MaskPlanner: A Framework for 3D Learning-Based Object-Centric Motion Generation and Applications to Robotic Spray Painting

Object-centric motion generation (OCMG) plays a key role in a variety of industrial applications - such as robotic spray painting and welding - requiring efficient, scalable, and generalizable algorithms to plan multiple long-horizon trajectories over free-form 3D objects. However, existing solutions rely on specialized heuristics, expensive optimization routines, or restrictive geometry assumptions that limit their adaptability to real-world scenarios. In this work, we introduce a novel, fully data-driven framework that tackles OCMG directly from 3D point clouds, learning to generalize expert path patterns across free-form surfaces. We propose MaskPlanner, a deep learning method that predicts local path segments for a given object while simultaneously inferring 'path masks' to group these segments into distinct paths. This design induces the network to capture both local geometric patterns and global task requirements in a single forward pass. Extensive experimentation on a realistic robotic spray painting scenario shows that our approach attains near-complete coverage (above 99%) for unseen objects, while it remains task-agnostic and does not explicitly optimize for paint deposition. Moreover, our real-world validation on a 6-DoF specialized painting robot demonstrates that the generated paths are directly executable and yield expert-level painting quality. We additionally provide empirical evidence that our approach remains complementary to downstream trajectory optimization methods, and applicable to tasks beyond spray painting.