Certain actuators hold a pointer to an objects: Property,
SceneCamera, AddObject, Camera, Parent, TractTo. When a
group is duplicated, the actuators that point to objects
within the group will be relinked to point to the
replicated objects and not to the original objects.
This helps to setup self-contained group with a camera
following a character for example.
This feature also works when adding a single object
(and all its children) with the AddObject actuator.
The second part of the patch extends the protection
against object deletion to all the actuators of the above
list (previously, only the TrackTo, AddObject and
Property actuators were protected). In case the target
object of these actuators is deleted, the BGE won't
crash.
This patch consists in new KX_GameObject::SetParent() and KX_GameObject::RemoveParent() functions to create and destroy parent relation during game. These functions are accessible through python and through a new actuator KX_ParentActuator. Function documentation in PyDoc.
The object keeps its orientation, position and scale when it is parented but will further rotate, move and scale with its parent from that point on. When the parent relation is broken, the object keeps the orientation, position and scale it had at that time.
The function has no effect if any of the X/Y/Z scale of the object or its new parent are below Epsilon.
