Standard Behavior Tree Nodes

Want to learn the fundamentals of behavior trees? Check out my tutorial, Get Started With Behavior Trees in Unity.

The Standard Nodes sample project contains a set of standard behavior tree nodes that can be used for your game. You can import it into your project through Package Manager.

Here's what you need to know:

1. There are 11 specialized composite and decorator nodes.
2. When creating new nodes, make sure to inherit from Composite, Condition and Decorator when creating new nodes of those types.
3. Action/Leaf nodes can be inherited from Node directly.
4. Make sure to configure the settings file!

General

There are two general node types:

Name	Description
Node	Base class for all node types - Everything should ultimately derive from this.
Condition	Base class for all condition node types. Does not do anything special. Exists so that you can stylize all conditions in the debugger tool easily.

Composites

Composites are essentially instructions for your behavior tree on how it should run a group of child nodes.

Name	Description
Composite	Base class for all composite node types.
Selector	Runs each child until one of them returns status Success. Will return failure if no child runs successfully.
RandomSelector	Shuffles the child nodes the first time the behavior tree is constructed (only once). Executes the same as Selector
AlwaysRandomSelector	Shuffles the child nodes every time it runs for the first time. Executes the same as Selector.
Sequence	Will continue to run if all children return the status of Running or Success. Return a status code of Failure if any children return status Failure. Returns status code of Success if all children return Success.
RandomSequence	Shuffles the child nodes the first time the behavior tree is constructed (only once). Executes the same as Sequence.
AlwaysRandomSequence	Shuffles the child nodes every time it runs for the first time. Executes the same as Sequence.

Decorators

Decorators are a way to alter how an individual node is run. These can range from changing the return status code (Inverter) to defining how many times to execute (Repeater).

Name	Description
Decorator	Base class for all decorator node types. Supports a single child.
Delay	Executes a timer and then runs the child node once.
Inverter	Inverts the final result of the node - Success will return Failure and Failure will return Success.
Repeater	Run the child node a specified amount of times before exiting.
Succeeder	Returns Running status if running otherwise returns the Success status. Never the failure status.
Timer	Run the child node a specified amount of time in seconds.
UntilFail	Continues to run the child node until the child returns a status of Failure.