Investigating Pointing Performance for Tangible Surfaces with Physical 3D Targets

One of the most fundamental interactions -pointing- is well understood on flat surfaces. However, pointing performance on tangible surfaces with physical targets is still limited for Tangible User Interfaces (TUIs). We investigate the effect of a target's physical width, height, and distance on user pointing performance. We conducted a study using a reciprocal tapping task (n=19) with physical rods arranged in a circle. We compared our data with five conventional interaction models designed for 2D/3D tasks rather than tangible targets. We show that variance in the movement times was only satisfactorily explained by a model established for volumetric displays (r2=0.954). Analysis shows that movement direction and height should be included as parameters to this model to generalize for 3D tangible targets. Qualitative feedback from participants suggests that pointing at physical targets involves additional human factors (e.g., perception of sharpness or robustness) that need to be investigated further to understand how performance with tangible objects is affected.