Beyond size, other items introduced

Beyond size, other items introduced challenges in percep-
tion and graspsing due to other parameters, such as shape,
deformation and the existence of transparent or reflective
surfaces. For instance, unpackaged dog toys whose shape
varied depending on how items shifted inside their collective
packaging, or a pencil cup holder made of black wire mesh that
foiled most sensors. Still other items were chosen because they
were easy to damage, like two soft-cover books or a package of
crushable Oreo cookies. The books introduced the additional
challenge that they could potentially open after lifted from
the bin with a vacuum gripper and then collide with the shelf
during the retraction process. Objects with reflective covers
are challenging for many depth sensors