BehaviorTree

BehaviorTree Editor

The editor is used to edit a behavior tree(BT) asset. The editor can be opened via doucble clicking an BT asset or via Window->BehaviorTreeEditor. You can load, save or save as a copy of an asset from the file menu located in the editor. New nodes can be creted via the create node menu, each new node is created from a base template and more templates can be added for quicker node creation, the default nodes that can be created is base node, task, decorator, service, utility action and utility consideration.

Creating a new tree or blackbaord can be found in the unity create asset menu Create->AI->BehaviorTree|Blackbaord.

Features

Save, Save As, Load Behavior Tree Asset
Create new nodes
Minimap
Inspector for selected node
Inspector for blackboard to be used
Access Blackboard keys via nodes
Utility AI Nodes
Realtime node updates
Breakpoints - via node context menu
New nodes can be created using the search menu, spacebar or the graph context menu

Project Requirements:

NavMeshAgent
NavMesh

Blackboard

The blackboard asset allows the user to add keys that can be access via the graph. The blackboard uses a dictionary to store keys so each key must have an unique name to be serilaized to the asset.

BlackboardTreeComponent

To use the behavior tree asset a gameobject needs the behavior tree component and select a BT asset the component will create an instance of.

Default Nodes

Each nodes displayed name and description can be edit via the inspector.

Root- Created by default when opening an BT asset for the first time, all trees use this as the top most node
Composites:

Selector - Fails if all nodes fail and is a success if one node is a success, stops executing when on child succeeds
Sequence - Stops executing when one child fails. if a child fails the sequence fails, otherwise success when all childen succeeds.

Decorators:

Is At Location

Tolerance - acceptable distance from the location to succeed
Destination

Loop - Loops child

Repeats - Number of times to loop, -1 = inifintly

Loop Until Fail - Loops child inifintly until the child fails
Cooldown - Loacks execution of the child until the timer expires

Abort Type
Timer

Interval - the time it takes to expire
Deviation - range of time from the interval that determines time it takes to expire

Force Success - forces a child to return success
Inverter - inverts the returned state from the child
BlackboardbaseCondition - determines if a key is set or not

Abort Type
Query - Is Set or not set
Key

Tasks:

Log Message - logs to the unity debug console
MoveTo - move the agent to a destination

Speed
Stopping distance
Update Rotation
Acceleration
Tolerance
Destination Key

Wait- waits an amount of time before finishing executing
Run behavior - runs a sub behavior tree for more complex behaviors
Random Location - finds a random location on the navmesh to set the destionation to in certain radius from agent

Destination Key

Action Seletor - selects an action if the action score is the highest
Action - takes to nodes the first takses in multiple considerations, the second takes a node to be executed if the action is selected to be executed

API and Custom Nodes

The nodes that can extended include the follwing:

Decorators
Services
Conditional Abort
Task
UtilityAI
consideration

The follwing methods can be overriden:

Base Node, Decorator, Task:

protected override void OnStart() {}

protected override void OnBeginExecute(NavMeshAgent agent) {}

protected override ENodeState OnExecute(NavMeshAgent agent){} 

protected override void OnEndExecute() {}

protected override void OnAbort() {}

Conditioanl Abort:

public abstract bool OnConditionCheck(){}

protected virtual void OnObserverBegin() {}

protected virtual void OnObserverEnd() {}

Consideration:

protected override float OnEvaluateScore(NavMeshAgent agent){}

Service:

protected override void OnServiceTick(){}

Misc Classes

BlackboardKeySelector - a utility class that can be used to access the keys on a current blackboard asset set in the behavior Tree