## 5 Discussion
In contrast to prior studies, the aim of recruiting participants with multi-cultural backgrounds was to build mappings between 3D microgestures and commands so they were not required to design gestures for a given command with a 'think out loud' strategy [41]. Thus, a comparison to the selection of microgestures for similar commands in other elicitation studies is vital to support the feasibility of our experimental design. Gesture \(q\) (_form the okay posture_) was assigned by 29 participants to activate the interface to accept hand gestures as input. The same gesture was preferred by users from China while gesture _thumb up_ was preferred by users from the US to commit the command [42,44]. From our study, gesture _form the okay posture_ can be a replacement for the gesture _thumb up_ to execute commands like _confirmation_, _accept_, and _activation_ for users from the US and Europe. Studies [25, 26, 27] pointed out that the consensus on the importance of designing gestures for commonly used commands _navigation_ and _selection_. The gesture _index finger points forward with the forearm in a neutral position_ was adopted to control the 3D virtual cursor while the gesture _index finger points forward with the forearm in a pronated position_ was utilized to translate the virtual target which was the same as prior studies [25,27,41]. Moving the cursor movement is usually required for selecting a virtual object, so the choices of gesture combinations for controlling the virtual cursor and for object selection are important so that users can execute the sequential commands continuously with fluid movements and transitions. The microgestures assigned to the commands' cursor and selection were similar to those of a prior study where users preferred the gestures _index finger points forward with the forearm in a neutral position_ and _thumb taps on the side of the middle finger with the index finger pointing forward and forearm in a neutral position_[27]. Similarly, the gesture _index finger points forward with the palm down_ and _the gesture index finger tops on the table with the palm down_ were selected for the two commands, respectively, by more than 20 participants. Therefore, gesture developers may provide the above two combinations as choices for users to control the cursor and select an object. The commands _confirm_, _reject_, and _undo_ are commonly used in human-computer interaction. The microgesture _index fingertip taps thumb tip_ was performed to complete commands _select_, _play_, _next_, and _accept_, while gesture middle fingertip taps thumb tip was assigned to complete _pause_, _previous_, and _reject_ commands in the study [37]. However, such connections between gesture and commands may not be intuitive. In our study, participants preferred performing gestures _palm scrolls repeatedly with palm down_ and _index finger scrolls repeatedly with palm down_ to reject the call and delete the object, respectively. The same gesture was proposed to undo an operation while interacting through a touch screen [41]. For the command _rotation objects_, it has been shown that users preferred to match the rotation of the hand wrist with the rotation of the object in a metaphor [42]. However, the rotation of the object based on such mapping is limited by the dexterity of the hand/wrist, and over-extreme hand/wrist postures pose a health risk [34]. Importantly, the accurate detection of the hand/wrist angle for rotating an object is a challenge, and hand tremors are inevitable while performing mid-air gestures. To address the above problems, we converted the distance of hand translation to the amount of object rotation. Users could rotate an object with high accuracy while removing the negative consequences caused by hand tremors in mid-air. In the future, users may work or engage in recreational activities with VR or AR HMD for long periods of time. Watching a movie with a virtual display created with a large size and high resolution is a potential replacement for cinemas.