What's the Thumb Doing? Improving Precision for Thumb-to-Finger Interactions on Hand Proximate User Interfaces

Hand Proximate User Interfaces (HPUI) on Head Mounted Displays (HMD) leverage hand tracking to anchor content on the hand and interact with it using thumb-to-finger interactions. Similar to many other interaction techniques on HMDs, HPUI realizes these interactions by combining simple geometry in game engines. This, in turn, leads to accidental triggers, akin to the 'fat-finger problem' on touch screens. To address this, we explore and provide insight into how the thumb's surface interacts when using HPUI by approximating the thumb's surface with a large number of raycasts. We observe that different regions of the thumb are used when interacting with different parts of the hand. The results also highlight the need to consider the temporal component. We then propose approaches to improving the precision of thumb-to-finger interactions on HPUI and show that these improve target selection accuracy with denser target layouts.

Shariff AM Faleel, Rishav Banerjee, Omang Baheti, Khalad Hasan, and Pourang Irani. 2025. “What’s the Thumb Doing?Improving Precision for Thumb-to-Finger Interactions on Hand Proximate User Interfaces”, Accepted at Graphics Interface 2025.