PaCaPa - A Handheld VR Device for Rendering Size, Shape, and Stiffness of Virtual Objects in Tool-based Interactions.

We present PaCaPa, a handheld device that renders haptics on a user's palm when the user interacts with virtual objects using virtual tools such as a stick. PaCaPa is a cuboid device with two wings that open and close. As the user's stick makes contact with a virtual object, the wings open by a specific degree to dynamically change the pressure on the palm and fingers. The open angle of the wings is calculated from the angle between the virtual stick and hand direction. As the stick bites into the target object, a large force is generated. Our device enables three kinds of renderings: size, shape, and stiffness. We conducted user studies to evaluate the performance of our device. We also evaluated our device in two application scenarios. User feedback and qualitative ratings indicated that our device can make indirect interaction with handheld tools more realistic.