It is impossible to prevent a flock from penetrating the volume defined by the mesh of a Director Type = Arrive.

For example, in the second part of the asteroid tutorial in the LW 11-5 Addendum no matter what I do (e.g. including manipulating the size and strength of the associated Avoid mesh), some of the flock agents will crash straight through the mesh of the goal object as they try to settle onto its surface.

It would be a huge improvement to the realism of the flocking behaviour if the agents could sense that the goal object has a volume defined by the mesh which should not be penetrated.

Cheers,
Peter Inkpen