  Roboticists compare robot motions for tasks such as parameter tuning,
troubleshooting, and deciding between possible motions. However, most existing
visualization tools are designed for individual motions and lack the features
necessary to facilitate robot motion comparison. In this paper, we utilize a
rigorous design framework to develop Motion Comparator, a web-based tool that
facilitates the comprehension, comparison, and communication of robot motions.
Our design process identified roboticists' needs, articulated design
challenges, and provided corresponding strategies. Motion Comparator includes
several key features such as multi-view coordination, quaternion visualization,
time warping, and comparative designs. To demonstrate the applications of
Motion Comparator, we discuss four case studies in which our tool is used for
motion selection, troubleshooting, parameter tuning, and motion review.
