Defining Size Parameters for Touch Interaction in Substitutional Reality Environments<bold> </bold>

The physical support of touch interaction for a 2D interface when wearing a fully immersive head-mounted display (HMD), e.g., by using the kitchen table in a home environment, improves the user's quality of interaction. To define interface parameters - button size, adaption over time-we conducted a user study. In two experiments with 30 participants in total, we compared the ability of the HMD user's pointing to targets on a 2D surface without visual feedback, with visual feedback of the touched position and a real-world baseline. As a result, we give estimates for button dimensions, interaction design based on the learning curve of the user and present insights on the tested feedback modalities. We show that providing no feedback has limitations, presenting the touched position helps to increase accuracy and a head-mounted finger tracker has advantages but also comes with restrictions.<bold> </bold>