T2IRay🤛

Design of Thumb-to-Index based Indirect Pointing
for Continuous and Robust AR/VR Input

Jina Kim1, Yang Zhang2, Sang Ho Yoon1
(1) KAIST (2) UCLA
CHI 2025 (CHI 2025)
Paper (5.25 MB) Low-res Paper (3.78 MB) DOI

Abstract

Free-hand interactions have been widely deployed for AR/VR interfaces to promote a natural and seamless interaction experience. Among various types of hand interactions, microgestures are still limited to support discrete inputs and lack of continuous interaction theme. To this end, we propose a new pointing technique, T2IRay, which enables continuous indirect pointing by microgestures for continuous spatial input. We employ a own local coordinate system based on the thumb-to-index finger relationship to map computed raycasting direction for indirect pointing in a virtual environment. Furthermore, we examine various mapping methodologies and collected thumb-click behaviors to formulate thumb-to-index microgesture design guidelines to foster continuous, yet reliable input. We evaluated the design parameter for mapping indirect pointing with acceptable speed, depth, and range. We collected and analyzed the characteristics of click behaviors for future detection implementation. Our research demonstrates the potential and practicality of free-hand micro-finger input methods for advancing future interaction paradigms.

Core Contributions

Thumb-to-Index based Pointing Framework

  • free-hand fine-motor pointing to extend the previously limited discrete thumb-to-index (T2I) gesture into a readily available indirect input for pointing in AR/VR.
    Rather than constrained to a fixed interaction plane, we focus on bringing indirect input with any hand position or orientation

T2IRay Component

  • Finger Local Coordinate System Origin reference point at a semi-fist pose to maximize comfort for fine controllability.
  • Absolute Indirect Position Mapping Absolute pointing naturally allows unrestricted movement within the thumb’s motion range.
  • Head Engagement: Head movement expand the usable range of indirect input while maintaining the control performance of continuous input.

T2IRay's Local Coordinate System?

Video Presentation

BibTeX


        @inproceedings{kim2025t2iray,
        author = {Jina Kim and Yang Zhang and Sang Ho Yoon},
        title = {T2IRay: Design of Thumb-to-Index based Indirect Pointing for Continuous and Robust AR/VR Input},
        booktitle = {CHI Conference on Human Factors in Computing Systems (CHI '25)},
        year = {2025},
        month = {April},
        location = {Yokohama, Japan},
        publisher = {ACM},
        address = {New York, NY, USA},
        pages = {16},
        doi = {10.1145/3706598.3713442}
      }