Guiding Handrays in Virtual Reality: Comparison of Gaze- and Object-Based Assistive Raycast Redirection

Handray selection is widely used for hand-tracking-based interactions in head-mounted displays, as it is a simple and straightforward interaction technique. However, selection performance decreases for small and distant objects. It is also negatively affected by input inaccuracies due to natural hand tremors, tracking issues, and movement caused by pinch gestures. Recent work introduced assistive raycast redirection for controller raycasting which facilitates object selection in virtual reality. It applies a gradual proximity and gain-based redirection of the ray towards the target center within a predefined redirection zone. Inspired by this approach, we implemented two redirection techniques for improving handray selection while maintaining ease of use: (1) RayToTarget, which adapts existing controller-based raycast redirection to hand-tracking, and (2) gaze-assisted RayToGaze as a novel technique. We evaluated them together with classic handray in a Fitts' Law user study. Our findings suggest that both redirection techniques perform significantly better than classic handray, but performance for RayToGaze decreases at greater target depth compared to RayToTarget. Generally, handray redirection was well received and did not decrease the sense of agency. However, different individual preferences and target acquisition strategies affect the user experience for both redirection techniques and might impact selection performance.