation already beats autoregressive decoding, which is the paper's own ablation finding.
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