  In this paper, we tackle the challenging task of learning a generalizable
human NeRF model from a monocular video. Although existing generalizable human
NeRFs have achieved impressive results, they require muti-view images or videos
which might not be always available. On the other hand, some works on
free-viewpoint rendering of human from monocular videos cannot be generalized
to unseen identities. In view of these limitations, we propose GHuNeRF to learn
a generalizable human NeRF model from a monocular video of the human performer.
We first introduce a visibility-aware aggregation scheme to compute vertex-wise
features, which is used to construct a 3D feature volume. The feature volume
can only represent the overall geometry of the human performer with
insufficient accuracy due to the limited resolution. To solve this, we further
enhance the volume feature with temporally aligned point-wise features using an
attention mechanism. Finally, the enhanced feature is used for predicting
density and color for each sampled point. A surface-guided sampling strategy is
also adopted to improve the efficiency for both training and inference. We
validate our approach on the widely-used ZJU-MoCap dataset, where we achieve
comparable performance with existing multi-view video based approaches. We also
test on the monocular People-Snapshot dataset and achieve better performance
than existing works when only monocular video is used. Our code is available at
the project website.
