The development of mobile devices nowadays shows an increasing trend toward interacting with 3D digital content on a 2D touch screen. However, many issues regarding the appropriateness of the control mode require further exploration. The experimental design in this study designates displays of two sizes—five inches and seven inches—with three groups of hand gestures controlling the X-, Y-, and Z-axis, respectively. The three groups of gestures are compared in terms of how they interact with the 3D content. In the experiment, 30 adult research subjects twice completed a task that involved rotating three 3D immersive-heritage models. Their characteristics, completion time, subjective evaluation, and frequency of gesture change were measured and examined. The results from the experiment and the statistics from a two-way Analysis of Variance (ANOVA) indicate: (1) the display size and the task-completion time are inversely related. Under the effect of the Control–Display ratio, using a smaller display results in a shorter completion time while using a larger display results in a longer completion time; (2) tasks with obvious characteristics for the 3D objects require a shorter time to complete, but those with no obvious characteristics require more time; and (3) using familiar hand gestures leads to a shorter task-completion time, while using unfamiliar hand gestures leads to a longer completion time. The findings of this study show that the Control–Display ratio is an important factor that affects the operational performance of the 3D immersive-heritage model’s rotation tasks completed with hand gestures on small displays. In addition, adaptability and familiarity should be taken into consideration when introducing new hand gestures. Hence, the suggestions in this study constitute important guidelines for museums designing technology for the interaction between mobile devices and 3D immersive-heritage models. 
The effects of screen size on rotating 3D contents using compound gestures on a mobile device