Entity Hierarchy (parenting)

When a group of entities are parented together, they form a movement hierarchy family which will move together as if all the entities were one physical object. Each child-entity will follow its parent's movement.

A simple example would be parenting a light_dynamic to a lamp prop so the light becomes part of the lamp and moves with it.

The child-parent relationship is always defined in the object properties of the child-entity. The parent-entity doesn't have any say in choosing its followers! This leads to the rather awkward use of 'parenting' as a reflexive verb throughout the documentation, eg "must be parented", "parent the child to the parent", "entities can have parents", etc. Hey ho.

Only certain entities can have parents (see Category:Parentable Entities for a list). For example, a prop_physics cannot because it is its own physics object. In this case, use a prop_dynamic or prop_dynamic_override instead, or use an info_constraint_anchor to link up with the physics constraint system.

Parentname

To create a child-parent relationship between two entities, set the child-entity's parentname keyvalue to the parent-entity's targetname.

SetParent

You can also fire a SetParent input at the child-entity to change it's child-parent relationship.

• Use the targetname of the new parent as the input parameter to make the child follow the new parent.
• If you leave the parameter blank, it has the same effect as the ClearParent input (see below).

SetParentAttachment

Note:Entities must be parented before being sent this input.

You can also fire a SetParentAttachment input at the child-entity to attach it to a specific attachment point on its parent.

• The parameter passed in should be the name of the attachment point.

SetParentAttachmentMaintainOffset

Note:Entities must be parented before being sent this input.

You can also fire a SetParentAttachmentMaintainOffset input at the child-entity to attach it to a specific attachment point on it's parent. This works exactly the same as the SetParentAttachment input except the child-entity will maintain it's relative position to and distance from the parent at the time it is attached.

ClearParent

You can also fire a ClearParent input at the child-entity to remove it's child-parent relationship. This simply 'unparents' or 'detaches' the child-entity from its current parent, so the child is then free to move (or not) independently of its former parent.

KillHierarchy

Note:This is the only movement hierarchy-related input that can be fired at the parent-entity.

If you fire a KillHierarchy input at the parent-entity, it Removes the parent-entity and all of its children from the world.

• By contrast, of you fire a Kill input at the parent-entity, it Removes only the parent-entity from the world; the 'orphaned' children remain in the world to fend for themselves.

FollowEntity()

Programmers can use FollowEntity() to control parenting.