One feature of immersive environments such as augmented reality is that users can be looking in any direction. Users may not always be looking in the direction you’d like them to look. It is thus important to consider how your AR safety pattern will behave across different orientations, and what is the most appropriate behavior for that particular orientation.
A 3D fence that delineates a street edge may be a clear approach, but this would not be obvious to a user who is looking straight up at the sky, or down on the ground. Accompanying patterns (audio, haptic and others) may have to be incorporated to complement that core pattern of the fence.
One recommendation is for your AR safety pattern to be more obvious when the user’s view is directed away from the hazard. When the user has the hazard in view, the sight of the hazard zone may already alert her. When the user is not looking at the hazard, however, she loses a visual signal of the risk she’s approaching.
The orientation of the user can also determine the scale of the Buffer. While a user who is approaching the hazard zone is positioned further away from the hazard than their AR device, a user that is backing towards the zone would be closer to the hazard than their AR device. The user should thus be alerted when their device is detected within a wider buffer.