Noise-Invariant Spatial Encoding for 3D Manipulation Policies under Depth Corruption

Overview & Synopsis

3D manipulation policies derive actions from explicit scene geometry rather than color images alone, enabling them to reason over metric distances, object relations, and robot-scene reachability. This geometric interface is also a vulnerability: commodity RGB-D sensors return missing measurements, boundary artifacts, and plausible but wrong surfaces around transparent, reflective, thin, or textureless objects. We study this failure under realistic depth corruption and observe a sharp depth-noise cliff across modern 3D policies, even when they are trained with matched noisy depth. This residual gap motivates a spatial-encoding approach: corrupted depth becomes entangled with the token coordinates and geometry features consumed by the action expert. We propose Noise-Invariant Spatial Encoding (NISE), a 3D policy architecture that learns trustworthy geometry features even facing imperfect depth. NISE uses Geometric Cross-View Self-Supervision to shape shared policy features with calibrated multi-view depth, and Gaussian Marginalized 3D Attention to carry position uncertainty into deployed attention rather than treating every lifted token as exact. Across simulated benchmarks with sensor-realistic corruption and real-robot tasks involving transparent and reflective materials, NISE improves depth-noise robustness while preserving clean-depth performance, supporting 3D policies designed for commodity RGB-D deployment rather than clean-depth benchmarks alone.