  An appropriate user interface to collect human demonstration data for
deformable object manipulation has been mostly overlooked in the literature. We
present an interaction design for demonstrating cloth folding to robots. Users
choose pick and place points on the cloth and can preview a visualization of a
simulated cloth before real-robot execution. Two interfaces are proposed: A 2D
display-and-mouse interface where points are placed by clicking on an image of
the cloth, and a 3D Augmented Reality interface where the chosen points are
placed by hand gestures. We conduct a user study with 18 participants, in which
each user completed two sequential folds to achieve a cloth goal shape. Results
show that while both interfaces were acceptable, the 3D interface was found to
be more suitable for understanding the task, and the 2D interface suitable for
repetition. Results also found that fold previews improve three key metrics:
task efficiency, the ability to predict the final shape of the cloth and
overall user satisfaction.
