Behavior Tree Node Types

This page provides a complete reference of all node types available in the Behavior Tree Editor. Understanding these nodes is essential for creating effective AI behaviors.

Node Categories

Nodes are organized into four main categories:

Composite Nodes - Control flow nodes with multiple children
Decorator Nodes - Modify behavior of a single child node
Condition Nodes - Check game state (return Success/Failure)
Action Nodes - Perform actions (movement, combat, etc.)

Composite Nodes

Composite nodes control execution flow by evaluating multiple children in sequence or by priority.

Selector (OR Node)

Icon: 🔀 | Color: Purple | Type: Composite

Executes children in order until one succeeds.

Behavior:

Tries each child from left to right (or top to bottom)
Returns Success if any child succeeds
Returns Failure if all children fail
Returns Running if current child is running

Use Cases:

Priority-based behaviors (combat → investigate → patrol)
Fallback logic (try A, if fails try B, if fails try C)
Decision-making with multiple options

Example:

Selector "AI Decision"
 ├─ Sequence "Combat" (tries first)
 ├─ Sequence "Investigate" (tries if combat fails)
 └─ Sequence "Patrol" (tries if investigation fails)

Real-world analogy: "Try to attack, OR investigate, OR patrol"

Sequence (AND Node)

Icon: ➡️ | Color: Blue | Type: Composite

Executes children in order until one fails.

Behavior:

Tries each child from left to right (or top to bottom)
Returns Success only if all children succeed
Returns Failure if any child fails
Returns Running if current child is running

Use Cases:

Multi-step processes (check condition → perform action)
Guarded actions (verify before executing)
Sequential behaviors (step 1, then step 2, then step 3)

Example:

Sequence "Attack Target"
 ├─ Condition "Target in Range"
 ├─ Condition "Can Attack" (cooldown check)
 └─ Action "Attack Melee"

Real-world analogy: "Check if close AND check if ready AND attack"

Decorator Nodes

Decorators modify the behavior of their single child node.

Inverter (NOT Node)

Icon: ↩️ | Color: Orange | Type: Decorator

Inverts the result of its child node.

Behavior:

Returns Success if child returns Failure
Returns Failure if child returns Success
Returns Running if child returns Running

Use Cases:

"If NOT condition" logic
Negating conditions (e.g., "target NOT in range")
Reverse success/failure semantics

Example:

Inverter "Target NOT Visible"
 └─ Condition "Target Visible"

Parameters: None

Real-world analogy: "Do the opposite of what the child says"

Repeater (Loop Node)

Icon: 🔁 | Color: Green | Type: Decorator

Repeats its child node N times or infinitely.

Behavior:

Executes child node multiple times
Returns Success after N successful executions
Returns Failure if child fails (early exit)
Returns Running while repeating

Parameters:

count (int): Number of repetitions (-1 for infinite)

Use Cases:

Firing multiple projectiles
Patrolling waypoints repeatedly
Continuous behaviors (infinite loop)

Example:

Repeater (count=3) "Fire 3 Shots"
 └─ Action "Fire Projectile"

Real-world analogy: "Do this action N times in a row"

Condition Nodes

Conditions check game state and return Success or Failure (never Running).

Target Visible (HasTarget)

Type: Condition | Category: Detection

Checks if the entity can see its target.

Parameters: None

Returns:

Success if target exists and is visible
Failure if no target or target not visible

Use Cases:

Before pursuing target
Entering combat mode
Breaking from patrol

Related Blackboard:

Reads: targetEntity (EntityID)

Target In Range

Type: Condition | Category: Detection

Checks if target is within a specified distance.

Parameters:

range (float): Maximum distance in pixels

Returns:

Success if target within range
Failure if no target or target too far

Use Cases:

Before attacking (melee/ranged range check)
Trigger special abilities
Proximity detection

Example:

{
  "type": "Condition",
  "conditionType": "TargetInRange",
  "conditionParam": 150.0
}

Related Blackboard:

Reads: targetEntity, lastKnownTargetPosition

Health Below

Type: Condition | Category: State

Checks if entity's health is below a threshold.

Parameters:

threshold (float): Health value (0-100)

Returns:

Success if health < threshold
Failure otherwise

Use Cases:

Trigger flee behavior
Call for help
Switch to defensive tactics

Example:

{
  "type": "Condition",
  "conditionType": "HealthBelow",
  "conditionParam": 30.0
}

Related Components:

Reads: Health_data.current

Has Move Goal

Type: Condition | Category: Navigation

Checks if entity has an active movement goal.

Parameters: None

Returns:

Success if moveGoal is set
Failure if no movement goal

Use Cases:

Before executing movement
Check if pathfinding succeeded
Validate navigation state

Related Blackboard:

Reads: moveGoal (Vector)

Can Attack

Type: Condition | Category: Combat

Checks if entity can perform an attack (cooldown check).

Parameters: None

Returns:

Success if attack cooldown expired
Failure if still on cooldown

Use Cases:

Guard attack action
Prevent spam attacks
Check weapon readiness

Related Components:

Reads: Combat_data.attackCooldown

Heard Noise

Type: Condition | Category: Detection

Checks if entity detected a noise event.

Parameters: None

Returns:

Success if noise detected recently
Failure if no noise

Use Cases:

Trigger investigation
Alert state
Sound-based detection

Related Blackboard:

Reads: heardNoise (bool), noisePosition (Vector)

Is Wait Timer Expired

Type: Condition | Category: Timing

Checks if a timer has expired.

Parameters: None

Returns:

Success if timer <= 0
Failure if timer > 0

Use Cases:

Wander behavior (wait before moving)
Timed pauses
Delayed actions

Related Blackboard:

Reads: waitTimer (float)

Has Navigable Destination

Type: Condition | Category: Navigation

Checks if a valid navigable destination has been chosen.

Parameters: None

Returns:

Success if destination is set and navigable
Failure otherwise

Use Cases:

Wander behaviors
Random movement
Pathfinding validation

Related Blackboard:

Reads: moveGoal (Vector)

Has Valid Path

Type: Condition | Category: Navigation

Checks if pathfinding succeeded and a path exists.

Parameters: None

Returns:

Success if path calculated successfully
Failure if pathfinding failed

Use Cases:

Before following path
Validate navigation
Handle unreachable destinations

Related Components:

Reads: Navigation_data.hasPath

Has Reached Destination

Type: Condition | Category: Navigation

Checks if entity reached its movement goal.

Parameters: None

Returns:

Success if arrived at destination
Failure if still moving

Use Cases:

After movement actions
Patrol waypoint completion
Trigger next behavior

Related Blackboard:

Reads: reachedDestination (bool)

Action Nodes

Actions perform actual behaviors and typically return Running until complete.

Set Move Goal To Target

Type: Action | Category: Navigation

Sets the movement goal to the current target's position.

Parameters: None

Effect:

Sets moveGoal to target entity's position
Returns Success if target exists
Returns Failure if no target

Use Cases:

Pursue enemy
Chase player
Follow entity

Set Move Goal To Last Known Target Position

Type: Action | Category: Navigation

Sets movement goal to the last known position of target.

Parameters: None

Effect:

Sets moveGoal to lastKnownTargetPosition
Returns Success if last position exists
Returns Failure otherwise

Use Cases:

Investigate where target was seen
Search last known location
Lost target behavior

Set Move Goal To Patrol Point

Type: Action | Category: Navigation

Sets movement goal to the current patrol waypoint.

Parameters: None

Effect:

Sets moveGoal to current patrol point
Returns Success if patrol point exists
Returns Failure if no patrol data

Use Cases:

Patrol behaviors
Waypoint navigation
Guard routes

Related Components:

Reads: Patrol_data.waypoints, Patrol_data.currentIndex

Move To Goal

Type: Action | Category: Navigation

Executes movement toward the current move goal.

Parameters:

acceptanceRadius (float): Distance to consider "arrived" (default: 10.0)

Returns:

Running while moving
Success when arrived at goal
Failure if no goal or pathfinding fails

Effect:

Requests pathfinding
Follows calculated path
Updates entity position

Example:

{
  "type": "Action",
  "actionType": "MoveToGoal",
  "actionParam1": 20.0
}

Attack If Close (Attack Melee)

Type: Action | Category: Combat

Performs a melee attack if target is in range.

Parameters: None

Returns:

Running during attack animation
Success if attack executed
Failure if no target or out of range

Effect:

Deals damage to target
Triggers attack animation
Starts attack cooldown

Related Components:

Uses: Combat_data
Checks: targetEntity, attack range

Patrol Pick Next Point

Type: Action | Category: Navigation

Advances to the next patrol waypoint.

Parameters: None

Returns:

Success if next point selected
Failure if no patrol data

Effect:

Increments Patrol_data.currentIndex
Wraps around to start if at end

Use Cases:

Cyclic patrol routes
Waypoint progression
Guard patterns

Clear Target

Type: Action | Category: State

Clears the current target entity.

Parameters: None

Returns:

Success always

Effect:

Sets targetEntity to 0 (null)
Clears related target data

Use Cases:

After losing target
End of combat
Reset detection state

Idle

Type: Action | Category: State

Does nothing (no-op action).

Parameters: None

Returns:

Success always (instantly)

Use Cases:

Placeholder node
Explicit wait state
Default behavior

Wait Random Time

Type: Action | Category: Timing

Initializes a random timer between min and max seconds.

Parameters:

param1 (float): Minimum time in seconds
param2 (float): Maximum time in seconds

Returns:

Success after initializing timer

Effect:

Sets waitTimer to random value in [min, max]

Example:

{
  "type": "Action",
  "actionType": "WaitRandomTime",
  "actionParam1": 2.0,
  "actionParam2": 5.0
}

Use Cases:

Wander behavior pauses
Variable timing
Natural movement

Choose Random Navigable Point

Type: Action | Category: Navigation

Chooses a random point within a radius that is navigable.

Parameters:

param1 (float): Search radius in pixels
param2 (int): Max attempts (default: 10)

Returns:

Success if navigable point found
Failure if no valid point after max attempts

Effect:

Sets moveGoal to random navigable position

Example:

{
  "type": "Action",
  "actionType": "ChooseRandomNavigablePoint",
  "actionParam1": 200.0,
  "actionParam2": 10
}

Use Cases:

Wander behaviors
Random exploration
Idle movement

Request Pathfinding

Type: Action | Category: Navigation

Requests pathfinding to the current move goal.

Parameters: None

Returns:

Running while calculating path
Success if path found
Failure if pathfinding fails

Effect:

Submits pathfinding request to NavigationSystem
Updates Navigation_data.path when complete

Use Cases:

Before following a path
Long-distance navigation
Dynamic obstacles

Follow Path

Type: Action | Category: Navigation

Follows the currently calculated path.

Parameters: None

Returns:

Running while following path
Success when destination reached
Failure if path lost or blocked

Effect:

Moves entity along waypoints
Updates position each frame
Checks for path validity

Use Cases:

After pathfinding succeeds
Multi-waypoint navigation
Dynamic movement

Node Color Reference

In the debugger, nodes are color-coded by type:

Node Type	Color	Hex Code
Selector	Purple	`#9C27B0`
Sequence	Blue	`#2196F3`
Condition	Yellow	`#FFC107`
Action	Green	`#4CAF50`
Inverter	Orange	`#FF9800`
Repeater	Teal	`#009688`

Status Colors

Nodes also show execution status with color overlays:

Status	Color	Hex Code
Idle	Gray	`#808080`
Running	Blue	`#2196F3`
Success	Green	`#4CAF50`
Failure	Red	`#F44336`

Choosing the Right Node

Decision Tree

Follow this guide to choose the correct node:

Do you need to:

Make a decision? → Use Selector
Do multiple things in order? → Use Sequence
Check game state? → Use Condition
Change the world? → Use Action
Invert logic? → Use Inverter
Repeat behavior? → Use Repeater

Common Mistakes

❌ Using Actions as Conditions

Action "Move To Goal" as a condition check

✅ Use Conditions to check, Actions to execute

Condition "Has Move Goal" → Action "Move To Goal"

❌ Deep nesting without clear purpose

Selector → Sequence → Selector → Sequence → Action (5 levels)

✅ Keep hierarchies shallow and logical

Selector → Sequence → Action (3 levels)

❌ Forgetting Inverter for "NOT" logic

Creating custom "NotInRange" condition

✅ Use Inverter with existing conditions

Inverter → Condition "Target In Range"

Next Steps

Now that you understand all node types:

Connection Rules - Learn how to connect nodes properly
First BT Tutorial - Build a complete behavior tree
BT Debugger - Debug your trees at runtime

Additional Resources

Custom Nodes - Create your own node types in C++
Nodes Technical Reference - Deep implementation details
Behavior Tree Basics - Complete tutorial with examples

Node Categories​

Composite Nodes​

Selector (OR Node)​

Sequence (AND Node)​

Decorator Nodes​

Inverter (NOT Node)​

Repeater (Loop Node)​

Condition Nodes​

Target Visible (HasTarget)​

Target In Range​

Health Below​

Has Move Goal​

Can Attack​

Heard Noise​

Is Wait Timer Expired​

Has Navigable Destination​

Has Valid Path​

Has Reached Destination​

Action Nodes​

Set Move Goal To Target​

Set Move Goal To Last Known Target Position​

Set Move Goal To Patrol Point​

Move To Goal​

Attack If Close (Attack Melee)​

Patrol Pick Next Point​

Clear Target​

Idle​

Wait Random Time​

Choose Random Navigable Point​

Request Pathfinding​

Follow Path​

Node Color Reference​

Status Colors​

Choosing the Right Node​

Decision Tree​

Common Mistakes​

Next Steps​

Additional Resources​

Node Categories

Composite Nodes

Selector (OR Node)

Sequence (AND Node)

Decorator Nodes

Inverter (NOT Node)

Repeater (Loop Node)

Condition Nodes

Target Visible (HasTarget)

Target In Range

Health Below

Has Move Goal

Can Attack

Heard Noise

Is Wait Timer Expired

Has Navigable Destination

Has Valid Path

Has Reached Destination

Action Nodes

Set Move Goal To Target

Set Move Goal To Last Known Target Position

Set Move Goal To Patrol Point

Move To Goal

Attack If Close (Attack Melee)

Patrol Pick Next Point

Clear Target

Idle

Wait Random Time

Choose Random Navigable Point

Request Pathfinding

Follow Path

Node Color Reference

Status Colors

Choosing the Right Node

Decision Tree

Common Mistakes

Next Steps

Additional Resources