CurvedTouch: Effects of Surface Curvature and Cursor Mapping Method for XR Touch Input on Curved Surface

Extended reality (XR) systems now use everyday physical surfaces as touch input spaces. However, existing systems rely primarily on flat surfaces due to the given device form factor and sensing capabilities. Despite advancements in sensing technologies that allow touch input across surfaces with diverse curvatures, the effects of surface curvature on user behavior and performance in indirect XR touch interaction remain underexplored. To this end, we present CurvedTouch, a study that investigates the effects of surface curvature and cursor mapping methods on XR indirect touch interaction. We evaluated 4 surface curvatures (flat, R = 75mm, 60mm, and 45mm) and two cursor mapping methods (Projection-based and Distance-based) in a within-subject study by measuring task performance, behavioral pattern, workload, and usability. 16 participants performed the indirect Tap, Drag, and Trace task under certain conditions. Our results reveal that the task performance and usability significantly dropped for a curvature between R = 45mm and R = 60mm. As curvature increases, users change their input strategy from finger-level motion to whole-hand movement. Unlike prior findings in direct touch interaction, we found that minimum button size increases on a high curvature surface in an indirect touch scenario. For the cursor mapping method, distance-based mapping showed higher usability under high curvature. Based on these findings, we came up with design guidelines for interaction type, button size, interaction area, and cursor mapping method for the XR indirect touch interface on a curved surface.