{{tag>dragonscript behavior}}
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[[:start|Start Page]] >> [[main|DragonScript Scripting Language]] >> [[dragengine:modules:dragonscript:abstractions|Abstraction Layers: How you want to build your Game]] >> [[dragengine:modules:dragonscript:behavior_elements|Behavior Elements]] >> **ECBehaviorLookedAt**
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  * [[behaviors_use_cases|Behaviors Explained: By Use-Case]]
  * [[behaviors_a_to_z|Behaviors Explained: From A to Z]]

====== ECBehaviorLookedAt ======

Behavior element behavior adding support to track if actors look at element.

This behavior tracks if actors are looking at the element. If actors start looking at the element they are added to the list and listeners are notified. If the actors stop looking at the element they are removed from the list and listeners are notified. The actors can be an NPC or the player.

The behavior itself is passive. It requires to be triggered by the actor elements. The [[behavior_lookat|ECBehaviorLookAt]] behavior provides this functionality.

====== Instance Counts ======
This behavior can be used only once on an element. The behavior always has identifier empty string.

====== Element Class Properties ======

Element class properties have the prefix ''lookedAt.''.

====== Events ======

This behavior supports adding listeners. These events can be received:

===== actorStartsLookingAt =====

Actors starts looking at object.

===== actorStopsLookingAt =====

Actors stops looking at object.

====== Behavior Tree Actions ======

This behavior adds these behavior tree actions if behavior tree is present.

===== lookedAt.check =====

Check one or more looked-at parameters. Action succeeds if all parameter value matches their respective looked-at parameter otherwise action fails. This action is typically used as first action in a sequence to run the sequence only if a looked-at parameter matches (or not).

^Parameter^Value^Description^
|count|integer|Count of actors looking at element equals integer value|
|count.not|integer|Count of actors looking at element does not equal integer value|
|count.less|integer|Count of actors looking at element is less than integer value|
|count.greater|integer|Count of actors looking at element is greater than integer value|
|player|''true'', ''false''|Player is looking at element|
|wait| |If present action returns BTResult.running instead of BTResult.failed to wait until the checks are all fulfilled|

This is an example of using this action:
<code xml>
<sequence>
  <action name='lookedAt.check'>
    <parameter name='player'>true</parameter>
  </action>
  <!-- actions here run only if element is looked at by player -->
</sequence>
</code>

====== Behavior Tree Conditions ======

This behavior adds these behavior tree conditions if behavior tree is present.

===== lookedAt.check =====

Check one or more looked-at parameters. Conditions returns true if all parameter value match their respective looked-at parameter. This condition is typically used to run an action or sequence of actions as long as looked-at conditions are true.

^Parameter^Value^Description^
|lookedAt.count|integer|Count of actors looking at element equals integer value|
|lookedAt.count.not|integer|Count of actors looking at element does not equal integer value|
|lookedAt.count.less|integer|Count of actors looking at element is less than integer value|
|lookedAt.count.greater|integer|Count of actors looking at element is greater than integer value|
|lookedAt.player|''true'', ''false''|Player is looking at element|

This is an example of using this condition:
<code xml>
<action name='myAction' id='doing something'>
  <parameter name='lookedAt.player'>true</parameter>
  <condition>lookedAt.check</condition>
</action>
</code>

====== State Machine Actions ======

Same as [[#behavior_tree_actions|Behavior Tree Actions]].

====== State Machine Conditions ======

Same as [[#behavior_tree_conditions|Behavior Tree Conditions]].

====== State Machine Events ======

This behavior sends these state machine events.

===== lookedAt.start =====

Actors starts looking at object.

===== lookedAt.stop =====

Actors stops looking at object.

====== Required Behaviors ======

This behavior does not required other behaviors to be present.

====== Optional Behaviors ======

  * [[behavior_behaviortree|ECBehaviorBehaviorTree]]: Add actions and conditions for behavior trees to use.
  * [[behavior_statemachine|ECBehaviorStateMachine]]: Add actions and conditions for state machine to use and events to send to the state machine.

====== Persistency ======

This behavior does support element class to be persistable (setPersistable).

====== API Documentation ======

#@LinkApiDocDEDS2_HTML~classDragengine_1_1Scenery_1_1ECBehaviorLookedAt.html,ECBehaviorLookedAt~@#.

Since DragonScript Module Version ''1.1''

====== Use Cases ======

  * Show outline and interact prompts if player looks at object.
  * For NPCs to react to player (or other actors) looking at them (for example looking back at player).
  * Show target information if player aims at objects.

====== Element Class Example ======

<code>
class ExampleElementClass extends BehaviorElementClass
   public var ECBehaviorLookedAt lookedAt
   
   public func new() super("ExampleElement")
     // add looked at behavior. by itself this does nothing yet. add listeners to the
     // behavior to react to looking-at changes. this is typically done by other
     // behaviors to provide their functionality
     lookedAt = ECBehaviorLookedAt.new(this)
   end
end
</code>

====== Behavior Factory ======

Using element class supporting adding behaviors the behavior can be added like this:
<code xml>
<?xml version='1.0' encoding='UTF-8'?>
<elementClass name='MyClass' class='GenericBehaviorElement'>
  <behavior type='ECBehaviorLookedAt'>
    <!-- optional: use behavior tree with id instead of empty string -->
    <string name='behaviorTree'>second</string>
    
    <!-- optional: use state machine with id instead of empty string -->
    <string name='stateMachine'>second</string>
    
    <!-- set element properties. omit property prefix if used inside behavior tag -->
    <string name='.name'>value</string>
  </behavior>
</elementClass>
</code>

====== Live Examples ======

  * [[https://github.com/LordOfDragons/deexamples|DEExamples Repository]]