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 children!

Only certain entities can have parents. For example, a prop_physics cannot because it is its own physics object. In this case, a prop_dynamic or prop_dynamic_override could be used 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.

KillHierarchy

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 and merely 'orphans' its children.

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 Setparent parameter blank, it has the same effect as the ClearParent input (see below).

SetParentAttachment

You can also fire a SetParentAttachment input at the child-entity to attach it to a specific attachment point on its parent. Entities must be parented before being sent this input. The parameter passed in should be the name of the attachment point.

SetParentAttachmentMaintainOffset

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.

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