  High-fidelity 3D scene reconstruction from monocular videos continues to be
challenging, especially for complete and fine-grained geometry reconstruction.
The previous 3D reconstruction approaches with neural implicit representations
have shown a promising ability for complete scene reconstruction, while their
results are often over-smooth and lack enough geometric details. This paper
introduces a novel neural implicit scene representation with volume rendering
for high-fidelity online 3D scene reconstruction from monocular videos. For
fine-grained reconstruction, our key insight is to incorporate geometric priors
into both the neural implicit scene representation and neural volume rendering,
thus leading to an effective geometry learning mechanism based on volume
rendering optimization. Benefiting from this, we present MonoNeuralFusion to
perform the online neural 3D reconstruction from monocular videos, by which the
3D scene geometry is efficiently generated and optimized during the on-the-fly
3D monocular scanning. The extensive comparisons with state-of-the-art
approaches show that our MonoNeuralFusion consistently generates much better
complete and fine-grained reconstruction results, both quantitatively and
qualitatively.
