On Bundle Adjustment for Multiview Point Cloud Registration


Related Publications

  1. On Bundle Adjustment for Multiview Point Cloud Registration
    Huaiyang Huang, Yuxiang Sun, Jin Wu, Jianhao Jiao and 4 more authors.
    IEEE Robotics and Automation Letters (RA-L), 2021

Abstract

Multiview registration is used to estimate Rigid Body Transformations (RBTs) from multiple frames and reconstruct a scene with corresponding scans. Despite the success of pairwise registration and pose synchronization, the concept of Bundle Adjustment (BA) has been proven to better maintain global consistency. So in this work, we make the multiview point-cloud registration more tractable from a different perspective in resolving range-based BA. Based on this analysis, we propose an objective function that takes both measurement noises and computational cost into account. For the feature parameter update, instead of calculating the global distribution parameters from the raw measurements, we aggregate the local distributions upon the pose update at each iteration. The computational cost of feature update is then only dependent on the number of scans. Finally, we develop a multiview registration system using voxel-based quantization that can be applied in real-world scenarios. The experimental results demonstrate our superiority over the baselines in terms of both accuracy and speed. Moreover, the results also show that our average positioning errors achieve the centimeter level.


Method

  • Least-squares formulation for the objective function.
  • Frame-wise aggregation of covariance instead of point-wise: $$\left\{ \begin{aligned} & \boldsymbol{\mu} = \sum_{k} \frac{n_k}{n} \boldsymbol{\mu}_k \\ & \boldsymbol{\Sigma} = \sum_{k} \frac{n_k}{n} \left( \boldsymbol{\Sigma}_k + \boldsymbol{\Sigma}_{\boldsymbol{\mu}_k} \right) \end{aligned} \right. ,$$ $$\boldsymbol{\Sigma}_{\boldsymbol{\mu}_k} = (\boldsymbol{\mu}_k -\boldsymbol{\mu}) (\boldsymbol{\mu}_k -\boldsymbol{\mu})^T.$$
  • Conditions for optimality of Eigenvalue Minimization (EVM) formulation: $$\left\{ \begin{aligned} & \mathbf{R}_k \cdot (\mathbf{R}_{\boldsymbol{\Sigma}_k} \mathbf{e}_{z}) \parallel \hat{\mathbf{n}}, \quad \forall k, \\ & \left( \boldsymbol{\mu}_k - \boldsymbol{\mu}_{k^\prime} \right) \perp \hat{\mathbf{n}}, \quad \forall k, k^\prime \end{aligned} \right. ,$$ which can be analogous to aligning the isoplane of each component.


    Results

    overview
    Dense point cloud reconstructed by TEASER + BA refinement, colored by height (top) and error (bottom).