In this article, we propose an algorithm for aligning three-dimensional objects when represented as density maps, motivated by applications in cryogenic electron microscopy. The algorithm is based on minimizing the 1-Wasserstein distance between the density maps after a rigid transformation. The induced loss function enjoys a more benign landscape than its Euclidean counterpart and Bayesian optimization is employed for computation. Numerical experiments show improved accuracy and efficiency over existing algorithms on the alignment of real protein molecules. In the context of aligning heterogeneous pairs, we illustrate a potential need for new distance functions.
Impact StatementThis article proposes a fast algorithm for aligning three-dimensional volumes represented as density maps with a particular focus on applications in cryogenic electron microscopy. The algorithm achieves both improved accuracy and efficiency over existing methods on the alignment of real protein molecules. The article also demonstrates a potential need for new distance functions for the alignment of heterogeneous pairs of volumes.