73 lines
3.3 KiB
ReStructuredText
73 lines
3.3 KiB
ReStructuredText
.. _blackboard:
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Sharing data using Blackboard
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=============================
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To share data between different tasks and states, we employ a feature known as the :ref:`Blackboard<class_Blackboard>`.
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The :ref:`Blackboard<class_Blackboard>` serves as a central repository where tasks and states can store and retrieve named variables,
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allowing for seamless data interchange. Each instance of a behavior tree or a state machine gets its own dedicated :ref:`Blackboard<class_Blackboard>`. It has the capability to store various data types,
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including objects and resources.
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Using the :ref:`Blackboard<class_Blackboard>`, you can easily share data in your behavior trees, making the tasks in the behavior tree more flexible.
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Accessing the Blackboard in a Task
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----------------------------------
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Every :ref:`BTTask<class_BTTask>` has access to the :ref:`Blackboard<class_Blackboard>`, providing a
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straightforward mechanism for data exchange.
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Here's an example of how you can interact with the :ref:`Blackboard<class_Blackboard>` in GDScript:
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.. code:: gdscript
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@export var speed_var: String = "speed"
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func _tick(delta: float) -> Status:
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# Set the value of the "speed" variable:
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blackboard.set_var(speed_var, 200.0)
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# Get the value of the "speed" variable, with a default value of 100.0 if not found:
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var speed: float = blackboard.get_var(speed_var, 100.0)
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# Check if the "speed" variable exists:
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if blackboard.has_var(speed_var):
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# ...
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..
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**🛈 Note:** The variable doesn't need to exist when you set it.
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Editing the Blackboard Plan
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---------------------------
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The Blackboard Plan, associated with each :ref:`BehaviorTree<class_BehaviorTree>`
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resource, dictates how the :ref:`Blackboard<class_Blackboard>` initializes for each
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new instance of the :ref:`BehaviorTree<class_BehaviorTree>`.
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BlackboardPlan resource stores default values, type information, and data bindings
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necessary for :ref:`BehaviorTree<class_BehaviorTree>` initialization.
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To add, modify, or remove variables from the Blackboard Plan, follow these steps:
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1. Load the behavior tree in the LimboAI editor.
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2. Click on the resource header to access :ref:`BehaviorTree<class_BehaviorTree>` data in the Inspector.
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3. In the Inspector, select the "Blackboard Plan" property and click the "Manage..." button.
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4. A popup window will appear, allowing you to edit behavior tree variables, reorder them, and modify property types and hints.
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Overriding variables in BTPlayer
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--------------------------------
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Each :ref:`BTPlayer<class_BTPlayer>` node also has a "Blackboard Plan" property,
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providing the ability to override values of the BehaviorTree's blackboard variables.
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These overrides are specific to the BTPlayer's scene
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and do not impact other scenes using the same :ref:`BehaviorTree<class_BehaviorTree>`.
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To modify these values:
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1. Select the BTPlayer node in the scene tree.
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2. In the Inspector, locate the "Blackboard Plan" property.
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3. Override the desired values to tailor the blackboard variables for the specific scene.
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Advanced topic: Blackboard scopes
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---------------------------------
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**🛈 Note:** This section is not finished.
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**🛈 Note:** Blackboard scopes isolate variable namespaces and enable advanced techniques like sharing data between agents in a group.
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