## 1 Introduction
Therefore, this paper proposes a comparative and substantial evaluation of user interactions for wearable AR concerning the visual context and interaction gesture using AR smart glasses. It also suggests new guidelines for visual augmentation focused on task assistance. We performed quantitative and qualitative analyses, including performance measurement and questionnaire evaluation. By analyzing the advantages and disadvantages of wearable AR for visualization and interaction, we could provide more effective guidance for user-centric task assistance. In this research, the visual augmentation, according to the visual context in the see-through display of AR smart glasses, is classified as follows. 1. Stereo rendering and direct augmentation  
Figure 1: Visual and interactive assistance through wearable augmented reality (AR) applied to manufacturing services, such as visualization of the status of machines and robot. Non-stereo rendering and indirect augmentation with video background  
3 Non-stereo rendering and indirect augmentation without video background  
The stereo rendering and direct augmentation method superimposes virtual information directly onto its physical artifact through the see-through display of smart glasses (Figures 2d and 3a). The stereo rendering can provide stereo rendering-based immersive visualization, and the overlaid virtual information is almost matched or registered with its corresponding physical artifact. For this reason, a registration process is required to match the virtual information with the physical artifact. The non-stereo rendering and indirect augmentation with video background overlays virtual information indirectly onto the physical artifact in the image taken by the smart glasses' AR camera and then provides the augmented image to the user through the see-through display of AR smart glasses (Figures 2e and 3b). In this case, the virtual information does not match with the physical artifact concerning the user's viewpoint. The non-stereo rendering and indirect augmentation without video background method removes the camera image from the non-stereo rendering and indirect augmentation with video background and presents only the virtual information on the display (Figures 2f and 3c). This method also does not support matching virtual information with the physical artifact. For most AR smart glasses, such as Epson Moverio (Figure 2a), the stereo rendering and direct augmentation approach has narrower FOV than the non-stereo rendering and indirect augmentation through the see-through display. Instead, it can provide consistent visual augmentation with physical objects. Therefore, different visual contexts have their advantage and disadvantage concerning FOV and visual registration, which can influence task performance and usability. However, there is little research to evaluate this issue substantially. Besides, since most AR smart glasses can only support simple interactions using the touch gesture and hand gesture, it is challenging to provide more user-centric interactions using full hand gestures. However, one drawback is to attach another sensor, such as a depth sensor to the smart AR glasses, which may prevent the worker from conducting tasks and cause another cognitive load. Besides, it is essential to calibrate the coordinate of wearable AR and that of the hand tracking sensor. Furthermore, it is still necessary to evaluate the usability of interactions concerning task performance and the cognitive load of the industrial worker in an actual manufacturing environment. Figure 2: Visual augmentation concerning visual contexts in the real AR smart glasses. As the most popular gesture interactions in wearable AR are touch-based and gesture-based [6], we have classified them as follows. * Multi-touch interaction Through the hand gesture-based interaction, the user wearing AR smart glasses can manipulate virtual objects through hand gestures directly (Figure 3(a)). Besides, it supports bi-manual operations as the worker can use both hands.