Despite the potential of Virtual Reality as the next computing platform for general purposes, current systems are tailored to stationary settings to support expansive interaction in mid-air. However, in mobile scenarios, the physical constraints of the space surrounding the user may be prohibitively small for spatial interaction in VR with classical controllers. In this paper, we present HandyCast, a smartphone-based input technique that enables full-range 3D input with two virtual hands in VR while requiring little physical space, allowing users to operate large virtual environments in mobile settings. HandyCast defines a pose-and-touch transfer function that fuses the phone's position and orientation with touch input to derive two individual 3D hand positions. Holding their phone like a gamepad, users can thus move and turn it to independently control their virtual hands. Touch input using the thumbs fine-tunes the respective virtual hand position and controls object selection. We evaluated HandyCast in three studies, comparing its performance with that of Go-Go, a classic bimanual controller technique. In our open-space study, participants required significantly less physical motion using HandyCast with no decrease in completion time or body ownership. In our space-constrained study, participants achieved significantly faster completion times, smaller interaction volumes, and shorter path lengths with HandyCast compared to Go-Go. In our technical evaluation, HandyCast's fully standalone inside-out 6D tracking performance again incurred no decrease in completion time compared to an outside-in tracking baseline.
https://doi.org/10.1145/3544548.3580677
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