Neural implicit representation, the parameterization of distance function as a coordinate neural field, has emerged as a promising lead in tackling surface reconstruction from unoriented point clouds. To enforce consistent orientation, existing methods focus on regularizing the gradient of the distance function, such as constraining it to be of the unit norm, minimizing its divergence, or aligning it with the eigenvector of Hessian that corresponds to zero eigenvalue. However, under the presence of large scanning noise, they tend to either overfit the noise input or produce an excessively smooth reconstruction. In this work, we propose to guide the surface reconstruction under a new variant of neural field, the octahedral field, leveraging the spherical harmonics representation of octahedral frames originated in the hexahedral meshing. Such field automatically snaps to geometry features when constrained to be smooth, and naturally preserves sharp angles when interpolated over creases. By simultaneously fitting and smoothing the octahedral field alongside the implicit geometry, it behaves analogously to bilateral filtering, resulting in smooth reconstruction while preserving sharp edges. Despite being operated purely pointwise, our method outperforms various traditional and neural approaches across extensive experiments, and is very competitive with methods that require normal and data priors. Our full implementation is available at: https://github.com/Ankbzpx/frame-field.

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