World Tracing: Pixel-Aligned Geometry Beyond the Visible

Single-image 3D methods often trade off pixel alignment and completeness: monocular reconstructors stay registered to visible pixels but stop at the first surface, while image-to-3D generators complete shapes in a canonical frame that is no longer aligned to the input. We introduce methodlong (method), a pixel-aligned multilayer geometry representation that keeps generated 3D in the input camera frame while completing geometry beyond the visible surface. For each input ray, method predicts an ordered stack of camera-space 3D points, where the first entry explains the observed surface and subsequent entries complete occluded surfaces along the same pixel ray. methodnet, a flow-matching diffusion transformer with a frozen 2D foundation encoder, learns this representation from depth-filled dense targets, removing the need for a separate per-layer visibility-mask head. The same objective covers static objects, static scenes, and dynamic clips, with temporal attention added for video. Because the output preserves the input camera frame, intrinsics, and pixel correspondences, it provides a direct 2D-to-3D interface for downstream systems, including text-driven 3D scene editing, geometry-conditioned novel-camera video generation, and training-free integration with existing textured-mesh generators. Across object, scene, and dynamic benchmarks, method improves visible-surface accuracy and complete-geometry quality over strong reconstruction and generation baselines.