A non-text notification bubble or other graphical object can be presented during an augmented reality, mixed reality, or virtual reality simulation to notify a user that a real-world object is approaching or has crossed a boundary for an interaction space within which the user is to interact with the simulation. Responsive to the system identifying the user as looking at the bubble or other graphical object, the system may then present another notification about the real-world object approaching or crossing the boundary. The real-world object may be an intrusion into the interaction space, such as a human or animal crossing into the space.