Nodes

The AI system comes with many built in nodes ready for creating AI. The following gives you a general understanding of the node’s purpose. For more information on the node, hit the show information icon in the inspector.

Action
Add Item	Add the specified item to this inventory.
Contains Item	Does the following inventory contain this item?
Use Item	Use and remove the item from the inventory.
Cannon Enter	Enter a cannon.
Cannon Exit	Exit a cannon.
Follow Graph Points	Navigate to points with the specified speed. Target must be TargetPoints.
Follow Platform Walls	The AI will walk around platforms or walls, cutting corners. A probability of 1 will ensure it always moves to the next corner or it might change direction.
Follow Target	The AI will follow the specified target.
Guard Territory	The AI will follow the target if the target is inside the territory.Else, the AI will move to the guard point. This returns Success when the target is within the stop distance;
Ignore Block Units	The AI will ignore or block other AI units along the pathfinding path.
Pathfinder	The AI will follow a path generated by the pathfinding algorithm. This works with gravity, making it ideal for platformers.
Pathfinder Basic	The AI will follow a path generated by the pathfinding basic algorithm. This ignores the effect of gravity.
Jump	Make the AI Jump.
Jump To	The AI will jump towards the specified target.
Jump In Object	The player can jump into this object to hide from AI.
Jump Out Object	The player will jump out this object on button press.
Push Back	If damaged, the AI will be pushed back (and flash).
Monitor Variable	Check if a blackboard variable has changed value. Typically used for float variables.
Monitor World Variable	Check if a world variable has changed value. This will also work with Health.
Apply Character Velocity	Apply a character’s velocity to this AI.
Apply Gravity	This will simulate gravity. Mostly needed by moving platforms.
Control Player	Control the player in the x-direction by moving it to a point. This will also block player input.
Control Player Transform	Move the player’s transform along a set of points. These points are local to the AI.
Idle	Sometimes it’s useful to have an action where the AI just waits idly.
Indefinite Walk	If the AI hits a wall or air gap, it will change walking direction.
Lets Wiggle	Execute a Lets Wiggle tween. If this AI is a moving platform, then only its position should be modified.
Melee Attack	Perform a melee attack.
Move	This will move the AI with the specified velocity.
Nullify Gravity	Stop the effect of gravity on the AI.
Rotate Around	Rotate the transform around the specified target.
Rotate Position	Rotate the transform’s position around the center point at the specified radius.
Scene Door Enter	After entering a scene, the player will be placed at the door’s position.
Scene Door Exit	If the player enters the door area, the specified scene will load by calling the manage scenes component.
Set Transform	Set the position, rotation, or scale of a transform instantly or by lerping.
Shake	This will shake the AI. Only shake an object if it’s standing still.
Water Float	The AI will float on the waterline.
Find Collider	Find a target collider on the specified layer.
Face Target	The AI will point towards the specified target in the x-axis.
Get Nearest Target	Get the nearest target to the AI from a list and set the reference to this target.
Get Random Target	Get a random target from a list and set the reference to this target.
Nearest 2D Results	Get the nearest target to the AI from a list of physics results and set the reference to this target.
Target Changed	This will return success when the target’s position has changed by the specified distance.
Add To List	Add the specified item to a list.
Animation Signal	Sets an animation signal true for the AI.
BoxCollider2D Size	Change the size and offset of a BoxCollider2D.
Branch On Object Tag	This will read an object’s tag and jump to the specified state. Create as many options as necessary.
Captured By Yoshi	This AI can be captured by Yoshi.
Character Animation Signal	Set the following animation signal true for the specified character.
Chain	A chain created from gameobjects.
Clock	Wait the specified time.
Enable Behaviour	This will enable or disable the specified behaviour or renderer.
Enable Tree	Pause or remove the BehaviorTree from executing. Also specify the active state of the gameobject that belongs to the BehaviorTree.
Flip Children Objects	Flip the children objects of this AI in the x direction of the AI. This will flip the x scale. Run this inside an Always state.
Go To Next State	Jump to another state. Useful if a node you are working with can’t jump to a state.
IncDec Float	Increase or decrease a float variable by the specified amount.
Kill AI	Disable the AI’s Collider and Sprite Renderer.
On Event	Invoke and event.
PauseCollisions	Pause world collisions. If enabled, choose to move transform with Translate or not.
Player Death	Play a death animation for the specified time. This will block player input and disable its collider.
Random Loot	Add a random item from the list to an inventory.
Remove From List	Remove the specified item from a list.
Repeat	This will run the amount of times specified in the repeat value and then return Success.
Reset	This will reset the AI’s position and health. If WorldBool or TransformTracker exists and is true, the AI will be considered dead and deactivated. If so, this will return Success
Set As Child	Set the specified transform as child of the AI or remove it as a child of the AI.
Set Direction	Set the direction of a character.
Set Value	Set the value of the blackboard data.
Set Value From blackboard	Set the value of the blackboard data with that of another blackboard variable.
Set World Float At Rate	Increase or decrease a World Float value at the specified rate.
Skip A Frame	This will wait one frame and then return Success.
Spawn GameObject	Spawn a gameObject at the specified position.
Spawn Point	Reset the AI to the position it had at the beginning of the scene.
Sprite Color	This will modify a sprite’s color by lerping to a new one.
Wait For Player Input	Wait for the player to enter the territory and then for the button to be pressed.
World Effect	Call a world effect at the AI’s position.
Damage Effect	Slow down the enemy, apply damage, and play the specified animation signal for the duration amount.
Damage Flash	Show damage flash.

Composite
Parallel	Runs all child nodes at the same time. This will return Running as long as one of them is running. Once all child nodes complete, it will return Success if one child succeeded, else failure.
Parallel Success	Runs all child nodes at the same time until one of them returns Success. Returns Failure if all them fail.
Parallel Success All	Runs all child nodes at the same time until they all return Success. Will return failure if not all of them succeeded.
Random Selector	This will run one random child node.
Random Sequence	This will shuffle the list of nodes so that the execution order is always randomized.
Selector	This will run every node in the list until one returns Success.
Sequence	This will run every node in the list until one returns Failure.

Decorator
Delay	Run the child node after a time delay.
Inverter	This will invert the output logic of the child node (except for Running). Interrupt logic will work with this decorator.
Repeater	This will execute the child node by the amount of times specified in the repeat value.
Running	This will always return Running.
Timer	This will run a child node for the specified time.
Until Fail	This will run the child node until it returns Failure.
Until Success	This will run the child node until it returns Success.

Conditional
Find Target	Find the specified Target in relation to the AI or Territory.
List Logic	This will compare the size of the specified list to a value.
Variable Logic	This will compare a float variable to a float value.
World Float Logic	Compare a world float to a float value.
CircleCast	Implement a CircleCast using Physics2D. The results can be accessed by Nearest2DResults.
LineCast	Implement a LineCast using Physics2D. The results can be accessed by Nearest2DResults.
OverlapBox	Implement an OverlapBox using Physics2D. The results can be accessed by Nearest2DResults.
OverlapCircle	Implement an OverlapCircle using Physics2D. The results can be accessed by Nearest2DResults.
OverlapCollider	Implement an OverlapCollider using Physics2D. The results can be accessed by Nearest2DResults.
OverlapPoint	Implement an OverlapPoint using Physics2D. The results can be accessed by Nearest2DResults.
RayCast	Implement a RayCast using Physics2D. The results can be accessed by Nearest2DResults.
Layer Result	Rays casted using Single Hit can compare if the resulting object belongs to the specified layer.
Touching Layers	Check if the specified collider is touching any other collider in the specified layer.
Collision Status	Check what a character/AI is interacting with.
Return Failure	This will always return Failure.
InputButtonSO Get	Returns success if InputButtonSO is true.
Input Get	Get Input KeyDown or MouseDown.
Is Quest Active	Is this quest active?
Is Quest Complete	Is this quest complete?
Positional	Check the AI’s position in relation to a target.
Field Of View	Returns Success if the specified target is inside the field of view.
Has Passengers	Does this moving platform have passengers?

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Create Nodes

The most common nodes to create will be Conditional and Action nodes. Once the script is created, place it inside the AI/BehaviorTree/Nodes folder and it will become available for use in the AI system. Follow the template below to code your own functionality. The first example is of the Move Action node, which simply adds velocity to the AI.

 using UnityEngine;

 namespace TwoBitMachines.FlareEngine.AI// Include this namespace
 {
    public class Move : Action // Specify the type of node - Action/Conditional/Composite/Decorator
    {
            [SerializeField] public Vector2 velocity;

            // Use this method to implement the behavior
            public override NodeState RunNodeLogic (Root root)
            {
                    if (nodeSetup == NodeSetup.NeedToInitialize)
                    {
                    //       Any member fields that need to be reset/initialized go here.
                    }

                    root.velocity += velocity;// Root is basically the AI
                    return NodeState.Running; // Return Running
                                              // If the behavior completes, return Success or Failure.
            }

            // Use this to reset important variables
            public override void OnReset ( )
            {

            }

// Root contains a few variables to be aware of

// root.velocity  -- the velocity of the AI, read and write to it
// root.direction -- the direction of the AI on the x-axis, read and write to it
// root.position  -- the position of the AI in the game world, read only

// root.hasJumped -- set true if you have added a jumping force to the AI's root.velocity.y
// root.onSurface -- set true if you are creating a hard surface for the AI to stand on

// root.signals.Set ("relevantSignalName") -- set an animation signal if necessary
// root.world     -- reference to WorldCollision, read settings like onGround, onMovingPlatform, etc.
// root.gravity   -- reference to Gravity, if jumping use root.gravity.SetJump (velocity.y);
//                   see the Jump node for more information
// root.movingPlatform   -- reference to MovingPlatform if the AI is of this type, use it to read
//                          hasPassengers or passengerCount
    }

  }

using UnityEngine;

namespace TwoBitMachines.FlareEngine.AI
{
     // This is a Conditional node. This will simply check if the AI is on the ground.
     // This class doesn't actually exist, but it can be created using this code
     // to get this functionality.
     public class AIOnGround : Conditional
     {
             public override NodeState RunNodeLogic (Root root)
             {
                     return root.world.onGround ? NodeState.Success : NodeState.Failure;
             }
     }
 }

using UnityEngine;

namespace TwoBitMachines.FlareEngine.AI
{
    // This is a Decorator, and it will run its child node until it fails.
    public class UntilFail : Decorator
    {
           public override NodeState RunNodeLogic (Root root)
           {
                  NodeState nodeState = children[0].RunChild (root);
                  return nodeState == NodeState.Failure ? NodeState.Success : NodeState.Running;
           }
    }
}