Imagine a guard robot trying to apprehend an intruder or catch an escaped prisoner. Instead of simply tracking the target, ideally the robot would know how to creep up stealthily, by crouching behind objects and hiding in the shadows. This way, it could surprise and apprehend its target before it can get away.

Creepy as this might sound, a team at Seoul National University in Korea has created an algorithm that models just this sort of stealthy behavior. Professor of engineering Beom Lee and first author Jung-Hee Park designed simulations in which a robot waits in the shadows and moves quickly between obstacles to intercept a target.

The simulations take into account the size of the robot, the size of objects it can hide behind and the speeds of moving target. In the videos below, the robot, blue, tracks the invader, red. The blue line marks the robot’s planned path and its projected interception point. In this movie, the system is in “stealthy mode”, moving only when the intruder won’t see it:

In this movie, the system moves with only the “intercept intruder” program, leaving itself visible to the intruder: