phys.attachSoftRegion

Hold a region of a soft body to a rigid body, two-way: the region follows the rigid body and the rigid body carries its weight and pull (a flag on its pole, a body shell on a car's chassis). The region is { box = { min, max } } or { nearest = point } in the soft entity's unit box, or space = "world" coordinates; omitted, the whole body is held. Returns the attachment's index in the soft body's attachments.