  This paper presents a mixed-reality human-robot teaming system. It allows
human operators to see in real-time where robots are located, even if they are
not in line of sight. The operator can also visualize the map that the robots
create of their environment and can easily send robots to new goal positions.
The system mainly consists of a mapping and a control module. The mapping
module is a real-time multi-agent visual SLAM system that co-localizes all
robots and mixed-reality devices to a common reference frame. Visualizations in
the mixed-reality device then allow operators to see a virtual life-sized
representation of the cumulative 3D map overlaid onto the real environment. As
such, the operator can effectively "see through" walls into other rooms. To
control robots and send them to new locations, we propose a drag-and-drop
interface. An operator can grab any robot hologram in a 3D mini map and drag it
to a new desired goal pose. We validate the proposed system through a user
study and real-world deployments. We make the mixed-reality application
publicly available at https://github.com/cvg/HoloLens_ros.
