PumpVR: Rendering theWeight of Objects and Avatars through Liquid Mass Transfer in Virtual Reality

Perceiving objects' and avatars' weight in Virtual Reality (VR) is important to understand their properties and naturally interact with them. However, commercial VR controllers cannot render weight. Controllers presented by previous work are single-handed, slow, or only render a small mass. In this paper, we present PumpVR that renders weight by varying the controllers' mass according to the properties of virtual objects or bodies. Using a bi-directional pump and solenoid valves, the system changes the controllers' absolute weight by transferring water in or out with an average error of less than 5%. We implemented VR use cases with objects and avatars of different weights to compare the system with standard controllers. A study with 24 participants revealed signifcantly higher realism and enjoyment when using PumpVR to interact with virtual objects. Using the system to render body weight had significant effects on virtual embodiment, perceived exertion, and self-perceived fitness.