  Achieving an immersive experience enabling users to explore virtual
environments with six degrees of freedom (6DoF) is essential for various
applications such as virtual reality (VR). Wide-baseline panoramas are commonly
used in these applications to reduce network bandwidth and storage
requirements. However, synthesizing novel views from these panoramas remains a
key challenge. Although existing neural radiance field methods can produce
photorealistic views under narrow-baseline and dense image captures, they tend
to overfit the training views when dealing with \emph{wide-baseline} panoramas
due to the difficulty in learning accurate geometry from sparse $360^{\circ}$
views. To address this problem, we propose PanoGRF, Generalizable Spherical
Radiance Fields for Wide-baseline Panoramas, which construct spherical radiance
fields incorporating $360^{\circ}$ scene priors. Unlike generalizable radiance
fields trained on perspective images, PanoGRF avoids the information loss from
panorama-to-perspective conversion and directly aggregates geometry and
appearance features of 3D sample points from each panoramic view based on
spherical projection. Moreover, as some regions of the panorama are only
visible from one view while invisible from others under wide baseline settings,
PanoGRF incorporates $360^{\circ}$ monocular depth priors into spherical depth
estimation to improve the geometry features. Experimental results on multiple
panoramic datasets demonstrate that PanoGRF significantly outperforms
state-of-the-art generalizable view synthesis methods for wide-baseline
panoramas (e.g., OmniSyn) and perspective images (e.g., IBRNet, NeuRay).
