Traditional VR controllers cause fatigue by requiring a significant amount of wrist and arm movements. TwinSpin solves this by enabling object rotation with fingers, mimicking the natural motion of rolling a ball in the hand.

People naturally use precise finger movements in daily life, whether turning a key or fitting puzzle pieces together. However, conventional Virtual Reality (VR) controllers have failed to utilize this manual dexterity. Instead, users are forced to repeatedly twist their wrists or swing their entire arms to rotate virtual objects, leading to physical strain.

To address this issue, a research team led by Professor Geehyuk Lee at KAIST has developed TwinSpin, a novel controller that allows users to rotate virtual objects using their fingers. The core idea involves placing small trackballs where the thumb and index finger naturally rest on the controller. By rolling these trackballs, users can rotate objects intuitively, mimicking the gesture of rolling a large physical ball between their fingers. This innovative design enables precise rotation through intuitive finger manipulation without significantly altering the form factor of traditional controllers (Figure 1).

Figure 1: Comparison between the conventional arm-based rotation and the proposed finger-based rotation. Users can rotate objects using small trackballs located at the thumb and index finger, mimicking the motion of rolling a large virtual ball in the hand.

The research team validated the device's performance through a Docking Task involving both near and far objects (Figure 2). The results showed that TwinSpin significantly reduced task completion times compared to conventional arm-based methods. Furthermore, movements of the wrist, elbow, and shoulder were markedly reduced. User surveys also confirmed a substantial decrease in physical fatigue, with participants reporting that they could perform tasks much more comfortably and proficiently than with existing methods.

Figure 2: A user performing a docking task using TwinSpin in a VR environment. Trackers are attached to measure arm movements.

TwinSpin represents the first attempt in history to fully utilize fingers for complex rotation tasks within the power-grip style form factor of VR controllers. The researchers anticipate that this technology will significantly contribute to reducing user fatigue and enhancing efficiency in productivity tasks, such as VR 3D modeling.

Led by Changsung Lim (MS student, First Author) and Taejun Kim (PhD student, Second Author) from the KAIST HCI Lab (advised by Professor Geehyuk Lee), this research was presented at ACM Symposium on User Interface Software and Technology (UIST) 2025, a premier global conference in the field of Human-Computer Interaction (HCI). The study was recognized for its excellence with a Best Paper Honorable Mention Award. Additionally, the on-site demo session, conducted with Yohan Yun (MS student), received a positive reception from fellow researchers and won the People's Choice Demo Honorable Mention Award.

[Paper Title] : TwinSpin: A Virtual Ball in a VR Controller Enabling In-Hand 3DoF Rotation

[Paper Link] : https://doi.org/10.1145/3746059.3747735

[Video Link] : https://youtu.be/pTvxs5ChnCY?si=aJuZzHKGjwC3eH02