Resumen
Augmented reality (AR) technologies can blend digital and physical space and serve a variety of applications intuitively and effectively. Specifically, wearable AR enabled by optical see-through (OST) AR head-mounted displays (HMDs) might provide users with a direct view of the physical environment containing digital objects. Besides, users could directly interact with three-dimensional (3D) digital artefacts using freehand gestures captured by OST HMD sensors. However, as an emerging user interaction paradigm, freehand interaction with OST AR still requires further investigation to improve user performance and satisfaction. Thus, we conducted two studies to investigate various freehand selection design aspects in OST AR, including target placement, size, distance, position, and haptic feedback on the hand and body. The user evaluation results indicated that 40 cm might be an appropriate target distance for freehand gestural selection. A large target size might lower the selection time and error rate, and a small target size could minimise selection effort. The targets positioned in the centre are the easiest to select, while those in the corners require extra time and effort. Furthermore, we discovered that haptic feedback on the body could lead to high user preference and satisfaction. Based on the research findings, we conclude with design recommendations for effective and comfortable freehand gestural interaction in OST AR.