SphereBridge: Single-Panorama 3D Gaussian Reconstruction for High-Resolution Real-Time Multi-Sphere Rendering

Immersive 360-degree browsing in VR/AR and spatial photography requires turning a single panorama into a high-resolution scene representation that supports nearby views. Feed-forward 3D Gaussian Splatting (3DGS) has made nearby-view synthesis practical for perspective images, but its pinhole recipe assumes a planar local view, whereas a panorama covers the full sphere and must be reconstructed as one 360-degree scene. Tangent-crop workarounds restore pinhole compatibility at the cost of stitching seams and scale drift, and single-panorama pipelines that respect spherical geometry need over an hour of per-scene optimization. We present SphereBridge, a panorama-native pipeline that predicts a panorama-wide 3D Gaussian field from a single equirectangular panorama in one forward pass and bakes it into a Multi-Sphere Image (MSI) for high-resolution rendering. The Multi-Sphere Rendering Bridge routes the Gaussians onto concentric spherical layers, which reduces each frame to closed-form ray-sphere compositing with no per-frame Gaussian sorting, and injects the source panorama's high-frequency detail into the layer textures, which preserves detail at high output resolution. Because real captures rarely provide registered nearby views, training relies on synthetic data, and a training-free Tangent-View Scaffolding extends it to unlabeled real panoramas, using a stitched tangent-view reconstruction as a displaced input view and the real capture as supervision. Across indoor and outdoor benchmarks, SphereBridge reaches state-of-the-art single-panorama quality on LPIPS and DISTS, and its MSI renderer raises perceptual quality at high output resolution while rendering $4096\times 4096$ perspective views at 23.92 FPS on a single NVIDIA A800 GPU.