Beyond Observed Rays: Query-Guided Completion of Layered Gaussian Driving Worlds

Driving-scene reconstruction with 3D Gaussian Splatting (3DGS) turns sensor logs into 3D environments, making recorded driving scenes renderable and editable for closed-loop simulation. However, reconstructing scenes solely from recorded camera observations leaves weakly observed or unseen object surfaces and occluded background regions poorly reconstructed. During closed-loop simulation, ego-vehicle motion may shift the camera away from the recorded trajectory, exposing previously unobserved regions and associated reconstruction defects, which can compromise simulation reliability. We introduce FullSplat, a task-query completion framework that uses expected exposure within a bounded camera–action distribution to identify low-support regions that later queries may expose and complete them in a reusable 3D scene. A structured 3D prior generates object-canonical Gaussian residuals that follow rigid object motion, while masked rectified flow generates world-fixed background residuals; cross-layer conflict resolution and observation-preserving gates integrate both into one persistent scene for later rendering and editing without further generation. Experiments on Waymo and nuScenes cover reconstruction and novel-view synthesis, with rigid-object edits and 4–6 m camera-offset stress tests beyond the 3 m range on Waymo. Results show better captured-view fidelity, novel-view quality, and temporal consistency, with improvements under object translation, rotation, and removal and in views beyond the completion range.