LU-NeRF: Scene and Pose Estimation by Synchronizing Local Unposed NeRFs
Authors: name: Zezhou Cheng, name: Carlos Esteves, name: Varun Jampani, name: Abhishek Kar, name: Subhransu Maji, name: Ameesh Makadia

A critical obstacle preventing NeRF models from being deployed broadly in the
wild is their reliance on accurate camera poses. Consequently, there is growing
interest in extending NeRF models to jointly optimize camera poses and scene
representation, which offers an alternative to off-the-shelf SfM pipelines
which have well-understood failure modes. Existing approaches for unposed NeRF
operate under limited assumptions, such as a prior pose distribution or coarse
pose initialization, making them less effective in a general setting. In this
work, we propose a novel approach, LU-NeRF, that jointly estimates camera poses
and neural radiance fields with relaxed assumptions on pose configuration. Our
approach operates in a local-to-global manner, where we first optimize over
local subsets of the data, dubbed mini-scenes. LU-NeRF estimates local pose and
geometry for this challenging few-shot task. The mini-scene poses are brought
into a global reference frame through a robust pose synchronization step, where
a final global optimization of pose and scene can be performed. We show our
LU-NeRF pipeline outperforms prior attempts at unposed NeRF without making
restrictive assumptions on the pose prior. This allows us to operate in the
general SE(3) pose setting, unlike the baselines. Our results also indicate our
model can be complementary to feature-based SfM pipelines as it compares
favorably to COLMAP on low-texture and low-resolution images.