Entity Hierarchy (parenting)

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Revision as of 07:43, 14 October 2012 by Gambini (talk | contribs) (KillHierarchy)

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When a group of entities are parented together, they form a rigid 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.

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.

  • The Offset is the distance (and any rotational offset) between the Child and Parent entities at the time the relationship is activated. Whilst the offset is maintained, the Child will move parallel to its parent's movements, and "orbit" the parent's origin at the offset distance when the parent rotates. Only the SetParentAttachment input changes the offset; it instantly "teleports" the child to the parent's attachment point and holds it there instead.
  • Collision : The Child's Solidity is suspended whilst it is parented. It will pass through walls and other solid objects.
  • If the Parent is Killed, all of its current Children are also removed from the game.


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

  • Maintains offset.
    Bug: The parent field does not work correctly for some entities in CS:S. Instead, use a logic_auto and call SetParent at the start of the map
    Bug: Children may lost their parents on HL2:DM Linux Dedicated Server. So, it's highly recommended to use a logic_auto and use output "OnMapSpawn child SetParent parent"


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).
  • Maintains offset.


Note:Entities must be parented before being sent this input. Use at least a 0.01 second delay between SetParent and SetParentAttachment inputs.

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

  • The Child instantly teleports to the attachment point. This is the only method which does not maintain the offset.


Note:Entities must be parented before being sent this input. Use at least a 0.01 second delay between SetParent and SetParentAttachmentMaintainOffset inputs.

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.

  • Maintains offset, but the Child shadows/orbits the attachment point position instead of the parent's EntityOrigin.


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.


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.

  • If you fire a Kill input at the parent-entity, it also Removes the parent-entity and its children from the world ... ?

Bug: If you have a point_spotlight child of another entity, and you kill the parent entity without removing the point_spotlight using an input, it will spawn in the center of the map (0,0,0) facing north.


Programmers can use FollowEntity() to control parenting.