# Virtual Marker Technique to Enhance User Interactions in a Marker-Based AR System
## 3 Virtual Marker Technique
### Manipulating Virtual Marker  
Virtual markers are essentially virtual objects. The user can interact with physical markers by grabbing and moving. Similarly, users can use hand gestures to manipulate and interact with markers in our system. In the current design, we use right-hand gestures.  
There are some descriptions of these hand gestures (see Figure 5):  
Figure 4: Examples of generating a virtual marker containing combined information from basic virtual markers. The first virtual marker (X = 1) is generated by a variable virtual marker (X) and a virtual number marker (1). The second is generated by three virtual number markers. The user can determine the information of the 3D vector marker by changing the marker selection order.  
(a) Defining gesture: This gesture is a thumb-up gesture which will tell the system to define the current command and execute it.  
(b) Selecting gesture: The user needs to spread his thumb finger and index finger. The index finger will emit finger rays for selection in the AR scene. The user can use the finger ray to select virtual markers for manipulation. In order to express the selected state of the virtual marker, the system will highlight the selected virtual markers in red.  
(c) Deselecting gesture: When the user makes a clenched fist, the state of the selected marker at this time will be restored to the unselected state.  
(d) Dragging gesture: The dragging gesture needs to gather all fingers in one point. Using this gesture, the user can drag and change the position of the virtual markers in the selected state. The user can use this gesture to arrange virtual markers.  
(e) Copy gesture: The user stretches their index finger, middle finger, and thumb while tightening the other two fingers. The user can use this gesture to copy the selected virtual markers. After the copy is complete, the virtual markers will be restored to the unselected state.  
(f) Parameter/value change gesture: If the index finger and middle finger are extended and the other fingers are retracted, accompanied by a certain rightward movement speed, this is regarded as an increase in the number or parameter. Each time the user swipes to the right, the parameter value will increase by one. If the index finger and middle finger are extended and the other fingers are retracted while moving to the left at a certain speed, this is considered as a decrease in the number or parameter. Each time the user swipes to the left, the parameter value will decrease by one.  
(g) Deleting gesture: To make this gesture, the user needs to open all their fingers and hand palm and move their hand left and right with some speed. With this gesture, the user can delete the selected virtual markers in the scenery.  
It is worth noting that different users may be accustomed to different gestures. In fact, we are more concerned with what kind of interaction users can perform using hand gestures.  
Figure 5: Hand gestures can be used to control virtual markers. (**a**) is a defining gesture. (**b**) is a selecting gesture. (**c**) is deselecting gesture. (**d**) is a dragging gesture. (**e**) is a copy gesture. (**f**) is a parameter/value change gesture. (**g**) is a deleting gesture.