Efficient Initial Pose-Graph Generation for Global SfM

We propose ways to speed up the initial pose-graph generation for global Structure-from-Motion algorithms. To avoid forming tentative point correspondences by FLANN and geometric verification by RANSAC, which are the most time-consuming steps of the pose-graph creation, we propose two new methods -built on the fact that image pairs usually are matched consecutively. Thus, candidate relative poses can be recovered from paths in the partly-built posegraph. We propose a heuristic for the A * traversal, considering global similarity of images and the quality of the posegraph edges. Given a relative pose from a path, descriptorbased feature matching is made "light-weight" by exploiting the known epipolar geometry. To speed up PROSACbased sampling when RANSAC is applied, we propose a third method to order the correspondences by their inlier probabilities from previous estimations. The algorithms are tested on 402 130 image pairs from the 1DSfM dataset and they speed up the feature matching 17 times and pose estimation 5 times. Source code: https://github.com/ danini/pose-graph-initialization