Height and Uprightness Invariance for 3D Prediction From a Single View

Current state-of-the-art methods that predict 3D from single images ignore the fact that the height of objects and their upright orientation is invariant to the camera pose and intrinsic parameters. To account for this, we propose a system that directly regresses 3D world coordinates for each pixel. First, our system predicts the camera position with respect to the ground plane and its intrinsic parameters. Followed by that, it predicts the 3D position for each pixel along the rays spanned by the camera. The predicted 3D coordinates and normals are invariant to a change in the camera position or its model, and we can directly impose a regression loss on these world coordinates. Our approach yields competitive results for depth and camera pose estimation (while not being explicitly trained to predict any of these) and improves across-dataset generalization performance over existing state-of-the-art methods.