Voxel heatmap action heads for VLA manipulation policies
Teams training OpenVLA-OFT, π0.5, or similar VLA policies should test the action head as a replaceable component. ActionMap keeps the backbone fixed and replaces single-point action prediction with voxel heatmaps for translation, rotation, and gripper state. The training target is a soft Gaussian blob over the action grid, and inference recovers a continuous command with top-k soft argmax.
The practical test is small: run the same training budget with the native decoder and with a voxel heatmap head on LIBERO-Spatial and LIBERO-Long, then repeat on one real Franka pick or place task with grasp-position error logged. ActionMap reports a LIBERO four-suite gain for OpenVLA-OFT from 89.1% to 97.3%, a 10% data LIBERO-Spatial gain from 67.2% to 93.2%, and real Franka full-data trials rising from 7/30 to 20/30. Those numbers make the decoder swap a credible first experiment for teams seeing millimeter-scale end-effector errors or low-data failures.