# Virtual Marker Technique to Enhance User Interactions in a Marker-Based AR System
## 7 Discussion  
The proposed multi-marker AR system framework with virtual markers has some advantages. In traditional marker-based AR systems, an image is registered in advance [53]. It is difficult for users to add customized information to the system. The virtual marker technique does not require pre-registration of custom information, meaning that users have the ability to freely create content. Since users are allowed to customize the information of the marker, the system becomes more flexible. In addition, due to the accuracy of this information, it can be used to perform more accurate operations on AR content.  
Another technical problem in AR applications is FOV [54; 55; 56]. Due to the limited FOV, it is difficult to obtain a large amount of information from multiple markers. The multi-marker framework solves the field of vision problem in AR applications to a certain extent. The content of multiple markers can be integrated and stored in the first marker. The first marker can continue to be combined to incorporate more information. Therefore, the user only needs to combine the markers in batches to avoid the original problem of not being able to combine multiple markers in the FOV at the same time.  
The preparation cost for using TUI is usually high because of the need for special equipment and tools. Previous studies have proposed a tangible programming learning environment using paper cards as objects [34; 57]. We extended such a system environment and used paper cards as physical markers. Therefore, the ease of use issues such as the hardware requirements and the acceptance of the technology have been addressed well. For the operation of virtual markers, gestures are used as methods of interaction based on previous research [58; 59].  
Through a pilot study, we examined the design of the proposed system framework. We found that the introduction of virtual markers and gestures did not impose significant time and operational burdens on users. According to the user's subjective feedback on the system, they can master the system operation after basic training. Even if the experimenter, such as [PERSON], did not noticeably improve the use of leap motion in a short time, he still affirmed the design of the system framework and took a positive attitude towards using the system.  
Based on the above considerations, the design of the system meets the standards from a technical point of view and a user point of view.  
The system still has some areas that can be improved. Currently, the number input marker and the keyboard input marker are separated and only integers are supported. We considered constructing more realistic input marker by combining these two input markers in the future. In this way, the user can construct variables with a combination of letters and numbers, for example. In addition, we considered adding a case switch button and a decimal point button to allow users to create lowercase letters and floating numbers.  
In the system, we use a vision-based image processing method to obtain the user's input from input markers. To this end, an input algorithm is developed to process image information from different frames. The survey found that precise input from input markers has an impact on the user experience. Therefore, we consider optimizing the input algorithm for the input markers in the future to provide a better user experience.