Distortion Reduction for Off-Center Perspective Projection of Panoramas

A key assumption of perspective projection is that linear features in 3D shall remain linear after being projected to the 2D screen. This assumption is preserved when we draw a spherical panorama perspectively in arbitrary viewing directions and field-of-views as long as the camera position is fixed at the center. However, when the camera moves away from the center, barrel-like distortions appear and such assumption breaks. To address this issue, we propose modifications to the equirectangular-to-perspective (E2P) projection that significantly reduced distortion of linear features when the camera position is away from the center. We compared with other common methods that aim to augment panoramas with 3D information including: 1) building a point cloud augmented with per-pixel depth and 2) building a 3D room model according to room layouts, and found that our method produced rendering results with less linearity distortion measured quantitatively and qualitatively.