Many traditional challenges in reconstructing 3D motion, such as matching across wide baselines and handling occlusion, reduce in significance as the number of unique viewpoints increases. However, to obtain this benefit, a new challenge arises: estimating precisely which cameras observe which points at each instant in time. We present a maximum a posteriori (MAP) estimate of the time-varying visibility of the target points to reconstruct the 3D motion of an event from a large number of cameras. Our algorithm takes, as input, camera poses and image sequences, and outputs the time-varying set of the cameras in which a target patch is visible and its reconstructed trajectory. We model visibility estimation as a MAP estimate by incorporating various cues including photometric consistency, motion consistency, and geometric consistency, in conjunction with a prior that rewards consistent visibilities in proximal cameras. An optimal estimate of visibility is obtained by finding the minimum cut of a capacitated graph over cameras. We demonstrate that our method estimates visibility with greater accuracy, and increases tracking performance producing longer trajectories, at more locations, and at higher accuracies than methods that ignore visibility or use photometric consistency alone.
Joint work with Hyun Soo Park and Yaser Sheikh.
Hanbyul Joo is a Ph.D. student at the Robotics Institute, Carnegie Mellon University, supervised by Prof. Yaser Sheikh. Before joining CMU, he worked as a researcher at ETRI, Korea, and received M.S. and B.S. from KAIST, Korea. He focuses on developing large-scale dynamic reconstruction using about 500 synchronized cameras. He is a recipient of Samsung Scholarship.