  In recent years, there has been increasing interest in applying stylization
on 3D scenes from a reference style image, in particular onto neural radiance
fields (NeRF). While performing stylization directly on NeRF guarantees
appearance consistency over arbitrary novel views, it is a challenging problem
to guide the transfer of patterns from the style image onto different parts of
the NeRF scene. In this work, we propose a stylization framework for NeRF based
on local style transfer. In particular, we use a hash-grid encoding to learn
the embedding of the appearance and geometry components, and show that the
mapping defined by the hash table allows us to control the stylization to a
certain extent. Stylization is then achieved by optimizing the appearance
branch while keeping the geometry branch fixed. To support local style
transfer, we propose a new loss function that utilizes a segmentation network
and bipartite matching to establish region correspondences between the style
image and the content images obtained from volume rendering. Our experiments
show that our method yields plausible stylization results with novel view
synthesis while having flexible controllability via manipulating and
customizing the region correspondences.
