This feature exists because of an awkward dilemma in the Particle Flocker system. If a seek target is placed inside an obstacle, what exactly should the particles do in this situation? On the one hand they want to get to the seek target, but on the other hand they want to avoid the obstacle. The solution…wall following!
Any time that a target is detected inside a volume, particles will immediately choose a different target location at the closest point to the target location, but projected onto the surface of the obstacle.
As a consequence, placing a target inside an obstacle’s volume effectively turns the target and obstacle into a wall following target.
This technique also works with Path Following targets. If a path follow target intersects an obstacle, particles will attempt to wall follow around the obstacle until they find a point of the curve which is outside the obstacle’s volume again, at which point normal path following will resume.